app.py

import os
import httpx
from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel

app = FastAPI(
    title="SAP Purchase Order API Demo",
    description=(
        "Fetches purchase order data from SAP Sandbox API.\n\n"
        "Designed for integration with OpenAI Agentkit UI — "
        "Agentkit auto-discovers endpoints from `/openapi.json`."
    ),
    version="1.0.0",
)

# Allow all origins for Agentkit / external calls
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# Read secret from Hugging Face environment
SAP_API_KEY = os.getenv("SAP_API_KEY")
SAP_BASE_URL = (
    "https://sandbox.api.sap.com/s4hanacloud/sap/opu/odata4/"
    "sap/api_purchaseorder_2/srvd_a2x/sap/purchaseorder/0001/PurchaseOrder?$top=50"
)

# --- Models ---

class PurchaseOrderItem(BaseModel):
    PurchaseOrder: str | None = None
    Supplier: str | None = None
    CreatedByUser: str | None = None
    CreatedDateTime: str | None = None


class PurchaseOrderResponse(BaseModel):
    source: str
    count: int
    data: list[PurchaseOrderItem] | dict


# --- Routes ---

@app.get("/health", summary="Health check", tags=["System"])
async def health_check():
    """Simple endpoint to verify the backend is running."""
    return {"status": "ok", "message": "SAP Purchase Order API backend is running"}


@app.get(
    "/purchase-orders",
    response_model=PurchaseOrderResponse,
    summary="Get Purchase Orders",
    tags=["Purchase Orders"],
    description="Fetch top 50 purchase orders from SAP Sandbox API.",
)
async def get_purchase_orders():
    """Fetches purchase orders from SAP Sandbox API"""
    if not SAP_API_KEY:
        raise HTTPException(status_code=500, detail="SAP_API_KEY not found in environment")

    headers = {"APIKey": SAP_API_KEY}

    try:
        async with httpx.AsyncClient(timeout=30.0) as client:
            resp = await client.get(SAP_BASE_URL, headers=headers)
            resp.raise_for_status()
            data = resp.json()
            po_items = data.get("value", [])
            return {"source": "SAP Sandbox", "count": len(po_items), "data": po_items}
    except httpx.HTTPStatusError as e:
        raise HTTPException(status_code=e.response.status_code, detail=f"SAP API error: {e.response.text}")
    except Exception as e:
        raise HTTPException(status_code=500, detail=str(e))