// In TypeScript 3.7, could be written as a single type:
// `type DeepHashChunk = Uint8Array | DeepHashChunk[];`
import { getCryptoDriver, concatBuffers, stringToBuffer } from "$/utils";
import { createHash } from "crypto";

export type DeepHashChunk = Uint8Array | AsyncIterable<Buffer> | DeepHashChunks;
export type DeepHashChunks = DeepHashChunk[];

export async function deepHash(data: DeepHashChunk): Promise<Uint8Array> {
  if (typeof data[Symbol.asyncIterator as keyof AsyncIterable<Buffer>] === "function") {
    const _data = data as AsyncIterable<Buffer>;

    const context = createHash("sha384");

    let length = 0;

    for await (const chunk of _data) {
      length += chunk.byteLength;
      context.update(chunk);
    }

    const tag = concatBuffers([stringToBuffer("blob"), stringToBuffer(length.toString())]);

    const taggedHash = concatBuffers([await getCryptoDriver().hash(tag, "SHA-384"), context.digest()]);

    return await getCryptoDriver().hash(taggedHash, "SHA-384");
  } else if (Array.isArray(data)) {
    const tag = concatBuffers([stringToBuffer("list"), stringToBuffer(data.length.toString())]);

    return await deepHashChunks(data, await getCryptoDriver().hash(tag, "SHA-384"));
  }

  const _data = data as Uint8Array;

  const tag = concatBuffers([stringToBuffer("blob"), stringToBuffer(_data.byteLength.toString())]);

  const taggedHash = concatBuffers([await getCryptoDriver().hash(tag, "SHA-384"), await getCryptoDriver().hash(_data, "SHA-384")]);

  return await getCryptoDriver().hash(taggedHash, "SHA-384");
}

export async function deepHashChunks(chunks: DeepHashChunks, acc: Uint8Array): Promise<Uint8Array> {
  if (chunks.length < 1) {
    return acc;
  }

  const hashPair = concatBuffers([acc, await deepHash(chunks[0])]);
  const newAcc = await getCryptoDriver().hash(hashPair, "SHA-384");
  return await deepHashChunks(chunks.slice(1), newAcc);
}

export async function hashStream(stream: AsyncIterable<Buffer>): Promise<Buffer> {
  const context = createHash("sha384");

  for await (const chunk of stream) {
    context.update(chunk);
  }

  return context.digest();
}

export default deepHash;