renderer.ts

import { createRenderer } from 'vue-bundle-renderer/runtime'
import type { RenderResponse } from 'nitropack'
import type { Manifest } from 'vite'
import { appendHeader, getQuery } from 'h3'
import devalue from '@nuxt/devalue'
import { joinURL } from 'ufo'
import { renderToString as _renderToString } from 'vue/server-renderer'
import { useRuntimeConfig, useNitroApp, defineRenderHandler } from '#internal/nitro'
// eslint-disable-next-line import/no-restricted-paths
import type { NuxtApp, NuxtSSRContext } from '#app'

// @ts-ignore
import { buildAssetsURL } from '#paths'

export interface NuxtRenderHTMLContext {
  htmlAttrs: string[]
  head: string[]
  bodyAttrs: string[]
  bodyPreprend: string[]
  body: string[]
  bodyAppend: string[]
}

export interface NuxtRenderResponse {
  body: string,
  statusCode: number,
  statusMessage?: string,
  headers: Record<string, string>
}

interface ClientManifest {}

// @ts-ignore
const getClientManifest: () => Promise<Manifest> = () => import('#build/dist/server/client.manifest.mjs')
  .then(r => r.default || r)
  .then(r => typeof r === 'function' ? r() : r) as Promise<ClientManifest>

// @ts-ignore
const getServerEntry = () => import('#build/dist/server/server.mjs').then(r => r.default || r)

// @ts-ignore
const getSSRStyles = (): Promise<Record<string, () => Promise<string[]>>> => import('#build/dist/server/styles.mjs').then(r => r.default || r)

// -- SSR Renderer --
const getSSRRenderer = lazyCachedFunction(async () => {
  // Load client manifest
  const manifest = await getClientManifest()
  if (!manifest) { throw new Error('client.manifest is not available') }

  // Load server bundle
  const createSSRApp = await getServerEntry()
  if (!createSSRApp) { throw new Error('Server bundle is not available') }

  const options = {
    manifest,
    renderToString,
    buildAssetsURL
  }
  // Create renderer
  const renderer = createRenderer(createSSRApp, options)

  type RenderToStringParams = Parameters<typeof _renderToString>
  async function renderToString (input: RenderToStringParams[0], context: RenderToStringParams[1]) {
    const html = await _renderToString(input, context)
    // In development with vite-node, the manifest is on-demand and will be available after rendering
    if (process.dev && process.env.NUXT_VITE_NODE_OPTIONS) {
      renderer.rendererContext.updateManifest(await getClientManifest())
    }
    return `<div id="__nuxt">${html}</div>`
  }

  return renderer
})

// -- SPA Renderer --
const getSPARenderer = lazyCachedFunction(async () => {
  const manifest = await getClientManifest()

  const options = {
    manifest,
    renderToString: () => '<div id="__nuxt"></div>',
    buildAssetsURL
  }
  // Create SPA renderer and cache the result for all requests
  const renderer = createRenderer(() => () => {}, options)
  const result = await renderer.renderToString({})

  const renderToString = (ssrContext: NuxtSSRContext) => {
    const config = useRuntimeConfig()
    ssrContext!.payload = {
      serverRendered: false,
      config: {
        public: config.public,
        app: config.app
      },
      data: {},
      state: {}
    }
    ssrContext!.renderMeta = ssrContext!.renderMeta ?? (() => ({}))
    return Promise.resolve(result)
  }

  return { renderToString }
})

const PAYLOAD_CACHE = (process.env.NUXT_PAYLOAD_EXTRACTION && process.env.prerender) ? new Map() : null // TODO: Use LRU cache
const PAYLOAD_URL_RE = /\/_payload(\.[a-zA-Z0-9]+)?.js(\?.*)?$/

const PRERENDER_NO_SSR_ROUTES = new Set(['/index.html', '/200.html', '/404.html'])

export default defineRenderHandler(async (event) => {
  // Whether we're rendering an error page
  const ssrError = event.req.url?.startsWith('/__nuxt_error')
    ? getQuery(event) as Exclude<NuxtApp['payload']['error'], Error>
    : null
  let url = ssrError?.url as string || event.req.url!

  // Whether we are rendering payload route
  const isRenderingPayload = PAYLOAD_URL_RE.test(url)
  if (isRenderingPayload) {
    url = url.substring(0, url.lastIndexOf('/')) || '/'
    event.req.url = url
    if (process.env.prerender && PAYLOAD_CACHE!.has(url)) {
      return PAYLOAD_CACHE!.get(url)
    }
  }

  // Initialize ssr context
  const ssrContext: NuxtSSRContext = {
    url,
    event,
    req: event.req,
    res: event.res,
    runtimeConfig: useRuntimeConfig() as NuxtSSRContext['runtimeConfig'],
    noSSR:
      !!(process.env.NUXT_NO_SSR) ||
      !!(event.req.headers['x-nuxt-no-ssr']) ||
      (process.env.prerender ? PRERENDER_NO_SSR_ROUTES.has(url) : false),
    error: !!ssrError,
    nuxt: undefined!, /* NuxtApp */
    payload: (ssrError ? { error: ssrError } : {}) as NuxtSSRContext['payload']
  }

  // Whether we are prerendering route
  const _PAYLOAD_EXTRACTION = process.env.prerender && process.env.NUXT_PAYLOAD_EXTRACTION && !ssrContext.noSSR
  const payloadURL = _PAYLOAD_EXTRACTION ? joinURL(useRuntimeConfig().app.baseURL, url, '_payload.js') : undefined
  if (process.env.prerender) {
    ssrContext.payload.prerenderedAt = Date.now()
  }

