app/core/security.py

from datetime import datetime, timedelta, timezone
from typing import Any, Union, Optional
import jwt
import bcrypt
from app.core.config import settings

def verify_password(plain_password: str, hashed_password: str) -> bool:
    try:
        return bcrypt.checkpw(plain_password.encode('utf-8'), hashed_password.encode('utf-8'))
    except Exception:
        return False

def get_password_hash(password: str) -> str:
    salt = bcrypt.gensalt()
    return bcrypt.hashpw(password.encode('utf-8'), salt).decode('utf-8')


def validate_password_strength(password: str) -> bool:
    # Minimum 8 characters, maximum 128 characters
    if len(password) < 8 or len(password) > 128:
        return False
    return True

def create_access_token(subject: Union[str, Any], expires_delta: Optional[timedelta] = None) -> str:
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
    
    to_encode = {"exp": expire, "sub": str(subject)}
    encoded_jwt = jwt.encode(to_encode, settings.JWT_SECRET_KEY, algorithm=settings.ALGORITHM)
    return encoded_jwt

def decode_access_token(token: str) -> Optional[str]:
    try:
        # Explicitly verify signature with the expected algorithm (rejection of 'none' algorithm is implicit by specifying algorithms parameter)
        payload = jwt.decode(token, settings.JWT_SECRET_KEY, algorithms=[settings.ALGORITHM])
        user_id: str = payload.get("sub")
        if user_id is None:
            return None
        return user_id
    except jwt.PyJWTError:
        return None