from sqlalchemy.orm import Session
from sqlalchemy import text, MetaData, Table, Column, create_engine, inspect
from sqlalchemy.exc import SQLAlchemyError
from typing import List, Dict, Any, Optional
from ..core.database import engine
import pandas as pd

class DatabaseService:
    @staticmethod
    def execute_sql(db: Session, sql: str) -> Dict[str, Any]:
        """执行SQL语句"""
        try:
            result = db.execute(text(sql))

            # 判断是否为SELECT查询
            if sql.strip().upper().startswith('SELECT'):
                data = []
                columns = result.keys()
                for row in result:
                    data.append(dict(zip(columns, row)))

                return {
                    "success": True,
                    "message": "查询成功",
                    "data": data
                }
            else:
                # 非SELECT语句，提交事务
                db.commit()
                return {
                    "success": True,
                    "message": "执行成功",
                    "rows_affected": result.rowcount
                }

        except SQLAlchemyError as e:
            db.rollback()
            return {
                "success": False,
                "message": f"SQL执行失败: {str(e)}"
            }
        except Exception as e:
            db.rollback()
            return {
                "success": False,
                "message": f"未知错误: {str(e)}"
            }

    @staticmethod
    def get_table_data(db: Session, table_name: str, limit: int = 100, offset: int = 0) -> Dict[str, Any]:
        """获取表数据"""
        try:
            # 先检查表是否存在
            inspector = inspect(engine)
            if table_name not in inspector.get_table_names():
                return {
                    "success": False,
                    "message": f"表 {table_name} 不存在"
                }

            # 获取总数
            count_sql = f"SELECT COUNT(*) as total FROM {table_name}"
            count_result = db.execute(text(count_sql)).fetchone()
            total_count = count_result.total if count_result else 0

            # 获取数据
            sql = f"SELECT * FROM {table_name} LIMIT {limit} OFFSET {offset}"
            result = db.execute(text(sql))

            data = []
            columns = result.keys()
            for row in result:
                data.append(dict(zip(columns, row)))

            return {
                "success": True,
                "message": "获取数据成功",
                "data": data,
                "total_count": total_count
            }

        except SQLAlchemyError as e:
            return {
                "success": False,
                "message": f"获取表数据失败: {str(e)}"
            }
        except Exception as e:
            return {
                "success": False,
                "message": f"未知错误: {str(e)}"
            }

    @staticmethod
    def create_table(db: Session, table_name: str, columns: Dict[str, str], primary_key: Optional[str] = None) -> Dict[str, Any]:
        """创建表"""
        try:
            # 构建CREATE TABLE语句
            column_definitions = []
            for col_name, col_type in columns.items():
                column_definitions.append(f"{col_name} {col_type}")

            if primary_key:
                column_definitions.append(f"PRIMARY KEY ({primary_key})")

            sql = f"CREATE TABLE {table_name} ({', '.join(column_definitions)})"

            db.execute(text(sql))
            db.commit()

            return {
                "success": True,
                "message": f"表 {table_name} 创建成功"
            }

        except SQLAlchemyError as e:
            db.rollback()
            return {
                "success": False,
                "message": f"创建表失败: {str(e)}"
            }
        except Exception as e:
            db.rollback()
            return {
                "success": False,
                "message": f"未知错误: {str(e)}"
            }

    @staticmethod
    def drop_table(db: Session, table_name: str) -> Dict[str, Any]:
        """删除表"""
        try:
            sql = f"DROP TABLE IF EXISTS {table_name}"
            db.execute(text(sql))
            db.commit()

            return {
                "success": True,
                "message": f"表 {table_name} 删除成功"
            }

        except SQLAlchemyError as e:
            db.rollback()
            return {
                "success": False,
                "message": f"删除表失败: {str(e)}"
            }
        except Exception as e:
            db.rollback()
            return {
                "success": False,
                "message": f"未知错误: {str(e)}"
            }

    @staticmethod
    def import_data(db: Session, table_name: str, data: List[Dict[str, Any]]) -> Dict[str, Any]:
        """导入数据到表"""
        try:
            if not data:
                return {
                    "success": False,
                    "message": "导入数据不能为空"
                }

            # 使用pandas DataFrame来处理数据导入
            df = pd.DataFrame(data)

            # 使用pandas的to_sql方法
            df.to_sql(table_name, engine, if_exists='append', index=False)

            return {
                "success": True,
                "message": f"成功导入 {len(data)} 条数据到表 {table_name}"
            }

        except SQLAlchemyError as e:
            db.rollback()
            return {
                "success": False,
                "message": f"导入数据失败: {str(e)}"
            }
        except Exception as e:
            db.rollback()
            return {
                "success": False,
                "message": f"未知错误: {str(e)}"
            }

    @staticmethod
    def get_table_list() -> List[str]:
        """获取所有表名"""
        try:
            inspector = inspect(engine)
            return inspector.get_table_names()
        except Exception as e:
            return []