from __future__ import annotations

from datetime import datetime, timedelta, timezone
import os

from fastapi import APIRouter, HTTPException
from jose import jwt
from pydantic import BaseModel

from app.config import settings
from app.models.user import User
from app.services.wechat import code_to_session

router = APIRouter()

DEV_MODE = os.environ.get("DEV_MODE", "").lower() in ("1", "true", "yes")
# 固定测试账号 openid（dev 模式下使用）
DEV_OPENID = "dev_test_account_001"


class ExchangeCodeRequest(BaseModel):
    code: str
    mobile: str | None = None


class TokenResponse(BaseModel):
    token: str
    user_id: str
    openid: str
    mobile: str


def _build_token(user: User) -> str:
    """生成自包含 JWT：sub + openid + mobile"""
    expire = datetime.now(timezone.utc) + timedelta(days=30)
    payload = {
        "sub": str(user.id),
        "openid": user.openid,
        "mobile": user.phone or "",
        "exp": expire,
    }
    return jwt.encode(payload, settings.jwt_secret_key, algorithm=settings.jwt_algorithm)


@router.post("/exchange-code")
async def exchange_code(req: ExchangeCodeRequest) -> TokenResponse:
    """小程序登录：code → openid → 创建/查找 User → 返回自包含 JWT"""
    wechat_data = await code_to_session(req.code)
    openid = wechat_data["openid"]

    user = await User.find_one(User.openid == openid)
    if not user:
        user = User(
            openid=openid,
            session_key=wechat_data.get("session_key"),
            union_id=wechat_data.get("unionid"),
            phone=req.mobile or None,
        )
        await user.insert()
    else:
        # 更新 session_key + 手机号
        user.session_key = wechat_data.get("session_key")
        if req.mobile:
            user.phone = req.mobile
        await user.save()

    token = _build_token(user)
    return TokenResponse(
        token=token,
        user_id=str(user.id),
        openid=user.openid,
        mobile=user.phone or "",
    )


@router.post("/dev-login")
async def dev_login() -> TokenResponse:
    """开发环境：使用固定测试账号，不依赖微信"""
    if not DEV_MODE:
        raise HTTPException(status_code=403, detail="仅开发环境可用")

    user = await User.find_one(User.openid == DEV_OPENID)
    if not user:
        user = User(
            openid=DEV_OPENID,
            name="开发测试用户",
            phone="13800000000",
        )
        await user.insert()

    token = _build_token(user)
    return TokenResponse(
        token=token,
        user_id=str(user.id),
        openid=user.openid,
        mobile=user.phone or "",
    )