refactor(webserver): extract SPA dist serving to the frontend-static fallback seat

The webserver's built-in static dist serving becomes a single-owner fallback seat (registerFallback/applyIndexTaps); the SPA server moves to the new @deepseek-ai/dsh-frontend-static plugin so the composing application owns its dist as composition, not carrier config. distIndex leaves the webserver schema; unclaimed fallback answers 404.
2026-08-06 04:39:52 +08:00
parent d0cb6770a9
commit 2ee2ee2f96
23 changed files with 567 additions and 141 deletions
@@ -0,0 +1,109 @@
+/**
+ * @deepseek-ai/dsh-frontend-static — SPA dist server over the webserver
+ * fallback seat: serves the built frontend directory with the semantics the
+ * Web shell locked at step1 — traversal outside the dist root is 403, any
+ * miss falls back to index.html with HTTP 200 (SPA routing), unknown
+ * extensions ship as octet-stream, non-GET/HEAD is 405. Every index response
+ * runs through the webserver's registered index taps (boot-manifest
+ * injection). The dist location is workspace knowledge of the composing
+ * application, so `distIndex` is typically supplied through a `!!js`
+ * expression, never hardcoded by a deployment.
+ * @module @deepseek-ai/dsh-frontend-static
+ */
+
+import type { ServerResponse } from 'node:http'
+import { readFile } from 'node:fs/promises'
+import { dirname, extname, join, normalize, resolve, sep } from 'node:path'
+import type { Context } from 'cordis'
+import z from 'schemastery'
+import type {} from '@deepseek-ai/dsh-host-webserver'
+
+/** Stable Cordis plugin name. */
+export const name = 'frontend-static'
+
+/** Service required before the fallback seat can be claimed. */
+export const inject = ['httpServer']
+
+/** Plugin config: the dist anchor. */
+export interface Config {
+  /** Absolute path of index.html inside the dist root. */
+  distIndex: string
+}
+
+export const Config: z<Config> = z.object({
+  distIndex: z.string().required(),
+})
+
+const MIME: Record<string, string> = {
+  '.html': 'text/html; charset=utf-8',
+  '.js': 'text/javascript; charset=utf-8',
+  '.css': 'text/css; charset=utf-8',
+  '.svg': 'image/svg+xml',
+  '.json': 'application/json',
+  '.map': 'application/json',
+}
+
+/**
+ * Serve one GET/HEAD static request from the dist root.
+ * @param pathname - decoded URL pathname of the request.
+ * @param res - the node:http response to write.
+ * @param distRoot - absolute dist root directory (resolved by the caller).
+ * @param distIndex - absolute path of index.html inside distRoot.
+ * @param renderIndex - produces the index.html body (index-tap injection) for
+ * `/` and every SPA fallback.
+ */
+export async function serveStatic(
+  pathname: string, res: ServerResponse, distRoot: string, distIndex: string,
+  renderIndex: () => Promise<string>,
+): Promise<void> {
+  const target = resolve(normalize(join(distRoot, pathname)))
+  // Traversal rejection: the target must be distRoot itself (`/`) or stay under
+  // it. `sep`, not '/': resolve() emits backslash paths on Windows, where a '/'
+  // suffix would reject every legitimate subpath as traversal.
+  if (target !== distRoot && !target.startsWith(distRoot + sep)) {
+    res.writeHead(403)
+    res.end()
+    return
+  }
+  const serveIndex = async (): Promise<void> => {
+    const body = await renderIndex()
+    res.writeHead(200, { 'content-type': MIME['.html'] })
+    res.end(body)
+  }
+  if (target === distRoot || target === distIndex) {
+    await serveIndex()
+    return
+  }
+  try {
+    const body = await readFile(target)
+    res.writeHead(200, { 'content-type': MIME[extname(target)] ?? 'application/octet-stream' })
+    res.end(body)
+  } catch {
+    // Miss (ENOENT/EISDIR) falls back to index.html with 200 (SPA routing).
+    await serveIndex()
+  }
+}
+
+/**
+ * Claim the webserver fallback seat and serve the dist.
+ * @param ctx - plugin context carrying the httpServer service.
+ * @param config - validated {@link Config}.
+ */
+export function apply(ctx: Context, config: Config): void {
+  const distIndex = config.distIndex
+  const distRoot = dirname(distIndex)
+  const renderIndex = async (): Promise<string> =>
+    ctx.httpServer.applyIndexTaps(await readFile(distIndex, 'utf8'))
+  ctx.effect(() => ctx.httpServer.registerFallback(async (req, res) => {
+    // Non-GET/HEAD without a matching named route is 405 (fallback-only
+    // semantics: named routes own their method handling).
+    if (req.method !== 'GET' && req.method !== 'HEAD') {
+      res.writeHead(405)
+      res.end()
+      return
+    }
+    /* v8 ignore next -- node:http always sets url on server requests */
+    const rawPath = new URL(req.url ?? '/', 'http://x').pathname
+    await serveStatic(decodeURIComponent(rawPath), res, distRoot, distIndex, renderIndex)
+  }), 'frontend-static: fallback seat')
+}
@@ -0,0 +1,53 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-frontend-static`.
+ * @module @deepseek-ai/dsh-frontend-static/invariant
+ */
+
+import type { Context } from 'cordis'
+// Empty type import carries the Loader's Fiber#entry merge read below.
+import type {} from '@cordisjs/plugin-loader'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-frontend-static'
+
+/** Cordis companion plugin name. */
+export const name = 'frontend-static-invariant'
+/** Service required before the companion can register. */
+export const inject = ['invariants']
+
+/**
+ * Owned relation: the fallback seat and the owning fiber must stay symmetric —
+ * after the fiber holding the seat unloads, the seat must be claimable again
+ * (a stale fallback would keep serving a disposed plugin's dist). Checked on
+ * every fiber teardown by probing the registerFallback single-owner contract:
+ * when this package's plugin is not mounted, a claim+release cycle must
+ * succeed twice; residue from a leaked disposer makes the second claim throw.
+ */
+const install: InvariantInstaller = (ctx, fail) => {
+  ctx.on('internal/plugin', (fiber) => {
+    // Only audit teardowns of this package's own rows: while a live
+    // frontend-static row legitimately holds the seat, the probe would
+    // false-positive on the legitimate owner.
+    if (fiber.entry?.options.name !== PACKAGE_NAME) return
+    const server = ctx.get('httpServer') as
+      | { registerFallback(handler: () => void): () => void }
+      | undefined
+    if (server === undefined) return // torn down with the webserver itself
+    // The probe handlers are registered and immediately released, never invoked.
+    /* v8 ignore next 4 -- the arrow bodies are dead by design */
+    try {
+      server.registerFallback(() => {})()
+      server.registerFallback(() => {})()
+    } catch {
+      fail('frontend-static fallback disposer left the seat claimed — seat ownership and fiber lifecycle diverged')
+    }
+  }, { global: true })
+}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))