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 HTTPBearer, HTTPAuthorizationCredentials
from sqlalchemy.orm import Session
from database import get_db, User
from config import settings
import secrets
import string

# Password hashing
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
security = HTTPBearer()

# Utility functions
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)

def generate_otp() -> str:
    """Generate a 6-digit OTP"""
    return ''.join(secrets.choice(string.digits) for _ in range(6))

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=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
    
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
    return encoded_jwt

def create_refresh_token(data: dict):
    to_encode = data.copy()
    expire = datetime.utcnow() + timedelta(days=settings.REFRESH_TOKEN_EXPIRE_DAYS)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
    return encoded_jwt

def verify_token(token: str) -> Optional[str]:
    try:
        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM])
        user_id: str = payload.get("sub")
        if user_id is None:
            return None
        return user_id
    except JWTError:
        return None

def get_user_by_email(db: Session, email: str) -> Optional[User]:
    return db.query(User).filter(User.email == email).first()

def get_user_by_id(db: Session, user_id: str) -> Optional[User]:
    return db.query(User).filter(User.id == user_id).first()

def authenticate_user(db: Session, email: str, password: str) -> Optional[User]:
    user = get_user_by_email(db, email)
    if not user or not verify_password(password, user.password_hash):
        return None
    return user

async def get_current_user(
    credentials: HTTPAuthorizationCredentials = Depends(security),
    db: Session = Depends(get_db)
) -> User:
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    
    try:
        token = credentials.credentials
        user_id = verify_token(token)
        if user_id is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    
    user = get_user_by_id(db, user_id)
    if user is None:
        raise credentials_exception
    
    if not user.is_active:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Inactive user"
        )
    
    return user

async def get_current_active_user(current_user: User = Depends(get_current_user)) -> User:
    if not current_user.is_active:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user