use axum::Router;
use axum::routing::{delete, get, put};
use uuid::Uuid;

use erp_core::error::AppResult;
use erp_core::events::EventBus;
use erp_core::module::ErpModule;

use crate::handler::{
    message_handler, subscription_handler, template_handler,
};

/// 消息中心模块，实现 ErpModule trait。
pub struct MessageModule;

impl MessageModule {
    pub fn new() -> Self {
        Self
    }

    /// 构建需要认证的路由。
    pub fn protected_routes<S>() -> Router<S>
    where
        crate::message_state::MessageState: axum::extract::FromRef<S>,
        S: Clone + Send + Sync + 'static,
    {
        Router::new()
            // 消息路由
            .route(
                "/messages",
                get(message_handler::list_messages).post(message_handler::send_message),
            )
            .route(
                "/messages/unread-count",
                get(message_handler::unread_count),
            )
            .route(
                "/messages/{id}/read",
                put(message_handler::mark_read),
            )
            .route(
                "/messages/read-all",
                put(message_handler::mark_all_read),
            )
            .route(
                "/messages/{id}",
                delete(message_handler::delete_message),
            )
            // 模板路由
            .route(
                "/message-templates",
                get(template_handler::list_templates).post(template_handler::create_template),
            )
            // 订阅偏好路由
            .route(
                "/message-subscriptions",
                put(subscription_handler::update_subscription),
            )
    }

    /// 启动后台事件监听任务，将工作流事件转化为消息通知。
    ///
    /// 在 main.rs 中调用，因为需要 db 连接。
    pub fn start_event_listener(db: sea_orm::DatabaseConnection, event_bus: EventBus) {
        let mut rx = event_bus.subscribe();
        tokio::spawn(async move {
            loop {
                match rx.recv().await {
                    Ok(event) => {
                        let db = db.clone();
                        let event_bus = event_bus.clone();
                        tokio::spawn(async move {
                            if let Err(e) =
                                handle_workflow_event(&event, &db, &event_bus).await
                            {
                                tracing::warn!(
                                    event_type = %event.event_type,
                                    error = %e,
                                    "Failed to handle workflow event for messages"
                                );
                            }
                        });
                    }
                    Err(tokio::sync::broadcast::error::RecvError::Lagged(n)) => {
                        tracing::warn!(skipped = n, "Event listener lagged, skipping events");
                    }
                    Err(tokio::sync::broadcast::error::RecvError::Closed) => {
                        tracing::info!("Event bus closed, stopping message event listener");
                        break;
                    }
                }
            }
        });
    }
}

impl Default for MessageModule {
    fn default() -> Self {
        Self::new()
    }
}

#[async_trait::async_trait]
impl ErpModule for MessageModule {
    fn name(&self) -> &str {
        "message"
    }

    fn version(&self) -> &str {
        env!("CARGO_PKG_VERSION")
    }

    fn dependencies(&self) -> Vec<&str> {
        vec!["auth"]
    }

    fn register_routes(&self, router: Router) -> Router {
        router
    }

    fn register_event_handlers(&self, _bus: &EventBus) {}

    async fn on_tenant_created(&self, _tenant_id: Uuid) -> AppResult<()> {
        Ok(())
    }

    async fn on_tenant_deleted(&self, _tenant_id: Uuid) -> AppResult<()> {
        Ok(())
    }

    fn as_any(&self) -> &dyn std::any::Any {
        self
    }
}

/// 处理工作流事件，生成对应的消息通知。
async fn handle_workflow_event(
    event: &erp_core::events::DomainEvent,
    db: &sea_orm::DatabaseConnection,
    event_bus: &EventBus,
) -> Result<(), String> {
    match event.event_type.as_str() {
        "process_instance.started" => {
            let instance_id = event.payload.get("instance_id")
                .and_then(|v| v.as_str())
                .unwrap_or("unknown");
            let starter_id = event.payload.get("started_by")
                .and_then(|v| v.as_str());

            if let Some(starter) = starter_id {
                let recipient = match uuid::Uuid::parse_str(starter) {
                    Ok(id) => id,
                    Err(_) => return Ok(()),
                };
                let _ = crate::service::message_service::MessageService::send_system(
                    event.tenant_id,
                    recipient,
                    "流程已启动".to_string(),
                    format!("您的流程实例 {} 已启动执行。", instance_id),
                    "normal",
                    Some("workflow_instance".to_string()),
                    uuid::Uuid::parse_str(instance_id).ok(),
                    db,
                    event_bus,
                )
                .await
                .map_err(|e| e.to_string())?;
            }
        }
        "task.completed" => {
            // 任务完成时通知发起人（此处简化处理）
            tracing::debug!("Task completed event received, skipping notification for now");
        }
        _ => {}
    }
    Ok(())
}