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'))();

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