use anyhow::{Context as _, Result};
use collections::BTreeMap;
use credentials_provider::CredentialsProvider;
use futures::{FutureExt, StreamExt, future::BoxFuture};
use google_ai::GenerateContentResponse;
pub use google_ai::completion::{GoogleEventMapper, into_google};
use gpui::{App, AppContext, AsyncApp, Context, Entity, SharedString, Task};
use http_client::{CustomHeaders, HttpClient};
use language_model::{
    ApiKeyConfiguration, AuthenticateError, EnvVar, LanguageModelCompletionError,
    LanguageModelCompletionEvent, LanguageModelToolChoice, LanguageModelToolSchemaFormat,
};
use language_model::{
    GOOGLE_PROVIDER_ID, GOOGLE_PROVIDER_NAME, IconOrSvg, LanguageModel, LanguageModelEffortLevel,
    LanguageModelId, LanguageModelName, LanguageModelProvider, LanguageModelProviderId,
    LanguageModelProviderName, LanguageModelProviderState, LanguageModelRequest,
    ProviderSettingsView, 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::IconName;

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>,
    pub custom_headers: CustomHeaders,
}

#[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 settings_view(&self, cx: &mut App) -> Option<ProviderSettingsView> {
        let state = self.state.read(cx);
        Some(ProviderSettingsView::ApiKey(ApiKeyConfiguration::new(
            state.api_key_state.has_key(),
            state.api_key_state.is_from_env_var(),
            state.api_key_state.env_var_name().clone(),
            "https://aistudio.google.com/app/apikey".into(),
        )))
    }

    fn set_api_key(&self, api_key: Option<String>, cx: &mut App) -> Task<Result<()>> {
        self.state
            .update(cx, |state, cx| state.set_api_key(api_key, 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, extra_headers) = self.state.read_with(cx, |state, cx| {
            let api_url = GoogleLanguageModelProvider::api_url(cx);
            let extra_headers = GoogleLanguageModelProvider::settings(cx)
                .custom_headers
                .clone();
            (state.api_key_state.key(&api_url), api_url, extra_headers)
        });

        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,
                &extra_headers,
            );
            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 {
        self.model.supports_thinking()
    }

    fn supported_effort_levels(&self) -> Vec<LanguageModelEffortLevel> {
        let default_level = self.model.default_thinking_level();
        self.model
            .supported_thinking_levels()
            .iter()
            .map(|level| LanguageModelEffortLevel {
                name: level.name().into(),
                value: level.value().into(),
                is_default: Some(*level) == default_level,
            })
            .collect()
    }

    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 stream_completion(
        &self,
        request: LanguageModelRequest,
        cx: &AsyncApp,
    ) -> BoxFuture<
        'static,
        Result<
            futures::stream::BoxStream<
                'static,
                Result<LanguageModelCompletionEvent, LanguageModelCompletionError>,
            >,
            LanguageModelCompletionError,
        >,
    > {
        let request = match into_google(
            request,
            self.model.request_id().to_string(),
            self.model.mode(),
        ) {
            Ok(request) => request,
            Err(error) => return async move { Err(error.into()) }.boxed(),
        };
        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()
    }
}