# app/services/auth_service.py

import uuid
import bcrypt
import random
import string
from datetime import datetime, timedelta
from typing import Dict

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

from app.core.biz_exception import (
    NotFoundError,
    PermissionDeniedError,
    BizLogicError,
)
from app.models.user import VasUser
from app.models.session import VasSession
from app.models.verification_token import VasVerificationToken
from app.schemas.auth import (
    AutoRegisterRequest,
    SendBindCodeRequest,
    SendResetCodeRequest,
    BindEmailRequest,
    ResetPasswordRequest,
    LoginRequest,
)
from app.services.notification_service import NotificationService


def _random_password(length: int = 16) -> str:
    return "".join(
        random.choices(
            string.ascii_letters + string.digits + "!@#$%",
            k=length,
        )
    )


ADJECTIVES = [
    "Silent", "Lucky", "Happy", "Brave", "Quick", "Bright",
    "Quiet", "Crazy", "Cool", "Swift", "Blue", "Red", "Golden"
]

NOUNS = [
    "Fox", "Wolf", "Tiger", "Eagle", "Lion", "Bear",
    "River", "Cloud", "Storm", "Nova", "Shadow"
]

def human_like_nickname(max_number: int = 999) -> str:
    adj = random.choice(ADJECTIVES)
    noun = random.choice(NOUNS)
    number = random.randint(1, max_number)

    return f"{adj}{noun}{number}"

class AuthService:
    # =========================
    # 自动注册（游客）
    # =========================
    @staticmethod
    async def auto_register(
        db: AsyncSession,
        req: AutoRegisterRequest,
        ip: str = None,
        user_agent = None
    ) -> Dict:
        uid = f"usr-{uuid.uuid4().hex[:8]}"

        user = VasUser(
            id=uid,
            role="user",
            nickname=human_like_nickname(),
            preferred_language="en",
            timezone="Asia/Shanghai",
            register_ip=ip or '',
        )
        db.add(user)

        token = "tok_" + uuid.uuid4().hex
        session = VasSession(
            id=token,
            user_id=uid,
            user_agent=user_agent or '',
            ip=ip or '',
            expire_at=datetime.utcnow() + timedelta(days=7),
        )
        db.add(session)

        await db.commit()
        await db.refresh(user)

        return {"user": user, "token": token}

    # =========================
    # 发送绑定邮箱验证码
    # =========================
    @staticmethod
    async def send_bind_code(
        db: AsyncSession,
        payload: SendBindCodeRequest,
        auth_user: VasUser,
        redis_client: Redis,
    ):
        token = uuid.uuid4().hex[:6]
        expiration_time = datetime.utcnow() + timedelta(minutes=10)
        record = VasVerificationToken(
            token=token,
            expire_at=expiration_time,
        )
        db.add(record)
        await db.commit()

        await NotificationService.post_message(
            db=db,
            channel="email",
            payload={
                "template_id": "email_verification_for_bind",
                "receiver": payload.email,
                "payload": {
                    "app_name": "TextSkin",
                    "code": token,
                    "expiration_time":  "10 minutes"
                },
            },
        )

    # =========================
    # 发送重置密码验证码
    # =========================
    @staticmethod
    async def send_reset_code(
        db: AsyncSession,
        payload: SendResetCodeRequest,
        redis_client: Redis,
    ):
        stmt = select(VasUser).where(
            VasUser.email == payload.email,
            VasUser.email_verified == 1,
        )
        user = (await db.execute(stmt)).scalar_one_or_none()

        if not user:
            raise BizLogicError("User not exist")

        expiration_time = datetime.utcnow() + timedelta(minutes=10)
        token = uuid.uuid4().hex[:6]
        record = VasVerificationToken(
            token=token,
            expire_at=expiration_time,
        )
        db.add(record)
        await db.commit()

        await NotificationService.post_message(
            db=db,
            channel="email",
            payload={
                "template_id": "email_verification_for_reset",
                "receiver": payload.email,
                "payload": {
                    "app_name": "TextSkin",
                    "code": token,
                    "expiration_time": "10 minutes"
                },
            },
        )

