Generate the Pages demo from web/ at deploy time

.github/workflows/pages.yml

@@ -5,6 +5,7 @@ on:
     branches: [main]
     paths:
       - "demo/**"
+      - "web/**"
       - ".github/workflows/pages.yml"
   workflow_dispatch:
 
@@ -26,8 +27,10 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: actions/configure-pages@v5
+      - name: Build demo from web/ assets
+        run: python3 demo/build_demo.py _site
       - uses: actions/upload-pages-artifact@v3
         with:
-          path: demo
+          path: _site
       - id: deployment
         uses: actions/deploy-pages@v4

.gitignore

@@ -3,3 +3,4 @@ tokencache.json
 stats.db*
 credentials.json
 *.swp
+_site/

demo/build_demo.py

@@ -0,0 +1,93 @@
+#!/usr/bin/env python3
+"""Build the static GitHub Pages demo from the local viewer's assets.
+
+web/ is the single source of truth for the UI. This script copies the
+viewer's index.html/app.css/app.js into an output directory and applies the
+demo deltas mechanically: data comes from a committed ./summary.json instead
+of the live /api/summary, asset paths become relative (Pages serves under a
+subpath), and the page is labeled as a synthetic-data demo.
+
+Every substitution asserts that its anchor text matched exactly once, so if
+web/ drifts in a way this transform doesn't understand, the Pages deploy
+fails instead of silently publishing a broken or stale demo.
+
+Run:  python3 demo/build_demo.py [output-dir]   (default: _site)
+"""
+
+import shutil
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parent.parent
+WEB = ROOT / "web"
+DEMO = ROOT / "demo"
+
+DEMO_BANNER = (
+    '<div class="demo-banner">\n'
+    "    Demo — all data on this page is synthetic, for a fictional Gmail account.\n"
+    "    No real inbox was scanned.\n"
+    "  </div>\n\n  "
+)
+
+DEMO_FOOTER = (
+    '  <p class="muted">\n'
+    "    This is a static demo of the\n"
+    '    <a href="https://github.com/zbuc/gmail-stats">gmail-stats</a> local web\n'
+    "    viewer, populated with synthetic data. All sender addresses use reserved\n"
+    "    example domains; no real email data is involved.\n"
+    "  </p>\n"
+)
+
+DEMO_EXTRA_CSS = """
+/* Demo-only additions, appended by demo/build_demo.py */
+.demo-banner {
+  background: color-mix(in srgb, var(--accent) 12%, var(--card));
+  border: 1px solid var(--accent);
+  border-radius: 8px;
+  padding: 0.6rem 0.9rem;
+  margin: 0 0 1rem;
+  font-size: 0.9rem;
+}
+a { color: var(--accent); }
+"""
+
+
+def replace_exactly(text, old, new, what):
+    count = text.count(old)
+    assert count == 1, (
+        f"demo build: expected exactly one occurrence of {what!r} in the viewer "
+        f"assets, found {count}. web/ has drifted — update demo/build_demo.py."
+    )
+    return text.replace(old, new)
+
+
+def main():
+    out = Path(sys.argv[1]) if len(sys.argv) > 1 else ROOT / "_site"
+    out.mkdir(parents=True, exist_ok=True)
+
+    js = (WEB / "app.js").read_text()
+    js = replace_exactly(js, 'fetch("/api/summary")', 'fetch("./summary.json")',
+                         "the /api/summary fetch")
+    (out / "app.js").write_text(js)
+
+    (out / "app.css").write_text((WEB / "app.css").read_text() + DEMO_EXTRA_CSS)
+
+    html = (WEB / "index.html").read_text()
+    html = replace_exactly(html, '<link rel="stylesheet" href="/app.css">',
+                           '<link rel="stylesheet" href="./app.css">', "the stylesheet link")
+    html = replace_exactly(html, '<script src="/app.js" defer></script>',
+                           '<script src="./app.js" defer></script>', "the script tag")
+    html = replace_exactly(html, "<title>gmail-stats</title>",
+                           "<title>gmail-stats · demo</title>", "the page title")
+    html = replace_exactly(html, "<h1>gmail-stats <span>· local viewer</span></h1>",
+                           "<h1>gmail-stats <span>· public demo</span></h1>", "the heading")
+    html = replace_exactly(html, "<main>\n  ", "<main>\n  " + DEMO_BANNER, "the main open tag")
+    html = replace_exactly(html, "</main>", DEMO_FOOTER + "</main>", "the main close tag")
+    (out / "index.html").write_text(html)
+
+    shutil.copy(DEMO / "summary.json", out / "summary.json")
+    print(f"demo built into {out}: " + ", ".join(sorted(p.name for p in out.iterdir())))
+
+
+if __name__ == "__main__":
+    main()