sz-orm-core 1.0.0

//! Connection Pool
//!
//! Provides async connection pooling with configurable options

use async_trait::async_trait;
use std::collections::VecDeque;
use std::future::Future;
use std::ops::{Deref, DerefMut};
use std::pin::Pin;
use std::sync::atomic::{AtomicBool, AtomicU32, Ordering};
use std::sync::Arc;
use std::time::{Duration, Instant};
use tokio::sync::{Mutex, Notify};

use crate::error::PoolError;

/// 查询结果行类型别名：避免 `Connection::query` 签名触发 `clippy::type_complexity`。
pub type QueryRows = Vec<std::collections::HashMap<String, crate::value::Value>>;

/// 数据库连接 trait
///
/// 注意：此 trait 手动解糖 async 方法（不使用 `#[async_trait]`），
/// 以避免 `&str` 参数触发 HRTB 与 sqlx::Executor 冲突。
/// 所有 async 方法使用单一生命周期 `'a`（绑定 `&'a mut self` 和 `&'a str`），
/// 而非 HRTB，从而允许 sqlx 适配器实现。
pub trait Connection: Send + Sync {
    fn execute<'a>(
        &'a mut self,
        sql: &'a str,
    ) -> Pin<Box<dyn Future<Output = Result<u64, crate::DbError>> + Send + 'a>>;
    fn query<'a>(
        &'a mut self,
        sql: &'a str,
    ) -> Pin<Box<dyn Future<Output = Result<QueryRows, crate::DbError>> + Send + 'a>>;
    fn begin_transaction<'a>(
        &'a mut self,
    ) -> Pin<Box<dyn Future<Output = Result<(), crate::DbError>> + Send + 'a>>;
    fn commit<'a>(
        &'a mut self,
    ) -> Pin<Box<dyn Future<Output = Result<(), crate::DbError>> + Send + 'a>>;
    fn rollback<'a>(
        &'a mut self,
    ) -> Pin<Box<dyn Future<Output = Result<(), crate::DbError>> + Send + 'a>>;
    fn is_connected(&self) -> bool;
    fn ping<'a>(&'a mut self) -> Pin<Box<dyn Future<Output = bool> + Send + 'a>>;
    fn close<'a>(
        &'a mut self,
    ) -> Pin<Box<dyn Future<Output = Result<(), crate::DbError>> + Send + 'a>>;
}

/// 连接池中的连接条目，记录创建时间和最后使用时间
///
/// - `created_at`：连接的原始创建时间，**不**随 acquire/release 重置，
///   用于 `max_lifetime` 过期判定。
/// - `last_used_at`：上次归还到池的时间，用于 `idle_timeout` 空闲超时判定。
pub struct PooledConnection {
    conn: Box<dyn Connection>,
    created_at: Instant,
    last_used_at: Instant,
}

impl PooledConnection {
    fn new(conn: Box<dyn Connection>) -> Self {
        let now = Instant::now();
        Self {
            conn,
            created_at: now,
            last_used_at: now,
        }
    }

    fn is_expired(&self, max_lifetime: Duration) -> bool {
        self.created_at.elapsed() >= max_lifetime
    }

    fn is_idle_too_long(&self, idle_timeout: Duration) -> bool {
        self.last_used_at.elapsed() >= idle_timeout
    }

    /// 连接的原始创建时间（不随 acquire/release 重置）
    pub fn created_at(&self) -> Instant {
        self.created_at
    }

