Add forwarder cloud function

Procfile

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+web: gunicorn -w 2 -k uvicorn.workers.UvicornWorker main:app

app.json

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+{
+    "name": "GitHub Webhook Forwarder",
+    "description": "Forwards GitHub webhooks to dev instances of Pangeo Forge API.",
+    "image": "heroku/python",
+    "repository": "https://github.com/pangeo-forge/github-webhook-forwarder",
+    "keywords": [],
+    "addons": [],
+    "env": {},
+    "environments": {
+      "test": {
+        "scripts": {
+          "test-setup": "python -m pip install -r dev-requirements.txt",
+          "test": "pytest test.py -v"
+        }
+      }
+    }
+  }

dev-requirements.txt

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+pytest

main.py

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+import httpx
+from fastapi import FastAPI, HTTPException, Request, status
+from pydantic import BaseModel
+
+app = FastAPI()
+
+
+class GitHubLabel(BaseModel):
+    name: str
+
+
+@app.post("/", status_code=status.HTTP_200_OK)
+async def forwarder(request: Request):
+    """
+
+    """
+
+    event = request.headers.get("X-GitHub-Event")
+    print(f"{event = }")
+
+    request_json = await request.json()
+    request_bytes = await request.body()
+
+    if event == "pull_request":
+        label_containing_obj = "pull_request"
+    elif event == "issue_comment":
+        label_containing_obj = "issue"
+    else:
+        raise NotImplementedError
+
+    labels = [
+        GitHubLabel(**label)
+        for label in request_json[label_containing_obj]["labels"]
+    ]
+    if not labels:
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+            detail="No labels."
+        )
+
+    forward_to = [
+        l.name.split("fwd:")[-1]
+        for l in labels
+        if l.name.startswith("fwd:")
+    ]
+    if not forward_to:
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+            detail="No labels starting with 'fwd:'",
+        )
+
+    responses = {}
+    for recipient in forward_to:
+        print(f"Forwarding GitHub webhook to {recipient = }")
+        async with httpx.AsyncClient() as client:
+            r = await client.post(
+                f"https://{recipient}",
+                headers={
+                    "X-GitHub-Event": request.headers.get("X-GitHub-Event"),
+                    "X-Hub-Signature-256": request.headers.get("X-Hub-Signature-256"),
+                    "content-type": "application/json",
+                },
+                data=request_bytes,
+            )
+            print(f"{recipient = } responded with {r.status_code = }")
+            responses |= {recipient: r.status_code}
+
+    return f"Forwarded to {responses}"

requirements.txt

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+fastapi==0.87.0
+gunicorn==20.1.0
+httpx==0.23.3
+uvicorn==0.20.0

runtime.txt

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+python-3.11.1

test.py

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+def test_main():
+    ...