text: import { validate, isJS, onEmit } from './util'
  
  export default class VueSSRServerPlugin {
    constructor (options = {}) {
      this.options = Object.assign({
        filename: 'vue-ssr-server-bundle.json',
      }, options)
    }
  
    apply (compiler) {
      validate(compiler)
  
      onEmit(compiler, 'vue-server-plugin', (compilation, cb) => {
        const stats = compilation.getStats().toJson()
        const entryName = Object.keys(stats.entrypoints)[0]
        const entryInfo = stats.entrypoints[entryName]
  
        if (!entryInfo) {
          // #5553
          return cb()
        }
  
        const entryAssets = entryInfo.assets.filter(isJS)
  
        if (entryAssets.length > 1) {
          throw new Error(
            `Server-side bundle should have one single entry file. ` +
            `Avoid using CommonsChunkPlugin in the server config.`,
          )
        }
  
        const entry = entryAssets[0]
        if (!entry || typeof entry !== 'string') {
          throw new Error(
            `Entry "${entryName}" not found. Did you specify the correct entry option?`,
          )
        }
  
        const bundle = {
          entry,
          files: {},
          maps: {},
        }
  
        stats.assets.forEach(asset => {
          if (isJS(asset.name)) {
            bundle.files[asset.name] = compilation.assets[asset.name].source()
          } else if (asset.name.match(/\.js\.map$/)) {
            bundle.maps[asset.name.replace(/\.map$/, '')] = JSON.parse(compilation.assets[asset.name].source())
          }
          // do not emit anything else for server
          delete compilation.assets[asset.name]
        })
  
        const json = JSON.stringify(bundle, null, 2)
        const filename = this.options.filename
  
        compilation.assets[filename] = {
          source: () => json,
          size: () => json.length,
        }
  
        cb()
      })
    }
  }
  