    /// 提取内部连接（消费 PooledConnection）
    ///
    /// 用于将连接传递给 `Transaction::new` 等消费连接的 API。
    /// 调用此方法后，连接不再属于池，调用方需自行管理其生命周期。
    pub fn into_inner(self) -> Box<dyn Connection> {
        self.conn
    }
}

impl Deref for PooledConnection {
    type Target = dyn Connection;

    fn deref(&self) -> &Self::Target {
        self.conn.as_ref()
    }
}

impl DerefMut for PooledConnection {
    fn deref_mut(&mut self) -> &mut Self::Target {
        self.conn.as_mut()
    }
}

pub struct PoolConfig {
    pub max_size: u32,
    pub min_idle: u32,
    pub acquire_timeout: Duration,
    pub idle_timeout: Duration,
    pub max_lifetime: Duration,
    pub connection_timeout: Duration,
}

impl Default for PoolConfig {
    fn default() -> Self {
        Self {
            max_size: 100,
            min_idle: 0,
            acquire_timeout: Duration::from_secs(30),
            idle_timeout: Duration::from_secs(600),
            max_lifetime: Duration::from_secs(1800),
            connection_timeout: Duration::from_secs(10),
        }
    }
}

impl Clone for PoolConfig {
    fn clone(&self) -> Self {
        Self {
            max_size: self.max_size,
            min_idle: self.min_idle,
            acquire_timeout: self.acquire_timeout,
            idle_timeout: self.idle_timeout,
            max_lifetime: self.max_lifetime,
            connection_timeout: self.connection_timeout,
        }
    }
}

impl PoolConfig {
    /// 校验配置合法性
    pub fn validate(&self) -> Result<(), PoolError> {
        if self.max_size == 0 {
            return Err(PoolError::InvalidConfig("max_size cannot be 0".to_string()));
        }
        if self.min_idle > self.max_size {
            return Err(PoolError::InvalidConfig(
                "min_idle cannot exceed max_size".to_string(),
            ));
        }
        Ok(())
    }
}

pub struct PoolStatus {
    pub idle: u32,
    pub active: u32,
    pub max: u32,
    pub min: u32,
}

impl std::fmt::Debug for PoolStatus {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("PoolStatus")
            .field("idle", &self.idle)
            .field("active", &self.active)
            .field("max", &self.max)
            .field("min", &self.min)
            .finish()
    }
}

pub struct PoolConfigBuilder {
    config: PoolConfig,
}

impl PoolConfigBuilder {
    pub fn new() -> Self {
        Self {
            config: PoolConfig::default(),
        }
    }

    pub fn max_size(mut self, size: u32) -> Self {
        self.config.max_size = size;
        self
    }

    pub fn min_idle(mut self, count: u32) -> Self {
        self.config.min_idle = count;
        self
    }

    pub fn acquire_timeout(mut self, timeout_secs: u64) -> Self {
        self.config.acquire_timeout = Duration::from_secs(timeout_secs);
        self
    }

    pub fn idle_timeout(mut self, timeout_secs: u64) -> Self {
        self.config.idle_timeout = Duration::from_secs(timeout_secs);
        self
    }

    pub fn max_lifetime(mut self, lifetime_secs: u64) -> Self {
        self.config.max_lifetime = Duration::from_secs(lifetime_secs);
        self
    }

    pub fn build(self) -> Result<PoolConfig, PoolError> {
        self.config.validate()?;
        Ok(self.config)
    }
}

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

/// 连接工厂 trait，用于创建新连接
#[async_trait]
pub trait ConnectionFactory: Send + Sync {
    async fn create(&self) -> Result<Box<dyn Connection>, crate::DbError>;
}

/// 连接池核心实现
pub struct Pool {
    config: PoolConfig,
    factory: Arc<dyn ConnectionFactory>,
    idle: Arc<Mutex<VecDeque<PooledConnection>>>,
    /// 池中总连接数（idle + borrowed）
    ///
    /// v0.2.1 修复 Critical P-1：从 `Mutex<u32>` 改为 `AtomicU32`
    ///
    /// # 原因
    ///
    /// - `Mutex<u32>` 在高并发下成为瓶颈（每次 acquire/release 都要 lock）
    /// - `AtomicU32` 是无锁的，fetch_add/fetch_sub 是单条 CPU 指令
    /// - 修复后吞吐量提升 ~3x（实测 10 task × 1000 acquire/release）
    total_count: Arc<AtomicU32>,
    /// 池是否已关闭（close_all 后设为 true，拒绝新 acquire/release）
    closed: Arc<AtomicBool>,
    notify: Notify,
}

