app.py

import os
import json
import httpx
from fastapi import FastAPI, Request, HTTPException
from mcp.server import Server
from mcp.server.sse import sse_server
from mcp.types import Tool, TextContent

# Create MCP Server
server = Server("sap-mcp-proxy")

# SAP function
async def fetch_supplier_invoices():
    api_key = os.getenv("API_KEY")
    if not api_key:
        return {"error": "API_KEY not configured"}
    url = "https://sandbox.api.sap.com/s4hanacloud/sap/opu/odata/sap/API_SUPPLIERINVOICE_PROCESS_SRV/A_BR_SupplierInvoiceNFDocument?$top=50&$inlinecount=allpages"
    headers = {"APIKey": api_key, "Accept": "application/json"}
    async with httpx.AsyncClient() as client:
        resp = await client.get(url, headers=headers)
        return resp.json() if resp.status_code == 200 else {"error": resp.status_code}

# Register tools
@server.list_tools()
async def list_tools() -> list[Tool]:
    return [Tool(name="get_supplier_invoices", description="Fetch supplier invoices from SAP", inputSchema={"type": "object", "properties": {}})]

@server.call_tool()
async def call_tool(name: str, arguments: dict) -> list[TextContent]:
    if name == "get_supplier_invoices":
        result = await fetch_supplier_invoices()
        return [TextContent(type="text", text=json.dumps(result))]
    raise ValueError(f"Unknown tool: {name}")

# Create app using MCP's built-in SSE server helper
app = sse_server(server)

# Add auth middleware
API_GATEWAY_KEY = os.getenv("API_GATEWAY_KEY")

@app.middleware("http")
async def check_api_key(request: Request, call_next):
    if request.url.path in ["/", "/health"]:
        return await call_next(request)
    token = request.headers.get("X-API-Key")
    if not token or token != API_GATEWAY_KEY:
        raise HTTPException(status_code=401, detail="Unauthorized")
    return await call_next(request)