import uuid
from datetime import datetime, timedelta, timezone

from sqlalchemy import select, func, and_, case
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.usage_record import UsageRecord


_PERIOD_CUTOFF_DAYS = {"day": 0, "week": 7, "month": 30}
_QUOTA_WARNING_PCT = 80.0
_QUOTA_EXCEEDED_PCT = 100.0


def _compute_cutoff(period: str, now: datetime) -> datetime:
    days = _PERIOD_CUTOFF_DAYS.get(period, 30)
    if days == 0:
        return now.replace(hour=0, minute=0, second=0, microsecond=0)
    return now - timedelta(days=days)


def _quota_status(usage_pct: float) -> str:
    if usage_pct >= _QUOTA_EXCEEDED_PCT:
        return "exceeded"
    if usage_pct >= _QUOTA_WARNING_PCT:
        return "warning"
    return "ok"


class UsageRepository:
    def __init__(self, session: AsyncSession):
        self.session = session

    async def create(self, data: dict) -> UsageRecord:
        record = UsageRecord(
            user_id=data["user_id"],
            brand_id=data.get("brand_id"),
            engine_type=data["engine_type"],
            query=data["query"],
            input_tokens=data.get("input_tokens", 0),
            output_tokens=data.get("output_tokens", 0),
            cost=data.get("cost", 0.0),
            extra_data=data.get("extra_data", {}),
            timestamp=data.get("timestamp", datetime.now(timezone.utc)),
        )
        self.session.add(record)
        await self.session.commit()
        await self.session.refresh(record)
        return record

    async def get_summary(
        self,
        user_id: str | uuid.UUID,
        period: str = "month",
        brand_id: str | uuid.UUID | None = None,
    ) -> dict:
        now = datetime.now(timezone.utc)
        cutoff = _compute_cutoff(period, now)
        
        if isinstance(user_id, str):
            user_id = uuid.UUID(user_id)
        if brand_id and isinstance(brand_id, str):
            brand_id = uuid.UUID(brand_id)

        conditions = [
            UsageRecord.user_id == user_id,
            UsageRecord.timestamp >= cutoff,
        ]
        if brand_id:
            conditions.append(UsageRecord.brand_id == brand_id)

        result = await self.session.execute(
            select(UsageRecord).where(and_(*conditions))
        )
        records = list(result.scalars().all())

        total_queries = len(records)
        total_input_tokens = sum(r.input_tokens for r in records)
        total_output_tokens = sum(r.output_tokens for r in records)
        total_cost = round(sum(r.cost for r in records), 4)

        by_engine: dict[str, dict] = {}
        for r in records:
            bucket = by_engine.setdefault(
                r.engine_type,
                {"queries": 0, "input_tokens": 0, "output_tokens": 0, "cost": 0.0}
            )
            bucket["queries"] += 1
            bucket["input_tokens"] += r.input_tokens
            bucket["output_tokens"] += r.output_tokens
            bucket["cost"] = round(bucket["cost"] + r.cost, 4)

        by_day: dict[str, dict] = {}
        for r in records:
            day_key = r.timestamp.strftime("%Y-%m-%d")
            bucket = by_day.setdefault(
                day_key,
                {"queries": 0, "input_tokens": 0, "output_tokens": 0, "cost": 0.0}
            )
            bucket["queries"] += 1
            bucket["input_tokens"] += r.input_tokens
            bucket["output_tokens"] += r.output_tokens
            bucket["cost"] = round(bucket["cost"] + r.cost, 4)

        return {
            "period": period,
            "start_date": cutoff.isoformat(),
            "end_date": now.isoformat(),
            "total_queries": total_queries,
            "total_input_tokens": total_input_tokens,
            "total_output_tokens": total_output_tokens,
            "total_cost": total_cost,
            "by_engine": by_engine,
            "by_day": by_day,
        }

    async def check_quota(
        self,
        user_id: str | uuid.UUID,
        monthly_limit: float = 100.0,
    ) -> dict:
        summary = await self.get_summary(user_id=user_id, period="month")
        usage_pct = (summary["total_cost"] / monthly_limit * 100) if monthly_limit > 0 else 0
        return {
            "used": summary["total_cost"],
            "limit": monthly_limit,
            "usage_percentage": round(usage_pct, 1),
            "status": _quota_status(usage_pct),
        }

    async def get_by_id(self, record_id: uuid.UUID) -> UsageRecord | None:
        result = await self.session.execute(
            select(UsageRecord).where(UsageRecord.id == record_id)
        )
        return result.scalar_one_or_none()

    async def get_by_user(
        self,
        user_id: str | uuid.UUID,
        limit: int = 100,
        offset: int = 0,
    ) -> list[UsageRecord]:
        if isinstance(user_id, str):
            user_id = uuid.UUID(user_id)

        result = await self.session.execute(
            select(UsageRecord)
            .where(UsageRecord.user_id == user_id)
            .order_by(UsageRecord.timestamp.desc())
            .limit(limit)
            .offset(offset)
        )
        return list(result.scalars().all())

    async def get_by_user_and_engine(
        self,
        user_id: str | uuid.UUID,
        engine_type: str,
        limit: int = 100,
    ) -> list[UsageRecord]:
        if isinstance(user_id, str):
            user_id = uuid.UUID(user_id)

        result = await self.session.execute(
            select(UsageRecord)
            .where(
                and_(
                    UsageRecord.user_id == user_id,
                    UsageRecord.engine_type == engine_type,
                )
            )
            .order_by(UsageRecord.timestamp.desc())
            .limit(limit)
        )
        return list(result.scalars().all())