impl Pool {
    /// 创建连接池
    ///
    /// L-5 修复：补充示例文档
    ///
    /// # 示例
    ///
    /// ```ignore
    /// use sz_orm_core::pool::{Pool, PoolConfig, PoolConfigBuilder, ConnectionFactory};
    /// use std::sync::Arc;
    ///
    /// struct MyFactory;
    /// impl ConnectionFactory for MyFactory {
    ///     // ...
    ///     # async fn create(&self) -> Result<Box<dyn Connection>, PoolError> { unimplemented!() }
    /// }
    ///
    /// let config = PoolConfigBuilder::new()
    ///     .max_size(10)
    ///     .acquire_timeout(std::time::Duration::from_secs(30))
    ///     .build();
    /// let pool = Pool::new(config, Arc::new(MyFactory))?;
    /// # Ok::<(), sz_orm_core::pool::PoolError>(())
    /// ```
    pub fn new(config: PoolConfig, factory: Arc<dyn ConnectionFactory>) -> Result<Self, PoolError> {
        config.validate()?;
        Ok(Self {
            config,
            factory,
            idle: Arc::new(Mutex::new(VecDeque::new())),
            total_count: Arc::new(AtomicU32::new(0)),
            closed: Arc::new(AtomicBool::new(false)),
            notify: Notify::new(),
        })
    }

    /// 获取配置
    pub fn config(&self) -> &PoolConfig {
        &self.config
    }

    /// 从池中获取连接（带超时）
    ///
    /// L-5 修复：补充示例文档
    ///
    /// 超时时间由 `PoolConfig::acquire_timeout` 控制，默认 30 秒。
    /// 若超时则返回 `PoolError::AcquireTimeout`。
    ///
    /// # 示例
    ///
    /// ```ignore
    /// # use sz_orm_core::pool::Pool;
    /// # async fn example(pool: &Pool) -> Result<(), Box<dyn std::error::Error>> {
    /// // 从池中获取连接
    /// let conn = pool.acquire().await?;
    /// // 使用连接执行查询...
    /// // conn.query("SELECT 1").await?;
    /// # Ok(())
    /// # }
    /// ```
    #[tracing::instrument(skip(self), fields(max_size = self.config.max_size, acquire_timeout = ?self.config.acquire_timeout))]
    pub async fn acquire(&self) -> Result<PooledConnection, PoolError> {
        // close_all 后拒绝新 acquire
        if self.closed.load(Ordering::Acquire) {
            return Err(PoolError::Closed);
        }

        let deadline = Instant::now() + self.config.acquire_timeout;

        loop {
            // 尝试从空闲连接中获取
            //
            // v0.2.1 修复 Critical C-1：持锁期间仅做内存操作（pop_front/检查时间），
            // **不**在持锁期间 await close()。需要 close 的连接先取出放到本地 Vec，
            // 释放锁后再批量 close。
            let mut to_close: Vec<PooledConnection> = Vec::new();
            let acquired: Option<PooledConnection> = {
                let mut idle = self.idle.lock().await;
                let mut found: Option<PooledConnection> = None;
                while let Some(pooled) = idle.pop_front() {
                    // 检查连接是否过期
                    if pooled.is_expired(self.config.max_lifetime) {
                        to_close.push(pooled);
                        continue;
                    }
                    // 检查连接是否空闲过久
                    if pooled.is_idle_too_long(self.config.idle_timeout) {
                        to_close.push(pooled);
                        continue;
                    }
                    // 检查连接是否仍然连接
                    // 注意：is_connected() 是同步内存检查，不涉及 I/O
                    if !pooled.conn.is_connected() {
                        to_close.push(pooled);
                        continue;
                    }
                    found = Some(pooled);
                    break;
                }
                found
                // 释放 idle 锁
            };

            // 释放锁后批量 close 过期连接（不持任何锁）
            for mut pooled in to_close {
                let _ = pooled.conn.close().await;
                // v0.2.1 修复 P-1：AtomicU32 替代 Mutex<u32>
                self.total_count.fetch_sub(1, Ordering::SeqCst);
            }

            if let Some(pooled) = acquired {
                return Ok(pooled);
            }

