use std::cmp::Reverse;
use std::ops::Range;
use std::path::PathBuf;
use std::sync::Arc;
use std::sync::atomic::AtomicBool;

use crate::DEFAULT_THREAD_TITLE;
use crate::thread_metadata_store::{ThreadMetadata, ThreadMetadataStore};
use acp_thread::MentionUri;
use agent_client_protocol::schema::v1 as acp;
use anyhow::Result;
use editor::{CompletionProvider, Editor, code_context_menus::COMPLETION_MENU_MAX_WIDTH};
use futures::FutureExt as _;
use fuzzy::{PathMatch, StringMatch, StringMatchCandidate};
use gpui::{
    App, BackgroundExecutor, Entity, Focusable, Hsla, SharedString, Task, WeakEntity, Window,
};
use language::{Buffer, CodeLabel, CodeLabelBuilder, HighlightId};
use lsp::CompletionContext;
use multi_buffer::ToOffset as _;
use ordered_float::OrderedFloat;
use project::lsp_store::{CompletionDocumentation, SymbolLocation};
use project::{
    Completion, CompletionDisplayOptions, CompletionGroup, CompletionIntent, CompletionResponse,
    DiagnosticSummary, PathMatchCandidateSet, Project, ProjectPath, Symbol, WorktreeId,
};

use rope::Point;
use settings::Settings;
use terminal::terminal_settings::TerminalSettings;
use terminal_view::{TerminalView, terminal_panel::TerminalPanel};
use text::{Anchor, ToOffset as _, ToPoint as _};
use ui::IconName;
use ui::prelude::*;
use util::ResultExt as _;
use util::paths::PathStyle;
use util::rel_path::RelPath;
use util::truncate_and_remove_front;
use workspace::Workspace;

use crate::AgentPanel;
use crate::mention_set::MentionSet;

#[derive(Clone)]
pub(crate) enum AgentContextSelection {
    Editor(Vec<(Entity<Buffer>, Range<text::Anchor>)>),
    Terminal(Vec<String>),
}

#[derive(Clone)]
pub(crate) enum AgentContextSource {
    Editor(WeakEntity<Editor>),
    TerminalView(WeakEntity<TerminalView>),
    TerminalPanel,
}

impl AgentContextSource {
    pub(crate) fn read_selection(
        &self,
        workspace: &Workspace,
        include_current_line: bool,
        cx: &mut App,
    ) -> Option<AgentContextSelection> {
        match self {
            Self::Editor(handle) => {
                let editor = handle.upgrade()?;
                let ranges = editor_selection_ranges(&editor, include_current_line, cx);
                (!ranges.is_empty()).then_some(AgentContextSelection::Editor(ranges))
            }
            Self::TerminalView(handle) => {
                let terminal_view = handle.upgrade()?;
                terminal_view_selection(&terminal_view, cx)
                    .map(|text| AgentContextSelection::Terminal(vec![text]))
            }
            Self::TerminalPanel => {
                let panel = workspace.panel::<TerminalPanel>(cx)?;
                let selections = panel.read(cx).terminal_selections(cx);
                (!selections.is_empty()).then_some(AgentContextSelection::Terminal(selections))
            }
        }
    }

    pub(crate) fn from_focused(workspace: &Workspace, window: &Window, cx: &App) -> Option<Self> {
        if let Some(agent_panel) = workspace.panel::<AgentPanel>(cx)
            && agent_panel.focus_handle(cx).contains_focused(window, cx)
        {
            return None;
        }

        if let Some(active_item) = workspace.active_item(cx) {
            if let Some(editor) = active_item.act_as::<Editor>(cx) {
                if editor.focus_handle(cx).is_focused(window) {
                    return Some(Self::Editor(editor.downgrade()));
                }
            } else if let Some(terminal_view) = active_item.act_as::<TerminalView>(cx)
                && terminal_view.focus_handle(cx).is_focused(window)
            {
                return Some(Self::TerminalView(terminal_view.downgrade()));
            }
        }

        if let Some(panel) = workspace.panel::<TerminalPanel>(cx)
            && panel.focus_handle(cx).contains_focused(window, cx)
        {
            return Some(Self::TerminalPanel);
        }

        None
    }

    pub(crate) fn from_active(workspace: &Workspace, cx: &App) -> Option<Self> {
        if let Some(active_item) = workspace.active_item(cx) {
            if let Some(editor) = active_item.act_as::<Editor>(cx) {
                return Some(Self::Editor(editor.downgrade()));
            } else if let Some(terminal_view) = active_item.act_as::<TerminalView>(cx) {
                return Some(Self::TerminalView(terminal_view.downgrade()));
            }
        }
        if terminal_panel_dock_is_open(workspace, cx) {
            return Some(Self::TerminalPanel);
        }
        None
    }

    pub(crate) fn exists(&self, workspace: &Workspace, cx: &App) -> bool {
        match self {
            Self::Editor(handle) => handle.upgrade().is_some(),
            Self::TerminalView(handle) => handle.upgrade().is_some(),
            Self::TerminalPanel => terminal_panel_dock_is_open(workspace, cx),
        }
    }
}

fn terminal_panel_dock_is_open(workspace: &Workspace, cx: &App) -> bool {
    if workspace.panel::<TerminalPanel>(cx).is_none() {
        return false;
    }
    let position = TerminalSettings::get_global(cx).dock.into();
    workspace.dock_at_position(position).read(cx).is_open()
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum PromptContextEntry {
    Mode(PromptContextType),
    Action(PromptContextAction),
}

impl PromptContextEntry {
    pub fn keyword(&self) -> &'static str {
        match self {
            Self::Mode(mode) => mode.keyword(),
            Self::Action(action) => action.keyword(),
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum PromptContextType {
    File,
    Symbol,
    Fetch,
    Thread,
    Skill,
    Diagnostics,
    BranchDiff,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum PromptContextAction {
    AddSelections,
}

impl PromptContextAction {
    pub fn keyword(&self) -> &'static str {
        match self {
            Self::AddSelections => "selection",
        }
    }

    pub fn label(&self) -> &'static str {
        match self {
            Self::AddSelections => "Selection",
        }
    }

    pub fn icon(&self) -> IconName {
        match self {
            Self::AddSelections => IconName::Reader,
        }
    }
}

/// A slash command that runs a local UI action against the conversation
/// (sending feedback) instead of being sent to the agent as part of a prompt.
/// Each variant maps to a method on `ThreadView`; the completion provider only
/// surfaces them and emits an event, while `ThreadView` performs the actual
/// work (see `handle_message_editor_event`).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum PromptLocalCommand {
    ThumbsUp,
    ThumbsDown,
}

impl PromptLocalCommand {
    pub fn keyword(&self) -> &'static str {
        match self {
            Self::ThumbsUp => "helpful",
            Self::ThumbsDown => "not-helpful",
        }
    }

    pub fn label(&self) -> &'static str {
        match self {
            Self::ThumbsUp => "Positive Feedback",
            Self::ThumbsDown => "Negative Feedback",
        }
    }

    pub fn description(&self) -> &'static str {
        match self {
            Self::ThumbsUp => {
                "Rate this response as helpful. Sends the current conversation to the Zed team."
            }
            Self::ThumbsDown => {
                "Rate this response as not helpful. Sends the current conversation to the Zed team."
            }
        }
    }

    pub fn icon(&self) -> IconName {
        match self {
            Self::ThumbsUp => IconName::ThumbsUp,
            Self::ThumbsDown => IconName::ThumbsDown,
        }
    }
}

impl TryFrom<&str> for PromptContextType {
    type Error = String;

    fn try_from(value: &str) -> Result<Self, Self::Error> {
        match value {
            "file" => Ok(Self::File),
            "symbol" => Ok(Self::Symbol),
            "fetch" => Ok(Self::Fetch),
            "thread" => Ok(Self::Thread),
            "skill" => Ok(Self::Skill),
            "diagnostics" => Ok(Self::Diagnostics),
            "diff" => Ok(Self::BranchDiff),
            _ => Err(format!("Invalid context picker mode: {}", value)),
        }
    }
}

impl PromptContextType {
    pub fn keyword(&self) -> &'static str {
        match self {
            Self::File => "file",
            Self::Symbol => "symbol",
            Self::Fetch => "fetch",
            Self::Thread => "thread",
            Self::Skill => "skill",
            Self::Diagnostics => "diagnostics",
            Self::BranchDiff => "branch diff",
        }
    }

    pub fn label(&self) -> &'static str {
        match self {
            Self::File => "Files & Directories",
            Self::Symbol => "Symbols",
            Self::Fetch => "Fetch",
            Self::Thread => "Threads",
            Self::Skill => "Skills",
            Self::Diagnostics => "Diagnostics",
            Self::BranchDiff => "Branch Diff",
        }
    }

    pub fn icon(&self) -> IconName {
        match self {
            Self::File => IconName::File,
            Self::Symbol => IconName::Code,
            Self::Fetch => IconName::ToolWeb,
            Self::Thread => IconName::Thread,
            Self::Skill => IconName::Sparkle,
            Self::Diagnostics => IconName::Warning,
            Self::BranchDiff => IconName::GitBranch,
        }
    }
}

pub(crate) enum Match {
    File(FileMatch),
    Symbol(SymbolMatch),
    Thread(SessionMatch),
    RecentThread(SessionMatch),
    Fetch(SharedString),
    Skill(AvailableSkill),
    Entry(EntryMatch),
    BranchDiff(BranchDiffMatch),
}

#[derive(Debug, Clone)]
pub struct BranchDiffMatch {
    pub base_ref: SharedString,
}

impl Match {
    pub fn score(&self) -> f64 {
        match self {
            Match::File(file) => file.mat.score,
            Match::Entry(mode) => mode.mat.as_ref().map(|mat| mat.score).unwrap_or(1.),
            Match::Thread(_) => 1.,
            Match::RecentThread(_) => 1.,
            Match::Symbol(_) => 1.,
            Match::Skill(_) => 1.,
            Match::Fetch(_) => 1.,
            Match::BranchDiff(_) => 1.,
        }
    }
}

#[derive(Debug, Clone)]
pub struct SessionMatch {
    session_id: acp::SessionId,
    title: SharedString,
}

pub struct EntryMatch {
    mat: Option<StringMatch>,
    entry: PromptContextEntry,
}

fn session_title(title: Option<SharedString>) -> SharedString {
    title
        .filter(|title| !title.is_empty())
        .unwrap_or_else(|| SharedString::new_static(DEFAULT_THREAD_TITLE))
}

#[derive(Debug, Clone)]
pub struct AvailableSkill {
    pub name: Arc<str>,
    pub description: Arc<str>,
    /// Scope prefix for this skill: empty for global skills, or the
    /// worktree root name for project-local skills.
    pub source: SharedString,
    pub skill_file_path: PathBuf,
    pub warning: Option<SharedString>,
}

fn skill_completion_icon_path(
    skill: &AvailableSkill,
    uri: &MentionUri,
    cx: &mut App,
) -> SharedString {
    if skill.warning.is_some() {
        IconName::Warning.path().into()
    } else {
        uri.icon_path(cx)
    }
}

fn skill_completion_icon_color(skill: &AvailableSkill, cx: &App) -> Option<Hsla> {
    skill.warning.is_some().then(|| cx.theme().status().warning)
}

fn skill_completion_documentation(skill: &AvailableSkill) -> CompletionDocumentation {
    let text = match &skill.warning {
        Some(warning) => warning.clone(),
        None => skill.description.to_string().into(),
    };
    CompletionDocumentation::MultiLinePlainText(text)
}

#[derive(Debug, Clone)]
pub struct AvailableCommand {
    pub name: Arc<str>,
    pub description: Arc<str>,
    pub requires_argument: bool,
    pub source: Option<SharedString>,
    /// Source category used to group the command in the slash popup. `None`
    /// means the command came from an external ACP agent.
    pub category: Option<acp_thread::CommandCategory>,
}

impl AvailableCommand {
    fn category_order(&self) -> u8 {
        match self.category {
            Some(acp_thread::CommandCategory::Native) => 0,
            Some(acp_thread::CommandCategory::Mcp) => 1,
            None => 2,
        }
    }

    /// Completion group key and header label for this command's category.
    fn group(&self) -> CompletionGroup {
        let (key, label) = match self.category {
            Some(acp_thread::CommandCategory::Native) => ("commands", "Commands"),
            Some(acp_thread::CommandCategory::Mcp) => ("mcp-commands", "MCP Server Commands"),
            None => ("acp-commands", "Commands"),
        };
        CompletionGroup {
            key: key.into(),
            label: Some(label.into()),
        }
    }
}