    # =========================
    # 绑定邮箱
    # =========================
    @staticmethod
    async def bind_email(
        db: AsyncSession,
        payload: BindEmailRequest,
        auth_user: VasUser,
        redis_client: Redis,
        ip: str = None,
        user_agent = None
    ) -> Dict:
        # 邮箱是否已被绑定
        stmt = select(VasUser).where(
            VasUser.email == payload.email,
            VasUser.email_verified == 1,
        )
        if (await db.execute(stmt)).scalar_one_or_none():
            raise BizLogicError("Email already bound")

        # 校验验证码
        stmt = select(VasVerificationToken).where(
            VasVerificationToken.token == payload.code,
            VasVerificationToken.used == 0,
        )
        record = (await db.execute(stmt)).scalar_one_or_none()
        if not record:
            raise BizLogicError("Token invalid")

        if record.expire_at < datetime.utcnow():
            raise BizLogicError("Token expired")

        user = await db.get(VasUser, auth_user.id)

        plain_pwd = _random_password()
        hashed_pwd = bcrypt.hashpw(
            plain_pwd.encode(),
            bcrypt.gensalt(),
        ).decode()

        user.email = payload.email
        user.password_hash = hashed_pwd
        user.email_verified = 1
        record.used = 1

        token = "tok_" + uuid.uuid4().hex
        session = VasSession(
            id=token,
            user_id=user.id,
            ip=ip or '',
            user_agent=user_agent or '',
            expire_at=datetime.utcnow() + timedelta(days=30),
        )
        db.add(session)

        await db.commit()
        await db.refresh(user)
        
        await NotificationService.post_message(
            db=db,
            channel="email",
            payload={
                "template_id": "login_credentials",
                "receiver": payload.email,
                "payload": {
                    "app_name": "TextSkin",
                    "username": payload.email,
                    "password": plain_pwd,
                    "login_url": "https://text.skin/login"
                },
            },
        )

        return {"user": user, "token": token}

    # =========================
    # 重置密码
    # =========================
    @staticmethod
    async def reset_password(
        db: AsyncSession,
        payload: ResetPasswordRequest,
    ) -> bool:
        stmt = select(VasUser).where(
            VasUser.email == payload.email,
            VasUser.email_verified == 1,
        )
        user = (await db.execute(stmt)).scalar_one_or_none()
        if not user:
            raise BizLogicError("User not exist")

        stmt = select(VasVerificationToken).where(
            VasVerificationToken.token == payload.code,
            VasVerificationToken.used == 0,
        )
        record = (await db.execute(stmt)).scalar_one_or_none()
        if not record:
            raise BizLogicError("Token invalid")

        if record.expire_at < datetime.utcnow():
            raise BizLogicError("Token expired")

        user.password_hash = bcrypt.hashpw(
            payload.new_password.encode(),
            bcrypt.gensalt(),
        ).decode()
        record.used = 1

        await db.commit()
        return True

    # =========================
    # 登录
    # =========================
    @staticmethod
    async def login(
        db: AsyncSession,
        req: LoginRequest,
        ip: str = None,
        user_agent: str = None
    ) -> Dict:
        stmt = select(VasUser).where(VasUser.email == req.email)
        user = (await db.execute(stmt)).scalar_one_or_none()
        if not user:
            raise NotFoundError("User not found")

        if not bcrypt.checkpw(
            req.password.encode(),
            user.password_hash.encode(),
        ):
            raise PermissionDeniedError("Password incorrect")

        token = "tok_" + uuid.uuid4().hex
        session = VasSession(
            id=token,
            user_id=user.id,
            user_agent=user_agent or "",
            ip=ip or "",
            expire_at=datetime.utcnow() + timedelta(days=7),
        )
        db.add(session)
        await db.commit()

        return {"user": user, "token": token}