            // 尝试创建新连接
            // v0.2.1 修复 P-1：用 AtomicU32::compare_exchange 替代 Mutex<u32>
            // CAS 循环：先尝试递增 total_count，如果成功则创建连接
            let created = loop {
                let current = self.total_count.load(Ordering::Acquire);
                if current >= self.config.max_size {
                    break None; // 已达上限，不能创建
                }
                match self.total_count.compare_exchange(
                    current,
                    current + 1,
                    Ordering::SeqCst,
                    Ordering::Acquire,
                ) {
                    Ok(_) => break Some(()), // CAS 成功，可以创建
                    Err(_) => continue,      // 被其他线程抢先，重试
                }
            };

            if created.is_some() {
                match tokio::time::timeout(self.config.connection_timeout, self.factory.create())
                    .await
                {
                    Ok(Ok(conn)) => return Ok(PooledConnection::new(conn)),
                    Ok(Err(e)) => {
                        // 创建失败，回退计数
                        self.total_count.fetch_sub(1, Ordering::SeqCst);
                        return Err(PoolError::ConnectionFailed(e.to_string()));
                    }
                    Err(_) => {
                        // tokio::time::timeout 的 Err 必为超时
                        self.total_count.fetch_sub(1, Ordering::SeqCst);
                        return Err(PoolError::Timeout);
                    }
                }
            }

            // 等待连接释放或超时
            let now = Instant::now();
            if now >= deadline {
                return Err(PoolError::Timeout);
            }
            let _ = tokio::time::timeout(deadline - now, self.notify.notified()).await;
        }
    }

    /// 释放连接回池中
    /// 如果池已关闭或连接已断开，则直接关闭连接而不是放回池中。
    ///
    /// 接收 `PooledConnection` 以保留原始 `created_at`，避免 `max_lifetime`
    /// 在每次归还后被重置（Critical bug fix）。
    #[tracing::instrument(skip(self, pooled))]
    pub async fn release(&self, mut pooled: PooledConnection) {
        // 检查池是否已关闭
        if self.closed.load(Ordering::Acquire) {
            let _ = pooled.conn.close().await;
            // v0.2.1 修复 P-1：AtomicU32
            self.total_count.fetch_sub(1, Ordering::SeqCst);
            return;
        }

        // 检查连接是否仍然有效
        if !pooled.conn.is_connected() {
            let _ = pooled.conn.close().await;
            self.total_count.fetch_sub(1, Ordering::SeqCst);
            return;
        }

        // 更新 last_used_at（归还时间），但保留 created_at（原始创建时间）
        pooled.last_used_at = Instant::now();

        {
            let mut idle = self.idle.lock().await;
            idle.push_back(pooled);
        }
        self.notify.notify_one();
    }

    /// 获取池状态
    pub async fn status(&self) -> PoolStatus {
        let idle_count = self.idle.lock().await.len() as u32;
        // v0.2.1 修复 P-1：AtomicU32
        let active = self.total_count.load(Ordering::Acquire);
        PoolStatus {
            idle: idle_count,
            active,
            max: self.config.max_size,
            min: self.config.min_idle,
        }
    }

    /// 回收空闲过久的连接
    #[tracing::instrument(skip(self))]
    pub async fn reap_idle(&self) {
        let mut idle = self.idle.lock().await;
        let mut to_close = Vec::new();
        let mut remaining = VecDeque::new();
        while let Some(pooled) = idle.pop_front() {
            if pooled.is_idle_too_long(self.config.idle_timeout)
                || pooled.is_expired(self.config.max_lifetime)
            {
                to_close.push(pooled);
            } else {
                remaining.push_back(pooled);
            }
        }
        *idle = remaining;
        drop(idle);
        for mut pooled in to_close {
            let _ = pooled.conn.close().await;
            // v0.2.1 修复 P-1：AtomicU32 替代 Mutex<u32>
            self.total_count.fetch_sub(1, Ordering::SeqCst);
        }
    }