#[derive(Debug, Clone)]
enum SlashCompletionCandidate {
    Skill(AvailableSkill),
    Command(AvailableCommand),
    LocalCommand(PromptLocalCommand),
}

impl SlashCompletionCandidate {
    fn name(&self) -> &str {
        match self {
            Self::Skill(skill) => &skill.name,
            Self::Command(command) => &command.name,
            Self::LocalCommand(command) => command.keyword(),
        }
    }
}

/// Stable group identity for a slash completion: skills are one group, commands
/// are grouped by category. This identifies which section header an entry sits
/// under; the order the groups appear in is decided by relevance (see
/// [`group_by_relevance`]).
fn slash_completion_group_key(candidate: &SlashCompletionCandidate) -> u32 {
    match candidate {
        SlashCompletionCandidate::Skill(_) => 0,
        SlashCompletionCandidate::Command(command) => 1 + command.category_order() as u32,
        SlashCompletionCandidate::LocalCommand(_) => 4,
    }
}

/// Reorders `items` (which must already be in relevance/score order, best
/// first) so that each group's entries stay contiguous while the groups
/// themselves are ordered by their best-ranked member. The sort is stable, so
/// within a group the original order is preserved.
fn group_by_relevance<T>(items: &mut [T], group_key: impl Fn(&T) -> u32) {
    let mut group_best_rank: collections::HashMap<u32, usize> = collections::HashMap::default();
    for (rank, item) in items.iter().enumerate() {
        group_best_rank.entry(group_key(item)).or_insert(rank);
    }
    items.sort_by_key(|item| group_best_rank[&group_key(item)]);
}

pub trait PromptCompletionProviderDelegate: Send + Sync + 'static {
    fn supports_context(&self, mode: PromptContextType, cx: &App) -> bool {
        self.supported_modes(cx).contains(&mode)
    }
    fn supported_modes(&self, cx: &App) -> Vec<PromptContextType>;
    fn supports_images(&self, cx: &App) -> bool;

    fn available_commands(&self, cx: &App) -> Vec<AvailableCommand>;
    fn available_skills(&self, _cx: &App) -> Vec<AvailableSkill> {
        Vec::new()
    }

    fn available_local_commands(&self, _cx: &App) -> Vec<PromptLocalCommand> {
        Vec::new()
    }

    fn run_local_command(&self, _command: PromptLocalCommand, _cx: &mut App) {}

    fn confirm_command(&self, cx: &mut App);

    /// Called once each time the user opens slash-command autocomplete
    /// in the editor this delegate serves. Implementations may use it
    /// to lazily kick off work that produces commands (for example,
    /// scanning the global skills directory). The default is a no-op.
    fn slash_autocomplete_invoked(&self, _cx: &mut App) {}
}

pub struct PromptCompletionProvider<T: PromptCompletionProviderDelegate> {
    source: Arc<T>,
    editor: WeakEntity<Editor>,
    mention_set: Entity<MentionSet>,
    workspace: WeakEntity<Workspace>,
}

impl<T: PromptCompletionProviderDelegate> PromptCompletionProvider<T> {
    pub fn new(
        source: T,
        editor: WeakEntity<Editor>,
        mention_set: Entity<MentionSet>,
        workspace: WeakEntity<Workspace>,
    ) -> Self {
        Self {
            source: Arc::new(source),
            editor,
            mention_set,
            workspace,
        }
    }

    fn completion_for_entry(
        entry: PromptContextEntry,
        source_range: Range<Anchor>,
        editor: WeakEntity<Editor>,
        mention_set: WeakEntity<MentionSet>,
        workspace: &Entity<Workspace>,
        cx: &mut App,
    ) -> Option<Completion> {
        match entry {
            PromptContextEntry::Mode(mode) => Some(Completion {
                replace_range: source_range,
                new_text: format!("@{} ", mode.keyword()),
                label: CodeLabel::plain(mode.label().to_string(), None),
                icon_path: Some(mode.icon().path().into()),
                icon_color: None,
                documentation: None,
                source: project::CompletionSource::Custom,
                match_start: None,
                snippet_deduplication_key: None,
                insert_text_mode: None,
                // This ensures that when a user accepts this completion, the
                // completion menu will still be shown after "@category " is
                // inserted
                confirm: Some(Arc::new(|_, _, _| true)),
                group: None,
            }),
            PromptContextEntry::Action(action) => {
                let selection = workspace.update(cx, |workspace, cx| {
                    AgentContextSource::from_active(workspace, cx)?
                        .read_selection(workspace, false, cx)
                });
                Self::completion_for_action(
                    action,
                    source_range,
                    editor,
                    mention_set,
                    workspace.downgrade(),
                    selection,
                )
            }
        }
    }

    fn completion_for_thread(
        session_id: acp::SessionId,
        title: Option<SharedString>,
        source_range: Range<Anchor>,
        recent: bool,
        source: Arc<T>,
        editor: WeakEntity<Editor>,
        mention_set: WeakEntity<MentionSet>,
        workspace: Entity<Workspace>,
        cx: &mut App,
    ) -> Completion {
        let title = session_title(title);
        let uri = MentionUri::Thread {
            id: session_id,
            name: title.to_string(),
        };

        let icon_for_completion = if recent {
            IconName::HistoryRerun.path().into()
        } else {
            uri.icon_path(cx)
        };

        let new_text = format!("{} ", uri.as_link());

        let new_text_len = new_text.len();
        Completion {
            replace_range: source_range.clone(),
            new_text,
            label: CodeLabel::plain(title.to_string(), None),
            documentation: None,
            insert_text_mode: None,
            source: project::CompletionSource::Custom,
            match_start: None,
            snippet_deduplication_key: None,
            icon_path: Some(icon_for_completion),
            icon_color: None,
            confirm: Some(confirm_completion_callback(
                title,
                source_range.start,
                new_text_len - 1,
                uri,
                source,
                editor,
                mention_set,
                workspace,
            )),
            group: None,
        }
    }

    fn completion_for_skill(
        skill: AvailableSkill,
        source_range: Range<Anchor>,
        source: Arc<T>,
        editor: WeakEntity<Editor>,
        mention_set: WeakEntity<MentionSet>,
        workspace: Entity<Workspace>,
        cx: &mut App,
    ) -> Completion {
        let uri = MentionUri::Skill {
            name: skill.name.to_string(),
            source: skill.source.to_string(),
            skill_file_path: skill.skill_file_path.clone(),
        };
        let new_text = format!("{} ", uri.as_link());
        let new_text_len = new_text.len();
        let icon_path = skill_completion_icon_path(&skill, &uri, cx);
        let crease_text: SharedString = uri.name().into();
        let source_highlight_id = cx
            .theme()
            .syntax()
            .highlight_id("variable")
            .map(HighlightId::new);
        let label = build_slash_item_label(&skill.name, Some(&skill.source), source_highlight_id);
        Completion {
            replace_range: source_range.clone(),
            new_text,
            label,
            documentation: Some(skill_completion_documentation(&skill)),
            insert_text_mode: None,
            source: project::CompletionSource::Custom,
            match_start: None,
            snippet_deduplication_key: None,
            icon_path: Some(icon_path),
            icon_color: skill_completion_icon_color(&skill, cx),
            confirm: Some(confirm_completion_callback(
                crease_text,
                source_range.start,
                new_text_len - 1,
                uri,
                source,
                editor,
                mention_set,
                workspace,
            )),
            group: None,
        }
    }

    pub(crate) fn completion_for_path(
        project_path: ProjectPath,
        path_prefix: &RelPath,
        is_recent: bool,
        is_directory: bool,
        source_range: Range<Anchor>,
        source: Arc<T>,
        editor: WeakEntity<Editor>,
        mention_set: WeakEntity<MentionSet>,
        workspace: Entity<Workspace>,
        project: Entity<Project>,
        label_max_chars: usize,
        cx: &mut App,
    ) -> Option<Completion> {
        let path_style = project.read(cx).path_style(cx);
        let (file_name, directory) =
            extract_file_name_and_directory(&project_path.path, path_prefix, path_style);

        let label = build_code_label_for_path(
            &file_name,
            directory.as_ref().map(|s| s.as_ref()),
            None,
            label_max_chars,
            cx,
        );

        let abs_path = project.read(cx).absolute_path(&project_path, cx)?;

        let uri = if is_directory {
            MentionUri::Directory { abs_path }
        } else {
            MentionUri::File { abs_path }
        };

        let crease_icon_path = uri.icon_path(cx);
        let completion_icon_path = if is_recent {
            IconName::HistoryRerun.path().into()
        } else {
            crease_icon_path
        };

        let new_text = format!("{} ", uri.as_link());
        let new_text_len = new_text.len();
        Some(Completion {
            replace_range: source_range.clone(),
            new_text,
            label,
            documentation: None,
            source: project::CompletionSource::Custom,
            icon_path: Some(completion_icon_path),
            icon_color: None,
            match_start: None,
            snippet_deduplication_key: None,
            insert_text_mode: None,
            confirm: Some(confirm_completion_callback(
                file_name,
                source_range.start,
                new_text_len - 1,
                uri,
                source,
                editor,
                mention_set,
                workspace,
            )),
            group: None,
        })
    }

    fn completion_for_symbol(
        symbol: Symbol,
        source_range: Range<Anchor>,
        source: Arc<T>,
        editor: WeakEntity<Editor>,
        mention_set: WeakEntity<MentionSet>,
        workspace: Entity<Workspace>,
        label_max_chars: usize,
        cx: &mut App,
    ) -> Option<Completion> {
        let project = workspace.read(cx).project().clone();

        let (abs_path, file_name) = match &symbol.path {
            SymbolLocation::InProject(project_path) => (
                project.read(cx).absolute_path(&project_path, cx)?,
                project_path.path.file_name()?.to_string().into(),
            ),
            SymbolLocation::OutsideProject {
                abs_path,
                signature: _,
            } => (
                PathBuf::from(abs_path.as_ref()),
                abs_path.file_name().map(|f| f.to_string_lossy())?,
            ),
        };

        let label = build_code_label_for_path(
            &symbol.name,
            Some(&file_name),
            Some(symbol.range.start.0.row + 1),
            label_max_chars,
            cx,
        );

        let uri = MentionUri::Symbol {
            abs_path,
            name: symbol.name.clone(),
            line_range: symbol.range.start.0.row..=symbol.range.end.0.row,
        };
        let new_text = format!("{} ", uri.as_link());
        let new_text_len = new_text.len();
        let icon_path = uri.icon_path(cx);
        Some(Completion {
            replace_range: source_range.clone(),
            new_text,
            label,
            documentation: None,
            source: project::CompletionSource::Custom,
            icon_path: Some(icon_path),
            icon_color: None,
            match_start: None,
            snippet_deduplication_key: None,
            insert_text_mode: None,
            confirm: Some(confirm_completion_callback(
                symbol.name.into(),
                source_range.start,
                new_text_len - 1,
                uri,
                source,
                editor,
                mention_set,
                workspace,
            )),
            group: None,
        })
    }

    fn completion_for_fetch(
        source_range: Range<Anchor>,
        url_to_fetch: SharedString,
        source: Arc<T>,
        editor: WeakEntity<Editor>,
        mention_set: WeakEntity<MentionSet>,
        workspace: Entity<Workspace>,
        cx: &mut App,
    ) -> Option<Completion> {
        let new_text = format!("@fetch {} ", url_to_fetch);
        let url_to_fetch = url::Url::parse(url_to_fetch.as_ref())
            .or_else(|_| url::Url::parse(&format!("https://{url_to_fetch}")))
            .ok()?;
        let mention_uri = MentionUri::Fetch {
            url: url_to_fetch.clone(),
        };
        let icon_path = mention_uri.icon_path(cx);
        Some(Completion {
            replace_range: source_range.clone(),
            new_text: new_text.clone(),
            label: CodeLabel::plain(url_to_fetch.to_string(), None),
            documentation: None,
            source: project::CompletionSource::Custom,
            icon_path: Some(icon_path),
            icon_color: None,
            match_start: None,
            snippet_deduplication_key: None,
            insert_text_mode: None,
            confirm: Some(confirm_completion_callback(
                url_to_fetch.to_string().into(),
                source_range.start,
                new_text.len() - 1,
                mention_uri,
                source,
                editor,
                mention_set,
                workspace,
            )),
            group: None,
        })
    }

    pub(crate) fn completion_for_action(
        action: PromptContextAction,
        source_range: Range<Anchor>,
        editor: WeakEntity<Editor>,
        mention_set: WeakEntity<MentionSet>,
        workspace: WeakEntity<Workspace>,
        selection: Option<AgentContextSelection>,
    ) -> Option<Completion> {
        let (new_text, on_action) = match action {
            PromptContextAction::AddSelections => match selection? {
                AgentContextSelection::Editor(editor_selections) => {
                    completion_text_for_editor_selections(
                        source_range.clone(),
                        editor,
                        mention_set,
                        workspace,
                        editor_selections,
                    )
                }
                AgentContextSelection::Terminal(terminal_selections) => {
                    completion_text_for_terminal_selections(
                        source_range.clone(),
                        editor,
                        mention_set,
                        terminal_selections,
                    )
                }
            },
        };

