#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
PostgreSQL 数据库操作模块
支持基本的增删改查操作
"""

import sys
try:
    import psycopg2
    from psycopg2.extras import RealDictCursor
except ImportError as e:
    print(f"错误: 无法导入 psycopg2 库，请确保已安装: pip install psycopg2-binary")
    print(f"详细错误: {e}")
    sys.exit(1)


class PostgreSQLDatabase:
    """PostgreSQL 数据库连接和操作类"""
    
    def __init__(self, host='localhost', port=5432, user='postgres', password='', database='postgres'):
        """
        初始化 PostgreSQL 连接参数
        :param host: 数据库主机地址
        :param port: 数据库端口
        :param user: 用户名
        :param password: 密码
        :param database: 数据库名（默认postgres系统数据库）
        """
        self.host = host
        self.port = port
        self.user = user
        self.password = password
        self.database = database
        self.connection = None
    
    def connect(self):
        """建立数据库连接"""
        try:
            self.connection = psycopg2.connect(
                host=self.host,
                port=self.port,
                user=self.user,
                password=self.password,
                database=self.database,
                cursor_factory=RealDictCursor,
                connect_timeout=5
            )
            return True, "PostgreSQL 连接成功"
        except Exception as e:
            return False, f"PostgreSQL 连接失败: {str(e)}"
    
    def execute(self, sql, params=None):
        """
        执行 SQL 语句
        :param sql: SQL 语句
        :param params: 参数（可选）
        :return: 执行结果
        """
        if not self.connection:
            return False, "未连接到数据库"
        
        try:
            with self.connection.cursor() as cursor:
                cursor.execute(sql, params)
                
                # 判断是查询还是修改操作
                if sql.strip().upper().startswith(('SELECT', 'SHOW', 'WITH')):
                    result = cursor.fetchall()
                    # 转换为字典列表
                    return True, [dict(row) for row in result]
                else:
                    self.connection.commit()
                    return True, f"影响行数: {cursor.rowcount}"
        except Exception as e:
            self.connection.rollback()
            return False, f"执行失败: {str(e)}"
    
    def list_databases(self):
        """列出所有数据库"""
        if not self.connection:
            return False, "未连接到数据库"
        try:
            with self.connection.cursor() as cursor:
                cursor.execute("SELECT datname FROM pg_database WHERE datistemplate = false ORDER BY datname")
                result = cursor.fetchall()
                databases = [db['datname'] for db in result]
                return True, databases
        except Exception as e:
            return False, f"获取数据库列表失败: {str(e)}"
    
    def use_database(self, database):
        """切换到指定数据库（需要重新连接）"""
        if not self.connection:
            return False, "未连接到数据库"
        try:
            # PostgreSQL 需要重新连接来切换数据库
            self.connection.close()
            self.database = database
            return self.connect()
        except Exception as e:
            return False, f"切换数据库失败: {str(e)}"
    
    def close(self):
        """关闭数据库连接"""
        if self.connection:
            self.connection.close()
            self.connection = None
            return "PostgreSQL 连接已关闭"
        return "连接已经关闭"