Infra

server.py

@@ -3,9 +3,7 @@
 from __future__ import annotations
 
 import argparse
-import hashlib
 import io
-import json
 import os
 import posixpath
 import signal
@@ -13,59 +11,26 @@ import sys
 from functools import partial
 from http.server import SimpleHTTPRequestHandler, ThreadingHTTPServer
 
+from worker import WORKER, stamp_worker, walk
+
 NO_CACHE_NAMES = {"sw.js"}
 NO_CACHE_EXTS = {".html", ".njk", ".json", ".webmanifest"}
 
 BOOT_PAGE = "/boot.html"
 
-WORKER = "sw.js"
+_stamped = (None, None)
 
-VERSION_LINE = "const VERSION = 'dev';"
-LIBRARY_VERSION_LINE = "const LIBRARY_VERSION = 'dev';"
-LIBRARY_LINE = "const LIBRARY = [];"
-
-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):
-    out = hashlib.sha256()
-    for rel in sorted(files):
-        st = os.stat(files[rel])
-        out.update(("%s\0%d\0%d\0" % (rel, st.st_size, st.st_mtime_ns)).encode())
-    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")
+def cached_worker(roots):
+    # Stamping hashes every file the worker lists, 11 MB of them, and browsers
+    # ask for sw.js on almost every load. Stats are cheap, so redo the stamp
+    # only when one moves: often under compose, never in a baked image.
+    global _stamped
+    key = tuple((rel, st.st_size, st.st_mtime_ns)
+                for rel, st in ((rel, os.stat(path))
+                                for rel, path in sorted(walk(roots).items())))
+    if _stamped[0] != key:
+        _stamped = (key, stamp_worker(roots))
+    return _stamped[1]
 
 class Handler(SimpleHTTPRequestHandler):
     extensions_map = {
@@ -106,7 +71,7 @@ class Handler(SimpleHTTPRequestHandler):
 
     def send_worker(self):
         try:
-            body = stamp_worker(self.roots)
+            body = cached_worker(self.roots)
         except Exception as err:
             self.log_message("stamp failed: %s", err)
             self.send_error(500, "service worker unavailable")