        Some(Completion {
            replace_range: source_range,
            new_text,
            label: CodeLabel::plain(action.label().to_string(), None),
            icon_path: Some(action.icon().path().into()),
            icon_color: None,
            documentation: None,
            source: project::CompletionSource::Custom,
            match_start: None,
            snippet_deduplication_key: None,
            insert_text_mode: None,
            // This ensures that when a user accepts this completion, the
            // completion menu will still be shown after "@category " is
            // inserted
            confirm: Some(on_action),
            group: None,
        })
    }

    fn completion_for_diagnostics(
        source_range: Range<Anchor>,
        source: Arc<T>,
        editor: WeakEntity<Editor>,
        mention_set: WeakEntity<MentionSet>,
        workspace: Entity<Workspace>,
        cx: &mut App,
    ) -> Vec<Completion> {
        let summary = workspace
            .read(cx)
            .project()
            .read(cx)
            .diagnostic_summary(false, cx);
        if summary.error_count == 0 && summary.warning_count == 0 {
            return Vec::new();
        }
        let icon_path = MentionUri::Diagnostics {
            include_errors: true,
            include_warnings: false,
        }
        .icon_path(cx);

        let mut completions = Vec::new();

        let cases = [
            (summary.error_count > 0, true, false),
            (summary.warning_count > 0, false, true),
            (
                summary.error_count > 0 && summary.warning_count > 0,
                true,
                true,
            ),
        ];

        for (condition, include_errors, include_warnings) in cases {
            if condition {
                completions.push(Self::build_diagnostics_completion(
                    diagnostics_submenu_label(summary, include_errors, include_warnings),
                    source_range.clone(),
                    source.clone(),
                    editor.clone(),
                    mention_set.clone(),
                    workspace.clone(),
                    icon_path.clone(),
                    include_errors,
                    include_warnings,
                    summary,
                ));
            }
        }

        completions
    }

    fn build_diagnostics_completion(
        menu_label: String,
        source_range: Range<Anchor>,
        source: Arc<T>,
        editor: WeakEntity<Editor>,
        mention_set: WeakEntity<MentionSet>,
        workspace: Entity<Workspace>,
        icon_path: SharedString,
        include_errors: bool,
        include_warnings: bool,
        summary: DiagnosticSummary,
    ) -> Completion {
        let uri = MentionUri::Diagnostics {
            include_errors,
            include_warnings,
        };
        let crease_text = diagnostics_crease_label(summary, include_errors, include_warnings);
        let display_text = format!("@{}", crease_text);
        let new_text = format!("[{}]({}) ", display_text, uri.to_uri());
        let new_text_len = new_text.len();
        Completion {
            replace_range: source_range.clone(),
            new_text,
            label: CodeLabel::plain(menu_label, None),
            documentation: None,
            source: project::CompletionSource::Custom,
            icon_path: Some(icon_path),
            icon_color: None,
            match_start: None,
            snippet_deduplication_key: None,
            insert_text_mode: None,
            confirm: Some(confirm_completion_callback(
                crease_text,
                source_range.start,
                new_text_len - 1,
                uri,
                source,
                editor,
                mention_set,
                workspace,
            )),
            group: None,
        }
    }

    fn build_branch_diff_completion(
        base_ref: SharedString,
        source_range: Range<Anchor>,
        source: Arc<T>,
        editor: WeakEntity<Editor>,
        mention_set: WeakEntity<MentionSet>,
        workspace: Entity<Workspace>,
        cx: &mut App,
    ) -> Completion {
        let uri = MentionUri::GitDiff {
            base_ref: base_ref.to_string(),
        };
        let crease_text: SharedString = format!("Branch Diff (vs {})", base_ref).into();
        let display_text = format!("@{}", crease_text);
        let new_text = format!("[{}]({}) ", display_text, uri.to_uri());
        let new_text_len = new_text.len();
        let icon_path = uri.icon_path(cx);

        Completion {
            replace_range: source_range.clone(),
            new_text,
            label: CodeLabel::plain(crease_text.to_string(), None),
            documentation: None,
            source: project::CompletionSource::Custom,
            icon_path: Some(icon_path),
            icon_color: None,
            match_start: None,
            snippet_deduplication_key: None,
            insert_text_mode: None,
            confirm: Some(confirm_completion_callback(
                crease_text,
                source_range.start,
                new_text_len - 1,
                uri,
                source,
                editor,
                mention_set,
                workspace,
            )),
            group: None,
        }
    }

    fn search_slash_commands(
        &self,
        query: String,
        cx: &mut App,
    ) -> Task<Vec<SlashCompletionCandidate>> {
        // Notify the delegate that slash autocomplete is being
        // invoked, so it can lazily kick off any work that produces
        // additional commands or skills. Whatever it produces won't be
        // visible in the current autocomplete pass (we read available
        // items synchronously below), but will appear on the next
        // invocation.
        self.source.slash_autocomplete_invoked(cx);

        let mut candidates = self
            .source
            .available_commands(cx)
            .into_iter()
            .map(SlashCompletionCandidate::Command)
            .collect::<Vec<_>>();
        candidates.extend(
            self.source
                .available_skills(cx)
                .into_iter()
                .map(SlashCompletionCandidate::Skill),
        );
        candidates.extend(
            self.source
                .available_local_commands(cx)
                .into_iter()
                .map(SlashCompletionCandidate::LocalCommand),
        );
        if candidates.is_empty() {
            return Task::ready(Vec::new());
        }

        cx.spawn(async move |cx| {
            let string_match_candidates = candidates
                .iter()
                .enumerate()
                .map(|(id, candidate)| StringMatchCandidate::new(id, candidate.name()))
                .collect::<Vec<_>>();

            let matches = fuzzy::match_strings(
                &string_match_candidates,
                &query,
                false,
                true,
                100,
                &Arc::new(AtomicBool::default()),
                cx.background_executor().clone(),
            )
            .await;

            matches
                .into_iter()
                .map(|mat| candidates[mat.candidate_id].clone())
                .collect()
        })
    }

    fn fetch_branch_diff_match(
        &self,
        workspace: &Entity<Workspace>,
        cx: &mut App,
    ) -> Option<Task<Option<BranchDiffMatch>>> {
        let project = workspace.read(cx).project().clone();
        let repo = project.read(cx).active_repository(cx)?;

        let default_branch_receiver = repo.update(cx, |repo, _| repo.default_branch(true));

        Some(cx.spawn(async move |_cx| {
            let base_ref = default_branch_receiver
                .await
                .ok()
                .and_then(|r| r.ok())
                .flatten()?;

            Some(BranchDiffMatch { base_ref })
        }))
    }

    fn search_mentions(
        &self,
        mode: Option<PromptContextType>,
        query: String,
        cancellation_flag: Arc<AtomicBool>,
        cx: &mut App,
    ) -> Task<Vec<Match>> {
        let Some(workspace) = self.workspace.upgrade() else {
            return Task::ready(Vec::default());
        };
        match mode {
            Some(PromptContextType::File) => {
                let search_files_task = search_files(query, cancellation_flag, &workspace, cx);
                cx.background_spawn(async move {
                    search_files_task
                        .await
                        .into_iter()
                        .map(Match::File)
                        .collect()
                })
            }

            Some(PromptContextType::Symbol) => {
                let search_symbols_task = search_symbols(query, cancellation_flag, &workspace, cx);
                cx.background_spawn(async move {
                    search_symbols_task
                        .await
                        .into_iter()
                        .map(Match::Symbol)
                        .collect()
                })
            }

            Some(PromptContextType::Thread) => {
                let sessions = collect_session_matches(cx);
                if !sessions.is_empty() {
                    let search_task =
                        filter_sessions_by_query(query, cancellation_flag, sessions, cx);
                    cx.spawn(async move |_cx| {
                        search_task.await.into_iter().map(Match::Thread).collect()
                    })
                } else {
                    Task::ready(Vec::new())
                }
            }

            Some(PromptContextType::Fetch) => {
                if !query.is_empty() {
                    Task::ready(vec![Match::Fetch(query.into())])
                } else {
                    Task::ready(Vec::new())
                }
            }

            Some(PromptContextType::Skill) => {
                let skills = self.source.available_skills(cx);
                let search_skills_task = search_skills(query, cancellation_flag, skills, cx);
                cx.background_spawn(async move {
                    search_skills_task
                        .await
                        .into_iter()
                        .map(Match::Skill)
                        .collect::<Vec<_>>()
                })
            }

            Some(PromptContextType::Diagnostics) => Task::ready(Vec::new()),

            Some(PromptContextType::BranchDiff) => Task::ready(Vec::new()),

            None if query.is_empty() => {
                let recent_task = self.recent_context_picker_entries(&workspace, cx);
                let entries = self
                    .available_context_picker_entries(&workspace, cx)
                    .into_iter()
                    .map(|mode| {
                        Match::Entry(EntryMatch {
                            entry: mode,
                            mat: None,
                        })
                    })
                    .collect::<Vec<_>>();

                let branch_diff_task = if self
                    .source
                    .supports_context(PromptContextType::BranchDiff, cx)
                {
                    self.fetch_branch_diff_match(&workspace, cx)
                } else {
                    None
                };

                cx.spawn(async move |_cx| {
                    let mut matches = recent_task.await;
                    matches.extend(entries);

                    if let Some(branch_diff_task) = branch_diff_task {
                        if let Some(branch_diff_match) = branch_diff_task.await {
                            matches.push(Match::BranchDiff(branch_diff_match));
                        }
                    }

                    matches
                })
            }
            None => {
                let executor = cx.background_executor().clone();

                let search_files_task =
                    search_files(query.clone(), cancellation_flag, &workspace, cx);

                let entries = self.available_context_picker_entries(&workspace, cx);
                let entry_candidates = entries
                    .iter()
                    .enumerate()
                    .map(|(ix, entry)| StringMatchCandidate::new(ix, entry.keyword()))
                    .collect::<Vec<_>>();

                let branch_diff_task = if self
                    .source
                    .supports_context(PromptContextType::BranchDiff, cx)
                {
                    self.fetch_branch_diff_match(&workspace, cx)
                } else {
                    None
                };

                cx.spawn(async move |cx| {
                    let mut matches = search_files_task
                        .await
                        .into_iter()
                        .map(Match::File)
                        .collect::<Vec<_>>();

                    let entry_matches = fuzzy::match_strings(
                        &entry_candidates,
                        &query,
                        false,
                        true,
                        100,
                        &Arc::new(AtomicBool::default()),
                        executor,
                    )
                    .await;

                    matches.extend(entry_matches.into_iter().map(|mat| {
                        Match::Entry(EntryMatch {
                            entry: entries[mat.candidate_id],
                            mat: Some(mat),
                        })
                    }));

                    if let Some(branch_diff_task) = branch_diff_task {
                        let branch_diff_keyword = PromptContextType::BranchDiff.keyword();
                        let branch_diff_matches = fuzzy::match_strings(
                            &[StringMatchCandidate::new(0, branch_diff_keyword)],
                            &query,
                            false,
                            true,
                            1,
                            &Arc::new(AtomicBool::default()),
                            cx.background_executor().clone(),
                        )
                        .await;

