use anyhow::{Context as _, Result};
use collections::BTreeMap;
use credentials_provider::CredentialsProvider;
use futures::{FutureExt, StreamExt, future::BoxFuture};
pub use google_ai::completion::{GoogleEventMapper, count_google_tokens, into_google};
use google_ai::{GenerateContentResponse, GoogleModelMode};
use gpui::{AnyView, App, AsyncApp, Context, Entity, SharedString, Task, Window};
use http_client::HttpClient;
use language_model::{
    AuthenticateError, ConfigurationViewTargetAgent, EnvVar, LanguageModelCompletionError,
    LanguageModelCompletionEvent, LanguageModelToolChoice, LanguageModelToolSchemaFormat,
};
use language_model::{
    GOOGLE_PROVIDER_ID, GOOGLE_PROVIDER_NAME, IconOrSvg, LanguageModel, LanguageModelId,
    LanguageModelName, LanguageModelProvider, LanguageModelProviderId, LanguageModelProviderName,
    LanguageModelProviderState, LanguageModelRequest, RateLimiter,
};
use schemars::JsonSchema;
use serde::{Deserialize, Serialize};
pub use settings::GoogleAvailableModel as AvailableModel;
use settings::{Settings, SettingsStore};
use std::sync::{Arc, LazyLock};
use strum::IntoEnumIterator;
use ui::{ButtonLink, ConfiguredApiCard, List, ListBulletItem, prelude::*};
use ui_input::InputField;
use util::ResultExt;

use language_model::ApiKeyState;

const PROVIDER_ID: LanguageModelProviderId = GOOGLE_PROVIDER_ID;
const PROVIDER_NAME: LanguageModelProviderName = GOOGLE_PROVIDER_NAME;

#[derive(Default, Clone, Debug, PartialEq)]
pub struct GoogleSettings {
    pub api_url: String,
    pub available_models: Vec<AvailableModel>,
}

#[derive(Clone, Copy, Debug, Default, PartialEq, Serialize, Deserialize, JsonSchema)]
#[serde(tag = "type", rename_all = "lowercase")]
pub enum ModelMode {
    #[default]
    Default,
    Thinking {
        /// The maximum number of tokens to use for reasoning. Must be lower than the model's `max_output_tokens`.
        budget_tokens: Option<u32>,
    },
}

pub struct GoogleLanguageModelProvider {
    http_client: Arc<dyn HttpClient>,
    state: Entity<State>,
}

pub struct State {
    api_key_state: ApiKeyState,
    credentials_provider: Arc<dyn CredentialsProvider>,
}

const GEMINI_API_KEY_VAR_NAME: &str = "GEMINI_API_KEY";
const GOOGLE_AI_API_KEY_VAR_NAME: &str = "GOOGLE_AI_API_KEY";

static API_KEY_ENV_VAR: LazyLock<EnvVar> = LazyLock::new(|| {
    // Try GEMINI_API_KEY first as primary, fallback to GOOGLE_AI_API_KEY
    EnvVar::new(GEMINI_API_KEY_VAR_NAME.into()).or(EnvVar::new(GOOGLE_AI_API_KEY_VAR_NAME.into()))
});

impl State {
    fn is_authenticated(&self) -> bool {
        self.api_key_state.has_key()
    }

    fn set_api_key(&mut self, api_key: Option<String>, cx: &mut Context<Self>) -> Task<Result<()>> {
        let credentials_provider = self.credentials_provider.clone();
        let api_url = GoogleLanguageModelProvider::api_url(cx);
        self.api_key_state.store(
            api_url,
            api_key,
            |this| &mut this.api_key_state,
            credentials_provider,
            cx,
        )
    }

    fn authenticate(&mut self, cx: &mut Context<Self>) -> Task<Result<(), AuthenticateError>> {
        let credentials_provider = self.credentials_provider.clone();
        let api_url = GoogleLanguageModelProvider::api_url(cx);
        self.api_key_state.load_if_needed(
            api_url,
            |this| &mut this.api_key_state,
            credentials_provider,
            cx,
        )
    }
}

impl GoogleLanguageModelProvider {
    pub fn new(
        http_client: Arc<dyn HttpClient>,
        credentials_provider: Arc<dyn CredentialsProvider>,
        cx: &mut App,
    ) -> Self {
        let state = cx.new(|cx| {
            cx.observe_global::<SettingsStore>(|this: &mut State, cx| {
                let credentials_provider = this.credentials_provider.clone();
                let api_url = Self::api_url(cx);
                this.api_key_state.handle_url_change(
                    api_url,
                    |this| &mut this.api_key_state,
                    credentials_provider,
                    cx,
                );
                cx.notify();
            })
            .detach();
            State {
                api_key_state: ApiKeyState::new(Self::api_url(cx), (*API_KEY_ENV_VAR).clone()),
                credentials_provider,
            }
        });

