from sqlalchemy import create_engine
from sqlalchemy.engine import Engine
from sqlalchemy.orm import sessionmaker
from contextlib import contextmanager
from typing import Optional
from app.core.config import settings


class DatabaseConnector:
    """Управление подключениями к базам данных"""

    def __init__(self):
        self._src_engine: Optional[Engine] = None
        self._dst_engine: Optional[Engine] = None
        self.dst_session = None
        self.schedule_session = None

    @property
    def src_engine(self) -> Engine:
        """Подключение к MSSQL"""
        if not self._src_engine:
            self._src_engine = create_engine(
                settings.MSSQL_CONNECTION_STRING,
                pool_pre_ping=True,
                echo=settings.DEBUG
            )
        return self._src_engine

    @property
    def dst_engine(self) -> Engine:
        """Подключение к PostgreSQL (основная БД)"""
        if not self._dst_engine:
            self._dst_engine = create_engine(
                settings.POSTGRES_CONNECTION_STRING,
                pool_pre_ping=True,
                echo=settings.DEBUG
            )
            self.dst_session = sessionmaker(bind=self._dst_engine)
        return self._dst_engine

    @contextmanager
    def src_connection(self):
        """Контекстный менеджер для MSSQL соединения"""
        conn = self.src_engine.connect()
        try:
            yield conn
        finally:
            conn.close()

    @contextmanager
    def dst_connection(self):
        """Контекстный менеджер для PostgreSQL соединения"""
        conn = self.dst_engine.connect()
        try:
            yield conn
        finally:
            conn.close()

    def dispose_engines(self):
        """Закрытие всех соединений"""
        if self._src_engine:
            self._src_engine.dispose()
        if self._dst_engine:
            self._dst_engine.dispose()


# Глобальный экземпляр подключений
db_connector = DatabaseConnector()