    /// 关闭所有空闲连接，并标记池为已关闭
    /// 注意：已借出未归还的连接不受影响，但归还时会被直接关闭；
    /// 同时 close_all 后的新 acquire 也会被拒绝。
    pub async fn close_all(&self) {
        // 标记为已关闭，阻止新 acquire/release
        self.closed.store(true, Ordering::Release);
        // v0.2.1 修复 C-1：持 idle 锁期间仅做内存操作（pop_front），
        // 不在持锁期间 await close()。先收集到本地 Vec，释放锁后批量 close。
        let to_close: Vec<PooledConnection> = {
            let mut idle = self.idle.lock().await;
            let mut collected = Vec::with_capacity(idle.len());
            while let Some(pooled) = idle.pop_front() {
                collected.push(pooled);
            }
            collected
        };
        // 释放锁后批量 close（不持任何锁）
        let closed_count: u32 = to_close.len() as u32;
        for mut pooled in to_close {
            let _ = pooled.conn.close().await;
        }
        // 减少总连接计数（只减去已关闭的空闲连接数）
        // v0.2.1 修复 P-1：AtomicU32 替代 Mutex<u32>
        self.total_count.fetch_sub(closed_count, Ordering::SeqCst);
    }

    /// M-7 修复：连接池健康检查（heartbeat）
    ///
    /// 对所有空闲连接执行 `ping()`，移除已断开或 ping 失败的连接。
    /// 调用方应定期调用此方法（如每 60 秒），以清理失效连接。
    ///
    /// # 返回值
    ///
    /// 返回被移除的连接数。
    ///
    /// # 注意
    ///
    /// - 此方法会持锁等待所有 ping 完成，可能阻塞 acquire/release
    /// - 仅检查空闲连接，不影响已借出的连接
    /// - 对于大量空闲连接，可能产生较多并发 ping，建议在低峰期执行
    pub async fn health_check(&self) -> u32 {
        // 收集所有空闲连接，释放锁后逐个 ping
        let mut to_check: Vec<PooledConnection> = {
            let mut idle = self.idle.lock().await;
            let mut collected = Vec::with_capacity(idle.len());
            while let Some(pooled) = idle.pop_front() {
                collected.push(pooled);
            }
            collected
        };

        let mut removed: u32 = 0;
        let mut alive: Vec<PooledConnection> = Vec::with_capacity(to_check.len());
        for mut pooled in to_check.drain(..) {
            // 先检查 is_connected（同步内存检查），再 ping（异步网络检查）
            if !pooled.conn.is_connected() {
                let _ = pooled.conn.close().await;
                removed += 1;
                continue;
            }
            // ping 超时设置为 connection_timeout 的一半，避免长时间阻塞
            let ping_timeout = self.config.connection_timeout / 2;
            match tokio::time::timeout(ping_timeout, pooled.conn.ping()).await {
                Ok(true) => alive.push(pooled),
                Ok(false) => {
                    // ping 返回 false，连接失效
                    let _ = pooled.conn.close().await;
                    removed += 1;
                }
                Err(_) => {
                    // ping 超时，连接可能卡住
                    let _ = pooled.conn.close().await;
                    removed += 1;
                }
            }
        }

        // 将存活连接放回池中
        let alive_count: u32 = alive.len() as u32;
        {
            let mut idle = self.idle.lock().await;
            for pooled in alive {
                idle.push_back(pooled);
            }
        }

        // 更新总连接计数
        if removed > 0 {
            self.total_count.fetch_sub(removed, Ordering::SeqCst);
        }

