"""数据库连接池监控模块"""
import time
import threading
from typing import Dict, Any
from datetime import datetime
from sqlalchemy import event
from sqlalchemy.engine import Engine
from .logging_config import get_logger

logger = get_logger(__name__)
db_logger = get_logger("sqlalchemy.engine")

# 全局监控数据
_pool_stats = {
    'total_connections': 0,
    'checked_in': 0,
    'checked_out': 0,
    'overflow': 0,
    'slow_queries': [],
    'connection_errors': [],
    'peak_connections': 0,
    'last_reset': datetime.now()
}

_alert_thresholds = {
    'pool_usage_percent': 80,
    'slow_query_time': 5.0,
    'alert_cooldown': 300
}

_last_alerts = {}
_engines = []

def register_engine(engine):
    """注册引擎用于监控"""
    _engines.append(engine)

def get_pool_status() -> Dict[str, Any]:
    """获取连接池状态"""
    stats = {
        'total': 0,
        'checked_in': 0,
        'checked_out': 0,
        'overflow': 0,
        'usage_percent': 0
    }
    
    for engine in _engines:
        if hasattr(engine.pool, 'size'):
            pool = engine.pool
            stats['total'] += pool.size() if callable(pool.size) else pool.size
            stats['checked_in'] += pool.checkedin() if hasattr(pool, 'checkedin') else 0
            stats['checked_out'] += pool.checkedout() if hasattr(pool, 'checkedout') else 0
            stats['overflow'] += pool.overflow() if hasattr(pool, 'overflow') else 0
    
    if stats['total'] > 0:
        stats['usage_percent'] = round((stats['checked_out'] / stats['total']) * 100, 2)
    
    if stats['checked_out'] > _pool_stats['peak_connections']:
        _pool_stats['peak_connections'] = stats['checked_out']
    
    return stats

def check_pool_alerts():
    """检查连接池告警"""
    current_time = time.time()
    stats = get_pool_status()
    
    if stats.get('usage_percent', 0) >= _alert_thresholds['pool_usage_percent']:
        alert_key = 'pool_usage'
        if alert_key not in _last_alerts or (current_time - _last_alerts.get(alert_key, 0)) > _alert_thresholds['alert_cooldown']:
            db_logger.warning(
                f"数据库连接池告警: 使用率 {stats['usage_percent']}% 超过阈值 "
                f"(已使用: {stats['checked_out']}/{stats['total']})"
            )
            _last_alerts[alert_key] = current_time

def log_slow_query(sql: str, duration: float):
    """记录慢查询"""
    _pool_stats['slow_queries'].append({
        'sql': sql[:200] if len(sql) > 200 else sql,
        'duration': duration,
        'timestamp': time.time()
    })
    if len(_pool_stats['slow_queries']) > 1000:
        _pool_stats['slow_queries'] = _pool_stats['slow_queries'][-1000:]

def log_connection_error(error: str):
    """记录连接错误"""
    _pool_stats['connection_errors'].append({
        'error': error,
        'timestamp': time.time()
    })
    if len(_pool_stats['connection_errors']) > 100:
        _pool_stats['connection_errors'] = _pool_stats['connection_errors'][-100:]

def get_monitoring_report() -> Dict[str, Any]:
    """获取监控报告"""
    stats = get_pool_status()
    current_time = time.time()
    
    recent_slow_queries = [q for q in _pool_stats['slow_queries'] if (current_time - q['timestamp']) < 300]
    recent_errors = [e for e in _pool_stats['connection_errors'] if (current_time - e['timestamp']) < 300]
    
    return {
        'timestamp': datetime.now().isoformat(),
        'pool_status': stats,
        'peak_connections': _pool_stats['peak_connections'],
        'recent_5min': {
            'slow_queries_count': len(recent_slow_queries),
            'connection_errors_count': len(recent_errors)
        },
        'last_reset': _pool_stats['last_reset'].isoformat()
    }

def monitoring_task():
    """定时监控任务"""
    while True:
        try:
            check_pool_alerts()
            time.sleep(30)
        except Exception as e:
            db_logger.error(f"数据库监控任务异常: {e}")
            time.sleep(60)

def start_monitoring():
    """启动后台监控"""
    # 延迟导入避免循环依赖
    from .database import railway_engine, tunnel_engine
    register_engine(railway_engine)
    register_engine(tunnel_engine)
    
    monitor_thread = threading.Thread(target=monitoring_task, daemon=True)
    monitor_thread.start()
    db_logger.info("数据库连接池监控已启动")

# SQL执行时间监控
_query_start_times = {}

@event.listens_for(Engine, "before_cursor_execute")
def receive_before_cursor_execute(conn, cursor, statement, params, context, executemany):
    _query_start_times[id(cursor)] = time.time()

@event.listens_for(Engine, "after_cursor_execute")
def receive_after_cursor_execute(conn, cursor, statement, params, context, executemany):
    start_time = _query_start_times.pop(id(cursor), None)
    if start_time:
        duration = time.time() - start_time
        if duration >= _alert_thresholds['slow_query_time']:
            log_slow_query(statement, duration)
            db_logger.warning(f"慢查询: {duration:.2f}s - {statement[:100]}...")

@event.listens_for(Engine, "handle_error")
def receive_handle_error(exception_context):
    error_msg = str(exception_context.original_exception)
    log_connection_error(error_msg)
    db_logger.error(f"数据库错误: {error_msg}")

def log_pool_status():
    """记录连接池状态到日志"""
    stats = get_pool_status()
    db_logger.info(
        f"数据库连接池状态: 使用率 {stats['usage_percent']}% "
        f"(已用: {stats['checked_out']}, 空闲: {stats['checked_in']}, 总计: {stats['total']})"
    )