"""念念回音服务"""

import hashlib
import uuid
from datetime import datetime

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

from app.models.miss_echo import MissEcho
from app.models.user import User
from app.websocket.events import EventType
from app.websocket.manager import manager


class EchoService:
    def __init__(self, db: AsyncSession):
        self.db = db

    async def send_echo(self, from_user_id: str, to_user_id: str,
                        message: str | None = None) -> dict:
        """发送一片回音叶"""
        if from_user_id == to_user_id:
            raise ValueError("不能给自己回音")

        # 校验目标用户存在
        target_result = await self.db.execute(select(User).where(User.id == to_user_id))
        if not target_result.scalars().first():
            raise ValueError("目标用户不存在")

        # 派生叶子种子
        today = datetime.utcnow().strftime("%Y%m%d")
        seed = hashlib.md5(f"echo:{from_user_id}:{to_user_id}:{today}".encode()).hexdigest()[:16]

        is_online = manager.is_online(to_user_id)

        echo = MissEcho(
            id=str(uuid.uuid4()),
            from_user_id=from_user_id,
            to_user_id=to_user_id,
            leaf_seed=seed,
            message=message,
            delivered_online=is_online,
        )
        self.db.add(echo)
        await self.db.flush()

        # 发送者信息
        from_result = await self.db.execute(select(User).where(User.id == from_user_id))
        from_user = from_result.scalars().first()

        payload = {
            "id": echo.id,
            "from_user_id": from_user_id,
            "from_username": from_user.username if from_user else "未知",
            "from_nickname": from_user.nickname if from_user else None,
            "from_avatar": from_user.avatar_url if from_user else None,
            "leaf_seed": seed,
            "message": message,
            "delivered_online": is_online,
            "created_at": echo.created_at.isoformat(),
        }

        # 在线则实时推送，离线则在用户下次打开时收到（落入花园）
        if is_online:
            await manager.send_to_user(to_user_id, EventType.ECHO_SEND, payload)

        return payload

    async def get_echoes(self, user_id: str, limit: int = 30) -> list[dict]:
        """获取我收到的回音（花园里飘落的叶子）"""
        result = await self.db.execute(
            select(MissEcho).where(
                or_(
                    MissEcho.to_user_id == user_id,
                    MissEcho.from_user_id == user_id,
                )
            ).order_by(MissEcho.created_at.desc()).limit(limit)
        )
        echoes = []
        for e in result.scalars().all():
            from_result = await self.db.execute(select(User).where(User.id == e.from_user_id))
            fu = from_result.scalars().first()
            echoes.append({
                "id": e.id,
                "from_user_id": e.from_user_id,
                "to_user_id": e.to_user_id,
                "from_username": fu.username if fu else "未知",
                "from_nickname": fu.nickname if fu else None,
                "from_avatar": fu.avatar_url if fu else None,
                "leaf_seed": e.leaf_seed,
                "message": e.message,
                "delivered_online": e.delivered_online,
                "is_received": e.to_user_id == user_id,
                "created_at": e.created_at.isoformat(),
            })
        return echoes