const PLUGIN = 'CoreCSSModulesWebpackPlugin'

const isLoader = loader => loader !== 'string'

interface CoreCSSWebpackPluginOptions {
  suffix: string
}

export class CoreCSSWebpackPlugin {
  isDev: boolean = false
  suffix: string = ''

  constructor({ suffix = 'suffix' }: CoreCSSWebpackPluginOptions) {
    this.isDev = process.env.NODE_ENV === 'development'
    this.suffix = new Buffer(suffix || '').toString('base64').slice(0, 5)
  }

  apply(compiler) {
    compiler.hooks.compilation.tap(PLUGIN, compilation => {
      compilation.hooks.buildModule.tap(PLUGIN, module => {
        if (module.resource && module.resource.indexOf('/core-css/') >= 0) {
          // we need to find the css loader in the list of loaders for each module
          module.loaders &&
            module.loaders.filter(isLoader).forEach(loader => {
              if (loader.loader.indexOf('/css-loader/') >= 0) {
                // use existing options or default to empty object
                loader.options = loader.options || {}

                // turn css-modules on
                loader.options.modules = true

                if (
                  loader.options.getLocalIdent &&
                  loader.options.getLocalIdent.name !== 'customGetLocalIdent'
                ) {
                  // if css-loader is configured to use `getLocalIdentName` then we
                  // want to wrap the original function and prepend it's return value

                  const getLocalIdent = loader.options.getLocalIdent

                  const customGetLocalIdent = (...args) => {
                    return `${getLocalIdent(...args)}-${this.suffix}`
                  }

                  loader.options.getLocalIdent = customGetLocalIdent
                } else if (loader.options.localIdentName) {
                  // if css-loader is configured to use `localIdentName`, then we
                  // want to prepend the value to the suffix
                  loader.options.localIdentName = `${
                    loader.options.localIdentName
                  }-${this.suffix}`
                } else {
                  // css-loader is not configured to do any custom transform
                  // of classnames, set it up while accounting for dev/prod mode
                  loader.options.localIdentName = this.isDev
                    ? `[local]-[hash:base64:5]-${this.suffix}`
                    : `[hash:base64:5]-${this.suffix}`
                }
              }
            })
        }
      })
    })
  }
}