import { isArrayBuffer } from "@aws-sdk/is-array-buffer";
import { HashConstructor, HttpRequest } from "@aws-sdk/types";
import { toHex } from "@aws-sdk/util-hex-encoding";

import { SHA256_HEADER, UNSIGNED_PAYLOAD } from "./constants";

/**
 * @internal
 */
export async function getPayloadHash(
  { headers, body }: HttpRequest,
  hashConstructor: HashConstructor
): Promise<string> {
  for (const headerName of Object.keys(headers)) {
    if (headerName.toLowerCase() === SHA256_HEADER) {
      return headers[headerName];
    }
  }

  if (body == undefined) {
    return "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855";
  } else if (typeof body === "string" || ArrayBuffer.isView(body) || isArrayBuffer(body)) {
    const hashCtor = new hashConstructor();
    hashCtor.update(body);
    return toHex(await hashCtor.digest());
  }

  // As any defined body that is not a string or binary data is a stream, this
  // body is unsignable. Attempt to send the request with an unsigned payload,
  // which may or may not be accepted by the service.
  return UNSIGNED_PAYLOAD;
}