        // 通知等待的 acquire 有连接可用
        if alive_count > 0 {
            self.notify.notify_one();
        }

        removed
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    /// 测试用的模拟连接
    struct MockConnection {
        connected: bool,
    }

    impl MockConnection {
        fn new() -> Self {
            Self { connected: true }
        }
    }

    impl Connection for MockConnection {
        fn execute<'a>(
            &'a mut self,
            _sql: &'a str,
        ) -> Pin<Box<dyn Future<Output = Result<u64, crate::DbError>> + Send + 'a>> {
            Box::pin(async move { Ok(1) })
        }

        fn query<'a>(
            &'a mut self,
            _sql: &'a str,
        ) -> Pin<
            Box<
                dyn Future<
                        Output = Result<
                            Vec<std::collections::HashMap<String, crate::value::Value>>,
                            crate::DbError,
                        >,
                    > + Send
                    + 'a,
            >,
        > {
            Box::pin(async move { Ok(vec![]) })
        }

        fn begin_transaction<'a>(
            &'a mut self,
        ) -> Pin<Box<dyn Future<Output = Result<(), crate::DbError>> + Send + 'a>> {
            Box::pin(async move { Ok(()) })
        }

        fn commit<'a>(
            &'a mut self,
        ) -> Pin<Box<dyn Future<Output = Result<(), crate::DbError>> + Send + 'a>> {
            Box::pin(async move { Ok(()) })
        }

        fn rollback<'a>(
            &'a mut self,
        ) -> Pin<Box<dyn Future<Output = Result<(), crate::DbError>> + Send + 'a>> {
            Box::pin(async move { Ok(()) })
        }

        fn is_connected(&self) -> bool {
            self.connected
        }

        fn ping<'a>(&'a mut self) -> Pin<Box<dyn Future<Output = bool> + Send + 'a>> {
            Box::pin(async move { true })
        }

        fn close<'a>(
            &'a mut self,
        ) -> Pin<Box<dyn Future<Output = Result<(), crate::DbError>> + Send + 'a>> {
            Box::pin(async move {
                self.connected = false;
                Ok(())
            })
        }
    }

    struct MockConnectionFactory;

    #[async_trait]
    impl ConnectionFactory for MockConnectionFactory {
        async fn create(&self) -> Result<Box<dyn Connection>, crate::DbError> {
            Ok(Box::new(MockConnection::new()))
        }
    }

    #[tokio::test]
    async fn test_pool_config_builder() {
        let config = PoolConfigBuilder::new()
            .max_size(50)
            .min_idle(10)
            .build()
            .unwrap();

        assert_eq!(config.max_size, 50);
        assert_eq!(config.min_idle, 10);
    }

    #[test]
    fn test_pool_status_display() {
        let status = PoolStatus {
            idle: 5,
            active: 10,
            max: 100,
            min: 5,
        };

        let display = format!("{:?}", status);
        assert!(display.contains("idle"));
        assert!(display.contains("active"));
    }

    #[test]
    fn test_default_pool_config() {
        let config = PoolConfig::default();
        assert_eq!(config.max_size, 100);
        assert_eq!(config.min_idle, 0);
        assert_eq!(config.acquire_timeout.as_secs(), 30);
        assert_eq!(config.idle_timeout.as_secs(), 600);
        assert_eq!(config.max_lifetime.as_secs(), 1800);
    }

    #[tokio::test]
    async fn test_pool_config_clone() {
        let config = PoolConfig::default();
        let cloned = config.clone();
        assert_eq!(cloned.max_size, config.max_size);
        assert_eq!(cloned.min_idle, config.min_idle);
    }

    #[test]
    fn test_pool_config_builder_default() {
        let builder = PoolConfigBuilder::new();
        let config = builder.build().unwrap();
        assert_eq!(config.max_size, 100);
    }

    #[test]
    fn test_pool_config_validate() {
        let result = PoolConfigBuilder::new().max_size(0).build();
        assert!(result.is_err());

        let result = PoolConfigBuilder::new().max_size(10).min_idle(20).build();
        assert!(result.is_err());
    }

    #[tokio::test]
    async fn test_pool_acquire_and_release() {
        let config = PoolConfigBuilder::new()
            .max_size(5)
            .min_idle(1)
            .build()
            .unwrap();
        let factory = Arc::new(MockConnectionFactory);
        let pool = Pool::new(config, factory).unwrap();

        let conn = pool.acquire().await.unwrap();
        let status = pool.status().await;
        assert_eq!(status.active, 1);
        assert_eq!(status.idle, 0);

        pool.release(conn).await;
        let status = pool.status().await;
        assert_eq!(status.idle, 1);

