#!/usr/bin/env python3
# -*- coding: utf-8 -*-

"""
数据库连接管理
提供连接池和连接获取功能
"""

import logging
import os
import json
from typing import Dict, Any, Optional
from pathlib import Path
from contextlib import contextmanager

logger = logging.getLogger(__name__)

try:
    import mysql.connector
    from mysql.connector import pooling
    MYSQL_AVAILABLE = True
except ImportError:
    MYSQL_AVAILABLE = False
    logger.warning("mysql-connector-python 未安装")


class DatabaseConnection:
    """
    数据库连接管理器
    
    提供：
    - 连接池管理
    - 连接获取和释放
    - 配置加载
    """
    
    _instance: Optional['DatabaseConnection'] = None
    
    def __new__(cls, config_path: Optional[str] = None):
        """单例模式"""
        if cls._instance is None:
            cls._instance = super().__new__(cls)
            cls._instance._initialized = False
        return cls._instance
    
    def __init__(self, config_path: Optional[str] = None):
        if self._initialized:
            return
        
        self._config_path = config_path
        self._pool = None
        self._config: Dict[str, Any] = {}
        
        self._load_config()
        self._init_pool()
        self._initialized = True
    
    def _load_config(self):
        """加载数据库配置"""
        # 尝试从配置文件加载
        if self._config_path:
            config_file = Path(self._config_path)
        else:
            # 默认配置路径
            config_file = Path(__file__).parent.parent.parent / "config" / "database.json"
        
        if config_file.exists():
            try:
                with open(config_file, 'r', encoding='utf-8') as f:
                    raw_config = json.load(f)
                self._config = self._process_env_vars(raw_config)
                logger.info(f"从配置文件加载数据库配置: {config_file}")
            except Exception as e:
                logger.warning(f"加载配置文件失败: {e}")
        
        # 使用环境变量作为兜底
        if not self._config:
            self._config = {
                'host': os.getenv('DB_HOST', 'localhost'),
                'user': os.getenv('DB_USER', 'root'),
                'password': os.getenv('DB_PASSWORD', ''),
                'database': os.getenv('DB_NAME', 'travel_content'),
                'port': int(os.getenv('DB_PORT', '3306')),
                'charset': 'utf8mb4',
                'pool_size': int(os.getenv('DB_POOL_SIZE', '10'))
            }
            logger.info("使用环境变量构建数据库配置")
    
    def _process_env_vars(self, config: Dict[str, Any]) -> Dict[str, Any]:
        """处理配置中的环境变量引用"""
        processed = {}
        for key, value in config.items():
            if isinstance(value, str) and value.startswith('${') and value.endswith('}'):
                env_key = value[2:-1]
                processed[key] = os.getenv(env_key, '')
            else:
                processed[key] = value
        return processed
    
    def _init_pool(self):
        """初始化连接池"""
        if not MYSQL_AVAILABLE:
            logger.error("mysql-connector-python 未安装，无法创建连接池")
            return
        
        try:
            pool_config = {
                'pool_name': 'travel_pool',
                'pool_size': self._config.get('pool_size', 10),
                'host': self._config.get('host', 'localhost'),
                'port': self._config.get('port', 3306),
                'user': self._config.get('user', 'root'),
                'password': self._config.get('password', ''),
                'database': self._config.get('database', 'travel_content'),
                'charset': self._config.get('charset', 'utf8mb4'),
                'autocommit': True,
            }
            
            self._pool = pooling.MySQLConnectionPool(**pool_config)
            logger.info(f"数据库连接池初始化成功: {pool_config['host']}:{pool_config['port']}/{pool_config['database']}")
            
        except Exception as e:
            logger.error(f"初始化数据库连接池失败: {e}")
            self._pool = None
    
    @contextmanager
    def get_connection(self):
        """
        获取数据库连接 (上下文管理器)
        
        Usage:
            with db.get_connection() as conn:
                cursor = conn.cursor(dictionary=True)
                cursor.execute("SELECT * FROM ...")
        """
        if not self._pool:
            raise RuntimeError("数据库连接池未初始化")
        
        conn = None
        try:
            conn = self._pool.get_connection()
            yield conn
        finally:
            if conn:
                conn.close()
    
    @contextmanager
    def get_cursor(self, dictionary: bool = True):
        """
        获取数据库游标 (上下文管理器)
        
        Usage:
            with db.get_cursor() as cursor:
                cursor.execute("SELECT * FROM ...")
                results = cursor.fetchall()
        """
        with self.get_connection() as conn:
            cursor = conn.cursor(dictionary=dictionary)
            try:
                yield cursor
            finally:
                cursor.close()
    
    def execute_query(self, query: str, params: tuple = None) -> list:
        """
        执行查询并返回结果
        
        Args:
            query: SQL 查询语句
            params: 查询参数
            
        Returns:
            查询结果列表
        """
        with self.get_cursor() as cursor:
            cursor.execute(query, params or ())
            return cursor.fetchall()
    
    def execute_one(self, query: str, params: tuple = None) -> Optional[Dict[str, Any]]:
        """
        执行查询并返回单条结果
        
        Args:
            query: SQL 查询语句
            params: 查询参数
            
        Returns:
            单条结果或 None
        """
        with self.get_cursor() as cursor:
            cursor.execute(query, params or ())
            return cursor.fetchone()
    
    def execute_update(self, query: str, params: tuple = None) -> int:
        """
        执行更新语句
        
        Args:
            query: SQL 更新语句
            params: 更新参数
            
        Returns:
            影响的行数
        """
        with self.get_connection() as conn:
            cursor = conn.cursor()
            try:
                cursor.execute(query, params or ())
                conn.commit()
                return cursor.rowcount
            finally:
                cursor.close()
    
    @property
    def is_connected(self) -> bool:
        """检查连接池是否可用"""
        return self._pool is not None
    
    def get_info(self) -> Dict[str, Any]:
        """获取连接信息"""
        return {
            'host': self._config.get('host'),
            'port': self._config.get('port'),
            'database': self._config.get('database'),
            'pool_size': self._config.get('pool_size'),
            'is_connected': self.is_connected,
        }