from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select
from app.database import get_db
from app.api.v1.deps import get_current_user_id
from app.models.referral import ReferralCode, Referral
from app.models.subscription import Subscription
from app.models.user import User
from app.config import settings
from datetime import datetime, timedelta
import uuid
import secrets
import string

router = APIRouter()


def generate_code() -> str:
    return "TM" + "".join(secrets.choice(string.ascii_uppercase + string.digits) for _ in range(6))


@router.post("/code")
async def get_or_create_code(
    user_id: str = Depends(get_current_user_id),
    db: AsyncSession = Depends(get_db),
):
    result = await db.execute(select(ReferralCode).where(ReferralCode.user_id == user_id))
    existing = result.scalar_one_or_none()
    if existing:
        return {"code": existing.code, "url": f"/workspace/?ref={existing.code}"}

    code = generate_code()
    while True:
        check = await db.execute(select(ReferralCode).where(ReferralCode.code == code))
        if not check.scalar_one_or_none():
            break
        code = generate_code()

    rc = ReferralCode(user_id=user_id, code=code)
    db.add(rc)
    await db.commit()
    return {"code": code, "url": f"/workspace/?ref={code}"}


@router.get("/stats")
async def get_referral_stats(
    user_id: str = Depends(get_current_user_id),
    db: AsyncSession = Depends(get_db),
):
    result = await db.execute(select(Referral).where(Referral.referrer_id == user_id))
    referrals = result.scalars().all()
    total_reward_days = sum(r.reward_days for r in referrals if r.status == "completed")
    return {
        "total_referrals": len(referrals),
        "completed": sum(1 for r in referrals if r.status == "completed"),
        "total_reward_days": total_reward_days,
    }


async def apply_referral(code: str, new_user_id: str, db: AsyncSession):
    rc_result = await db.execute(select(ReferralCode).where(ReferralCode.code == code))
    rc = rc_result.scalar_one_or_none()
    if not rc:
        return

    if str(rc.user_id) == new_user_id:
        return

    existing = await db.execute(select(Referral).where(Referral.referred_id == new_user_id))
    if existing.scalar_one_or_none():
        return

    reward_days = 15

    referrer_sub = await db.execute(
        select(Subscription).where(
            Subscription.user_id == rc.user_id,
            Subscription.status == "active",
        ).order_by(Subscription.created_at.desc()).limit(1)
    )
    referrer_sub_row = referrer_sub.scalar_one_or_none()
    if referrer_sub_row:
        old_expiry = referrer_sub_row.expires_at or datetime.utcnow()
        referrer_sub_row.expires_at = old_expiry + timedelta(days=reward_days)
    else:
        new_sub = Subscription(
            user_id=rc.user_id,
            plan="pro_trial",
            status="active",
            started_at=datetime.utcnow(),
            expires_at=datetime.utcnow() + timedelta(days=reward_days),
        )
        db.add(new_sub)
        user_result = await db.execute(select(User).where(User.id == rc.user_id))
        u = user_result.scalar_one_or_none()
        if u and u.tier == "free":
            u.tier = "pro"

    user_result = await db.execute(select(User).where(User.id == new_user_id))
    ru = user_result.scalar_one_or_none()
    if ru and ru.tier in ("free", "guest"):
        ru.tier = "pro"
        ref_sub = Subscription(
            user_id=new_user_id,
            plan="pro_trial",
            status="active",
            started_at=datetime.utcnow(),
            expires_at=datetime.utcnow() + timedelta(days=reward_days),
        )
        db.add(ref_sub)

    referral = Referral(
        referrer_id=rc.user_id,
        referred_id=new_user_id,
        code=code,
        reward_days=reward_days,
    )
    db.add(referral)
    await db.flush()


@router.post("/claim")
async def claim_referral(
    code: str,
    user_id: str = Depends(get_current_user_id),
    db: AsyncSession = Depends(get_db),
):
    rc_result = await db.execute(select(ReferralCode).where(ReferralCode.code == code))
    rc = rc_result.scalar_one_or_none()
    if not rc:
        raise HTTPException(status_code=404, detail="无效的邀请码")

    if str(rc.user_id) == user_id:
        raise HTTPException(status_code=400, detail="不能使用自己的邀请码")

    existing = await db.execute(select(Referral).where(Referral.referred_id == user_id))
    if existing.scalar_one_or_none():
        raise HTTPException(status_code=400, detail="已经使用过邀请码了")

    await apply_referral(code, user_id, db)
    await db.commit()
    return {"success": True, "reward_days": 15}