feat(demo): add rolling cross-platform imports

edge-functions/api/demo/[[path]].js

@@ -0,0 +1,37 @@
+const DEMO_ORIGIN = 'https://chatlab.fun/assets/demo'
+const DEMO_LOCALES = new Set(['cn', 'en'])
+const DEMO_FILES = new Set([
+  'demo-group.json',
+  'demo-private-A-cuilan.json',
+  'demo-private-B-wukong.json',
+  'demo-private-C-spider.json',
+])
+
+export async function proxyDemoRequest(context, fetchRemote = fetch) {
+  const rawPath = Array.isArray(context.params.path) ? context.params.path.join('/') : String(context.params.path || '')
+  const [locale, filename, ...extra] = rawPath.split('/')
+  if (extra.length > 0 || !DEMO_LOCALES.has(locale) || !DEMO_FILES.has(filename)) {
+    return new Response('Not found', { status: 404 })
+  }
+
+  try {
+    const upstream = await fetchRemote(`${DEMO_ORIGIN}/${locale}/${filename}`)
+    if (!upstream.ok || !upstream.body) {
+      return new Response('Demo asset unavailable', { status: upstream.status || 502 })
+    }
+
+    return new Response(upstream.body, {
+      status: 200,
+      headers: {
+        'Content-Type': upstream.headers.get('content-type') || 'application/json',
+        'Cache-Control': 'public, max-age=86400',
+      },
+    })
+  } catch {
+    return new Response('Demo asset unavailable', { status: 502 })
+  }
+}
+
+export function onRequestGet(context) {
+  return proxyDemoRequest(context)
+}

edge-functions/api/demo/demo-proxy.test.js

@@ -0,0 +1,32 @@
+import assert from 'node:assert/strict'
+import { describe, it } from 'node:test'
+import { proxyDemoRequest } from './[[path]].js'
+
+describe('Web WASM demo asset proxy', () => {
+  it('only proxies known localized demo files', async () => {
+    const urls = []
+    const response = await proxyDemoRequest({ params: { path: 'cn/demo-group.json' } }, async (url) => {
+      urls.push(url)
+      return new Response('demo content', {
+        status: 200,
+        headers: { 'content-type': 'application/json' },
+      })
+    })
+
+    assert.equal(response.status, 200)
+    assert.equal(response.headers.get('content-type'), 'application/json')
+    assert.equal(await response.text(), 'demo content')
+    assert.deepEqual(urls, ['https://chatlab.fun/assets/demo/cn/demo-group.json'])
+  })
+
+  it('rejects unknown paths before making a remote request', async () => {
+    let requested = false
+    const response = await proxyDemoRequest({ params: { path: 'cn/../../secret.json' } }, async () => {
+      requested = true
+      return new Response()
+    })
+
+    assert.equal(response.status, 404)
+    assert.equal(requested, false)
+  })
+})