Infra

worker.py

@@ -0,0 +1,69 @@
+"""Stamping for the service worker.
+
+The dev server stamps sw.js on every request; the deploy stamps it once into
+the uploaded copy. Both import this, because a digest computed two different
+ways is a worker that thinks its caches are current when they are not.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import json
+import os
+
+WORKER = "sw.js"
+
+VERSION_LINE = "const VERSION = 'dev';"
+LIBRARY_VERSION_LINE = "const LIBRARY_VERSION = 'dev';"
+LIBRARY_LINE = "const LIBRARY = [];"
+
+CHUNK = 1 << 20
+
+def walk(roots):
+    found = {}
+    for root in roots:
+        for dirpath, _dirs, names in os.walk(root):
+            for name in sorted(names):
+                path = os.path.join(dirpath, name)
+                rel = os.path.relpath(path, root).replace(os.sep, "/")
+                found.setdefault(rel, path)
+    return found
+
+def digest(files):
+    # Contents, not size and mtime: a checkout, a rebuild and a rsync all move
+    # mtimes without changing a byte, and each one of those would otherwise
+    # throw away every cache on every device for nothing.
+    out = hashlib.sha256()
+    for rel in sorted(files):
+        out.update(rel.encode("utf-8") + b"\0")
+        with open(files[rel], "rb") as fh:
+            for chunk in iter(lambda: fh.read(CHUNK), b""):
+                out.update(chunk)
+        out.update(b"\0")
+    return out.hexdigest()[:12]
+
+def page_url(rel):
+    if rel == "index.html":
+        return "./"
+    return "./" + (rel[:-len(".html")] if rel.endswith(".html") else rel)
+
+def stamp_worker(roots):
+    chrome = walk(roots[:1])
+    library = {rel: path for rel, path in walk(roots).items() if rel not in chrome}
+
+    src = chrome.pop(WORKER, None)
+    if src is None:
+        return None
+    with open(src, encoding="utf-8") as fh:
+        body = fh.read()
+
+    for line, value in (
+        (VERSION_LINE, "const VERSION = '%s';" % digest(chrome)),
+        (LIBRARY_VERSION_LINE, "const LIBRARY_VERSION = '%s';" % digest(library)),
+        (LIBRARY_LINE, "const LIBRARY = %s;"
+                       % json.dumps(sorted(page_url(rel) for rel in library), indent=2)),
+    ):
+        if line not in body:
+            raise RuntimeError("%s: expected to find %r to stamp" % (WORKER, line))
+        body = body.replace(line, value, 1)
+    return body.encode("utf-8")