app.py

import os
import requests
from fastapi import FastAPI, HTTPException, Depends
from fastapi.responses import JSONResponse
from fastapi.security.api_key import APIKeyHeader
from fastapi.middleware.cors import CORSMiddleware

# -------------------------------------------------
# CONFIGURATION
# -------------------------------------------------
HUGGINGFACE_BACKEND = os.getenv(
    "SAP_BACKEND_URL",
    "https://sandbox.api.sap.com/s4hanacloud/sap/opu/odata4/"
    "sap/api_purchaseorder_2/srvd_a2x/sap/purchaseorder/0001/PurchaseOrder?$top=10"
)
AGENTKIT_API_KEY = os.getenv("AGENTKIT_API_KEY", None)
BASE_URL = os.getenv("PUBLIC_URL", "https://pd03-agentkit.hf.space")  # your Space URL

app = FastAPI(
    title="SAP MCP Server",
    description="MCP-compatible FastAPI server exposing live SAP Purchase Orders for demo and AgentKit integration.",
    version="2.0.0",
)

# -------------------------------------------------
# CORS MIDDLEWARE  (needed for Google AI Studio / front-end calls)
# -------------------------------------------------
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],      # for demo; restrict later if desired
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# -------------------------------------------------
# AUTHENTICATION
# -------------------------------------------------
api_key_header = APIKeyHeader(name="x-agentkit-api-key", auto_error=False)

def verify_api_key(api_key: str = Depends(api_key_header)):
    """Verifies the x-agentkit-api-key header, if configured."""
    if AGENTKIT_API_KEY is None:
        # open mode
        return True
    if api_key != AGENTKIT_API_KEY:
        raise HTTPException(status_code=401, detail="Invalid or missing API key")
    return True


# -------------------------------------------------
# MCP MANIFEST (for AgentKit autodiscovery)
# -------------------------------------------------
@app.get("/.well-known/mcp/manifest.json", include_in_schema=False)
async def get_manifest():
    """Manifest describing this MCP server and its tools."""
    manifest = {
        "name": "sap_mcp_server",
        "description": "MCP server exposing a tool for retrieving SAP purchase orders from the SAP Sandbox API.",
        "version": "2.0.0",
        "auth": {
            "type": "api_key",
            "location": "header",
            "header_name": "x-agentkit-api-key",
            "description": "Custom header used to authenticate MCP requests."
        },
        "tools": [
            {
                "name": "get_purchase_orders",
                "description": "Fetches the top 10 purchase orders from the SAP Sandbox API.",
                "input_schema": {"type": "object", "properties": {}},
                "output_schema": {"type": "object"},
                "http": {"method": "GET", "url": f"{BASE_URL}/tools/get_purchase_orders"}
            }
        ]
    }
    return JSONResponse(content=manifest)


# -------------------------------------------------
# TOOL: Fetch Purchase Orders
# -------------------------------------------------
@app.get("/tools/get_purchase_orders", tags=["MCP Tools"])
async def get_purchase_orders(auth=Depends(verify_api_key)):
    """
    Fetch the top purchase orders from SAP Sandbox API.
    Requires SAP_API_KEY secret and a valid SAP_BACKEND_URL.
    """
    sap_api_key = os.getenv("SAP_API_KEY")
    if not sap_api_key:
        raise HTTPException(status_code=500, detail="SAP_API_KEY not set in environment")

    headers = {"APIKey": sap_api_key}

    try:
        print(f"📡 Calling SAP Sandbox: {HUGGINGFACE_BACKEND}")
        resp = requests.get(HUGGINGFACE_BACKEND, headers=headers, timeout=60)
        resp.raise_for_status()
        data = resp.json()

        records = data.get("value", [])
        print(f"✅ SAP API returned {len(records)} records")

        return {
            "source": "SAP Sandbox",
            "count": len(records),
            "data": records
        }

    except requests.exceptions.HTTPError as e:
        print(f"❌ SAP API HTTP error: {e}")
        raise HTTPException(status_code=resp.status_code, detail=f"SAP API error: {e.response.text}")
    except Exception as e:
        print(f"❌ SAP API general error: {e}")
        raise HTTPException(status_code=500, detail=f"Failed to call SAP API: {e}")


# -------------------------------------------------
# HEALTH CHECK
# -------------------------------------------------
@app.get("/health", tags=["System"])
async def health():
    return {"status": "ok", "message": "SAP MCP Server is running"}


# -------------------------------------------------
# ROOT (friendly landing page)
# -------------------------------------------------
@app.get("/", tags=["Root"])
async def root():
    return {
        "message": "👋 Welcome to the SAP MCP Server",
        "available_endpoints": {
            "health": "/health",
            "manifest": "/.well-known/mcp/manifest.json",
            "purchase_orders": "/tools/get_purchase_orders"
        },
        "instructions": "Use /tools/get_purchase_orders with header x-agentkit-api-key to fetch live SAP sandbox data."
    }