from __future__ import annotations
from typing import Any


class DatabaseService:
    """MySQL 연결을 캡슐화하는 서비스. 미설정 시 graceful skip."""

    def __init__(self, host: str, port: int, db: str, user: str, password: str):
        self._config = dict(host=host, port=port, db=db, user=user, passwd=password)
        self._conn = None

    def connect(self) -> None:
        if not self._config["user"]:
            return
        try:
            import pymysql
            self._conn = pymysql.connect(**self._config)
        except Exception as e:
            print(f"[DB] 연결 실패 (선택적 기능): {e}")

    def execute(self, sql: str, params: tuple = ()) -> list[dict[str, Any]]:
        if self._conn is None:
            return []
        cursor = self._conn.cursor()
        cursor.execute(sql, params)
        columns = [d[0] for d in cursor.description or []]
        return [dict(zip(columns, row)) for row in cursor.fetchall()]

    def execute_write(self, sql: str, params: tuple = ()) -> int:
        """INSERT/UPDATE/DELETE 실행 후 lastrowid 반환."""
        if self._conn is None:
            return 0
        cursor = self._conn.cursor()
        cursor.execute(sql, params)
        self._conn.commit()
        return cursor.lastrowid

    def init_schema(self) -> None:
        if self._conn is None:
            return
        cursor = self._conn.cursor()
        cursor.execute("""
            CREATE TABLE IF NOT EXISTS td_conversations (
                id INT AUTO_INCREMENT PRIMARY KEY,
                created_at DATETIME DEFAULT CURRENT_TIMESTAMP
            )
        """)
        cursor.execute("""
            CREATE TABLE IF NOT EXISTS td_messages (
                id INT AUTO_INCREMENT PRIMARY KEY,
                conversation_id INT NOT NULL,
                role VARCHAR(20) NOT NULL,
                content TEXT NOT NULL,
                created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
                FOREIGN KEY (conversation_id) REFERENCES td_conversations(id)
            )
        """)
        self._conn.commit()

    def close(self) -> None:
        if self._conn:
            self._conn.close()
            self._conn = None