feat: token-protected site cache purge route

- POST /api/__journal__/cache/purge removes every Nitro route-cache entry
- 404 without a 32-character token or behind a proxy, 401 on a wrong bearer
  token (constant-time over sha256 digests)
- routeRules keep /api/__journal__/** out of the route cache
- runtimeConfig.journal.cachePurgeToken (NUXT_JOURNAL_CACHE_PURGE_TOKEN)
- fixture API reload(); testing/purge-check.mjs proves a cached page shows
  a change after a purge; the playground caches with swr 300

testing/fixture-api.mjs

@@ -18,7 +18,7 @@ const SORT_COLUMNS = new Set(['published_at', 'created_at', 'updated_at', 'title
 
 /**
  * @typedef {{ method: string, url: string, xff: string | null }} FixtureRequest
- * @typedef {{ url: string, requests: FixtureRequest[], close: () => Promise<void> }} FixtureApi
+ * @typedef {{ url: string, requests: FixtureRequest[], reload: () => void, close: () => Promise<void> }} FixtureApi
  */
 
 /** @param {string} dir @param {string} name @param {any} fallback */
@@ -118,19 +118,28 @@ function sibling(post) {
  */
 export function startFixtureApi({ dir, port = 0 }) {
   /** @type {any[]} */
-  const posts = readJson(dir, 'posts.json', [])
+  let posts = []
   /** @type {any[]} */
-  const categories = readJson(dir, 'categories.json', [])
+  let categories = []
   /** @type {any[]} */
-  const tags = readJson(dir, 'tags.json', [])
+  let tags = []
   /** @type {any[]} */
-  const authors = readJson(dir, 'authors.json', [])
+  let authors = []
   let rss = ''
-  try {
-    rss = readFileSync(join(dir, 'rss.xml'), 'utf8')
-  } catch {
-    rss = '<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"><channel></channel></rss>'
+  // Reads (or re-reads) the fixtures, so a check can change a fixture file
+  // while the API runs.
+  const load = () => {
+    posts = readJson(dir, 'posts.json', [])
+    categories = readJson(dir, 'categories.json', [])
+    tags = readJson(dir, 'tags.json', [])
+    authors = readJson(dir, 'authors.json', [])
+    try {
+      rss = readFileSync(join(dir, 'rss.xml'), 'utf8')
+    } catch {
+      rss = '<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"><channel></channel></rss>'
+    }
   }
+  load()
 
   /** @type {FixtureRequest[]} */
   const requests = []
@@ -240,6 +249,7 @@ export function startFixtureApi({ dir, port = 0 }) {
       resolve({
         url: `http://127.0.0.1:${addr.port}`,
         requests,
+        reload: load,
         close: () => new Promise((done) => server.close(() => done())),
       })
     })