                        if !branch_diff_matches.is_empty() {
                            if let Some(branch_diff_match) = branch_diff_task.await {
                                matches.push(Match::BranchDiff(branch_diff_match));
                            }
                        }
                    }

                    matches.sort_by(|a, b| {
                        b.score()
                            .partial_cmp(&a.score())
                            .unwrap_or(std::cmp::Ordering::Equal)
                    });

                    matches
                })
            }
        }
    }

    fn recent_context_picker_entries(
        &self,
        workspace: &Entity<Workspace>,
        cx: &mut App,
    ) -> Task<Vec<Match>> {
        let mut recent = Vec::with_capacity(6);

        let mut mentions = self
            .mention_set
            .read_with(cx, |store, _cx| store.mentions());
        let workspace = workspace.read(cx);
        let project = workspace.project().read(cx);
        let include_root_name = workspace.visible_worktrees(cx).count() > 1;

        if let Some(agent_panel) = workspace.panel::<AgentPanel>(cx)
            && let Some(thread) = agent_panel.read(cx).active_agent_thread(cx)
            && let Some(title) = thread.read(cx).title()
        {
            mentions.insert(MentionUri::Thread {
                id: thread.read(cx).session_id().clone(),
                name: title.to_string(),
            });
        }

        recent.extend(
            workspace
                .recent_navigation_history_iter(cx)
                .filter(|(_, abs_path)| {
                    abs_path.as_ref().is_none_or(|path| {
                        !mentions.contains(&MentionUri::File {
                            abs_path: path.clone(),
                        })
                    })
                })
                .take(4)
                .filter_map(|(project_path, _)| {
                    project
                        .worktree_for_id(project_path.worktree_id, cx)
                        .map(|worktree| {
                            let path_prefix = if include_root_name {
                                worktree.read(cx).root_name().into()
                            } else {
                                RelPath::empty_arc()
                            };
                            Match::File(FileMatch {
                                mat: fuzzy::PathMatch {
                                    score: 1.,
                                    positions: Vec::new(),
                                    worktree_id: project_path.worktree_id.to_usize(),
                                    path: project_path.path,
                                    path_prefix,
                                    is_dir: false,
                                    distance_to_relative_ancestor: 0,
                                },
                                is_recent: true,
                            })
                        })
                }),
        );

        if !self.source.supports_context(PromptContextType::Thread, cx) {
            return Task::ready(recent);
        }

        let sessions = collect_session_matches(cx);
        const RECENT_COUNT: usize = 2;
        recent.extend(
            sessions
                .into_iter()
                .filter(|session| {
                    let uri = MentionUri::Thread {
                        id: session.session_id.clone(),
                        name: session.title.to_string(),
                    };
                    !mentions.contains(&uri)
                })
                .take(RECENT_COUNT)
                .map(Match::RecentThread),
        );

        Task::ready(recent)
    }

    fn available_context_picker_entries(
        &self,
        workspace: &Entity<Workspace>,
        cx: &mut App,
    ) -> Vec<PromptContextEntry> {
        let mut entries = vec![
            PromptContextEntry::Mode(PromptContextType::File),
            PromptContextEntry::Mode(PromptContextType::Symbol),
        ];

        if self.source.supports_context(PromptContextType::Thread, cx) {
            entries.push(PromptContextEntry::Mode(PromptContextType::Thread));
        }

        let has_active_selection = workspace.update(cx, |workspace, cx| {
            AgentContextSource::from_active(workspace, cx)
                .and_then(|source| source.read_selection(workspace, false, cx))
                .is_some()
        });
        if has_active_selection {
            entries.push(PromptContextEntry::Action(
                PromptContextAction::AddSelections,
            ));
        }

        if self.source.supports_context(PromptContextType::Skill, cx)
            && !self.source.available_skills(cx).is_empty()
        {
            entries.push(PromptContextEntry::Mode(PromptContextType::Skill));
        }

        if self.source.supports_context(PromptContextType::Fetch, cx) {
            entries.push(PromptContextEntry::Mode(PromptContextType::Fetch));
        }

        if self
            .source
            .supports_context(PromptContextType::Diagnostics, cx)
        {
            let summary = workspace
                .read(cx)
                .project()
                .read(cx)
                .diagnostic_summary(false, cx);
            if summary.error_count > 0 || summary.warning_count > 0 {
                entries.push(PromptContextEntry::Mode(PromptContextType::Diagnostics));
            }
        }

        entries
    }
}

impl<T: PromptCompletionProviderDelegate> CompletionProvider for PromptCompletionProvider<T> {
    fn completions(
        &self,
        buffer: &Entity<Buffer>,
        buffer_position: Anchor,
        _trigger: CompletionContext,
        window: &mut Window,
        cx: &mut Context<Editor>,
    ) -> Task<Result<Vec<CompletionResponse>>> {
        let state = buffer.update(cx, |buffer, cx| {
            let position = buffer_position.to_point(buffer);
            let line_start = Point::new(position.row, 0);
            let offset_to_line = buffer.point_to_offset(line_start);
            let mut lines = buffer.text_for_range(line_start..position).lines();
            let line = lines.next()?;
            PromptCompletion::try_parse(line, offset_to_line, &self.source.supported_modes(cx))
        });
        let Some(state) = state else {
            return Task::ready(Ok(Vec::new()));
        };

        let Some(workspace) = self.workspace.upgrade() else {
            return Task::ready(Ok(Vec::new()));
        };

        let project = workspace.read(cx).project().clone();
        let snapshot = buffer.read(cx).snapshot();
        let source_range = snapshot.anchor_before(state.source_range().start)
            ..snapshot.anchor_after(state.source_range().end);

        let source = self.source.clone();
        let editor = self.editor.clone();
        let mention_set = self.mention_set.downgrade();
        match state {
            PromptCompletion::SlashCommand(SlashCommandCompletion {
                command, argument, ..
            }) => {
                let search_task = self.search_slash_commands(command.unwrap_or_default(), cx);
                // Keep the category section headers visible while the user is
                // still narrowing the command name (`/c`); only drop them once
                // they've moved on to typing the command's argument, where
                // grouping no longer applies.
                let show_section_headers = argument.is_none();

                let source_highlight_id = cx
                    .theme()
                    .syntax()
                    .highlight_id("variable")
                    .map(HighlightId::new);

                type SkillInfo = (
                    String,
                    SharedString,
                    Option<Hsla>,
                    Arc<dyn Fn(CompletionIntent, &mut Window, &mut App) -> bool + Send + Sync>,
                );
                let slash_candidates: Task<Vec<(SlashCompletionCandidate, Option<SkillInfo>)>> = {
                    let source = source.clone();
                    cx.spawn(async move |_this, cx| {
                        let candidates = search_task.await;
                        cx.update(|cx| {
                            candidates
                                .into_iter()
                                .map(|candidate| match &candidate {
                                    SlashCompletionCandidate::Skill(skill) => {
                                        let uri = MentionUri::Skill {
                                            name: skill.name.to_string(),
                                            source: skill.source.to_string(),
                                            skill_file_path: skill.skill_file_path.clone(),
                                        };
                                        let new_text = format!("{} ", uri.as_link());
                                        let new_text_len = new_text.len();
                                        let icon_path = skill_completion_icon_path(skill, &uri, cx);
                                        let icon_color = skill_completion_icon_color(skill, cx);
                                        let crease_text: SharedString = uri.name().into();
                                        let confirm = confirm_completion_callback(
                                            crease_text,
                                            source_range.start,
                                            new_text_len - 1,
                                            uri,
                                            source.clone(),
                                            editor.clone(),
                                            mention_set.clone(),
                                            workspace.clone(),
                                        );
                                        (
                                            candidate,
                                            Some((new_text, icon_path, icon_color, confirm)),
                                        )
                                    }
                                    SlashCompletionCandidate::Command(_)
                                    | SlashCompletionCandidate::LocalCommand(_) => {
                                        (candidate, None)
                                    }
                                })
                                .collect::<Vec<(SlashCompletionCandidate, Option<SkillInfo>)>>()
                        })
                    })
                };

                cx.background_spawn(async move {
                    let mut slash_candidates = slash_candidates.await;
                    // `slash_candidates` arrives in fuzzy-match order (best
                    // first). Keep each group's items contiguous so section
                    // headers render once, but order the groups by their
                    // best-scoring member. That way an exact/prefix match (e.g.
                    // `/compa` -> `compact`) floats its whole section to the top
                    // and becomes the default selection, instead of being
                    // buried under a less relevant skill. Within a group, the
                    // fuzzy-match order is preserved (the sort is stable).
                    group_by_relevance(&mut slash_candidates, |(candidate, _)| {
                        slash_completion_group_key(candidate)
                    });
                    let completions = slash_candidates
                        .into_iter()
                        .map(|(candidate, skill_info)| match candidate {
                            SlashCompletionCandidate::Skill(skill) => {
                                let label = build_slash_item_label(
                                    &skill.name,
                                    Some(&skill.source),
                                    source_highlight_id,
                                );
                                let Some((new_text, icon_path, icon_color, confirm)) = skill_info
                                else {
                                    unreachable!("skill candidates always have confirm callbacks")
                                };
                                Completion {
                                    replace_range: source_range.clone(),
                                    new_text,
                                    label,
                                    documentation: Some(skill_completion_documentation(&skill)),
                                    source: project::CompletionSource::Custom,
                                    icon_path: Some(icon_path),
                                    icon_color,
                                    match_start: None,
                                    snippet_deduplication_key: None,
                                    insert_text_mode: None,
                                    confirm: Some(confirm),
                                    group: show_section_headers.then(|| CompletionGroup {
                                        key: "skills".into(),
                                        label: Some("Skills".into()),
                                    }),
                                }
                            }
                            SlashCompletionCandidate::Command(command) => {
                                let label =
                                    build_slash_command_label(&command, source_highlight_id);
                                let new_text = match (command.source.as_ref(), argument.as_ref()) {
                                    (Some(source), Some(argument)) => {
                                        format!("/{}:{} {}", source, command.name, argument)
                                    }
                                    (Some(source), None) => {
                                        format!("/{}:{} ", source, command.name)
                                    }
                                    (None, Some(argument)) => {
                                        format!("/{} {}", command.name, argument)
                                    }
                                    (None, None) => format!("/{} ", command.name),
                                };

                                let is_missing_argument =
                                    command.requires_argument && argument.is_none();
                                let group = show_section_headers.then(|| command.group());

                                let icon_path = (command.category
                                    == Some(acp_thread::CommandCategory::Native)
                                    && command.name.as_ref() == agent::COMPACT_COMMAND_NAME)
                                    .then(|| IconName::Compact.path().into());

                                Completion {
                                    replace_range: source_range.clone(),
                                    new_text,
                                    label,
                                    documentation: Some(
                                        CompletionDocumentation::MultiLinePlainText(
                                            command.description.into(),
                                        ),
                                    ),
                                    source: project::CompletionSource::Custom,
                                    icon_path,
                                    icon_color: None,
                                    match_start: None,
                                    snippet_deduplication_key: None,
                                    insert_text_mode: None,
                                    confirm: Some(Arc::new({
                                        let source = source.clone();
                                        move |intent, _window, cx| {
                                            if !is_missing_argument {
                                                cx.defer({
                                                    let source = source.clone();
                                                    move |cx| match intent {
                                                        CompletionIntent::Complete
                                                        | CompletionIntent::CompleteWithInsert
                                                        | CompletionIntent::CompleteWithReplace => {
                                                            source.confirm_command(cx);
                                                        }
                                                        CompletionIntent::Compose => {}
                                                    }
                                                });
                                            }
                                            false
                                        }
                                    })),
                                    group,
                                }
                            }
                            SlashCompletionCandidate::LocalCommand(command) => {
                                let group = show_section_headers.then(|| CompletionGroup {
                                    key: "local-commands".into(),
                                    label: Some("Actions".into()),
                                });

                                Completion {
                                    replace_range: source_range.clone(),
                                    // Local commands aren't part of the prompt;
                                    // confirming one clears the typed text
                                    // rather than leaving `/keyword` behind.
                                    new_text: String::new(),
                                    label: CodeLabel::plain(command.label().to_string(), None),
                                    documentation: Some(
                                        CompletionDocumentation::MultiLinePlainText(
                                            command.description().into(),
                                        ),
                                    ),
                                    source: project::CompletionSource::Custom,
                                    icon_path: Some(command.icon().path().into()),
                                    icon_color: None,
                                    match_start: None,
                                    snippet_deduplication_key: None,
                                    insert_text_mode: None,
                                    confirm: Some(Arc::new({
                                        let source = source.clone();
                                        move |intent, _window, cx| {
                                            cx.defer({
                                                let source = source.clone();
                                                move |cx| match intent {
                                                    CompletionIntent::Complete
                                                    | CompletionIntent::CompleteWithInsert
                                                    | CompletionIntent::CompleteWithReplace => {
                                                        source.run_local_command(command, cx);
                                                    }
                                                    CompletionIntent::Compose => {}
                                                }
                                            });
                                            false
                                        }
                                    })),
                                    group,
                                }
                            }
                        })
                        .collect();

