import hashlib
import secrets
from datetime import UTC, datetime, timedelta

from argon2 import PasswordHasher
from argon2.exceptions import InvalidHashError, VerificationError
from fastapi import Cookie, Depends, HTTPException, Response, status
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from .config import get_settings
from .db import get_db
from .models import Session, User

password_hasher = PasswordHasher()
COOKIE_NAME = "dodo_session"


def hash_token(token: str) -> str:
    return hashlib.sha256(token.encode()).hexdigest()


def hash_password(password: str) -> str:
    return password_hasher.hash(password)


def verify_password(password_hash: str, password: str) -> bool:
    try:
        return password_hasher.verify(password_hash, password)
    except (InvalidHashError, VerificationError):
        return False


async def issue_session(db: AsyncSession, response: Response, user: User) -> None:
    token = secrets.token_urlsafe(32)
    expires = datetime.now(UTC) + timedelta(days=get_settings().session_days)
    db.add(Session(token_hash=hash_token(token), user_id=user.id, expires_at=expires))
    await db.commit()
    response.set_cookie(
        COOKIE_NAME, token, max_age=get_settings().session_days * 86400,
        httponly=True, secure=get_settings().cookie_secure, samesite="lax", path="/",
    )


async def session_token(
    token: str | None = Cookie(default=None, alias=COOKIE_NAME),
) -> str:
    if not token:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="请先登录")
    return token


async def current_user(
    token: str = Depends(session_token),
    db: AsyncSession = Depends(get_db),
) -> User:
    result = await db.execute(
        select(User).join(Session).where(
            Session.token_hash == hash_token(token), Session.expires_at > datetime.now(UTC)
        )
    )
    user = result.scalar_one_or_none()
    if user is None:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="会话已失效，请重新登录")
    return user