"""
SPARKNET Authentication Module
JWT-based authentication with OAuth2 support.
"""

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel
from datetime import datetime, timedelta
from typing import Optional, List
from pathlib import Path
import os
import json
import uuid

# Configuration (use environment variables in production)
SECRET_KEY = os.getenv("SPARKNET_SECRET_KEY", "sparknet-super-secret-key-change-in-production")
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

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

# OAuth2 scheme
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="api/auth/token", auto_error=False)

# Simple file-based user store (replace with database in production)
USERS_FILE = Path(__file__).parent.parent / "data" / "users.json"
USERS_FILE.parent.mkdir(parents=True, exist_ok=True)


class User(BaseModel):
    """User model."""
    user_id: str
    username: str
    email: str
    hashed_password: str
    is_active: bool = True
    is_admin: bool = False
    scopes: List[str] = []
    created_at: datetime = None

    class Config:
        json_encoders = {
            datetime: lambda v: v.isoformat() if v else None
        }


class UserInDB(User):
    """User model with password hash."""
    pass


class TokenData(BaseModel):
    """JWT token payload."""
    username: Optional[str] = None
    user_id: Optional[str] = None
    scopes: List[str] = []


def _load_users() -> dict:
    """Load users from file."""
    if USERS_FILE.exists():
        try:
            with open(USERS_FILE) as f:
                data = json.load(f)
                return {u["username"]: User(**u) for u in data}
        except Exception:
            pass
    return {}


def _save_users(users: dict):
    """Save users to file."""
    with open(USERS_FILE, "w") as f:
        json.dump([u.dict() for u in users.values()], f, default=str, indent=2)


def verify_password(plain_password: str, hashed_password: str) -> bool:
    """Verify a password against its hash."""
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password: str) -> str:
    """Hash a password."""
    return pwd_context.hash(password)


def get_user(username: str) -> Optional[UserInDB]:
    """Get a user by username."""
    users = _load_users()
    if username in users:
        return UserInDB(**users[username].dict())
    return None


def authenticate_user(username: str, password: str) -> Optional[UserInDB]:
    """Authenticate a user."""
    user = get_user(username)
    if not user:
        return None
    if not verify_password(password, user.hashed_password):
        return None
    return user


def create_access_token(data: dict, 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


async def get_current_user(token: str = Depends(oauth2_scheme)) -> Optional[UserInDB]:
    """Get the current user from JWT token."""
    if not token:
        return None

    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            return None
        token_data = TokenData(
            username=username,
            user_id=payload.get("user_id"),
            scopes=payload.get("scopes", [])
        )
    except JWTError:
        return None

    user = get_user(token_data.username)
    return user


async def get_current_active_user(
    current_user: Optional[UserInDB] = Depends(get_current_user)
) -> Optional[UserInDB]:
    """Get current active user (authentication optional)."""
    if current_user and not current_user.is_active:
        return None
    return current_user


async def require_auth(
    current_user: Optional[UserInDB] = Depends(get_current_user)
) -> UserInDB:
    """Require authentication (raises exception if not authenticated)."""
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    if not current_user:
        raise credentials_exception
    if not current_user.is_active:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


async def require_admin(
    current_user: UserInDB = Depends(require_auth)
) -> UserInDB:
    """Require admin privileges."""
    if not current_user.is_admin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Admin privileges required"
        )
    return current_user


def create_user(username: str, email: str, password: str, is_admin: bool = False) -> User:
    """Create a new user."""
    users = _load_users()

    if username in users:
        raise ValueError(f"User {username} already exists")

    user = User(
        user_id=str(uuid.uuid4()),
        username=username,
        email=email,
        hashed_password=get_password_hash(password),
        is_active=True,
        is_admin=is_admin,
        scopes=["read", "write"] if not is_admin else ["read", "write", "admin"],
        created_at=datetime.now()
    )

    users[username] = user
    _save_users(users)
    return user


def delete_user(username: str) -> bool:
    """Delete a user."""
    users = _load_users()
    if username in users:
        del users[username]
        _save_users(users)
        return True
    return False


# Initialize default admin user if none exists
def init_default_admin():
    """Create default admin user if no users exist."""
    users = _load_users()
    if not users:
        try:
            create_user(
                username="admin",
                email="admin@sparknet.local",
                password="admin123",  # Change in production!
                is_admin=True
            )
            print("Default admin user created: admin / admin123")
        except Exception as e:
            print(f"Could not create default admin: {e}")


# Auth routes
from fastapi import APIRouter

auth_router = APIRouter()


@auth_router.post("/token")
async def login_for_access_token(form_data: OAuth2PasswordRequestForm = Depends()):
    """OAuth2 compatible token login."""
    user = authenticate_user(form_data.username, form_data.password)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect username or password",
            headers={"WWW-Authenticate": "Bearer"},
        )
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={
            "sub": user.username,
            "user_id": user.user_id,
            "scopes": user.scopes
        },
        expires_delta=access_token_expires
    )
    return {
        "access_token": access_token,
        "token_type": "bearer",
        "expires_in": ACCESS_TOKEN_EXPIRE_MINUTES * 60
    }


@auth_router.post("/register")
async def register_user(
    username: str,
    email: str,
    password: str,
):
    """Register a new user."""
    try:
        user = create_user(username, email, password)
        return {
            "user_id": user.user_id,
            "username": user.username,
            "email": user.email,
            "message": "User created successfully"
        }
    except ValueError as e:
        raise HTTPException(status_code=400, detail=str(e))


@auth_router.get("/me")
async def read_users_me(current_user: UserInDB = Depends(require_auth)):
    """Get current user information."""
    return {
        "user_id": current_user.user_id,
        "username": current_user.username,
        "email": current_user.email,
        "is_active": current_user.is_active,
        "is_admin": current_user.is_admin,
        "scopes": current_user.scopes
    }


@auth_router.get("/users")
async def list_users(current_user: UserInDB = Depends(require_admin)):
    """List all users (admin only)."""
    users = _load_users()
    return [
        {
            "user_id": u.user_id,
            "username": u.username,
            "email": u.email,
            "is_active": u.is_active,
            "is_admin": u.is_admin
        }
        for u in users.values()
    ]


@auth_router.delete("/users/{username}")
async def delete_user_endpoint(
    username: str,
    current_user: UserInDB = Depends(require_admin)
):
    """Delete a user (admin only)."""
    if username == current_user.username:
        raise HTTPException(status_code=400, detail="Cannot delete yourself")
    if delete_user(username):
        return {"status": "deleted", "username": username}
    raise HTTPException(status_code=404, detail=f"User not found: {username}")