                    Ok(vec![CompletionResponse {
                        completions,
                        display_options: CompletionDisplayOptions {
                            dynamic_width: true,
                        },
                        is_incomplete: true,
                    }])
                })
            }
            PromptCompletion::Mention(MentionCompletion { mode, argument, .. }) => {
                if let Some(PromptContextType::Diagnostics) = mode {
                    if argument.is_some() {
                        return Task::ready(Ok(Vec::new()));
                    }

                    let completions = Self::completion_for_diagnostics(
                        source_range.clone(),
                        source.clone(),
                        editor.clone(),
                        mention_set.clone(),
                        workspace.clone(),
                        cx,
                    );
                    if !completions.is_empty() {
                        return Task::ready(Ok(vec![CompletionResponse {
                            completions,
                            display_options: CompletionDisplayOptions::default(),
                            is_incomplete: false,
                        }]));
                    }
                }

                let show_section_headers = mode.is_none() && argument.is_none();
                let query = argument.unwrap_or_default();
                let search_task =
                    self.search_mentions(mode, query, Arc::<AtomicBool>::default(), cx);

                // Calculate maximum characters available for the full label (file_name + space + directory)
                // based on maximum menu width after accounting for padding, spacing, and icon width
                let label_max_chars = {
                    // Base06 left padding + Base06 gap + Base06 right padding + icon width
                    let used_pixels = DynamicSpacing::Base06.px(cx) * 3.0
                        + IconSize::XSmall.rems() * window.rem_size();

                    let style = window.text_style();
                    let font_id = window.text_system().resolve_font(&style.font());
                    let font_size = TextSize::Small.rems(cx).to_pixels(window.rem_size());

                    // Fallback em_width of 10px matches file_finder.rs fallback for TextSize::Small
                    let em_width = cx
                        .text_system()
                        .em_width(font_id, font_size)
                        .unwrap_or(px(10.0));

                    // Calculate available pixels for text (file_name + directory)
                    // Using max width since dynamic_width allows the menu to expand up to this
                    let available_pixels = COMPLETION_MENU_MAX_WIDTH - used_pixels;

                    // Convert to character count (total available for file_name + directory)
                    (f32::from(available_pixels) / f32::from(em_width)) as usize
                };

                cx.spawn(async move |_, cx| {
                    let mut matches = search_task.await;
                    if show_section_headers {
                        matches.sort_by_key(|mat| match mat {
                            Match::File(FileMatch {
                                is_recent: true, ..
                            })
                            | Match::RecentThread(_) => 0,
                            Match::Entry(_) | Match::BranchDiff(_) => 1,
                            _ => 2,
                        });
                    }

                    let completions = cx.update(|cx| {
                        matches
                            .into_iter()
                            .filter_map(|mat| {
                                let group = if show_section_headers {
                                    match &mat {
                                        Match::File(FileMatch {
                                            is_recent: true, ..
                                        })
                                        | Match::RecentThread(_) => Some(CompletionGroup {
                                            key: "recent".into(),
                                            label: None,
                                        }),
                                        Match::Entry(_) | Match::BranchDiff(_) => {
                                            Some(CompletionGroup {
                                                key: "context".into(),
                                                label: None,
                                            })
                                        }
                                        _ => None,
                                    }
                                } else {
                                    None
                                };
                                let mut completion = match mat {
                                    Match::File(FileMatch { mat, is_recent }) => {
                                        let project_path = ProjectPath {
                                            worktree_id: WorktreeId::from_usize(mat.worktree_id),
                                            path: mat.path.clone(),
                                        };

                                        // If path is empty, this means we're matching with the root directory itself
                                        // so we use the path_prefix as the name
                                        let path_prefix = if mat.path.is_empty() {
                                            project
                                                .read(cx)
                                                .worktree_for_id(project_path.worktree_id, cx)
                                                .map(|wt| wt.read(cx).root_name().into())
                                                .unwrap_or_else(|| mat.path_prefix.clone())
                                        } else {
                                            mat.path_prefix.clone()
                                        };

                                        Self::completion_for_path(
                                            project_path,
                                            &path_prefix,
                                            is_recent,
                                            mat.is_dir,
                                            source_range.clone(),
                                            source.clone(),
                                            editor.clone(),
                                            mention_set.clone(),
                                            workspace.clone(),
                                            project.clone(),
                                            label_max_chars,
                                            cx,
                                        )
                                    }
                                    Match::Symbol(SymbolMatch { symbol, .. }) => {
                                        Self::completion_for_symbol(
                                            symbol,
                                            source_range.clone(),
                                            source.clone(),
                                            editor.clone(),
                                            mention_set.clone(),
                                            workspace.clone(),
                                            label_max_chars,
                                            cx,
                                        )
                                    }
                                    Match::Thread(thread) => Some(Self::completion_for_thread(
                                        thread.session_id,
                                        Some(thread.title),
                                        source_range.clone(),
                                        false,
                                        source.clone(),
                                        editor.clone(),
                                        mention_set.clone(),
                                        workspace.clone(),
                                        cx,
                                    )),
                                    Match::RecentThread(thread) => {
                                        Some(Self::completion_for_thread(
                                            thread.session_id,
                                            Some(thread.title),
                                            source_range.clone(),
                                            true,
                                            source.clone(),
                                            editor.clone(),
                                            mention_set.clone(),
                                            workspace.clone(),
                                            cx,
                                        ))
                                    }
                                    Match::Skill(skill) => Some(Self::completion_for_skill(
                                        skill,
                                        source_range.clone(),
                                        source.clone(),
                                        editor.clone(),
                                        mention_set.clone(),
                                        workspace.clone(),
                                        cx,
                                    )),
                                    Match::Fetch(url) => Self::completion_for_fetch(
                                        source_range.clone(),
                                        url,
                                        source.clone(),
                                        editor.clone(),
                                        mention_set.clone(),
                                        workspace.clone(),
                                        cx,
                                    ),
                                    Match::Entry(EntryMatch { entry, .. }) => {
                                        Self::completion_for_entry(
                                            entry,
                                            source_range.clone(),
                                            editor.clone(),
                                            mention_set.clone(),
                                            &workspace,
                                            cx,
                                        )
                                    }
                                    Match::BranchDiff(branch_diff) => {
                                        Some(Self::build_branch_diff_completion(
                                            branch_diff.base_ref,
                                            source_range.clone(),
                                            source.clone(),
                                            editor.clone(),
                                            mention_set.clone(),
                                            workspace.clone(),
                                            cx,
                                        ))
                                    }
                                };
                                if let Some(completion) = &mut completion {
                                    completion.group = group;
                                }
                                completion
                            })
                            .collect::<Vec<_>>()
                    });

                    Ok(vec![CompletionResponse {
                        completions,
                        display_options: CompletionDisplayOptions {
                            dynamic_width: true,
                        },
                        // Since this does its own filtering (see `filter_completions()` returns false),
                        // there is no benefit to computing whether this set of completions is incomplete.
                        is_incomplete: true,
                    }])
                })
            }
        }
    }

    fn is_completion_trigger(
        &self,
        buffer: &Entity<language::Buffer>,
        position: language::Anchor,
        _text: &str,
        _trigger_in_words: bool,
        cx: &mut Context<Editor>,
    ) -> bool {
        let buffer = buffer.read(cx);
        let position = position.to_point(buffer);
        let line_start = Point::new(position.row, 0);
        let offset_to_line = buffer.point_to_offset(line_start);
        let mut lines = buffer.text_for_range(line_start..position).lines();
        if let Some(line) = lines.next() {
            PromptCompletion::try_parse(line, offset_to_line, &self.source.supported_modes(cx))
                .filter(|completion| {
                    // Right now we don't support completing arguments of slash commands
                    let is_slash_command_with_argument = matches!(
                        completion,
                        PromptCompletion::SlashCommand(SlashCommandCompletion {
                            argument: Some(_),
                            ..
                        })
                    );
                    !is_slash_command_with_argument
                })
                .map(|completion| {
                    completion.source_range().start <= offset_to_line + position.column as usize
                        && completion.source_range().end
                            >= offset_to_line + position.column as usize
                })
                .unwrap_or(false)
        } else {
            false
        }
    }

    fn sort_completions(&self) -> bool {
        false
    }

    fn filter_completions(&self) -> bool {
        false
    }
}

fn confirm_completion_callback<T: PromptCompletionProviderDelegate>(
    crease_text: SharedString,
    start: Anchor,
    content_len: usize,
    mention_uri: MentionUri,
    source: Arc<T>,
    editor: WeakEntity<Editor>,
    mention_set: WeakEntity<MentionSet>,
    workspace: Entity<Workspace>,
) -> Arc<dyn Fn(CompletionIntent, &mut Window, &mut App) -> bool + Send + Sync> {
    Arc::new(move |_, window, cx| {
        let source = source.clone();
        let editor = editor.clone();
        let mention_set = mention_set.clone();
        let crease_text = crease_text.clone();
        let mention_uri = mention_uri.clone();
        let workspace = workspace.clone();
        window.defer(cx, move |window, cx| {
            if let Some(editor) = editor.upgrade() {
                mention_set
                    .clone()
                    .update(cx, |mention_set, cx| {
                        mention_set
                            .confirm_mention_completion(
                                crease_text,
                                start,
                                content_len,
                                mention_uri,
                                source.supports_images(cx),
                                editor,
                                &workspace,
                                window,
                                cx,
                            )
                            .detach();
                    })
                    .ok();
            }
        });
        false
    })
}

#[derive(Debug, PartialEq)]
enum PromptCompletion {
    SlashCommand(SlashCommandCompletion),
    Mention(MentionCompletion),
}

impl PromptCompletion {
    fn source_range(&self) -> Range<usize> {
        match self {
            Self::SlashCommand(completion) => completion.source_range.clone(),
            Self::Mention(completion) => completion.source_range.clone(),
        }
    }

    fn try_parse(
        line: &str,
        offset_to_line: usize,
        supported_modes: &[PromptContextType],
    ) -> Option<Self> {
        if line.contains('@') {
            if let Some(mention) =
                MentionCompletion::try_parse(line, offset_to_line, supported_modes)
            {
                return Some(Self::Mention(mention));
            }
        }
        SlashCommandCompletion::try_parse(line, offset_to_line).map(Self::SlashCommand)
    }
}

#[derive(Debug, Default, PartialEq)]
pub struct SlashCommandCompletion {
    pub source_range: Range<usize>,
    pub command: Option<String>,
    pub argument: Option<String>,
}

impl SlashCommandCompletion {
    pub fn try_parse(line: &str, offset_to_line: usize) -> Option<Self> {
        let mut last_command_start = None;
        for (idx, _) in line.rmatch_indices('/') {
            if line[idx + 1..]
                .chars()
                .next()
                .is_some_and(|c| c.is_whitespace())
            {
                continue;
            }

            if idx > 0
                && line[..idx]
                    .chars()
                    .last()
                    .is_some_and(|c| !c.is_whitespace())
            {
                continue;
            }

            last_command_start = Some(idx);
            break;
        }

        let last_command_start = last_command_start?;
        let last_command = &line[last_command_start + 1..];

        let mut argument = None;
        let mut command = None;
        if let Some((command_text, args)) = last_command.split_once(char::is_whitespace) {
            if !args.is_empty() {
                argument = Some(args.trim_end().to_string());
            }
            command = Some(command_text.to_string());
        } else if !last_command.is_empty() {
            command = Some(last_command.to_string());
        };

        Some(Self {
            source_range: last_command_start + offset_to_line
                ..line
                    .rfind(|c: char| !c.is_whitespace())
                    .unwrap_or_else(|| line.len())
                    + 1
                    + offset_to_line,
            command,
            argument,
        })
    }
}

#[derive(Debug, Default, PartialEq)]
struct MentionCompletion {
    source_range: Range<usize>,
    mode: Option<PromptContextType>,
    argument: Option<String>,
}

impl MentionCompletion {
    fn try_parse(
        line: &str,
        offset_to_line: usize,
        supported_modes: &[PromptContextType],
    ) -> Option<Self> {
        // Find the rightmost '@' that has a boundary before it and no whitespace immediately after.
        // A boundary is the start of the line, whitespace, or an opening bracket.
        let mut last_mention_start = None;
        for (idx, _) in line.rmatch_indices('@') {
            // No whitespace immediately after '@'.
            if line[idx + 1..]
                .chars()
                .next()
                .is_some_and(|c| c.is_whitespace())
            {
                continue;
            }

            if idx > 0
                && line[..idx]
                    .chars()
                    .last()
                    .is_some_and(|c| !c.is_whitespace() && !matches!(c, '(' | '[' | '{'))
            {
                continue;
            }

            last_mention_start = Some(idx);
            break;
        }

        let last_mention_start = last_mention_start?;

        let rest_of_line = &line[last_mention_start + 1..];

        let mut mode = None;
        let mut argument = None;

        let mut parts = rest_of_line.split_whitespace();
        let mut end = last_mention_start + 1;

        if let Some(mode_text) = parts.next() {
            // Safe since we check no leading whitespace above
            end += mode_text.len();

            if let Some(parsed_mode) = PromptContextType::try_from(mode_text).ok()
                && supported_modes.contains(&parsed_mode)
            {
                mode = Some(parsed_mode);
            } else {
                argument = Some(mode_text.to_string());
            }
            match rest_of_line[mode_text.len()..].find(|c: char| !c.is_whitespace()) {
                Some(whitespace_count) => {
                    if let Some(argument_text) = parts.next() {
                        // If mode wasn't recognized but we have an argument, don't suggest completions
                        // (e.g. '@something word')
                        if mode.is_none() && !argument_text.is_empty() {
                            return None;
                        }

