use crate::auth::AuthProvider;
use crate::auth::add_auth_headers;
use crate::error::ApiError;
use crate::provider::Provider;
use crate::telemetry::run_with_request_telemetry;
use codex_client::HttpTransport;
use codex_client::RequestTelemetry;
use codex_protocol::openai_models::ModelsResponse;
use http::HeaderMap;
use http::Method;
use http::header::ETAG;
use std::sync::Arc;

pub struct ModelsClient<T: HttpTransport, A: AuthProvider> {
    transport: T,
    provider: Provider,
    auth: A,
    request_telemetry: Option<Arc<dyn RequestTelemetry>>,
}

impl<T: HttpTransport, A: AuthProvider> ModelsClient<T, A> {
    pub fn new(transport: T, provider: Provider, auth: A) -> Self {
        Self {
            transport,
            provider,
            auth,
            request_telemetry: None,
        }
    }

    pub fn with_telemetry(mut self, request: Option<Arc<dyn RequestTelemetry>>) -> Self {
        self.request_telemetry = request;
        self
    }

    fn path(&self) -> &'static str {
        "models"
    }

    pub async fn list_models(
        &self,
        client_version: &str,
        extra_headers: HeaderMap,
    ) -> Result<ModelsResponse, ApiError> {
        let builder = || {
            let mut req = self.provider.build_request(Method::GET, self.path());
            req.headers.extend(extra_headers.clone());

            let separator = if req.url.contains('?') { '&' } else { '?' };
            req.url = format!("{}{}client_version={client_version}", req.url, separator);

            add_auth_headers(&self.auth, req)
        };

        let resp = run_with_request_telemetry(
            self.provider.retry.to_policy(),
            self.request_telemetry.clone(),
            builder,
            |req| self.transport.execute(req),
        )
        .await?;

        let header_etag = resp
            .headers
            .get(ETAG)
            .and_then(|value| value.to_str().ok())
            .map(ToString::to_string);

        let ModelsResponse { models, etag } = serde_json::from_slice::<ModelsResponse>(&resp.body)
            .map_err(|e| {
                ApiError::Stream(format!(
                    "failed to decode models response: {e}; body: {}",
                    String::from_utf8_lossy(&resp.body)
                ))
            })?;

        let etag = header_etag.unwrap_or(etag);

        Ok(ModelsResponse { models, etag })
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::provider::RetryConfig;
    use crate::provider::WireApi;
    use async_trait::async_trait;
    use codex_client::Request;
    use codex_client::Response;
    use codex_client::StreamResponse;
    use codex_client::TransportError;
    use http::HeaderMap;
    use http::StatusCode;
    use pretty_assertions::assert_eq;
    use serde_json::json;
    use std::sync::Arc;
    use std::sync::Mutex;
    use std::time::Duration;

    #[derive(Clone)]
    struct CapturingTransport {
        last_request: Arc<Mutex<Option<Request>>>,
        body: Arc<ModelsResponse>,
    }

    impl Default for CapturingTransport {
        fn default() -> Self {
            Self {
                last_request: Arc::new(Mutex::new(None)),
                body: Arc::new(ModelsResponse {
                    models: Vec::new(),
                    etag: String::new(),
                }),
            }
        }
    }

    #[async_trait]
    impl HttpTransport for CapturingTransport {
        async fn execute(&self, req: Request) -> Result<Response, TransportError> {
            *self.last_request.lock().unwrap() = Some(req);
            let body = serde_json::to_vec(&*self.body).unwrap();
            let mut headers = HeaderMap::new();
            if !self.body.etag.is_empty() {
                headers.insert(ETAG, self.body.etag.parse().unwrap());
            }
            Ok(Response {
                status: StatusCode::OK,
                headers,
                body: body.into(),
            })
        }

        async fn stream(&self, _req: Request) -> Result<StreamResponse, TransportError> {
            Err(TransportError::Build("stream should not run".to_string()))
        }
    }

    #[derive(Clone, Default)]
    struct DummyAuth;

    impl AuthProvider for DummyAuth {
        fn bearer_token(&self) -> Option<String> {
            None
        }
    }

    fn provider(base_url: &str) -> Provider {
        Provider {
            name: "test".to_string(),
            base_url: base_url.to_string(),
            query_params: None,
            wire: WireApi::Responses,
            headers: HeaderMap::new(),
            retry: RetryConfig {
                max_attempts: 1,
                base_delay: Duration::from_millis(1),
                retry_429: false,
                retry_5xx: true,
                retry_transport: true,
            },
            stream_idle_timeout: Duration::from_secs(1),
        }
    }

    #[tokio::test]
    async fn appends_client_version_query() {
        let response = ModelsResponse {
            models: Vec::new(),
            etag: String::new(),
        };

        let transport = CapturingTransport {
            last_request: Arc::new(Mutex::new(None)),
            body: Arc::new(response),
        };

        let client = ModelsClient::new(
            transport.clone(),
            provider("https://example.com/api/codex"),
            DummyAuth,
        );

        let result = client
            .list_models("0.99.0", HeaderMap::new())
            .await
            .expect("request should succeed");

        assert_eq!(result.models.len(), 0);

        let url = transport
            .last_request
            .lock()
            .unwrap()
            .as_ref()
            .unwrap()
            .url
            .clone();
        assert_eq!(
            url,
            "https://example.com/api/codex/models?client_version=0.99.0"
        );
    }

    #[tokio::test]
    async fn parses_models_response() {
        let response = ModelsResponse {
            models: vec![
                serde_json::from_value(json!({
                    "slug": "gpt-test",
                    "display_name": "gpt-test",
                    "description": "desc",
                    "default_reasoning_level": "medium",
                    "supported_reasoning_levels": [{"effort": "low", "description": "low"}, {"effort": "medium", "description": "medium"}, {"effort": "high", "description": "high"}],
                    "shell_type": "shell_command",
                    "visibility": "list",
                    "minimal_client_version": [0, 99, 0],
                    "supported_in_api": true,
                    "priority": 1,
                    "upgrade": null,
                }))
                .unwrap(),
            ],
            etag: String::new(),
        };

        let transport = CapturingTransport {
            last_request: Arc::new(Mutex::new(None)),
            body: Arc::new(response),
        };

        let client = ModelsClient::new(
            transport,
            provider("https://example.com/api/codex"),
            DummyAuth,
        );

        let result = client
            .list_models("0.99.0", HeaderMap::new())
            .await
            .expect("request should succeed");

        assert_eq!(result.models.len(), 1);
        assert_eq!(result.models[0].slug, "gpt-test");
        assert_eq!(result.models[0].supported_in_api, true);
        assert_eq!(result.models[0].priority, 1);
    }

    #[tokio::test]
    async fn list_models_includes_etag() {
        let response = ModelsResponse {
            models: Vec::new(),
            etag: "\"abc\"".to_string(),
        };

        let transport = CapturingTransport {
            last_request: Arc::new(Mutex::new(None)),
            body: Arc::new(response),
        };

        let client = ModelsClient::new(
            transport,
            provider("https://example.com/api/codex"),
            DummyAuth,
        );

        let result = client
            .list_models("0.1.0", HeaderMap::new())
            .await
            .expect("request should succeed");

        assert_eq!(result.models.len(), 0);
        assert_eq!(result.etag, "\"abc\"");
    }
}