html-rewriting-stream.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import { Readable, Writable } from 'stream';

export async function htmlRewritingStream(content: string): Promise<{
  rewriter: import('parse5-html-rewriting-stream'),
  transformedContent: Promise<string>,
}> {
  const chunks: Buffer[] = [];
  const rewriter = new (await import('parse5-html-rewriting-stream'))();

  return {
    rewriter,
    transformedContent: new Promise(resolve => {
      new Readable({
        encoding: 'utf8',
        read(): void {
          this.push(Buffer.from(content));
          this.push(null);
        },
      })
      .pipe(rewriter)
      .pipe(new Writable({
        write(chunk: string | Buffer, encoding: string | undefined, callback: Function): void {
          chunks.push(typeof chunk === 'string' ? Buffer.from(chunk, encoding) : chunk);
          callback();
        },
        final(callback: (error?: Error) => void): void {
          callback();
          resolve(Buffer.concat(chunks).toString());
        },
      }));
    }),
  };
}