from __future__ import annotations
from services.db.mysql_service import DatabaseService


class ConversationRepository:
    """td_conversations / td_messages 테이블 접근을 담당하는 Repository."""

    def __init__(self, db: DatabaseService):
        self._db = db

    def create_conversation(self) -> int:
        return self._db.execute_write(
            "INSERT INTO td_conversations () VALUES ()"
        )

    def get_latest_conversation_id(self) -> int | None:
        rows = self._db.execute(
            "SELECT id FROM td_conversations ORDER BY created_at DESC LIMIT 1"
        )
        return rows[0]["id"] if rows else None

    def save_message(self, conversation_id: int, role: str, content: str) -> None:
        self._db.execute_write(
            "INSERT INTO td_messages (conversation_id, role, content) VALUES (%s, %s, %s)",
            (conversation_id, role, content),
        )

    def save_summary(self, conversation_id: int, summary: str) -> None:
        self._db.execute_write(
            "INSERT INTO td_messages (conversation_id, role, content) VALUES (%s, %s, %s)",
            (conversation_id, "summary", summary),
        )

    def get_latest_summary(self, conversation_id: int) -> tuple[int | None, str | None]:
        """가장 최근 요약 메시지의 (id, content)를 반환. 없으면 (None, None)."""
        rows = self._db.execute(
            """SELECT id, content FROM td_messages
               WHERE conversation_id = %s AND role = 'summary'
               ORDER BY created_at DESC LIMIT 1""",
            (conversation_id,),
        )
        if rows:
            return rows[0]["id"], rows[0]["content"]
        return None, None

    def load_turns_after(
        self, conversation_id: int, after_id: int | None, limit: int
    ) -> list[dict]:
        """요약 이후의 user/assistant 턴을 최근 limit개 반환."""
        if after_id is not None:
            rows = self._db.execute(
                """SELECT role, content FROM td_messages
                   WHERE conversation_id = %s AND id > %s AND role IN ('user', 'assistant')
                   ORDER BY created_at DESC LIMIT %s""",
                (conversation_id, after_id, limit),
            )
        else:
            rows = self._db.execute(
                """SELECT role, content FROM td_messages
                   WHERE conversation_id = %s AND role IN ('user', 'assistant')
                   ORDER BY created_at DESC LIMIT %s""",
                (conversation_id, limit),
            )
        return list(reversed(rows))