html-rewriting-stream.ts

/**
 * @license
 * Copyright Google LLC 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')).default();

  return {
    rewriter,
    transformedContent: () => {
      return 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 as BufferEncoding)
                    : chunk,
                );
                callback();
              },
              final(callback: (error?: Error) => void): void {
                callback();
                resolve(Buffer.concat(chunks).toString());
              },
            }),
          );
      });
    },
  };
}