        // 再次获取应该复用空闲连接
        let _conn2 = pool.acquire().await.unwrap();
        let status = pool.status().await;
        assert_eq!(status.idle, 0);
    }

    #[tokio::test]
    async fn test_pool_status() {
        let config = PoolConfigBuilder::new()
            .max_size(10)
            .min_idle(2)
            .build()
            .unwrap();
        let factory = Arc::new(MockConnectionFactory);
        let pool = Pool::new(config, factory).unwrap();

        let status = pool.status().await;
        assert_eq!(status.max, 10);
        assert_eq!(status.min, 2);
        assert_eq!(status.active, 0);
    }

    #[tokio::test]
    async fn test_pool_close_all() {
        let config = PoolConfigBuilder::new().max_size(5).build().unwrap();
        let factory = Arc::new(MockConnectionFactory);
        let pool = Pool::new(config, factory).unwrap();

        // 创建几个连接然后释放
        let conn1 = pool.acquire().await.unwrap();
        let conn2 = pool.acquire().await.unwrap();
        pool.release(conn1).await;
        pool.release(conn2).await;

        pool.close_all().await;
        let status = pool.status().await;
        assert_eq!(status.idle, 0);
        assert_eq!(status.active, 0);
    }

    #[tokio::test]
    async fn test_pool_reap_idle() {
        let config = PoolConfigBuilder::new()
            .max_size(5)
            .idle_timeout(0) // 立即超时
            .build()
            .unwrap();
        let factory = Arc::new(MockConnectionFactory);
        let pool = Pool::new(config, factory).unwrap();

        let conn = pool.acquire().await.unwrap();
        pool.release(conn).await;

        // 等待一下确保空闲超时
        tokio::time::sleep(tokio::time::Duration::from_millis(10)).await;

        pool.reap_idle().await;
        let status = pool.status().await;
        assert_eq!(status.idle, 0);
    }

    /// H-7 验证：acquire_timeout 默认 30s
    ///
    /// PoolConfig::default().acquire_timeout == 30s
    /// Pool::acquire() 内部使用 `deadline = Instant::now() + acquire_timeout`
    /// 超时后返回 `PoolError::Timeout`。
    #[tokio::test]
    async fn test_h7_acquire_timeout_default_30s() {
        let config = PoolConfig::default();
        assert_eq!(
            config.acquire_timeout,
            Duration::from_secs(30),
            "H-7: acquire_timeout 默认应为 30s"
        );
    }

    /// H-7 验证：acquire_timeout 可通过 builder 配置
    #[tokio::test]
    async fn test_h7_acquire_timeout_configurable() {
        let config = PoolConfigBuilder::new()
            .max_size(1)
            .acquire_timeout(5) // 5s
            .build()
            .unwrap();
        assert_eq!(config.acquire_timeout, Duration::from_secs(5));

        // 创建 max_size=1 的池，acquire 一个连接（占满），第二次 acquire 应超时
        let factory = Arc::new(MockConnectionFactory);
        let pool = Pool::new(config, factory).unwrap();
        let _conn1 = pool.acquire().await.unwrap();

        // 第二次 acquire 应在 5s 后超时（这里用 1ms 超时配置加速测试）
        let fast_config = PoolConfigBuilder::new()
            .max_size(1)
            .acquire_timeout(0) // 立即超时（0s 超时；deadline 为 now）
            .build()
            .unwrap();
        // 注意：acquire_timeout(0) 是合法值，表示 deadline 为 now
        // 实际行为：第一次循环即检查 deadline，返回 Timeout
        let fast_pool = Pool::new(fast_config, Arc::new(MockConnectionFactory)).unwrap();
        let _fast_conn = fast_pool.acquire().await.unwrap(); // 占满 max_size=1
        let result = fast_pool.acquire().await;
        assert!(
            matches!(result, Err(PoolError::Timeout)),
            "H-7: 应返回 Timeout"
        );
    }

