use std::collections::HashMap;
use std::sync::Arc;
use std::time::Instant;

use tokio::sync::{Mutex, mpsc};

use crate::agent::AgentError;
use crate::protocol::WsOutbound;

use super::session::Session;
use super::session_factory::SessionFactory;

#[derive(Clone)]
pub(crate) struct SessionPool {
    inner: Arc<Mutex<SessionPoolInner>>,
    session_factory: SessionFactory,
}

struct SessionPoolInner {
    sessions: HashMap<String, Arc<Mutex<Session>>>,
    session_timestamps: HashMap<String, Instant>,
}

impl SessionPool {
    pub(crate) fn new(session_factory: SessionFactory) -> Self {
        Self {
            inner: Arc::new(Mutex::new(SessionPoolInner {
                sessions: HashMap::new(),
                session_timestamps: HashMap::new(),
            })),
            session_factory,
        }
    }

    pub(crate) async fn ensure_session(&self, channel_name: &str) -> Result<(), AgentError> {
        let mut inner = self.inner.lock().await;

        // 简化：只检查 session 是否存在，不做超时判断
        if inner.sessions.contains_key(channel_name) {
            return Ok(());
        }

        // Session 不存在则创建
        let (user_tx, _rx) = mpsc::channel::<WsOutbound>(100);
        let session = self
            .session_factory
            .create(channel_name.to_string(), user_tx)
            .await?;

        inner
            .sessions
            .insert(channel_name.to_string(), Arc::new(Mutex::new(session)));
        inner
            .session_timestamps
            .insert(channel_name.to_string(), Instant::now());

        Ok(())
    }

    pub(crate) async fn get(&self, channel_name: &str) -> Option<Arc<Mutex<Session>>> {
        self.inner.lock().await.sessions.get(channel_name).cloned()
    }

    pub(crate) async fn touch(&self, channel_name: &str) {
        self.inner
            .lock()
            .await
            .session_timestamps
            .insert(channel_name.to_string(), Instant::now());
    }

    pub(crate) async fn cleanup_expired_sessions(&self) -> usize {
        // Session 级别不再自动清理，返回 0
        0
    }
}