havre: update pill — notice a new version and offer a reload (as gandora does)

ventures/havre/update.js

@@ -0,0 +1,37 @@
+// update.js: an installed Havre has no address bar to refresh from, so the page notices when a new version has been
+// published and offers a reload, like gandora's pill. It fingerprints the files the app is made of when it opens,
+// checks again whenever it comes back to the foreground (and every ten minutes), and shows the pill when they differ.
+// Checking fetches with cache: "reload", which also refreshes the browser's copies, so the reload gets the new files.
+(() => {
+  const FILES = ["./", "app.js", "style.css", "workflows.js", "abilities.js", "card.js", "venice.js", "memory.js",
+    "threads.js", "media.js", "backup.js", "theme.js"];
+  let base = null, shown = false, busy = false;
+  async function print() {
+    const parts = await Promise.all(FILES.map((f) => fetch(f, { cache: "reload" }).then((r) => (r.ok ? r.text() : "")).catch(() => null)));
+    if (parts.some((p) => p === null)) return null;                        // offline: no verdict
+    const d = await crypto.subtle.digest("SHA-256", new TextEncoder().encode(parts.join("\u0000")));
+    return Array.from(new Uint8Array(d), (b) => b.toString(16).padStart(2, "0")).join("");
+  }
+  function show() {
+    if (shown) return;
+    shown = true;
+    const b = document.createElement("button");
+    b.id = "upd"; b.type = "button"; b.textContent = "NEW VERSION · RELOAD";
+    b.addEventListener("click", () => location.reload());
+    document.body.append(b);
+  }
+  async function check() {
+    if (busy || shown || !crypto.subtle) return;
+    busy = true;
+    try {
+      const now = await print();
+      if (!now) return;
+      if (!base) base = now;
+      else if (now !== base) show();
+    } finally { busy = false; }
+  }
+  if (location.protocol !== "https:") return;
+  setTimeout(check, 3000);
+  setInterval(check, 10 * 60 * 1000);
+  document.addEventListener("visibilitychange", () => { if (document.visibilityState === "visible") check(); });
+})();