        Self { http_client, state }
    }

    fn create_language_model(&self, model: google_ai::Model) -> Arc<dyn LanguageModel> {
        Arc::new(GoogleLanguageModel {
            id: LanguageModelId::from(model.id().to_string()),
            model,
            state: self.state.clone(),
            http_client: self.http_client.clone(),
            request_limiter: RateLimiter::new(4),
        })
    }

    fn settings(cx: &App) -> &GoogleSettings {
        &crate::AllLanguageModelSettings::get_global(cx).google
    }

    fn api_url(cx: &App) -> SharedString {
        let api_url = &Self::settings(cx).api_url;
        if api_url.is_empty() {
            google_ai::API_URL.into()
        } else {
            SharedString::new(api_url.as_str())
        }
    }
}

impl LanguageModelProviderState for GoogleLanguageModelProvider {
    type ObservableEntity = State;

    fn observable_entity(&self) -> Option<Entity<Self::ObservableEntity>> {
        Some(self.state.clone())
    }
}

impl LanguageModelProvider for GoogleLanguageModelProvider {
    fn id(&self) -> LanguageModelProviderId {
        PROVIDER_ID
    }

    fn name(&self) -> LanguageModelProviderName {
        PROVIDER_NAME
    }

    fn icon(&self) -> IconOrSvg {
        IconOrSvg::Icon(IconName::AiGoogle)
    }

    fn default_model(&self, _cx: &App) -> Option<Arc<dyn LanguageModel>> {
        Some(self.create_language_model(google_ai::Model::default()))
    }

    fn default_fast_model(&self, _cx: &App) -> Option<Arc<dyn LanguageModel>> {
        Some(self.create_language_model(google_ai::Model::default_fast()))
    }

    fn provided_models(&self, cx: &App) -> Vec<Arc<dyn LanguageModel>> {
        let mut models = BTreeMap::default();

        // Add base models from google_ai::Model::iter()
        for model in google_ai::Model::iter() {
            if !matches!(model, google_ai::Model::Custom { .. }) {
                models.insert(model.id().to_string(), model);
            }
        }

        // Override with available models from settings
        for model in &GoogleLanguageModelProvider::settings(cx).available_models {
            models.insert(
                model.name.clone(),
                google_ai::Model::Custom {
                    name: model.name.clone(),
                    display_name: model.display_name.clone(),
                    max_tokens: model.max_tokens,
                    mode: model.mode.unwrap_or_default(),
                },
            );
        }

        models
            .into_values()
            .map(|model| {
                Arc::new(GoogleLanguageModel {
                    id: LanguageModelId::from(model.id().to_string()),
                    model,
                    state: self.state.clone(),
                    http_client: self.http_client.clone(),
                    request_limiter: RateLimiter::new(4),
                }) as Arc<dyn LanguageModel>
            })
            .collect()
    }

    fn is_authenticated(&self, cx: &App) -> bool {
        self.state.read(cx).is_authenticated()
    }

    fn authenticate(&self, cx: &mut App) -> Task<Result<(), AuthenticateError>> {
        self.state.update(cx, |state, cx| state.authenticate(cx))
    }

    fn configuration_view(
        &self,
        target_agent: language_model::ConfigurationViewTargetAgent,
        window: &mut Window,
        cx: &mut App,
    ) -> AnyView {
        cx.new(|cx| ConfigurationView::new(self.state.clone(), target_agent, window, cx))
            .into()
    }

    fn reset_credentials(&self, cx: &mut App) -> Task<Result<()>> {
        self.state
            .update(cx, |state, cx| state.set_api_key(None, cx))
    }
}