  // Render app
  const renderer = (process.env.NUXT_NO_SSR || ssrContext.noSSR) ? await getSPARenderer() : await getSSRRenderer()
  const _rendered = await renderer.renderToString(ssrContext).catch((err) => {
    if (!ssrError) {
      // Use explicitly thrown error in preference to subsequent rendering errors
      throw ssrContext.payload?.error || err
    }
  })
  await ssrContext.nuxt?.hooks.callHook('app:rendered', { ssrContext })

  // Handle errors
  if (!_rendered) {
    return undefined!
  }
  if (ssrContext.payload?.error && !ssrError) {
    throw ssrContext.payload.error
  }

  // Directly render payload routes
  if (isRenderingPayload) {
    const response = renderPayloadResponse(ssrContext)
    if (process.env.prerender) {
      PAYLOAD_CACHE!.set(url, response)
    }
    return response
  }

  if (_PAYLOAD_EXTRACTION) {
    // Hint nitro to prerender payload for this route
    appendHeader(event, 'x-nitro-prerender', joinURL(url, '_payload.js'))
    // Use same ssr context to generate payload for this route
    PAYLOAD_CACHE!.set(url, renderPayloadResponse(ssrContext))
  }

  // Render meta
  const renderedMeta = await ssrContext.renderMeta?.() ?? {}

  // Render inline styles
  const inlinedStyles = process.env.NUXT_INLINE_STYLES
    ? await renderInlineStyles(ssrContext.modules ?? ssrContext._registeredComponents ?? [])
    : ''

  // Create render context
  const htmlContext: NuxtRenderHTMLContext = {
    htmlAttrs: normalizeChunks([renderedMeta.htmlAttrs]),
    head: normalizeChunks([
      renderedMeta.headTags,
      _PAYLOAD_EXTRACTION ? `<link rel="modulepreload" href="${payloadURL}">` : null,
      _rendered.renderResourceHints(),
      _rendered.renderStyles(),
      inlinedStyles,
      ssrContext.styles
    ]),
    bodyAttrs: normalizeChunks([renderedMeta.bodyAttrs!]),
    bodyPreprend: normalizeChunks([
      renderedMeta.bodyScriptsPrepend,
      ssrContext.teleports?.body
    ]),
    body: [
      // TODO: Rename to _rendered.body in next vue-bundle-renderer
      _rendered.html
    ],
    bodyAppend: normalizeChunks([
      process.env.NUXT_NO_SCRIPTS
        ? undefined
        : (_PAYLOAD_EXTRACTION
            ? `<script type="module">import p from "${payloadURL}";window.__NUXT__={...p,...(${devalue(splitPayload(ssrContext).initial)})}</script>`
            : `<script>window.__NUXT__=${devalue(ssrContext.payload)}</script>`
          ),
      _rendered.renderScripts(),
      // Note: bodyScripts may contain tags other than <script>
      renderedMeta.bodyScripts
    ])
  }

  // Allow hooking into the rendered result
  const nitroApp = useNitroApp()
  await nitroApp.hooks.callHook('render:html', htmlContext, { event })

  // Construct HTML response
  const response: RenderResponse = {
    body: renderHTMLDocument(htmlContext),
    statusCode: event.res.statusCode,
    statusMessage: event.res.statusMessage,
    headers: {
      'Content-Type': 'text/html;charset=UTF-8',
      'X-Powered-By': 'Nuxt'
    }
  }

  return response
})

function lazyCachedFunction <T> (fn: () => Promise<T>): () => Promise<T> {
  let res: Promise<T> | null = null
  return () => {
    if (res === null) {
      res = fn().catch((err) => { res = null; throw err })
    }
    return res
  }
}

function normalizeChunks (chunks: (string | undefined)[]) {
  return chunks.filter(Boolean).map(i => i!.trim())
}

function joinTags (tags: string[]) {
  return tags.join('')
}

function joinAttrs (chunks: string[]) {
  return chunks.join(' ')
}

function renderHTMLDocument (html: NuxtRenderHTMLContext) {
  return `<!DOCTYPE html>
<html ${joinAttrs(html.htmlAttrs)}>
<head>${joinTags(html.head)}</head>
<body ${joinAttrs(html.bodyAttrs)}>${joinTags(html.bodyPreprend)}${joinTags(html.body)}${joinTags(html.bodyAppend)}</body>
</html>`
}

async function renderInlineStyles (usedModules: Set<string> | string[]) {
  const styleMap = await getSSRStyles()
  const inlinedStyles = new Set<string>()
  for (const mod of ['entry', ...usedModules]) {
    if (mod in styleMap) {
      for (const style of await styleMap[mod]()) {
        inlinedStyles.add(`<style>${style}</style>`)
      }
    }
  }
  return Array.from(inlinedStyles).join('')
}

function renderPayloadResponse (ssrContext: NuxtSSRContext) {
  return <RenderResponse> {
    body: `export default ${devalue(splitPayload(ssrContext).payload)}`,
    statusCode: ssrContext.event.res.statusCode,
    statusMessage: ssrContext.event.res.statusMessage,
    headers: {
      'content-type': 'text/javascript;charset=UTF-8',
      'x-powered-by': 'Nuxt'
    }
  }
}

function splitPayload (ssrContext: NuxtSSRContext) {
  const { data, prerenderedAt, ...initial } = ssrContext.payload
  return {
    initial: { ...initial, prerenderedAt },
    payload: { data, prerenderedAt }
  }
}