Let each install pick its app icon

Settings > General gets an App icon (super admin): one of the seven
stones, or an uploaded image with the picked stone as a top-left corner
mark (inside a round launcher's crop, clear of the browser's badge),
previewed in both launcher crops before saving.

Uploads are decoded and cropped to a stored square (no SVG); the set is
drawn into DATA_DIR/install-icon/<version>/ and served publicly and
immutable. The manifest, head icon links and push notifications point at
it; the ember stone keeps the stock icons. The generator shares the icon
renderer.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/functions/backend/install-icon/save-install-icon.ts

@@ -0,0 +1,95 @@
+import { createHash } from "node:crypto";
+import { existsSync } from "node:fs";
+import { mkdir, readdir, rm, writeFile } from "node:fs/promises";
+import path from "node:path";
+import {
+    PwaInstallIconSettingKey,
+    type PwaInstallIcon,
+    type PwaInstallIconMode,
+} from "@/src/data/pwa-data";
+import type { BotHue } from "@/src/dict/bot-dict";
+import saveAppSetting from "@/src/functions/backend/db/app-settings/save-app-setting";
+import renderInstallIcons from "@/src/functions/server/pwa/render-install-icons";
+import AppError from "@/src/utils/app-error";
+import grabDirNames from "@/src/utils/grab-dir-names";
+import grabInstallIconDir from "./grab-install-icon-dir";
+import grabPwaBackground from "./grab-pwa-background";
+import normalizeInstallIconUpload from "./normalize-install-icon-upload";
+
+type Params = {
+    mode: PwaInstallIconMode;
+    stone: BotHue;
+    mark: boolean;
+    /**
+     * A newly picked image, decoded already.
+     */
+    image?: Buffer | null;
+};
+
+/**
+ * Saves the install's icon and draws its icon set. A new image replaces
+ * the stored one; going back to a stone drops it. The ember stone is the
+ * stock icon, so it needs no set. Older sets are removed once the new one
+ * is in place; each has its own folder, so a cached icon is never stale.
+ */
+export default async function saveInstallIcon({ mode, stone, mark, image }: Params) {
+    const dir = grabInstallIconDir();
+    const source_path = path.join(dir, "source.png");
+    const background = await grabPwaBackground();
+
+    await mkdir(dir, { recursive: true });
+
+    if (image) {
+        await writeFile(source_path, await normalizeInstallIconUpload({ buffer: image, background }));
+    }
+
+    if (mode == "stone") {
+        await rm(source_path, { force: true });
+    }
+
+    if (mode == "image" && !existsSync(source_path)) {
+        throw new AppError(`Upload an image first.`);
+    }
+
+    const source = mode == "image" ? Buffer.from(await Bun.file(source_path).arrayBuffer()) : null;
+    const is_stock = mode == "stone" && stone == "ember";
+
+    const version = is_stock
+        ? null
+        : createHash("sha256")
+              .update(JSON.stringify({ mode, stone, mark }))
+              .update(source || "")
+              .digest("hex")
+              .slice(0, 12);
+
+    const icon: PwaInstallIcon = { mode, stone, mark, version };
+
+    if (version) {
+        const stone_svg = Buffer.from(
+            await Bun.file(
+                path.join(grabDirNames().ROOT_DIR, "public/brand/icons", `${stone}.svg`),
+            ).arrayBuffer(),
+        );
+        const files = await renderInstallIcons({ icon, stone_svg, image: source, background });
+        const set_dir = path.join(dir, version);
+
+        await mkdir(set_dir, { recursive: true });
+
+        for (const [name, bytes] of Object.entries(files)) {
+            await writeFile(path.join(set_dir, `${name}.png`), bytes);
+        }
+    }
+
+    for (const entry of await readdir(dir, { withFileTypes: true })) {
+        if (entry.isDirectory() && entry.name != version) {
+            await rm(path.join(dir, entry.name), { recursive: true, force: true });
+        }
+    }
+
+    await saveAppSetting({
+        key: PwaInstallIconSettingKey,
+        value: is_stock ? null : JSON.stringify(icon),
+    });
+
+    return icon;
+}