source: frontend/node_modules/react-dev-utils/InterpolateHtmlPlugin.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

// This webpack plugin lets us interpolate custom variables into `index.html`.
// Usage: `new InterpolateHtmlPlugin(HtmlWebpackPlugin, { 'MY_VARIABLE': 42 })`
// Then, you can use %MY_VARIABLE% in your `index.html`.

// It works in tandem with HtmlWebpackPlugin.
// Learn more about creating plugins like this:
// https://github.com/ampedandwired/html-webpack-plugin#events

'use strict';
const escapeStringRegexp = require('escape-string-regexp');

class InterpolateHtmlPlugin {
  constructor(htmlWebpackPlugin, replacements) {
    this.htmlWebpackPlugin = htmlWebpackPlugin;
    this.replacements = replacements;
  }

  apply(compiler) {
    compiler.hooks.compilation.tap('InterpolateHtmlPlugin', compilation => {
      this.htmlWebpackPlugin
        .getHooks(compilation)
        .afterTemplateExecution.tap('InterpolateHtmlPlugin', data => {
          // Run HTML through a series of user-specified string replacements.
          Object.keys(this.replacements).forEach(key => {
            const value = this.replacements[key];
            data.html = data.html.replace(
              new RegExp('%' + escapeStringRegexp(key) + '%', 'g'),
              value
            );
          });
        });
    });
  }
}

module.exports = InterpolateHtmlPlugin;