from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.model.conversation import ConversationFeedback, ConversationMessage
from app.model.platform import AgentRun


class ConversationRepository:
    def __init__(self, session: AsyncSession) -> None:
        self.session = session

    async def messages(
        self, session_id: str, user_id: int, limit: int, before: int | None = None
    ) -> list[ConversationMessage]:
        """按会话取一页消息（默认 `id DESC`，即最新一页）。

        `before` 与 `PlatformRepository.rows` 的游标语义一致（`id < before`，取更旧的
        一页）；`None` 表示不翻页，行为与加游标前逐字相同。游标的合法性由入口的
        `parse_cursor` 负责，这里只接受已验证的整数边界。
        """
        query = select(ConversationMessage).where(
            ConversationMessage.session_id == session_id,
            ConversationMessage.customer_id == user_id,
        )
        if before is not None:
            query = query.where(ConversationMessage.id < before)
        return list(await self.session.scalars(
            query.order_by(ConversationMessage.id.desc()).limit(limit)))

    async def message(self, message_id: int, user_id: int) -> ConversationMessage | None:
        statement = select(ConversationMessage).where(
            ConversationMessage.id == message_id, ConversationMessage.customer_id == user_id,
        ).with_for_update()
        row: ConversationMessage | None = await self.session.scalar(statement)
        return row

    async def feedback(self, message_id: int, user_id: int) -> ConversationFeedback | None:
        statement = select(ConversationFeedback).where(
            ConversationFeedback.message_id == message_id,
            ConversationFeedback.customer_id == user_id,
        )
        row: ConversationFeedback | None = await self.session.scalar(statement)
        return row

    async def run_result(
        self, run_id: str, user_id: int
    ) -> tuple[AgentRun, ConversationMessage | None] | None:
        run = await self.session.scalar(select(AgentRun).where(
            AgentRun.run_id == run_id, AgentRun.user_id == user_id))
        if run is None:
            return None
        message = (await self.session.get(ConversationMessage, run.result_message_id)
                   if run.result_message_id else None)
        return run, message