Comment with the tour preview link

.github/scripts/preview_links.py

@@ -0,0 +1,119 @@
+#!/usr/bin/env python3
+"""Comment on a pull request with a preview link for each tour it changes.
+
+Driven by the `check_run` event of a finished Cloudflare Workers build: reads
+the event from $GITHUB_EVENT_PATH, works out which tour JSON the pull request
+changes, and posts a single comment (updated in place on later builds) playing
+each of them from the branch's preview deployment.
+"""
+import json
+import os
+import re
+import sys
+import urllib.error
+import urllib.request
+from typing import Any
+
+API_BASE = "https://api.github.com"
+LIFE_URL = "https://beta.onezoom.org/life?tour=/tour/remote.html"
+# Identifies our own comment so that later builds edit it rather than add another.
+MARKER = "<!-- tour-preview-links -->"
+# Directories build.py leaves out of _site, so nothing in them gets served.
+UNPUBLISHED = (".github/", "deployment/", "_site/")
+
+
+def worker_from_summary(summary: str) -> str | None:
+    """The Cloudflare worker URL this build is deployed to."""
+    for label in ("Preview Alias URL", "Preview URL"):
+        pattern = rf"{label}:\s*https://([a-z0-9-]+)\.onezoom\.workers\.dev"
+        match = re.search(pattern, summary, re.IGNORECASE)
+        if match:
+            return match.group(1)
+    return None
+
+
+def comment_body(worker: str, changed_tours: list[str]) -> str | None:
+    if not changed_tours:
+        return None
+    lines = [f"- [`{t}`]({LIFE_URL}/{worker}/{t})" for t in changed_tours]
+    return "\n".join([MARKER, "### Tour previews", ""] + lines) + "\n"
+
+
+def api(path: str, method: str = "GET", body: dict | None = None) -> Any:
+    """Call the GitHub API, returning the parsed body."""
+    url = API_BASE + path
+    payload = json.dumps(body).encode("utf-8") if body is not None else None
+
+    request = urllib.request.Request(url, data=payload, method=method)
+    request.add_header("Authorization", f"Bearer {os.environ['GITHUB_TOKEN']}")
+    request.add_header("Accept", "application/vnd.github+json")
+    request.add_header("X-GitHub-Api-Version", "2026-03-10")
+    if payload is not None:
+        request.add_header("Content-Type", "application/json; charset=utf-8")
+
+    try:
+        with urllib.request.urlopen(request) as response:
+            raw = response.read()
+            return json.loads(raw) if raw else None
+    except urllib.error.HTTPError as e:
+        print(
+            f"{method} {url} failed: {e}\n"
+            f"{e.read().decode('utf-8', errors='replace')}",
+            file=sys.stderr,
+        )
+        raise
+
+
+def changed_tour_paths(repo: str, number: int) -> list[str]:
+    """Tour identifiers for the changed files the preview deployment will serve."""
+    return sorted({
+        changed["filename"][: -len(".json")]
+        # first page only so won't show more than 100 changed files
+        for changed in api(f"/repos/{repo}/pulls/{number}/files?per_page=100")
+        if changed["status"] != "removed"
+        and changed["filename"].endswith(".json")
+        and not changed["filename"].startswith(UNPUBLISHED)
+    })
+
+
+def existing_comment(repo: str, number: int) -> dict | None:
+    for comment in api(f"/repos/{repo}/issues/{number}/comments?per_page=100"):
+        if MARKER in (comment.get("body") or ""):
+            return comment
+    return None
+
+
+def main() -> None:
+    repo = os.environ["GITHUB_REPOSITORY"]
+    with open(os.environ["GITHUB_EVENT_PATH"], encoding="utf-8") as f:
+        check_run = json.load(f)["check_run"]
+
+    worker = worker_from_summary((check_run.get("output") or {}).get("summary") or "")
+    if not worker:
+        print("No preview URL in the build summary, nothing to comment.")
+        return
+
+    for pull in check_run.get("pull_requests") or []:
+        number = pull["number"]
+        changed_tours = changed_tour_paths(repo, number)
+        body = comment_body(worker, changed_tours)
+        comment = existing_comment(repo, number)
+
+        if body:
+            if comment:
+                api(f"/repos/{repo}/issues/comments/{comment['id']}",
+                    "PATCH", {"body": body})
+                print(f"Updated the comment on #{number}: {', '.join(changed_tours)}")
+            else:
+                api(f"/repos/{repo}/issues/{number}/comments",
+                    "POST", {"body": body})
+                print(f"Commented on #{number}: {', '.join(changed_tours)}")
+        elif comment:
+            api(f"/repos/{repo}/issues/comments/{comment['id']}", "DELETE")
+            print(f"Deleted the comment on #{number}")
+        else:
+            print(f"No tour JSON changed in #{number}")
+
+
+if __name__ == "__main__":
+    main()

.github/workflows/preview-links.yml

@@ -0,0 +1,27 @@
+name: Comment tour preview links
+
+on:
+  check_run:
+    types: [completed]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  comment:
+    if: >-
+      github.event.check_run.conclusion == 'success' &&
+      startsWith(github.event.check_run.name, 'Workers Builds')
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.x"
+
+      - name: Comment with a preview link per changed tour
+        env:
+          GITHUB_TOKEN: ${{ github.token }}
+        run: python .github/scripts/preview_links.py