trading/services/api_gateway/auth/middleware.py

"""Auth middleware — FastAPI dependency for JWT-based authentication."""

from __future__ import annotations

from fastapi import Depends, HTTPException, status
from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer

import jwt as pyjwt

from services.api_gateway.auth.jwt import decode_token
from services.api_gateway.config import ApiGatewayConfig

# Shared config instance — injected via FastAPI dependency override in tests.
_config: ApiGatewayConfig | None = None

security = HTTPBearer(auto_error=False)


def get_config() -> ApiGatewayConfig:
    """Return the singleton config.  Overridden in tests."""
    global _config
    if _config is None:
        _config = ApiGatewayConfig()
    return _config


_DEV_USER = {
    "sub": "00000000-0000-0000-0000-000000000000",
    "username": "dev",
    "type": "access",
}


async def get_current_user(
    credentials: HTTPAuthorizationCredentials | None = Depends(security),
    config: ApiGatewayConfig = Depends(get_config),
) -> dict:
    """FastAPI dependency that extracts and validates a Bearer JWT.

    Returns the decoded token payload (contains ``sub``, ``username``, etc.)
    on success.  Raises a 401 ``HTTPException`` for missing, expired, or
    invalid tokens.

    When ``config.dev_mode`` is ``True``, authentication is bypassed and a
    synthetic dev user is returned.
    """
    if config.dev_mode:
        return _DEV_USER

    if credentials is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Missing authorization header",
            headers={"WWW-Authenticate": "Bearer"},
        )

    token = credentials.credentials
    try:
        payload = decode_token(token, config)
    except pyjwt.ExpiredSignatureError:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Token has expired",
            headers={"WWW-Authenticate": "Bearer"},
        )
    except pyjwt.InvalidTokenError:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid token",
            headers={"WWW-Authenticate": "Bearer"},
        )

    if payload.get("type") != "access":
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid token type",
            headers={"WWW-Authenticate": "Bearer"},
        )

    return payload