from datetime import datetime, timedelta
from typing import Optional
from jose import JWTError, jwt
from passlib.context import CryptContext
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from sqlmodel import Session, select
from database import get_session
from models import User
import os

# Configuration
SECRET_KEY = os.getenv("SECRET_KEY", "supersecretkey") # Change this in production!
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 10080 # 7 days

pwd_context = CryptContext(schemes=["argon2"], deprecated="auto")
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="auth/token")

def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)

def get_password_hash(password):
    return pwd_context.hash(password)

def create_access_token(data: dict, expires_delta: Optional[timedelta] = None):
    to_encode = data.copy()
    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=ALGORITHM)
    return encoded_jwt

async def get_current_user(token: str = Depends(oauth2_scheme), session: Session = Depends(get_session)):
    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=[ALGORITHM])
        email: str = payload.get("sub")
        if email is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    
    user = session.exec(select(User).where(User.email == email)).first()
    if user is None:
        raise credentials_exception
    return user

async def get_current_superuser(current_user: User = Depends(get_current_user)):
    if not current_user.is_superuser:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="The user doesn't have enough privileges"
        )
    return current_user


# Optional OAuth scheme that doesn't require auth
oauth2_scheme_optional = OAuth2PasswordBearer(tokenUrl="auth/token", auto_error=False)

async def get_current_user_optional(
    token: Optional[str] = Depends(oauth2_scheme_optional), 
    session: Session = Depends(get_session)
) -> Optional[User]:
    """Get current user if authenticated, otherwise return None (for public endpoints)"""
    if not token:
        return None
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        email: str = payload.get("sub")
        if email is None:
            return None
    except JWTError:
        return None
    
    user = session.exec(select(User).where(User.email == email)).first()
    return user

