import uuid
from decimal import Decimal

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

from app.models import User, Transaction
from app.core.exceptions import BadRequestError

# MVP: hardcoded redeem codes → amount mapping
REDEEM_CODES = {
    "SUPERDREAM10": Decimal("10"),
    "SUPERDREAM50": Decimal("50"),
    "SUPERDREAM100": Decimal("100"),
}


class WalletService:

    @staticmethod
    async def get_balance(db: AsyncSession, user_id: str) -> Decimal:
        user = await db.get(User, user_id)
        return user.balance

    @staticmethod
    async def redeem_code(db: AsyncSession, user_id: str, code: str) -> Transaction:
        amount = REDEEM_CODES.get(code.upper())
        if not amount:
            raise BadRequestError("无效的兑换码")

        user = await db.get(User, user_id)
        user.balance += amount
        new_balance = user.balance

        txn = Transaction(
            id=str(uuid.uuid4()),
            user_id=user_id,
            type="topup",
            amount=amount,
            balance_after=new_balance,
            reference_id=f"redeem:{code.upper()}",
        )
        db.add(txn)
        await db.commit()
        await db.refresh(txn)
        return txn

    @staticmethod
    async def list_transactions(
        db: AsyncSession, user_id: str, page: int = 1, size: int = 20
    ) -> list:
        offset = (page - 1) * size
        result = await db.execute(
            select(Transaction)
            .where(Transaction.user_id == user_id)
            .order_by(Transaction.created_at.desc())
            .offset(offset)
            .limit(size)
        )
        return result.scalars().all()