                        argument = Some(argument_text.to_string());
                        end += whitespace_count + argument_text.len();
                    }
                }
                None => {
                    // Rest of line is entirely whitespace
                    end += rest_of_line.len() - mode_text.len();
                }
            }
        }

        Some(Self {
            source_range: last_mention_start + offset_to_line..end + offset_to_line,
            mode,
            argument,
        })
    }
}

fn diagnostics_label(
    summary: DiagnosticSummary,
    include_errors: bool,
    include_warnings: bool,
) -> String {
    let mut parts = Vec::new();

    if include_errors && summary.error_count > 0 {
        parts.push(format!(
            "{} {}",
            summary.error_count,
            pluralize("error", summary.error_count)
        ));
    }

    if include_warnings && summary.warning_count > 0 {
        parts.push(format!(
            "{} {}",
            summary.warning_count,
            pluralize("warning", summary.warning_count)
        ));
    }

    if parts.is_empty() {
        return "Diagnostics".into();
    }

    let body = if parts.len() == 2 {
        format!("{} and {}", parts[0], parts[1])
    } else {
        parts
            .pop()
            .expect("at least one part present after non-empty check")
    };

    format!("Diagnostics: {body}")
}

fn diagnostics_submenu_label(
    summary: DiagnosticSummary,
    include_errors: bool,
    include_warnings: bool,
) -> String {
    match (include_errors, include_warnings) {
        (true, true) => format!(
            "{} {} & {} {}",
            summary.error_count,
            pluralize("error", summary.error_count),
            summary.warning_count,
            pluralize("warning", summary.warning_count)
        ),
        (true, _) => format!(
            "{} {}",
            summary.error_count,
            pluralize("error", summary.error_count)
        ),
        (_, true) => format!(
            "{} {}",
            summary.warning_count,
            pluralize("warning", summary.warning_count)
        ),
        _ => "Diagnostics".into(),
    }
}

fn diagnostics_crease_label(
    summary: DiagnosticSummary,
    include_errors: bool,
    include_warnings: bool,
) -> SharedString {
    diagnostics_label(summary, include_errors, include_warnings).into()
}

pub(crate) fn pluralize(noun: &str, count: usize) -> String {
    if count == 1 {
        noun.to_string()
    } else {
        format!("{noun}s")
    }
}

pub(crate) fn search_files(
    query: String,
    cancellation_flag: Arc<AtomicBool>,
    workspace: &Entity<Workspace>,
    cx: &App,
) -> Task<Vec<FileMatch>> {
    if query.is_empty() {
        let workspace = workspace.read(cx);
        let project = workspace.project().read(cx);
        let visible_worktrees = workspace.visible_worktrees(cx).collect::<Vec<_>>();
        let include_root_name = visible_worktrees.len() > 1;

        let recent_matches = workspace
            .recent_navigation_history(Some(10), cx)
            .into_iter()
            .map(|(project_path, _)| {
                let path_prefix = if include_root_name {
                    project
                        .worktree_for_id(project_path.worktree_id, cx)
                        .map(|wt| wt.read(cx).root_name().into())
                        .unwrap_or_else(|| RelPath::empty_arc())
                } else {
                    RelPath::empty_arc()
                };

                FileMatch {
                    mat: PathMatch {
                        score: 0.,
                        positions: Vec::new(),
                        worktree_id: project_path.worktree_id.to_usize(),
                        path: project_path.path,
                        path_prefix,
                        distance_to_relative_ancestor: 0,
                        is_dir: false,
                    },
                    is_recent: true,
                }
            });

        let file_matches = visible_worktrees.into_iter().flat_map(|worktree| {
            let worktree = worktree.read(cx);
            let path_prefix: Arc<RelPath> = if include_root_name {
                worktree.root_name().into()
            } else {
                RelPath::empty_arc()
            };
            worktree.entries(false, 0).map(move |entry| FileMatch {
                mat: PathMatch {
                    score: 0.,
                    positions: Vec::new(),
                    worktree_id: worktree.id().to_usize(),
                    path: entry.path.clone(),
                    path_prefix: path_prefix.clone(),
                    distance_to_relative_ancestor: 0,
                    is_dir: entry.is_dir(),
                },
                is_recent: false,
            })
        });

        Task::ready(recent_matches.chain(file_matches).collect())
    } else {
        let workspace = workspace.read(cx);
        let relative_to = workspace
            .recent_navigation_history_iter(cx)
            .next()
            .map(|(path, _)| path.path);
        let worktrees = workspace.visible_worktrees(cx).collect::<Vec<_>>();
        let include_root_name = worktrees.len() > 1;
        let candidate_sets = worktrees
            .into_iter()
            .map(|worktree| {
                let worktree = worktree.read(cx);

                PathMatchCandidateSet {
                    snapshot: worktree.snapshot(),
                    include_ignored: worktree.root_entry().is_some_and(|entry| entry.is_ignored),
                    include_root_name,
                    candidates: project::Candidates::Entries,
                }
            })
            .collect::<Vec<_>>();

        let executor = cx.background_executor().clone();
        cx.foreground_executor().spawn(async move {
            fuzzy::match_path_sets(
                candidate_sets.as_slice(),
                query.as_str(),
                &relative_to,
                false,
                100,
                &cancellation_flag,
                executor,
            )
            .await
            .into_iter()
            .map(|mat| FileMatch {
                mat,
                is_recent: false,
            })
            .collect::<Vec<_>>()
        })
    }
}

pub(crate) fn search_symbols(
    query: String,
    cancellation_flag: Arc<AtomicBool>,
    workspace: &Entity<Workspace>,
    cx: &mut App,
) -> Task<Vec<SymbolMatch>> {
    let symbols_task = workspace.update(cx, |workspace, cx| {
        workspace
            .project()
            .update(cx, |project, cx| project.symbols(&query, cx))
    });
    let project = workspace.read(cx).project().clone();
    cx.spawn(async move |cx| {
        let Some(symbols) = symbols_task.await.log_err() else {
            return Vec::new();
        };
        let (visible_match_candidates, external_match_candidates): (Vec<_>, Vec<_>) = project
            .update(cx, |project, cx| {
                symbols
                    .iter()
                    .enumerate()
                    .map(|(id, symbol)| StringMatchCandidate::new(id, symbol.label.filter_text()))
                    .partition(|candidate| match &symbols[candidate.id].path {
                        SymbolLocation::InProject(project_path) => project
                            .entry_for_path(project_path, cx)
                            .is_some_and(|e| !e.is_ignored),
                        SymbolLocation::OutsideProject { .. } => false,
                    })
            });
        // Try to support rust-analyzer's path based symbols feature which
        // allows to search by rust path syntax, in that case we only want to
        // filter names by the last segment
        // Ideally this was a first class LSP feature (rich queries)
        let query = query
            .rsplit_once("::")
            .map_or(&*query, |(_, suffix)| suffix)
            .to_owned();
        // Note if you make changes to this filtering below, also change `project_symbols::ProjectSymbolsDelegate::filter`
        const MAX_MATCHES: usize = 100;
        let mut visible_matches = cx.foreground_executor().block_on(fuzzy::match_strings(
            &visible_match_candidates,
            &query,
            false,
            true,
            MAX_MATCHES,
            &cancellation_flag,
            cx.background_executor().clone(),
        ));
        let mut external_matches = cx.foreground_executor().block_on(fuzzy::match_strings(
            &external_match_candidates,
            &query,
            false,
            true,
            MAX_MATCHES - visible_matches.len().min(MAX_MATCHES),
            &cancellation_flag,
            cx.background_executor().clone(),
        ));
        let sort_key_for_match = |mat: &StringMatch| {
            let symbol = &symbols[mat.candidate_id];
            (Reverse(OrderedFloat(mat.score)), symbol.label.filter_text())
        };

        visible_matches.sort_unstable_by_key(sort_key_for_match);
        external_matches.sort_unstable_by_key(sort_key_for_match);
        let mut matches = visible_matches;
        matches.append(&mut external_matches);

        matches
            .into_iter()
            .map(|mut mat| {
                let symbol = symbols[mat.candidate_id].clone();
                let filter_start = symbol.label.filter_range.start;
                for position in &mut mat.positions {
                    *position += filter_start;
                }
                SymbolMatch { symbol }
            })
            .collect()
    })
}

fn collect_session_matches(cx: &App) -> Vec<SessionMatch> {
    let Some(store) = ThreadMetadataStore::try_global(cx) else {
        return Vec::new();
    };
    let mut entries: Vec<&ThreadMetadata> = store
        .read(cx)
        .entries()
        .filter(|t| !t.archived && t.agent_id == *agent::ZED_AGENT_ID)
        .collect();
    entries.sort_by_key(|t| Reverse(t.updated_at));
    entries
        .into_iter()
        .map(|metadata| {
            let info = acp_thread::AgentSessionInfo::from(metadata);
            SessionMatch {
                session_id: info.session_id,
                title: session_title(info.title),
            }
        })
        .collect()
}

fn filter_sessions_by_query(
    query: String,
    cancellation_flag: Arc<AtomicBool>,
    sessions: Vec<SessionMatch>,
    cx: &mut App,
) -> Task<Vec<SessionMatch>> {
    if query.is_empty() {
        return Task::ready(sessions);
    }
    let executor = cx.background_executor().clone();
    cx.background_spawn(async move {
        filter_sessions(query, cancellation_flag, sessions, executor).await
    })
}

async fn filter_sessions(
    query: String,
    cancellation_flag: Arc<AtomicBool>,
    sessions: Vec<SessionMatch>,
    executor: BackgroundExecutor,
) -> Vec<SessionMatch> {
    let titles = sessions
        .iter()
        .map(|session| session.title.clone())
        .collect::<Vec<_>>();
    let candidates = titles
        .iter()
        .enumerate()
        .map(|(id, title)| StringMatchCandidate::new(id, title.as_ref()))
        .collect::<Vec<_>>();
    let matches = fuzzy::match_strings(
        &candidates,
        &query,
        false,
        true,
        100,
        &cancellation_flag,
        executor,
    )
    .await;

    matches
        .into_iter()
        .map(|mat| sessions[mat.candidate_id].clone())
        .collect()
}

pub(crate) fn search_skills(
    query: String,
    cancellation_flag: Arc<AtomicBool>,
    skills: Vec<AvailableSkill>,
    cx: &mut App,
) -> Task<Vec<AvailableSkill>> {
    if skills.is_empty() {
        return Task::ready(Vec::new());
    }
    let executor = cx.background_executor().clone();
    cx.background_spawn(async move {
        let candidates = skills
            .iter()
            .enumerate()
            .map(|(id, skill)| StringMatchCandidate::new(id, &skill.name))
            .collect::<Vec<_>>();
        let matches = fuzzy::match_strings(
            &candidates,
            &query,
            false,
            true,
            100,
            &cancellation_flag,
            executor,
        )
        .await;
        matches
            .into_iter()
            .map(|mat| skills[mat.candidate_id].clone())
            .collect()
    })
}

pub struct SymbolMatch {
    pub symbol: Symbol,
}

pub struct FileMatch {
    pub mat: PathMatch,
    pub is_recent: bool,
}

pub fn extract_file_name_and_directory(
    path: &RelPath,
    path_prefix: &RelPath,
    path_style: PathStyle,
) -> (SharedString, Option<SharedString>) {
    // If path is empty, this means we're matching with the root directory itself
    // so we use the path_prefix as the name
    if path.is_empty() && !path_prefix.is_empty() {
        return (path_prefix.display(path_style).to_string().into(), None);
    }

    let full_path = path_prefix.join(path);
    let file_name = full_path.file_name().unwrap_or_default();
    let display_path = full_path.display(path_style);
    let (directory, file_name) = display_path.split_at(display_path.len() - file_name.len());
    (
        file_name.to_string().into(),
        Some(SharedString::new(directory)).filter(|dir| !dir.is_empty()),
    )
}

fn build_slash_command_label(
    command: &AvailableCommand,
    source_highlight_id: Option<HighlightId>,
) -> CodeLabel {
    build_slash_item_label(&command.name, command.source.as_ref(), source_highlight_id)
}