testing/purge-check.mjs

@@ -0,0 +1,167 @@
+#!/usr/bin/env node
+// Site cache purge check: proves on a built Nuxt server with swr route rules
+// that a page cached before a content change shows the change on the first
+// request after a purge, and that the purge route refuses unauthenticated,
+// wrong-token and proxied requests.
+//
+//   node purge-check.mjs --output <.output dir> --fixtures <dir> --kind post|category --slug <slug> --path <page path>
+//
+// The fixtures are copied to a temporary directory, so the source fixtures
+// never change. The last line is "purge-check: ok (<n> checks)" on success;
+// every failure prints "purge-check: FAIL ..." and exits 1.
+
+import { randomBytes } from 'node:crypto'
+import { cpSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join, resolve } from 'node:path'
+import { startFixtureApi } from './fixture-api.mjs'
+import { startNuxtServer } from './nuxt-server.mjs'
+
+const PURGE_PATH = '/api/__journal__/cache/purge'
+
+/** @param {string[]} argv */
+function parseArgs(argv) {
+  /** @type {Record<string, string>} */
+  const out = {}
+  const names = new Set(['--output', '--fixtures', '--kind', '--slug', '--path'])
+  for (let i = 0; i < argv.length; i++) {
+    const arg = argv[i]
+    if (!names.has(arg)) throw new Error(`unknown argument ${arg}`)
+    const v = argv[++i]
+    if (v === undefined) throw new Error(`${arg} needs a value`)
+    out[arg.slice(2)] = v
+  }
+  for (const name of names) {
+    if (!out[name.slice(2)]) throw new Error('--output, --fixtures, --kind, --slug and --path are required')
+  }
+  if (out.kind !== 'post' && out.kind !== 'category') throw new Error(`--kind must be post or category, got ${out.kind}`)
+  if (!out.path.startsWith('/')) throw new Error(`--path must start with "/", got ${out.path}`)
+  return /** @type {{ output: string, fixtures: string, kind: 'post' | 'category', slug: string, path: string }} */ (out)
+}
+
+/** @param {any[]} nodes @returns {any[]} */
+function flatten(nodes) {
+  return (nodes ?? []).flatMap((n) => [n, ...flatten(n.children)])
+}
+
+/**
+ * Appends a marker paragraph to the post's content and content_html, or to
+ * the category's content, in the fixture directory.
+ * @param {string} dir @param {'post' | 'category'} kind @param {string} slug @param {string} marker
+ */
+function appendMarker(dir, kind, slug, marker) {
+  const file = join(dir, kind === 'post' ? 'posts.json' : 'categories.json')
+  const rows = JSON.parse(readFileSync(file, 'utf8'))
+  const row = (kind === 'post' ? rows : flatten(rows)).find((/** @type {any} */ r) => r.slug === slug)
+  if (!row) throw new Error(`no ${kind} with slug ${slug} in ${file}`)
+  const para = `\n<p>${marker}</p>\n`
+  if (kind === 'post') {
+    row.content = (row.content ?? '') + `\n\n${marker}\n`
+    row.content_html = (row.content_html ?? '') + para
+  } else {
+    row.content = (row.content ?? '') + para
+  }
+  writeFileSync(file, JSON.stringify(rows, null, 2))
+}
+
+async function main() {
+  const args = parseArgs(process.argv.slice(2))
+  const dir = mkdtempSync(join(tmpdir(), 'purge-check-'))
+  cpSync(resolve(args.fixtures), dir, { recursive: true })
+  const token = randomBytes(24).toString('hex')
+  const marker = `purge-check-marker-${randomBytes(6).toString('hex')}`
+
+  /** @type {string[]} */
+  const failures = []
+  let checks = 0
+  /** @param {boolean} ok @param {string} what */
+  const check = (ok, what) => {
+    checks++
+    if (!ok) failures.push(what)
+    return ok
+  }
+
+  const api = await startFixtureApi({ dir })
+  /** @type {{ url: string, close: () => Promise<void> } | null} */
+  let nuxt = null
+  try {
+    nuxt = await startNuxtServer({
+      outputDir: args.output,
+      apiBase: `${api.url}/_journal/api/v1`,
+      env: { NUXT_JOURNAL_CACHE_PURGE_TOKEN: token },
+    })
+    const base = nuxt.url
+    /** @param {string} path @param {Record<string, string>} [headers] */
+    const get = async (path, headers = {}) => {
+      const res = await fetch(base + path, { redirect: 'manual', headers, signal: AbortSignal.timeout(20000) })
+      return { status: res.status, headers: res.headers, body: await res.text() }
+    }
+    /** @param {Record<string, string>} headers */
+    const purge = async (headers) => {
+      const res = await fetch(base + PURGE_PATH, {
+        method: 'POST',
+        headers: { 'content-type': 'application/json', ...headers },
+        body: JSON.stringify({ kind: args.kind, slug: args.slug }),
+        signal: AbortSignal.timeout(20000),
+      })
+      const text = await res.text()
+      /** @type {any} */
+      let json = null
+      try {
+        json = JSON.parse(text)
+      } catch {
+        json = null
+      }
+      return { status: res.status, json, text }
+    }
+    const auth = { authorization: `Bearer ${token}` }
+
+    // The steps stop at the first failure that makes the later ones
+    // meaningless; the failures are reported after the servers stop.
+    const steps = async () => {
+    // 1. The page renders and is cached.
+    const first = await get(args.path)
+    if (!check(first.status === 200, `GET ${args.path} before the change: status ${first.status}, want 200`)) return
+
+    // 2. Change the content behind the API; the cached page must not show it.
+    appendMarker(dir, args.kind, args.slug, marker)
+    api.reload()
+    const cached = await get(args.path)
+    check(cached.status === 200, `GET ${args.path} after the change: status ${cached.status}, want 200`)
+    if (!check(!cached.body.includes(marker), `GET ${args.path} shows the change before any purge: the page is not route-cached (missing swr route rules?)`)) return
+
+    // 3. An authorized purge removes the cached page.
+    const purged = await purge(auth)
+    check(purged.status === 200, `authorized purge: status ${purged.status}, want 200 (${purged.text.slice(0, 200)})`)
+    check(typeof purged.json?.purged === 'number' && purged.json.purged >= 1, `authorized purge: answer ${purged.text.slice(0, 200)}, want purged >= 1`)
+
+    // 4. The next request shows the change.
+    const fresh = await get(args.path)
+    check(fresh.status === 200 && fresh.body.includes(marker), `GET ${args.path} after the purge: status ${fresh.status}, change shown: ${fresh.body.includes(marker)}`)
+
+    // 5. Refused purges.
+    const none = await purge({})
+    check(none.status === 401, `purge without a token: status ${none.status}, want 401`)
+    const wrong = await purge({ authorization: `Bearer ${randomBytes(24).toString('hex')}` })
+    check(wrong.status === 401, `purge with a wrong token: status ${wrong.status}, want 401`)
+    const proxied = await purge({ ...auth, 'x-forwarded-for': '203.0.113.7' })
+    check(proxied.status === 404, `proxied purge with the right token: status ${proxied.status}, want 404`)
+    }
+    await steps()
+  } finally {
+    if (nuxt) await nuxt.close()
+    await api.close()
+    rmSync(dir, { recursive: true, force: true })
+  }
+
+  if (failures.length > 0) {
+    for (const f of failures) console.error(`purge-check: FAIL ${f}`)
+    process.exit(1)
+  }
+  console.log(`purge-check: ok (${checks} checks)`)
+}
+
+main().catch((err) => {
+  console.error(`purge-check: FAIL setup: ${err instanceof Error ? err.message : String(err)}`)
+  process.exit(1)
+})