examples: github webhook event logger: Initial commit

Related: https://gist.github.com/2bb4bb6d7a6abaa07cebc7c04d1cafa5
Related: https://github.com/pdxjohnny/scitt-api-emulator/blob/7ec55acd2b09bb2e08df9c56aa90cfb431aa3fd2/docs/slsa_in_toto.md
Signed-off-by: John Andersen <[email protected]>

examples/github_webhook_event_logger.py

@@ -0,0 +1,90 @@
+"""
+Usage
+*****
+
+.. code-block:: console
+
+    $ python github_webhook_event_logger.py -R org/repo
+"""
+import os
+import sys
+import json
+import pathlib
+import argparse
+import subprocess
+import http.server
+
+import httptest
+
+
+class GitHubWebhookLogger(http.server.BaseHTTPRequestHandler):
+    def do_POST(self):
+        self.send_response(200)
+        self.send_header("Content-type", "text/plain")
+        self.send_header("Content-length", 3)
+        self.end_headers()
+        self.wfile.write(b"OK\n")
+
+        payload = json.loads(self.rfile.read())
+        payload_path = pathlib.Path(
+            ".".join(
+                [
+                    self.headers["X-github-event"],
+                    *(
+                        [
+                            ":".join([key, value])
+                            for key, value in payload.items()
+                            if isinstance(value, str) and not os.sep in value
+                        ]
+                        + ["json"]
+                    ),
+                ],
+            )
+        )
+
+        payload_path.write_text(json.dumps(payload, indent=4, sort_keys=True))
+
+    @classmethod
+    def cli(cls, argv=None):
+        parser = argparse.ArgumentParser(description="Log GitHub webhook events")
+        parser.add_argument(
+            "-R",
+            "--repo",
+            dest="org_and_repo",
+            required=True,
+            type=str,
+            help="GitHub repo in format org/repo",
+        )
+        parser.add_argument(
+            "--state-dir",
+            dest="state_dir",
+            type=pathlib.Path,
+            help="Directory to cache requests in",
+            default=pathlib.Path(os.getcwd(), ".cache", "httptest"),
+        )
+
+        args = parser.parse_args(argv)
+
+        if not args.state_dir.is_dir():
+            args.state_dir.mkdir(parents=True)
+
+        with httptest.Server(cls) as logging_server:
+            with httptest.Server(
+                httptest.CachingProxyHandler.to(
+                    logging_server.url(), state_dir=str(args.state_dir.resolve())
+                )
+            ) as cache_server:
+                subprocess.check_call(
+                    [
+                        "gh",
+                        "webhook",
+                        "forward",
+                        f"--repo={args.org_and_repo}",
+                        "--events=*",
+                        f"--url={cache_server.url()}",
+                    ]
+                )
+
+
+if __name__ == "__main__":
+    GitHubWebhookLogger.cli(sys.argv[1:])