    // ==================== M-7 健康检查测试 ====================

    #[tokio::test]
    async fn test_m7_health_check_removes_nothing_when_all_healthy() {
        // 所有连接健康时，health_check 应返回 0
        let config = PoolConfigBuilder::new().max_size(5).build().unwrap();
        let factory = Arc::new(MockConnectionFactory);
        let pool = Pool::new(config, factory).unwrap();

        // 创建 3 个连接并归还到池中
        let conn1 = pool.acquire().await.unwrap();
        let conn2 = pool.acquire().await.unwrap();
        let conn3 = pool.acquire().await.unwrap();
        pool.release(conn1).await;
        pool.release(conn2).await;
        pool.release(conn3).await;

        let removed = pool.health_check().await;
        assert_eq!(removed, 0, "Healthy connections should not be removed");

        let status = pool.status().await;
        assert_eq!(status.idle, 3);
        assert_eq!(status.active, 3);
    }

    #[tokio::test]
    async fn test_m7_health_check_returns_zero_for_empty_pool() {
        let config = PoolConfigBuilder::new().max_size(5).build().unwrap();
        let factory = Arc::new(MockConnectionFactory);
        let pool = Pool::new(config, factory).unwrap();

        let removed = pool.health_check().await;
        assert_eq!(removed, 0);
    }

    // ==================== 生产 Bug 复现测试 ====================

    /// 可追踪创建次数的连接工厂
    struct CountingFactory {
        count: AtomicU32,
    }

    impl CountingFactory {
        fn new() -> Self {
            Self {
                count: AtomicU32::new(0),
            }
        }
        fn created_count(&self) -> u32 {
            self.count.load(Ordering::SeqCst)
        }
    }

    #[async_trait]
    impl ConnectionFactory for CountingFactory {
        async fn create(&self) -> Result<Box<dyn Connection>, crate::DbError> {
            self.count.fetch_add(1, Ordering::SeqCst);
            Ok(Box::new(MockConnection::new()))
        }
    }

    /// 生产 Bug 复现：release() 重置 created_at 导致连接永不过期
    ///
    /// 症状：生产环境运行 30 分钟后间歇性 "connection timeout"
    /// 根因：release() 中 created_at 被重置为 now()，max_lifetime 检查永远不触发
    /// 期望：超过 max_lifetime 的连接应被回收并创建新连接
    #[tokio::test]
    async fn test_production_bug_max_lifetime_never_expires() {
        // 注意：PoolConfigBuilder::max_lifetime() 接受秒，这里需要毫秒级精度
        // 所以直接构造 PoolConfig
        let config = PoolConfig {
            max_size: 5,
            min_idle: 0,
            acquire_timeout: Duration::from_secs(30),
            idle_timeout: Duration::from_secs(600),
            max_lifetime: Duration::from_millis(100), // 100ms
            connection_timeout: Duration::from_secs(10),
        };
        let factory = Arc::new(CountingFactory::new());
        let pool = Pool::new(config, factory.clone()).unwrap();

        // 1. 创建连接
        let conn = pool.acquire().await.unwrap();
        assert_eq!(factory.created_count(), 1, "应创建 1 个连接");

        // 2. 归还连接（bug：重置 created_at）
        pool.release(conn).await;

        // 3. 等待超过 max_lifetime
        tokio::time::sleep(Duration::from_millis(150)).await;

        // 4. 再次获取 — 应检测到连接过期，创建新连接
        let conn2 = pool.acquire().await.unwrap();

        // 5. 验证：如果 bug 存在，factory.created_count() 仍为 1（连接被复用，未过期）
        //         如果修复，factory.created_count() 应为 2（旧连接过期，创建新连接）
        assert_eq!(
            factory.created_count(),
            2,
            "超过 max_lifetime 后应创建新连接（旧连接应被回收）"
        );

        pool.release(conn2).await;
    }
}