pub struct GoogleLanguageModel {
    id: LanguageModelId,
    model: google_ai::Model,
    state: Entity<State>,
    http_client: Arc<dyn HttpClient>,
    request_limiter: RateLimiter,
}

impl GoogleLanguageModel {
    fn stream_completion(
        &self,
        request: google_ai::GenerateContentRequest,
        cx: &AsyncApp,
    ) -> BoxFuture<
        'static,
        Result<futures::stream::BoxStream<'static, Result<GenerateContentResponse>>>,
    > {
        let http_client = self.http_client.clone();

        let (api_key, api_url) = self.state.read_with(cx, |state, cx| {
            let api_url = GoogleLanguageModelProvider::api_url(cx);
            (state.api_key_state.key(&api_url), api_url)
        });

        async move {
            let api_key = api_key.context("Missing Google API key")?;
            let request = google_ai::stream_generate_content(
                http_client.as_ref(),
                &api_url,
                &api_key,
                request,
            );
            request.await.context("failed to stream completion")
        }
        .boxed()
    }
}

impl LanguageModel for GoogleLanguageModel {
    fn id(&self) -> LanguageModelId {
        self.id.clone()
    }

    fn name(&self) -> LanguageModelName {
        LanguageModelName::from(self.model.display_name().to_string())
    }

    fn provider_id(&self) -> LanguageModelProviderId {
        PROVIDER_ID
    }

    fn provider_name(&self) -> LanguageModelProviderName {
        PROVIDER_NAME
    }

    fn supports_tools(&self) -> bool {
        self.model.supports_tools()
    }

    fn supports_images(&self) -> bool {
        self.model.supports_images()
    }

    fn supports_thinking(&self) -> bool {
        matches!(self.model.mode(), GoogleModelMode::Thinking { .. })
    }

    fn supports_tool_choice(&self, choice: LanguageModelToolChoice) -> bool {
        match choice {
            LanguageModelToolChoice::Auto
            | LanguageModelToolChoice::Any
            | LanguageModelToolChoice::None => true,
        }
    }

    fn tool_input_format(&self) -> LanguageModelToolSchemaFormat {
        LanguageModelToolSchemaFormat::JsonSchemaSubset
    }

    fn telemetry_id(&self) -> String {
        format!("google/{}", self.model.request_id())
    }

    fn max_token_count(&self) -> u64 {
        self.model.max_token_count()
    }

    fn max_output_tokens(&self) -> Option<u64> {
        self.model.max_output_tokens()
    }

    fn count_tokens(
        &self,
        request: LanguageModelRequest,
        cx: &App,
    ) -> BoxFuture<'static, Result<u64>> {
        let model_id = self.model.request_id().to_string();
        let request = into_google(request, model_id, self.model.mode());
        let http_client = self.http_client.clone();
        let api_url = GoogleLanguageModelProvider::api_url(cx);
        let api_key = self.state.read(cx).api_key_state.key(&api_url);

        async move {
            let Some(api_key) = api_key else {
                return Err(LanguageModelCompletionError::NoApiKey {
                    provider: PROVIDER_NAME,
                }
                .into());
            };
            let response = google_ai::count_tokens(
                http_client.as_ref(),
                &api_url,
                &api_key,
                google_ai::CountTokensRequest {
                    generate_content_request: request,
                },
            )
            .await?;
            Ok(response.total_tokens)
        }
        .boxed()
    }

    fn stream_completion(
        &self,
        request: LanguageModelRequest,
        cx: &AsyncApp,
    ) -> BoxFuture<
        'static,
        Result<
            futures::stream::BoxStream<
                'static,
                Result<LanguageModelCompletionEvent, LanguageModelCompletionError>,
            >,
            LanguageModelCompletionError,
        >,
    > {
        let request = into_google(
            request,
            self.model.request_id().to_string(),
            self.model.mode(),
        );
        let request = self.stream_completion(request, cx);
        let future = self.request_limiter.stream(async move {
            let response = request.await.map_err(LanguageModelCompletionError::from)?;
            Ok(GoogleEventMapper::new().map_stream(response))
        });
        async move { Ok(future.await?.boxed()) }.boxed()
    }
}

struct ConfigurationView {
    api_key_editor: Entity<InputField>,
    state: Entity<State>,
    target_agent: language_model::ConfigurationViewTargetAgent,
    load_credentials_task: Option<Task<()>>,
}

