# [DEF:AuthModule:Module]
# @SEMANTICS: auth, authentication, adfs, oauth, middleware
# @PURPOSE: Implements ADFS authentication using Authlib for FastAPI. It provides a dependency to protect endpoints.
# @LAYER: UI (API)
# @RELATION: Used by API routers to protect endpoints that require authentication.

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2AuthorizationCodeBearer
from authlib.integrations.starlette_client import OAuth
from starlette.config import Config

# Placeholder for ADFS configuration. In a real app, this would come from a secure source.
# Create an in-memory .env file
from io import StringIO
config_data = StringIO("""
ADFS_CLIENT_ID=your-client-id
ADFS_CLIENT_SECRET=your-client-secret
ADFS_SERVER_METADATA_URL=https://your-adfs-server/.well-known/openid-configuration
""")
config = Config(config_data)
oauth = OAuth(config)

oauth.register(
    name='adfs',
    server_metadata_url=config('ADFS_SERVER_METADATA_URL'),
    client_kwargs={'scope': 'openid profile email'}
)

oauth2_scheme = OAuth2AuthorizationCodeBearer(
    authorizationUrl="https://your-adfs-server/adfs/oauth2/authorize",
    tokenUrl="https://your-adfs-server/adfs/oauth2/token",
)

async def get_current_user(token: str = Depends(oauth2_scheme)):
    """
    Dependency to get the current user from the ADFS token.
    This is a placeholder and needs to be fully implemented.
    """
    # In a real implementation, you would:
    # 1. Validate the token with ADFS.
    # 2. Fetch user information.
    # 3. Create a user object.
    # For now, we'll just check if a token exists.
    if not token:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Not authenticated",
            headers={"WWW-Authenticate": "Bearer"},
        )
    # A real implementation would return a user object.
    return {"placeholder_user": "user@example.com"}
# [/DEF]