allNextJsPages.js

const { join }                        = require('path')
const { readFileSync, readJSONSync }  = require('fs-extra')
const { NEXT_DIST_DIR }               = require('./config')

// Return all NextJS pages with route, file, type, and any other params
const getAllPages = () => {
  const pages = []

  // Read pages manifest that tells us which SSR and HTML pages exist
  const ssrAndHtmlPages = readJSONSync(
    join(NEXT_DIST_DIR, "serverless", "pages-manifest.json")
  )

  // Read prerender manifest that tells us which SSG pages exist
  const { routes: staticSsgPages, dynamicRoutes: dynamicSsgPages } = readJSONSync(
    join(NEXT_DIST_DIR, "prerender-manifest.json")
  )

  // Read routes manifest that tells us which data routes should exist
  const routesManifest = readJSONSync(
    join(NEXT_DIST_DIR, "routes-manifest.json")
  )
  const dataRoutes = routesManifest.dataRoutes || []

  // Get build ID that is used for data routes, e.g. /_next/data/BUILD_ID/...
  const fileContents  = readFileSync(join(NEXT_DIST_DIR, "BUILD_ID"))
  const buildId       = fileContents.toString()


  // Parse SSR and HTML pages
  Object.entries(ssrAndHtmlPages).forEach(([route, filePath]) => {
    // Skip framework pages, such as _app and _error
    if(["/_app", "/_document", "/_error"].includes(route))
      return

    // Skip page if it is actually an SSG page
    const normalizedRoute = route === "/index" ? "/" : route
    if(normalizedRoute in staticSsgPages || normalizedRoute in dynamicSsgPages)
      return

    // Check if we already have a page pointing to this file
    // If so, just add the route
    const existingPage = pages.find(page => page.filePath == filePath)
    if(existingPage) {
      existingPage.alternativeRoutes.push(route)
      return
    }

    // Otherwise, create new page
    const type = filePath.endsWith(".html") ? "html" : "ssr"
    const alternativeRoutes = []

    // Check if we have a data route for this page
    // This is relevant only for pages with getServerSideProps.
    // We need to add a second route for redirecting requests for
    // the JSON data to the Netlify Function.
    const dataRoute = dataRoutes.find(({ page }) => page === route)
    if(dataRoute)
      alternativeRoutes.push(join('/_next/data', buildId, `${route}.json`))

    pages.push(new Page({ route, type, filePath, alternativeRoutes }))
  })

  // Parse SSG pages
  Object.entries(staticSsgPages).forEach(([ route, { dataRoute }]) => {
    pages.push(new Page({ route, type: "ssg", dataRoute, alternativeRoutes: route === "/" ? ["/index"] : [] }))
  })
  Object.entries(dynamicSsgPages).forEach(([ route, { dataRoute, fallback }]) => {
    // Ignore pages without fallback, these are already handled by the
    // static SSG page block above
    if(fallback === false)
      return

    const filePath = join("pages", `${route}.js`)
    pages.push(new Page({ route, filePath, type: "ssg-fallback", alternativeRoutes: [dataRoute] }))
  })

  return pages
}

// Represent a NextJS page
class Page {
  constructor({ route, type, ...otherParams }) {
    this.alternativeRoutes = []
    Object.assign(this, { route, type, ...otherParams })
  }

  isSsr() {
    return this.type === "ssr"
  }

  isHtml() {
    return this.type === "html"
  }

  isSsg() {
    return this.type === "ssg"
  }

  isSsgFallback() {
    return this.type === "ssg-fallback"
  }

  routeFile(ext) {
    return `${this.route.replace(/^\/$/, '/index')}${ext}`
  }

  get htmlFile() {
    return this.routeFile(".html")
  }

  get jsonFile() {
    return this.routeFile(".json")
  }

  // Return route and alternative routes as array
  get routesAsArray() {
    return [this.route, ...this.alternativeRoutes]
  }
}

const allNextJsPages = getAllPages()

module.exports = allNextJsPages