/// Build the autocomplete-popup label for a slash menu item, appending
/// the item origin after the name when one is present and non-empty.
/// The suffix is styled with the muted `variable` highlight and excluded
/// from the fuzzy filter range so typing the source doesn't match the entry.
fn build_slash_item_label(
    name: &Arc<str>,
    source: Option<&SharedString>,
    source_highlight_id: Option<HighlightId>,
) -> CodeLabel {
    let source = source.filter(|source| !source.is_empty());
    let Some(source) = source else {
        return CodeLabel::plain(name.to_string(), None);
    };
    let mut builder = CodeLabelBuilder::default();
    builder.push_str(name, None);
    builder.push_str(" ", None);
    builder.push_str(source, source_highlight_id);
    // The filter range defaults to the entire label after `build()`,
    // which would let the source text participate in fuzzy filtering.
    // Slash commands are matched up-front in `search_slash_commands`
    // against the command name, and the editor doesn't re-filter
    // (`filter_completions()` is false), so this is mostly defensive
    // — but it keeps the displayed filter consistent with what we
    // actually matched against.
    builder.respan_filter_range(Some(name));
    builder.build()
}

fn build_code_label_for_path(
    file: &str,
    directory: Option<&str>,
    line_number: Option<u32>,
    label_max_chars: usize,
    cx: &App,
) -> CodeLabel {
    let variable_highlight_id = cx
        .theme()
        .syntax()
        .highlight_id("variable")
        .map(HighlightId::new);
    let mut label = CodeLabelBuilder::default();

    label.push_str(file, None);
    label.push_str(" ", None);

    if let Some(directory) = directory {
        let file_name_chars = file.chars().count();
        // Account for: file_name + space (ellipsis is handled by truncate_and_remove_front)
        let directory_max_chars = label_max_chars
            .saturating_sub(file_name_chars)
            .saturating_sub(1);
        let truncated_directory = truncate_and_remove_front(directory, directory_max_chars.max(5));
        label.push_str(&truncated_directory, variable_highlight_id);
    }
    if let Some(line_number) = line_number {
        label.push_str(&format!(" L{}", line_number), variable_highlight_id);
    }
    label.build()
}

fn terminal_view_selection(terminal_view: &Entity<TerminalView>, cx: &App) -> Option<String> {
    terminal_view
        .read(cx)
        .terminal()
        .read(cx)
        .last_content
        .selection_text
        .clone()
        .filter(|text| !text.is_empty())
}

fn editor_selection_ranges(
    editor: &Entity<Editor>,
    include_current_line: bool,
    cx: &mut App,
) -> Vec<(Entity<Buffer>, Range<text::Anchor>)> {
    editor.update(cx, |editor, cx| {
        let selections = editor.selections.all_adjusted(&editor.display_snapshot(cx));

        let multi_buffer = editor.buffer().read(cx);
        let multi_buffer_snapshot = multi_buffer.snapshot(cx);

        let non_empty_rows: collections::HashSet<u32> = selections
            .iter()
            .filter(|s| !s.is_empty())
            .flat_map(|s| s.start.row..=s.end.row)
            .collect();

        let mut seen_current_line_rows = collections::HashSet::default();
        let mut results = Vec::new();

        for s in selections {
            if s.is_empty() {
                if !include_current_line
                    || non_empty_rows.contains(&s.start.row)
                    || !seen_current_line_rows.insert(s.start.row)
                {
                    continue;
                }
                let Some((buffer, anchor)) = multi_buffer.text_anchor_for_position(s.start, cx)
                else {
                    continue;
                };
                let buffer_snapshot = buffer.read(cx).snapshot();
                let row = anchor.to_point(&buffer_snapshot).row;
                let line_start = text::Point::new(row, 0);
                let line_end = text::Point::new(row, buffer_snapshot.line_len(row));
                let start = buffer_snapshot.anchor_after(line_start);
                let end = buffer_snapshot.anchor_before(line_end);
                if start.to_offset(&buffer_snapshot) == end.to_offset(&buffer_snapshot) {
                    continue;
                }
                results.push((buffer, start..end));
            } else {
                let mb_start = multi_buffer_snapshot.anchor_after(s.start);
                let mb_end = multi_buffer_snapshot.anchor_before(s.end);
                let Some((start_buffer, start)) =
                    multi_buffer.text_anchor_for_position(mb_start, cx)
                else {
                    continue;
                };
                let Some((end_buffer, end)) = multi_buffer.text_anchor_for_position(mb_end, cx)
                else {
                    continue;
                };
                if start_buffer != end_buffer {
                    continue;
                }
                let buffer_snapshot = start_buffer.read(cx).snapshot();
                if start.to_offset(&buffer_snapshot) == end.to_offset(&buffer_snapshot) {
                    continue;
                }
                results.push((start_buffer, start..end));
            }
        }

        results
    })
}

type ConfirmCallback = Arc<dyn Fn(CompletionIntent, &mut Window, &mut App) -> bool + Send + Sync>;

fn completion_text_for_editor_selections(
    source_range: Range<Anchor>,
    editor: WeakEntity<Editor>,
    mention_set: WeakEntity<MentionSet>,
    workspace: WeakEntity<Workspace>,
    editor_selections: Vec<(Entity<Buffer>, Range<text::Anchor>)>,
) -> (String, ConfirmCallback) {
    const EDITOR_PLACEHOLDER: &str = "selection ";

    let selections = editor_selections
        .into_iter()
        .enumerate()
        .map(|(ix, (buffer, range))| {
            (
                buffer,
                range,
                (EDITOR_PLACEHOLDER.len() * ix)..(EDITOR_PLACEHOLDER.len() * (ix + 1) - 1),
            )
        })
        .collect::<Vec<_>>();

    let new_text = EDITOR_PLACEHOLDER.repeat(selections.len());

    let callback: ConfirmCallback = Arc::new({
        move |_: CompletionIntent, window: &mut Window, cx: &mut App| {
            let editor = editor.clone();
            let selections = selections.clone();
            let mention_set = mention_set.clone();
            let workspace = workspace.clone();
            let source_range = source_range.clone();
            window.defer(cx, move |window, cx| {
                if let Some(editor) = editor.upgrade()
                    && !selections.is_empty()
                {
                    mention_set
                        .update(cx, |store, cx| {
                            store.confirm_mention_for_selection(
                                source_range.clone(),
                                selections,
                                editor.clone(),
                                workspace,
                                window,
                                cx,
                            )
                        })
                        .ok();
                }
            });
            false
        }
    });

    (new_text, callback)
}

fn completion_text_for_terminal_selections(
    source_range: Range<Anchor>,
    editor: WeakEntity<Editor>,
    mention_set: WeakEntity<MentionSet>,
    terminal_selections: Vec<String>,
) -> (String, ConfirmCallback) {
    const TERMINAL_PLACEHOLDER: &str = "terminal ";

    let mut new_text = String::new();
    let terminal_ranges: Vec<(String, std::ops::Range<usize>)> = terminal_selections
        .into_iter()
        .map(|text| {
            let start = new_text.len();
            new_text.push_str(TERMINAL_PLACEHOLDER);
            (text, start..(new_text.len() - 1))
        })
        .collect();

    let callback: ConfirmCallback = Arc::new({
        move |_: CompletionIntent, window: &mut Window, cx: &mut App| {
            let editor = editor.clone();
            let mention_set = mention_set.clone();
            let source_range = source_range.clone();
            let terminal_ranges = terminal_ranges.clone();
            window.defer(cx, move |window, cx| {
                let Some(editor) = editor.upgrade() else {
                    return;
                };
                for (terminal_text, terminal_range) in terminal_ranges {
                    let snapshot = editor.read(cx).buffer().read(cx).snapshot(cx);
                    let Some(start) = snapshot.anchor_in_excerpt(source_range.start) else {
                        return;
                    };
                    let offset = start.to_offset(&snapshot);

                    let line_count = terminal_text.lines().count() as u32;
                    let mention_uri = MentionUri::TerminalSelection { line_count };
                    let range = snapshot.anchor_after(offset + terminal_range.start)
                        ..snapshot.anchor_after(offset + terminal_range.end);

                    let crease = crate::mention_set::crease_for_mention(
                        mention_uri.name().into(),
                        mention_uri.icon_path(cx),
                        None,
                        None,
                        None,
                        range,
                        editor.downgrade(),
                    );

                    let Some(crease_id) = editor.update(cx, |editor, cx| {
                        let crease_ids = editor.insert_creases(vec![crease.clone()], cx);
                        editor.fold_creases(vec![crease], false, window, cx);
                        crease_ids.first().copied()
                    }) else {
                        log::error!("insert_creases returned no ids for terminal selection");
                        continue;
                    };

                    mention_set
                        .update(cx, |mention_set, cx| {
                            mention_set.insert_mention(
                                crease_id,
                                mention_uri.clone(),
                                Task::ready(Ok(crate::mention_set::Mention::Text {
                                    content: terminal_text,
                                    tracked_buffers: vec![],
                                }))
                                .shared(),
                                None,
                                cx,
                            );
                        })
                        .ok();
                }
            });
            false
        }
    });

    (new_text, callback)
}

#[cfg(test)]
mod tests {
    use super::*;
    use gpui::TestAppContext;

    #[test]
    fn test_prompt_completion_parse() {
        let supported_modes = vec![PromptContextType::File, PromptContextType::Symbol];

        assert_eq!(
            PromptCompletion::try_parse("/", 0, &supported_modes),
            Some(PromptCompletion::SlashCommand(SlashCommandCompletion {
                source_range: 0..1,
                command: None,
                argument: None,
            }))
        );

        assert_eq!(
            PromptCompletion::try_parse("@", 0, &supported_modes),
            Some(PromptCompletion::Mention(MentionCompletion {
                source_range: 0..1,
                mode: None,
                argument: None,
            }))
        );

        assert_eq!(
            PromptCompletion::try_parse("/test @file", 0, &supported_modes),
            Some(PromptCompletion::Mention(MentionCompletion {
                source_range: 6..11,
                mode: Some(PromptContextType::File),
                argument: None,
            }))
        );
    }

    #[test]
    fn test_slash_command_completion_parse() {
        assert_eq!(
            SlashCommandCompletion::try_parse("/", 0),
            Some(SlashCommandCompletion {
                source_range: 0..1,
                command: None,
                argument: None,
            })
        );

        assert_eq!(
            SlashCommandCompletion::try_parse("/help", 0),
            Some(SlashCommandCompletion {
                source_range: 0..5,
                command: Some("help".to_string()),
                argument: None,
            })
        );

        assert_eq!(
            SlashCommandCompletion::try_parse("/help ", 0),
            Some(SlashCommandCompletion {
                source_range: 0..5,
                command: Some("help".to_string()),
                argument: None,
            })
        );

        assert_eq!(
            SlashCommandCompletion::try_parse("/help arg1", 0),
            Some(SlashCommandCompletion {
                source_range: 0..10,
                command: Some("help".to_string()),
                argument: Some("arg1".to_string()),
            })
        );

        assert_eq!(
            SlashCommandCompletion::try_parse("/help arg1 arg2", 0),
            Some(SlashCommandCompletion {
                source_range: 0..15,
                command: Some("help".to_string()),
                argument: Some("arg1 arg2".to_string()),
            })
        );

        assert_eq!(
            SlashCommandCompletion::try_parse("/拿不到命令 拿不到命令 ", 0),
            Some(SlashCommandCompletion {
                source_range: 0..30,
                command: Some("拿不到命令".to_string()),
                argument: Some("拿不到命令".to_string()),
            })
        );

        assert_eq!(SlashCommandCompletion::try_parse("Lorem Ipsum", 0), None);

        assert_eq!(
            SlashCommandCompletion::try_parse("Lorem /", 0),
            Some(SlashCommandCompletion {
                source_range: 6..7,
                command: None,
                argument: None,
            })
        );

        assert_eq!(
            SlashCommandCompletion::try_parse("Lorem /help", 0),
            Some(SlashCommandCompletion {
                source_range: 6..11,
                command: Some("help".to_string()),
                argument: None,
            })
        );

        assert_eq!(
            SlashCommandCompletion::try_parse("Lorem /help /test", 0),
            Some(SlashCommandCompletion {
                source_range: 12..17,
                command: Some("test".to_string()),
                argument: None,
            })
        );

        assert_eq!(
            SlashCommandCompletion::try_parse("/help", 10),
            Some(SlashCommandCompletion {
                source_range: 10..15,
                command: Some("help".to_string()),
                argument: None,
            })
        );

        assert_eq!(SlashCommandCompletion::try_parse("Lorem/", 0), None);

        assert_eq!(SlashCommandCompletion::try_parse("/ ", 0), None);
    }

    #[test]
    fn test_section_headers_visible_until_argument() {
        // Section headers stay visible while the user narrows the command name
        // (`/`, `/comp`, `/compact `) and only disappear once they start typing
        // the command's argument, where category grouping no longer applies.
        let show_section_headers = |input: &str| {
            SlashCommandCompletion::try_parse(input, 0)
                .unwrap()
                .argument
                .is_none()
        };

        assert!(show_section_headers("/"));
        assert!(show_section_headers("/comp"));
        assert!(show_section_headers("/compact"));
        assert!(show_section_headers("/compact "));
        assert!(!show_section_headers("/compact now"));
    }

