feat: link desktop downloads to official GitHub releases

src/lib/desktop-platform.ts

@@ -0,0 +1,10 @@
+export type SuggestedPlatform = 'macos' | 'windows' | 'linux' | 'mobile' | null;
+
+/** A local display hint only; it never changes the available downloads. */
+export function suggestDesktopPlatform(platform: string, userAgent: string, touchPoints = 0): SuggestedPlatform {
+  if (/Android|iPhone|iPad|iPod/i.test(userAgent) || /Mac/i.test(platform) && touchPoints > 1) return 'mobile';
+  if (/Win/i.test(platform)) return 'windows';
+  if (/Mac/i.test(platform)) return 'macos';
+  if (/Linux/i.test(platform)) return 'linux';
+  return null;
+}

src/lib/desktop-release-server.ts

@@ -0,0 +1,7 @@
+import { unstable_cache } from 'next/cache';
+import { fetchDesktopRelease } from './desktop-releases';
+
+// Cache the bounded parsed result, including failures, for five minutes.
+export const latestDesktopRelease = unstable_cache(
+  () => fetchDesktopRelease(), ['official-smirk-desktop-release-v1'], { revalidate: 300 },
+);

src/lib/desktop-releases.ts

@@ -0,0 +1,70 @@
+export const OFFICIAL_RELEASES = 'https://github.com/Such-Software/smirk-monorepo/releases';
+export const LATEST_RELEASE_API = 'https://api.github.com/repos/Such-Software/smirk-monorepo/releases/latest';
+export const RELEASE_METADATA_MAX_BYTES = 512 * 1024;
+export type DesktopPlatform = 'macos' | 'windows' | 'linux';
+export interface DesktopRelease {
+  version: string;
+  releaseUrl: string;
+  downloads: Record<DesktopPlatform, string | null>;
+}
+
+function record(value: unknown): Record<string, unknown> | null {
+  return value !== null && typeof value === 'object' && !Array.isArray(value) ? value as Record<string, unknown> : null;
+}
+
+/** Only the published installer names used by the official release are offered. */
+export function parseDesktopRelease(input: unknown): DesktopRelease | null {
+  const release = record(input);
+  if (!release || release.draft !== false || release.prerelease !== false
+      || typeof release.tag_name !== 'string' || !/^v(?:0|[1-9][0-9]{0,5})\.(?:0|[1-9][0-9]{0,5})\.(?:0|[1-9][0-9]{0,5})$/.test(release.tag_name)
+      || release.html_url !== `${OFFICIAL_RELEASES}/tag/${release.tag_name}`
+      || typeof release.published_at !== 'string' || !Number.isFinite(Date.parse(release.published_at))
+      || !Array.isArray(release.assets) || release.assets.length > 100) return null;
+  const version = release.tag_name.slice(1);
+  const names: Record<DesktopPlatform, string> = {
+    macos: `Smirk-Wallet-${version}.dmg`,
+    linux: `Smirk.Wallet_${version}_amd64.AppImage`,
+    windows: `Smirk.Wallet_${version}_x64-setup.exe`,
+  };
+  const downloads = {} as DesktopRelease['downloads'];
+  for (const platform of ['macos', 'windows', 'linux'] as const) {
+    const matches = release.assets.map(record).filter(asset => asset?.name === names[platform]);
+    const asset = matches.length === 1 ? matches[0] : null;
+    const expected = `${OFFICIAL_RELEASES}/download/${release.tag_name}/${names[platform]}`;
+    downloads[platform] = asset?.state === 'uploaded' && Number.isSafeInteger(asset.size) && Number(asset.size) > 0
+      && asset.browser_download_url === expected ? expected : null;
+  }
+  return { version, releaseUrl: release.html_url as string, downloads };
+}
+
+/** Metadata only. No authentication, visitor headers, redirects or artifact proxy. */
+export async function fetchDesktopRelease(fetcher: typeof fetch = fetch): Promise<DesktopRelease | null> {
+  const controller = new AbortController();
+  const timer = setTimeout(() => controller.abort(), 5000);
+  let reader: ReadableStreamDefaultReader<Uint8Array> | undefined;
+  try {
+    const response = await fetcher(LATEST_RELEASE_API, {
+      method: 'GET', redirect: 'error', cache: 'no-store', signal: controller.signal,
+      headers: { Accept: 'application/vnd.github+json', 'User-Agent': 'Smirk-Website-Downloads', 'X-GitHub-Api-Version': '2022-11-28' },
+    });
+    if (!response.ok || !response.body || !response.headers.get('content-type')?.toLowerCase().includes('application/json')) return null;
+    const length = response.headers.get('content-length');
+    if (length !== null && (!/^[0-9]+$/.test(length) || Number(length) > RELEASE_METADATA_MAX_BYTES)) return null;
+    reader = response.body.getReader();
+    const chunks: Uint8Array[] = []; let size = 0;
+    for (;;) {
+      const next = await reader.read();
+      if (next.done) break;
+      size += next.value.byteLength;
+      if (size > RELEASE_METADATA_MAX_BYTES) return null;
+      chunks.push(next.value);
+    }
+    const bytes = new Uint8Array(size); let offset = 0;
+    for (const chunk of chunks) { bytes.set(chunk, offset); offset += chunk.byteLength; }
+    return parseDesktopRelease(JSON.parse(new TextDecoder('utf-8', { fatal: true }).decode(bytes)));
+  } catch { return null; }
+  finally {
+    controller.abort(); clearTimeout(timer);
+    if (reader) { void reader.cancel().catch(() => {}); reader.releaseLock(); }
+  }
+}