from fastapi import HTTPException
from sqlalchemy.orm import Session

from models.credit import CreditAccount, CreditTransaction
from models.user import User

DEFAULT_CREDIT_BALANCE = 130
DAILY_CHECKIN_CREDITS = 10

CREDIT_COSTS = {
    "courseware_generate": 8,
    "animation_generate": 6,
    "exercise_generate": 4,
    "lesson_plan_generate": 5,
    "exam_generate": 5,
    "essay_grade": 2,
    "chat_generate": 1,
    "material_parse": 1,
}


def ensure_credit_account(db: Session, user: User) -> CreditAccount:
    account = db.query(CreditAccount).filter(CreditAccount.user_id == user.id).first()
    if account:
        return account
    account = CreditAccount(
        user_id=user.id,
        balance=DEFAULT_CREDIT_BALANCE,
        total_granted=DEFAULT_CREDIT_BALANCE,
        total_used=0,
    )
    db.add(account)
    db.flush()
    return account


def spend_credits(db: Session, user: User, action: str, description: str = "") -> CreditAccount:
    cost = CREDIT_COSTS.get(action, 1)
    account = ensure_credit_account(db, user)
    if account.balance < cost:
        raise HTTPException(status_code=402, detail=f"积分不足，本次需要 {cost} 分，当前剩余 {account.balance} 分")
    account.balance -= cost
    account.total_used += cost
    db.add(CreditTransaction(
        user_id=user.id,
        amount=-cost,
        action=action,
        description=description,
        balance_after=account.balance,
    ))
    db.flush()
    return account


def credits_payload(account: CreditAccount, action: str) -> dict:
    return {
        "balance": account.balance,
        "cost": CREDIT_COSTS.get(action, 1),
        "action": action,
    }


def grant_credits(db: Session, user: User, amount: int, action: str = "grant", description: str = "") -> CreditAccount:
    if amount <= 0:
        raise HTTPException(status_code=400, detail="积分数量必须大于 0")
    account = ensure_credit_account(db, user)
    account.balance += amount
    account.total_granted += amount
    db.add(CreditTransaction(
        user_id=user.id,
        amount=amount,
        action=action,
        description=description,
        balance_after=account.balance,
    ))
    db.flush()
    return account


def has_credit_transaction_today(db: Session, user: User, action: str) -> bool:
    from datetime import datetime, time

    today = datetime.now().date()
    start = datetime.combine(today, time.min)
    end = datetime.combine(today, time.max)
    return db.query(CreditTransaction).filter(
        CreditTransaction.user_id == user.id,
        CreditTransaction.action == action,
        CreditTransaction.created_at >= start,
        CreditTransaction.created_at <= end,
    ).first() is not None


def grant_daily_checkin(db: Session, user: User) -> CreditAccount:
    if has_credit_transaction_today(db, user, "daily_checkin"):
        raise HTTPException(status_code=409, detail="今日积分已领取")
    return grant_credits(
        db,
        user,
        DAILY_CHECKIN_CREDITS,
        action="daily_checkin",
        description="每日登录领取积分",
    )