um-react/src/decrypt-worker/util/transformBlob.ts

import { Transformer, Parakeet, TransformResult, fetchParakeet } from '@jixun/libparakeet';
import { toArrayBuffer } from './buffer';
import { UnsupportedSourceFile } from './DecryptError';

export async function transformBlob(
  blob: Blob | ArrayBuffer,
  transformerFactory: (p: Parakeet) => Transformer | Promise<Transformer>,
  { cleanup, parakeet }: { cleanup?: () => void; parakeet?: Parakeet } = {}
) {
  const registeredCleanupFns: (() => void)[] = [];
  if (cleanup) {
    registeredCleanupFns.push(cleanup);
  }

  try {
    const mod = parakeet ?? (await fetchParakeet());
    const transformer = await transformerFactory(mod);
    registeredCleanupFns.push(() => transformer.delete());

    const reader = mod.make.Reader(await toArrayBuffer(blob));
    registeredCleanupFns.push(() => reader.delete());

    const sink = mod.make.WriterSink();
    const writer = sink.getWriter();
    registeredCleanupFns.push(() => writer.delete());

    const result = transformer.Transform(writer, reader);
    if (result === TransformResult.ERROR_INVALID_FORMAT) {
      throw new UnsupportedSourceFile(`transformer<${transformer.Name}> does not recognize this file`);
    } else if (result !== TransformResult.OK) {
      throw new Error(`transformer<${transformer.Name}> failed with error: ${TransformResult[result]} (${result})`);
    }

    return sink.collectBlob();
  } finally {
    registeredCleanupFns.forEach((cleanup) => cleanup());
  }
}