import jwt
import bcrypt
import secrets
from datetime import datetime, timedelta
from typing import Optional, Dict, Any
from fastapi import Header, HTTPException
from config import SECRET_KEY, ALGORITHM, ACCESS_TOKEN_EXPIRE_MINUTES

def hash_password(password: str) -> str:
    """Hash a password using bcrypt"""
    salt = bcrypt.gensalt()
    hashed = bcrypt.hashpw(password.encode('utf-8'), salt)
    return hashed.decode('utf-8')

def verify_password(plain_password: str, hashed_password: str) -> bool:
    """Verify a password against its hash"""
    return bcrypt.checkpw(plain_password.encode('utf-8'), hashed_password.encode('utf-8'))

def create_access_token(data: Dict[Any, Any], expires_delta: Optional[timedelta] = None) -> str:
    """Create a JWT access token"""
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.utcnow() + expires_delta
    else:
        expire = datetime.utcnow() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt

def decode_access_token(token: str) -> Optional[Dict[str, Any]]:
    """Decode and verify a JWT access token"""
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        return payload
    except jwt.PyJWTError:
        return None

def generate_session_token() -> str:
    """Generate a secure random session token"""
    return secrets.token_urlsafe(32)

async def authenticate_user(authorization: str = Header(None)) -> Dict[str, Any]:
    """
    Authenticate user from JWT token in Authorization header
    This is a FastAPI dependency that can be used with Depends()
    
    Usage:
        @router.post("/endpoint")
        async def endpoint(current_user: dict = Depends(authenticate_user)):
            # current_user contains user data from JWT token
    """
    # Import here to avoid circular dependency
    from auth_middleware import get_current_user_from_token
    
    return await get_current_user_from_token(authorization)