from __future__ import annotations
import threading
from typing import Any


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

    스레드별 독립 연결(thread-local)을 사용해 LangGraph ToolNode의
    스레드 풀 실행과 pymysql 비안전성 문제를 해결한다.
    """

    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._local = threading.local()

    # ── DB 연결 ────────────────────────────────────────────────────────

    def _get_conn(self):
        if not self._config["user"]:
            return None

        import pymysql
        conn = getattr(self._local, "conn", None)
        if conn is None:
            try:
                self._local.conn = pymysql.connect(**self._config)
            except Exception as e:
                print(f"[DB] 연결 실패: {e}")
                return None
        else:
            try:
                conn.ping(reconnect=True)
            except Exception:
                try:
                    self._local.conn = pymysql.connect(**self._config)
                except Exception as e:
                    print(f"[DB] 재연결 실패: {e}")
                    return None
        return self._local.conn

    def connect(self) -> None:
        self._get_conn()

    def execute(self, sql: str, params: tuple = ()) -> list[dict[str, Any]]:
        conn = self._get_conn()
        if conn is None:
            return []
        cursor = 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:
        conn = self._get_conn()
        if conn is None:
            return 0
        cursor = conn.cursor()
        cursor.execute(sql, params)
        conn.commit()
        return cursor.lastrowid

    def init_schema(self) -> None:
        conn = self._get_conn()
        if conn is None:
            return
        cursor = conn.cursor()
        cursor.execute("""
            CREATE TABLE IF NOT EXISTS td_conversations (
                id INT AUTO_INCREMENT PRIMARY KEY,
                user_id VARCHAR(50) NOT NULL DEFAULT 'default',
                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)
            )
        """)
        cursor.execute("""
            CREATE TABLE IF NOT EXISTS td_user_profile (
                id INT AUTO_INCREMENT PRIMARY KEY,
                user_id VARCHAR(50) NOT NULL DEFAULT 'default',
                key_name VARCHAR(100) NOT NULL,
                value TEXT NOT NULL,
                updated_at DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
                UNIQUE KEY uq_user_key (user_id, key_name)
            )
        """)
        cursor.execute("""
            CREATE TABLE IF NOT EXISTS td_feedback (
                id INT AUTO_INCREMENT PRIMARY KEY,
                user_id VARCHAR(50) NOT NULL DEFAULT 'default',
                message TEXT,
                response TEXT,
                rating TINYINT,
                langsmith_run_id VARCHAR(100),
                created_at DATETIME DEFAULT CURRENT_TIMESTAMP
            )
        """)
        cursor.execute("""
            CREATE TABLE IF NOT EXISTS td_reminders (
                id INT AUTO_INCREMENT PRIMARY KEY,
                user_id VARCHAR(50) NOT NULL,
                remind_date DATE NOT NULL,
                message TEXT NOT NULL,
                sent_d0 TINYINT(1) NOT NULL DEFAULT 0,
                sent_d1 TINYINT(1) NOT NULL DEFAULT 0,
                sent_d7 TINYINT(1) NOT NULL DEFAULT 0,
                created_at DATETIME DEFAULT CURRENT_TIMESTAMP
            )
        """)
        conn.commit()
        self._migrate_schema(conn)

    def _migrate_schema(self, conn) -> None:
        cursor = conn.cursor()
        for sql in [
            "ALTER TABLE td_conversations ADD COLUMN user_id VARCHAR(50) NOT NULL DEFAULT 'default'",
            "ALTER TABLE td_user_profile ADD COLUMN user_id VARCHAR(50) NOT NULL DEFAULT 'default'",
            "ALTER TABLE td_user_profile DROP INDEX key_name",
            "ALTER TABLE td_user_profile ADD UNIQUE KEY uq_user_key (user_id, key_name)",
        ]:
            try:
                cursor.execute(sql)
                conn.commit()
            except Exception:
                pass

    def close(self) -> None:
        conn = getattr(self._local, "conn", None)
        if conn:
            conn.close()
            self._local.conn = None