index.js

// Native
const { format } = require('url')
const { join, parse } = require('path')

// Packages
const isDev = require('electron-is-dev')
const { resolve } = require('app-root-path')
const { protocol } = require('electron')

const adjustProtocol = directory => {
  const paths = ['_next', 'static']
  const isWindows = process.platform === 'win32'

  protocol.interceptFileProtocol('file', (request, callback) => {
    let path = request.url.substr(isWindows ? 8 : 7)

    for (const replacement of paths) {
      if (!path.includes(replacement)) {
        continue
      }

      // Strip volume name from path on Windows
      if (isWindows) {
        path = path.replace(parse(path).root, '')
      }

      path = join(directory, 'out', path)
    }

    // Electron doesn't like anything in the path to be encoded,
    // so we need to undo that. This specifically allows for
    // Electron apps with spaces in their app names.
    path = decodeURIComponent(path)

    callback({ path })
  })
}

let protocolSet = false

exports.setWindowURL = (instance, page) => {
  const devPath = `http://localhost:5000/${page}`
  const renderer = resolve('renderer')

  if (isDev) {
    instance.loadURL(devPath)
    return
  }

  const prodPath = format({
    pathname: join(renderer, `out/${page}/index.html`),
    protocol: 'file:',
    slashes: true
  })

  // We only need to initialize the protocol once
  if (!protocolSet) {
    adjustProtocol(renderer)
    protocolSet = true
  }

  instance.loadURL(prodPath)
}