use std::collections::HashMap;
use std::net::SocketAddr;

use axum::{
    extract::{Path, State},
    http::{HeaderMap, StatusCode},
    response::Json,
    routing::{get, post},
    Router,
};
use serde::{Deserialize, Serialize};
use tauri::{AppHandle, Emitter};

use super::engine::DownloadEngine;
use super::task::{DownloadTask, TaskStatus};

/// 扩展 HTTP API 服务器
pub struct ExtensionServer;

#[derive(Serialize)]
struct HealthResponse {
    ok: bool,
    version: &'static str,
}

#[derive(Deserialize)]
struct CreateDownloadRequest {
    url: String,
    #[serde(default)]
    filename: Option<String>,
    #[serde(default)]
    dir: Option<String>,
    #[serde(default)]
    headers: HashMap<String, String>,
}

#[derive(Serialize)]
struct CreateDownloadResponse {
    id: String,
}

#[derive(Serialize)]
struct ErrorResponse {
    error: String,
}

impl ExtensionServer {
    /// 启动 HTTP API 服务器（绑定到 127.0.0.1:port）
    pub async fn start(engine: DownloadEngine, port: u16, secret: String, app_handle: AppHandle) {
        let addr: SocketAddr = format!("127.0.0.1:{}", port).parse().expect("无效端口");

        let app = Router::new()
            .route("/health", get(health))
            .route("/api/downloads", post(create_download).get(list_downloads))
            .route("/api/downloads/:id", axum::routing::delete(remove_download))
            .with_state(AppState {
                engine,
                secret,
                app_handle,
            });

        let listener = match tokio::net::TcpListener::bind(&addr).await {
            Ok(l) => l,
            Err(e) => {
                crate::logger::log_error("download", &format!("扩展 HTTP 服务启动失败 ({}): {}", addr, e));
                return;
            }
        };

        crate::logger::log_info("download", &format!("扩展 HTTP 服务已启动: http://{}", addr));

        if let Err(e) = axum::serve(listener, app).await {
            crate::logger::log_error("download", &format!("扩展 HTTP 服务异常: {}", e));
        }
    }
}

#[derive(Clone)]
struct AppState {
    engine: DownloadEngine,
    secret: String,
    app_handle: AppHandle,
}

/// 鉴权检查：如果配置了 secret，校验 Bearer token
fn check_auth(headers: &HeaderMap, secret: &str) -> bool {
    if secret.is_empty() {
        return true;
    }
    if let Some(auth) = headers.get("authorization") {
        if let Ok(s) = auth.to_str() {
            if let Some(token) = s.strip_prefix("Bearer ") {
                return token == secret;
            }
        }
    }
    false
}

async fn health(State(state): State<AppState>) -> Json<HealthResponse> {
    let _ = state; // 不需要鉴权
    Json(HealthResponse {
        ok: true,
        version: "thing-download-engine/1.0",
    })
}

async fn create_download(
    State(state): State<AppState>,
    headers: HeaderMap,
    Json(req): Json<CreateDownloadRequest>,
) -> Result<Json<CreateDownloadResponse>, (StatusCode, Json<ErrorResponse>)> {
    if !check_auth(&headers, &state.secret) {
        return Err((StatusCode::UNAUTHORIZED, Json(ErrorResponse { error: "未授权".into() })));
    }

    // 去重：同 URL 已有非终态任务（活跃/排队/暂停）时直接返回既有任务，
    // 避免浏览器重复转发同一下载造成重复下载
    if let Some(existing) = state.engine.get_tasks().into_iter().find(|t| {
        matches!(t.status, TaskStatus::Active | TaskStatus::Queued | TaskStatus::Paused) && t.url == req.url
    }) {
        return Ok(Json(CreateDownloadResponse { id: existing.id }));
    }

    match state.engine.add_task(req.url, req.filename, req.dir, req.headers, true, None).await {
        Ok(id) => {
            // 浏览器扩展发起下载：不再置前主窗口，改为带 task id 通知前端，
            // 由前端为该任务创建一个专属的一次性下载窗口（不打断主界面）
            let _ = state.app_handle.emit(
                crate::constants::events::DOWNLOAD_EXTENSION_ADDED,
                serde_json::json!({ "id": id }),
            );
            Ok(Json(CreateDownloadResponse { id }))
        }
        Err(e) => Err((StatusCode::BAD_REQUEST, Json(ErrorResponse { error: e }))),
    }
}

async fn list_downloads(
    State(state): State<AppState>,
    headers: HeaderMap,
) -> Result<Json<Vec<DownloadTask>>, (StatusCode, Json<ErrorResponse>)> {
    if !check_auth(&headers, &state.secret) {
        return Err((StatusCode::UNAUTHORIZED, Json(ErrorResponse { error: "未授权".into() })));
    }
    Ok(Json(state.engine.get_tasks()))
}

async fn remove_download(
    State(state): State<AppState>,
    headers: HeaderMap,
    Path(id): Path<String>,
) -> Result<StatusCode, (StatusCode, Json<ErrorResponse>)> {
    if !check_auth(&headers, &state.secret) {
        return Err((StatusCode::UNAUTHORIZED, Json(ErrorResponse { error: "未授权".into() })));
    }
    match state.engine.remove_task(&id, false) {
        Ok(()) => {
            // 通知前端刷新任务列表（扩展删除时前端无从感知，否则列表残留已删除任务）
            let _ = state.app_handle.emit(crate::constants::events::DOWNLOAD_REMOVED, serde_json::json!({ "id": id }));
            Ok(StatusCode::NO_CONTENT)
        }
        Err(e) => Err((StatusCode::NOT_FOUND, Json(ErrorResponse { error: e }))),
    }
}