    #[test]
    fn test_group_by_relevance_floats_best_group_and_keeps_groups_contiguous() {
        // Items arrive in fuzzy-score order (best first). The group containing
        // the best match floats to the top, groups stay contiguous, and the
        // within-group order is preserved.
        let mut items = [
            ("compact", 1u32),  // best match, group 1
            ("skill-a", 0u32),  // group 0
            ("deploy", 2u32),   // group 2
            ("skill-b", 0u32),  // group 0 (after skill-a in score order)
            ("native-b", 1u32), // group 1 (after compact)
        ];
        group_by_relevance(&mut items, |(_, key)| *key);
        let order: Vec<&str> = items.iter().map(|(name, _)| *name).collect();
        assert_eq!(
            order,
            vec!["compact", "native-b", "skill-a", "skill-b", "deploy"]
        );

        // When the best match is a skill, the skill group leads instead.
        let mut items = [("skill-a", 0u32), ("compact", 1u32)];
        group_by_relevance(&mut items, |(_, key)| *key);
        let order: Vec<&str> = items.iter().map(|(name, _)| *name).collect();
        assert_eq!(order, vec!["skill-a", "compact"]);
    }

    #[test]
    fn test_mention_completion_parse() {
        let supported_modes = vec![PromptContextType::File, PromptContextType::Symbol];
        let supported_modes_with_diagnostics = vec![
            PromptContextType::File,
            PromptContextType::Symbol,
            PromptContextType::Diagnostics,
        ];

        assert_eq!(
            MentionCompletion::try_parse("Lorem Ipsum", 0, &supported_modes),
            None
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem @", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 6..7,
                mode: None,
                argument: None,
            })
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem @file", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 6..11,
                mode: Some(PromptContextType::File),
                argument: None,
            })
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem @file ", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 6..12,
                mode: Some(PromptContextType::File),
                argument: None,
            })
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem @file main.rs", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 6..19,
                mode: Some(PromptContextType::File),
                argument: Some("main.rs".to_string()),
            })
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem @file main.rs ", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 6..19,
                mode: Some(PromptContextType::File),
                argument: Some("main.rs".to_string()),
            })
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem @file main.rs Ipsum", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 6..19,
                mode: Some(PromptContextType::File),
                argument: Some("main.rs".to_string()),
            })
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem @main", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 6..11,
                mode: None,
                argument: Some("main".to_string()),
            })
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem @main ", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 6..12,
                mode: None,
                argument: Some("main".to_string()),
            })
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem @main m", 0, &supported_modes),
            None
        );

        assert_eq!(
            MentionCompletion::try_parse("test@", 0, &supported_modes),
            None
        );

        // Allowed non-file mentions

        assert_eq!(
            MentionCompletion::try_parse("Lorem @symbol main", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 6..18,
                mode: Some(PromptContextType::Symbol),
                argument: Some("main".to_string()),
            })
        );

        assert_eq!(
            MentionCompletion::try_parse(
                "Lorem @symbol agent_ui::completion_provider",
                0,
                &supported_modes
            ),
            Some(MentionCompletion {
                source_range: 6..43,
                mode: Some(PromptContextType::Symbol),
                argument: Some("agent_ui::completion_provider".to_string()),
            })
        );

        assert_eq!(
            MentionCompletion::try_parse(
                "Lorem @diagnostics",
                0,
                &supported_modes_with_diagnostics
            ),
            Some(MentionCompletion {
                source_range: 6..18,
                mode: Some(PromptContextType::Diagnostics),
                argument: None,
            })
        );

        // Disallowed non-file mentions
        assert_eq!(
            MentionCompletion::try_parse("Lorem @symbol main", 0, &[PromptContextType::File]),
            None
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem@symbol", 0, &supported_modes),
            None,
            "Should not parse mention inside word"
        );

        assert_eq!(
            MentionCompletion::try_parse("Lorem @ file", 0, &supported_modes),
            None,
            "Should not parse with a space after @"
        );

        assert_eq!(
            MentionCompletion::try_parse("@ file", 0, &supported_modes),
            None,
            "Should not parse with a space after @ at the start of the line"
        );

        assert_eq!(
            MentionCompletion::try_parse(
                "@fetch https://www.npmjs.com/package/@matterport/sdk",
                0,
                &[PromptContextType::Fetch]
            ),
            Some(MentionCompletion {
                source_range: 0..52,
                mode: Some(PromptContextType::Fetch),
                argument: Some("https://www.npmjs.com/package/@matterport/sdk".to_string()),
            }),
            "Should handle URLs with @ in the path"
        );

        assert_eq!(
            MentionCompletion::try_parse(
                "@fetch https://example.com/@org/@repo/file",
                0,
                &[PromptContextType::Fetch]
            ),
            Some(MentionCompletion {
                source_range: 0..42,
                mode: Some(PromptContextType::Fetch),
                argument: Some("https://example.com/@org/@repo/file".to_string()),
            }),
            "Should handle URLs with multiple @ characters"
        );

        assert_eq!(
            MentionCompletion::try_parse(
                "@fetch https://example.com/@",
                0,
                &[PromptContextType::Fetch]
            ),
            Some(MentionCompletion {
                source_range: 0..28,
                mode: Some(PromptContextType::Fetch),
                argument: Some("https://example.com/@".to_string()),
            }),
            "Should parse URL ending with @ (even if URL is incomplete)"
        );

        // Bracketed mentions: opening brackets count as a boundary before '@' so
        // typing `(@`, `[@`, or `{@` still opens the completion menu.

        assert_eq!(
            MentionCompletion::try_parse("(@", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 1..2,
                mode: None,
                argument: None,
            }),
            "Should parse mention immediately after '('"
        );

        assert_eq!(
            MentionCompletion::try_parse("[@", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 1..2,
                mode: None,
                argument: None,
            }),
            "Should parse mention immediately after '['"
        );

        assert_eq!(
            MentionCompletion::try_parse("{@", 0, &supported_modes),
            Some(MentionCompletion {
                source_range: 1..2,
                mode: None,
                argument: None,
            }),
            "Should parse mention immediately after '{{'"
        );
    }

    #[gpui::test]
    async fn test_filter_sessions_by_query(cx: &mut TestAppContext) {
        let alpha = SessionMatch {
            session_id: acp::SessionId::new("session-alpha"),
            title: "Alpha Session".into(),
        };
        let beta = SessionMatch {
            session_id: acp::SessionId::new("session-beta"),
            title: "Beta Session".into(),
        };

        let sessions = vec![alpha.clone(), beta];

        let task = {
            let mut app = cx.app.borrow_mut();
            filter_sessions_by_query(
                "Alpha".into(),
                Arc::new(AtomicBool::default()),
                sessions,
                &mut app,
            )
        };

        let results = task.await;
        assert_eq!(results.len(), 1);
        assert_eq!(results[0].session_id, alpha.session_id);
    }

    #[gpui::test]
    async fn test_search_files_path_distance_ordering(cx: &mut TestAppContext) {
        use project::Project;
        use serde_json::json;
        use util::{path, rel_path::rel_path};
        use workspace::{AppState, MultiWorkspace};

        let app_state = cx.update(|cx| {
            let state = AppState::test(cx);
            theme_settings::init(theme::LoadThemes::JustBase, cx);
            editor::init(cx);
            state
        });

        app_state
            .fs
            .as_fake()
            .insert_tree(
                path!("/root"),
                json!({
                    "dir1": { "a.txt": "" },
                    "dir2": {
                        "a.txt": "",
                        "b.txt": ""
                    }
                }),
            )
            .await;

        let project = Project::test(app_state.fs.clone(), [path!("/root").as_ref()], cx).await;
        let (multi_workspace, cx) =
            cx.add_window_view(|window, cx| MultiWorkspace::test_new(project, window, cx));
        let workspace = multi_workspace.read_with(cx, |mw, _| mw.workspace().clone());

        let worktree_id = cx.read(|cx| {
            let worktrees = workspace.read(cx).worktrees(cx).collect::<Vec<_>>();
            assert_eq!(worktrees.len(), 1);
            worktrees[0].read(cx).id()
        });

        // Open a file in dir2 to create navigation history.
        // When searching for "a.txt", dir2/a.txt should be sorted first because
        // it is closer to the most recently opened file (dir2/b.txt).
        let b_path = ProjectPath {
            worktree_id,
            path: rel_path("dir2/b.txt").into(),
        };
        workspace
            .update_in(cx, |workspace, window, cx| {
                workspace.open_path(b_path, None, true, window, cx)
            })
            .await
            .unwrap();

        let results = cx
            .update(|_window, cx| {
                search_files(
                    "a.txt".into(),
                    Arc::new(AtomicBool::default()),
                    &workspace,
                    cx,
                )
            })
            .await;

        assert_eq!(results.len(), 2, "expected 2 matching files");
        assert_eq!(
            results[0].mat.path.as_ref(),
            rel_path("dir2/a.txt"),
            "dir2/a.txt should be first because it's closer to the recently opened dir2/b.txt"
        );
        assert_eq!(
            results[1].mat.path.as_ref(),
            rel_path("dir1/a.txt"),
            "dir1/a.txt should be second"
        );
    }

    #[gpui::test]
    async fn test_source_read_selection_editor_whole_line(cx: &mut TestAppContext) {
        use editor::Editor;
        use project::Project;
        use serde_json::json;
        use text::ToOffset as _;
        use util::path;
        use workspace::{AppState, MultiWorkspace};

        crate::conversation_view::tests::init_test(cx);

        let app_state = cx.update(AppState::test);

        app_state
            .fs
            .as_fake()
            .insert_tree(path!("/root"), json!({ "a.txt": "" }))
            .await;

        let project = Project::test(app_state.fs.clone(), [path!("/root").as_ref()], cx).await;
        let (multi_workspace, cx) =
            cx.add_window_view(|window, cx| MultiWorkspace::test_new(project, window, cx));
        let workspace = multi_workspace.read_with(cx, |mw, _| mw.workspace().clone());

        let buffer = cx.new(|cx| language::Buffer::local("abc\ndef\nghi", cx));
        let editor =
            cx.new_window_entity(|window, cx| Editor::for_buffer(buffer.clone(), None, window, cx));

        editor.update_in(cx, |editor, window, cx| {
            editor.change_selections(Default::default(), window, cx, |selections| {
                selections.select_ranges([text::Point::new(1, 1)..text::Point::new(1, 1)]);
            });
        });

        let source = AgentContextSource::Editor(editor.downgrade());

        workspace.update(cx, |workspace, cx| {
            let selection = source
                .read_selection(workspace, true, cx)
                .expect("editor source with cursor on a line should yield a selection");
            assert!(
                matches!(selection, AgentContextSelection::Editor(_)),
                "expected Editor variant"
            );
            if let AgentContextSelection::Editor(ranges) = selection {
                assert_eq!(
                    ranges.len(),
                    1,
                    "expected exactly one range for whole-line fallback"
                );
                let (range_buffer, range) = &ranges[0];
                let snapshot = range_buffer.read(cx).snapshot();
                let start_offset = range.start.to_offset(&snapshot);
                let end_offset = range.end.to_offset(&snapshot);
                assert_eq!(
                    &snapshot.text()[start_offset..end_offset],
                    "def",
                    "whole-line fallback should capture the current row"
                );
            }

            // With include_current_line = false and no non-empty selection, the
            // fallback is suppressed and read_selection should return None.
            assert!(source.read_selection(workspace, false, cx).is_none());
        });
    }
}