from datetime import datetime, timedelta
from typing import Any

from decouple import config
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from passlib.context import CryptContext
from sqlalchemy.ext.asyncio import AsyncSession

from med_backend.auth.schemas import TokenData, User
from med_backend.db.dependencies import get_db_session
from med_backend.settings import settings
from med_backend.users.crud import get_user_by_email

SECRET_KEY = config("SECRET")
JWT_ALGORITHM = settings.JWT_ALGORITHM
ACCESS_TOKEN_EXPIRE_MINUTES = settings.JWT_EAT


pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


def verify_password(plain_password: str, hashed_password: str) -> bool:
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password: str) -> str:
    return pwd_context.hash(password)


async def get_user(session: AsyncSession, email: str) -> User:
    db_user = await get_user_by_email(session, email=email)
    if db_user is None:
        raise HTTPException(status_code=404, detail="User not found")
    return db_user


async def authenticate_user(
    db: AsyncSession,
    username: str,
    password: str,
) -> bool | User:
    user = await get_user(db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(
    data: dict[str, Any],
    expires_delta: timedelta | None = None,
) -> str:
    to_encode = data.copy()
    # TODO: set datetime in settings
    if expires_delta:
        expire = datetime.utcnow() + expires_delta
    else:
        expire = datetime.utcnow() + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=JWT_ALGORITHM)
    return encoded_jwt


async def get_current_user(
    token: str = Depends(oauth2_scheme),
    session: AsyncSession = Depends(get_db_session),
) -> User:
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[JWT_ALGORITHM])
        email: str = payload.get("sub")
        if email is None:
            raise credentials_exception
        token_data = TokenData(email=email)
    except JWTError:
        raise credentials_exception
    user = await get_user(session, token_data.email)
    if user is None:
        raise credentials_exception
    return user


async def get_current_active_user(
    current_user: User = Depends(get_current_user),
) -> User:
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user