import os
import jwt
from datetime import datetime, timedelta
from typing import Optional
from fastapi import Depends, HTTPException, status
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from sqlalchemy.orm import Session
from .db import SessionLocal
from .models import User

# JWT Configuration
SECRET_KEY = os.environ.get("JWT_SECRET_KEY", "your-secret-key-change-in-production")
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 60 * 24 * 7  # 7 days

security = HTTPBearer()


def get_db():
    """Database dependency."""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def create_access_token(data: dict, expires_delta: Optional[timedelta] = None):
    """Create a JWT access token."""
    to_encode = data.copy()
    # Ensure 'sub' (subject) is a string, not an integer
    if "sub" in to_encode:
        to_encode["sub"] = str(to_encode["sub"])
    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 verify_token(token: str) -> dict:
    """Verify and decode a JWT token."""
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        return payload
    except jwt.ExpiredSignatureError:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Token has expired",
        )
    except jwt.InvalidTokenError:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Could not validate credentials",
        )


def get_current_user(
    credentials: HTTPAuthorizationCredentials = Depends(security),
    db: Session = Depends(get_db)
) -> User:
    """Get the current authenticated user from JWT token."""
    token = credentials.credentials
    payload = verify_token(token)
    user_id: int = payload.get("sub")
    
    if user_id is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Could not validate credentials",
        )
    
    # Convert user_id back to integer for database query
    try:
        user_id_int = int(user_id)
    except (ValueError, TypeError):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid user ID in token",
        )
    
    user = db.query(User).filter(User.id == user_id_int).first()
    if user is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="User not found",
        )
    
    return user