impl ConfigurationView {
    fn new(
        state: Entity<State>,
        target_agent: language_model::ConfigurationViewTargetAgent,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) -> Self {
        cx.observe(&state, |_, _, cx| {
            cx.notify();
        })
        .detach();

        let load_credentials_task = Some(cx.spawn_in(window, {
            let state = state.clone();
            async move |this, cx| {
                if let Some(task) = Some(state.update(cx, |state, cx| state.authenticate(cx))) {
                    // We don't log an error, because "not signed in" is also an error.
                    let _ = task.await;
                }
                this.update(cx, |this, cx| {
                    this.load_credentials_task = None;
                    cx.notify();
                })
                .log_err();
            }
        }));

        Self {
            api_key_editor: cx.new(|cx| InputField::new(window, cx, "AIzaSy...")),
            target_agent,
            state,
            load_credentials_task,
        }
    }

    fn save_api_key(&mut self, _: &menu::Confirm, window: &mut Window, cx: &mut Context<Self>) {
        let api_key = self.api_key_editor.read(cx).text(cx).trim().to_string();
        if api_key.is_empty() {
            return;
        }

        // url changes can cause the editor to be displayed again
        self.api_key_editor
            .update(cx, |editor, cx| editor.set_text("", window, cx));

        let state = self.state.clone();
        cx.spawn_in(window, async move |_, cx| {
            state
                .update(cx, |state, cx| state.set_api_key(Some(api_key), cx))
                .await
        })
        .detach_and_log_err(cx);
    }

    fn reset_api_key(&mut self, window: &mut Window, cx: &mut Context<Self>) {
        self.api_key_editor
            .update(cx, |editor, cx| editor.set_text("", window, cx));

        let state = self.state.clone();
        cx.spawn_in(window, async move |_, cx| {
            state
                .update(cx, |state, cx| state.set_api_key(None, cx))
                .await
        })
        .detach_and_log_err(cx);
    }

    fn should_render_editor(&self, cx: &mut Context<Self>) -> bool {
        !self.state.read(cx).is_authenticated()
    }
}

impl Render for ConfigurationView {
    fn render(&mut self, _: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
        let env_var_set = self.state.read(cx).api_key_state.is_from_env_var();
        let configured_card_label = if env_var_set {
            format!(
                "API key set in {} environment variable",
                API_KEY_ENV_VAR.name
            )
        } else {
            let api_url = GoogleLanguageModelProvider::api_url(cx);
            if api_url == google_ai::API_URL {
                "API key configured".to_string()
            } else {
                format!("API key configured for {}", api_url)
            }
        };

        if self.load_credentials_task.is_some() {
            div()
                .child(Label::new("Loading credentials..."))
                .into_any_element()
        } else if self.should_render_editor(cx) {
            v_flex()
                .size_full()
                .on_action(cx.listener(Self::save_api_key))
                .child(Label::new(format!("To use {}, you need to add an API key. Follow these steps:", match &self.target_agent {
                    ConfigurationViewTargetAgent::ZedAgent => "Zed's agent with Google AI".into(),
                    ConfigurationViewTargetAgent::Other(agent) => agent.clone(),
                })))
                .child(
                    List::new()
                        .child(
                            ListBulletItem::new("")
                                .child(Label::new("Create one by visiting"))
                                .child(ButtonLink::new("Google AI's console", "https://aistudio.google.com/app/apikey"))
                        )
                        .child(
                            ListBulletItem::new("Paste your API key below and hit enter to start using the agent")
                        )
                )
                .child(self.api_key_editor.clone())
                .child(
                    Label::new(
                        format!("You can also set the {GEMINI_API_KEY_VAR_NAME} environment variable and restart Zed."),
                    )
                    .size(LabelSize::Small).color(Color::Muted),
                )
                .into_any_element()
        } else {
            ConfiguredApiCard::new(configured_card_label)
                .disabled(env_var_set)
                .on_click(cx.listener(|this, _, window, cx| this.reset_api_key(window, cx)))
                .when(env_var_set, |this| {
                    this.tooltip_label(format!("To reset your API key, make sure {GEMINI_API_KEY_VAR_NAME} and {GOOGLE_AI_API_KEY_VAR_NAME} environment variables are unset."))
                })
                .into_any_element()
        }
    }
}