import { WASMInterface, IWASMInterface, IHasher } from './WASMInterface';
import Mutex from './mutex';
import wasmJson from '../wasm/xxhash32.wasm.json';
import lockedCreate from './lockedCreate';
import { IDataType } from './util';

const mutex = new Mutex();
let wasmCache: IWASMInterface = null;

function validateSeed(seed: number) {
  if (!Number.isInteger(seed) || seed < 0 || seed > 0xFFFFFFFF) {
    return new Error('Seed must be a valid 32-bit long unsigned integer.');
  }
  return null;
}
/**
 * Calculates xxHash32 hash
 * @param data Input data (string, Buffer or TypedArray)
 * @param seed Number used to initialize the internal state of the algorithm (defaults to 0)
 * @returns Computed hash as a hexadecimal string
 */
export function xxhash32(
  data: IDataType, seed = 0,
): Promise<string> {
  if (validateSeed(seed)) {
    return Promise.reject(validateSeed(seed));
  }

  if (wasmCache === null) {
    return lockedCreate(mutex, wasmJson, 4)
      .then((wasm) => {
        wasmCache = wasm;
        return wasmCache.calculate(data, seed);
      });
  }

  try {
    const hash = wasmCache.calculate(data, seed);
    return Promise.resolve(hash);
  } catch (err) {
    return Promise.reject(err);
  }
}

/**
 * Creates a new xxHash32 hash instance
 * @param data Input data (string, Buffer or TypedArray)
 * @param seed Number used to initialize the internal state of the algorithm (defaults to 0)
 */
export function createXXHash32(seed = 0): Promise<IHasher> {
  if (validateSeed(seed)) {
    return Promise.reject(validateSeed(seed));
  }

  return WASMInterface(wasmJson, 4).then((wasm) => {
    wasm.init(seed);
    const obj: IHasher = {
      init: () => { wasm.init(seed); return obj; },
      update: (data) => { wasm.update(data); return obj; },
      digest: (outputType) => wasm.digest(outputType) as any,
      save: () => wasm.save(),
      load: (data) => { wasm.load(data); return obj; },
      blockSize: 16,
      digestSize: 4,
    };
    return obj;
  });
}