# app/services/slot_snapshot_service.py

from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, func, desc, and_
from redis.asyncio import Redis
from typing import List, Dict, Any
from app.models.slot_snapshot import VasSlotSnapshot
from app.schemas.slot_snapshot import SlotSnapshotCreate, SlotSnapshotOut
from app.services.notification_service import NotificationService
from app.models.slot_snapshot import VasSlotSnapshot
from app.models.slot_refresh_status import VasSlotRefreshStatus


class SlotSnapshotService:

    @staticmethod
    async def report(
        db: AsyncSession,
        redis_client: Redis,
        data: SlotSnapshotCreate
    ) -> VasSlotSnapshot:
        rec = VasSlotSnapshot(**data.dict())
        db.add(rec)
        await db.commit()
        await db.refresh(rec) 
        # 修复点在这里：手动将 datetime 对象转为 string
        earliest_date_str = rec.earliest_date.isoformat() if rec.earliest_date else None
        snapshot_at_str = rec.snapshot_at.isoformat() if rec.snapshot_at else None

        await NotificationService.post_wechat(
            redis_client=redis_client,
            template_id="slot_snapshot",
            payload={
                "country": rec.country,
                "city": rec.city,
                "visa_type": rec.visa_type,
                "routing_key": rec.routing_key,
                "availability_status": rec.availability_status,
                # 使用转换后的字符串
                "earliest_date": earliest_date_str,
                "availability": rec.availability,
                "snapshot_source": rec.snapshot_source,
                "snapshot_at": snapshot_at_str
            }
        )
        return rec

    @staticmethod
    async def latest_for(
        db: AsyncSession,
        country: str,
        city: str,
        visa_type: str
    ) -> VasSlotSnapshot:
        stmt = (
            select(VasSlotSnapshot)
            .where(
                VasSlotSnapshot.country == country,
                VasSlotSnapshot.city == city,
                VasSlotSnapshot.visa_type == visa_type,
            )
            .order_by(VasSlotSnapshot.snapshot_at.desc())
            .limit(1)
        )

        return await db.scalar(stmt)
    
    async def get_slot_overview(db: AsyncSession, city: str) -> List[Dict[str, Any]]:
        """
        异步获取指定城市的最新 Slot 快照 dashboard 数据
        修正逻辑：按 (Country, City, VisaType) 这一组业务主键去重，只取最新的一条。
        """
        
        # 1. 子查询：找出该城市下，每个【业务类型】最新的一条记录 ID
        # 也就是：在同一个城市、同一个国家、同一个签证类型下，只取 ID 最大的那条
        subquery = (
            select(func.max(VasSlotSnapshot.id).label("max_id"))
            .where(VasSlotSnapshot.city == city)
            .group_by(
                VasSlotSnapshot.country, 
                VasSlotSnapshot.city, 
                VasSlotSnapshot.visa_type
            )
            .subquery()
        )

        # 2. 主查询
        # Join 逻辑修改：
        # - Inner Join 子查询：确保只拿到最新的 snapshot
        # - Outer Join 状态表：不再仅依赖 routing_key (因为 snapshot 里可能是 null)，
        #   而是通过 country/city/visa_type 强关联，这样即使 routing_key 丢失也能匹配到状态。
        stmt = (
            select(VasSlotSnapshot, VasSlotRefreshStatus)
            .join(subquery, VasSlotSnapshot.id == subquery.c.max_id)
            .outerjoin(
                VasSlotRefreshStatus, 
                and_(
                    VasSlotSnapshot.country == VasSlotRefreshStatus.country,
                    VasSlotSnapshot.city == VasSlotRefreshStatus.city,
                    VasSlotSnapshot.visa_type == VasSlotRefreshStatus.visa_type
                )
            )
            .order_by(VasSlotSnapshot.country)
        )

        # 3. 执行查询
        result = await db.execute(stmt)
        rows = result.all()

        # 4. 组装数据
        dashboard_data = []
        
        for row in rows:
            snap: VasSlotSnapshot = row[0]
            status: VasSlotRefreshStatus = row[1]

            item = {
                "id": snap.id,
                "country": snap.country,
                "city": snap.city,
                "visa_type": snap.visa_type,
                "routing_key": snap.routing_key, # 即使是 null 也没关系，展示用
                "availability_status": snap.availability_status,
                "earliest_date": snap.earliest_date,
                "snapshot_at": snap.snapshot_at,
                "website": snap.website,
                # 优先从 status 表取心跳，如果关联不上，就为 null
                "last_check_at": status.last_success_at if status else None
            }
            
            if snap.availability:
                item["availability"] = snap.availability

            dashboard_data.append(item)

        return dashboard_data