import {getJSModule, registerJSModules} from '@loaders.gl/loader-utils';
import {Hash} from './hash';

type CryptoHashOptions = {
  modules?: {[moduleName: string]: any};
  crypto: {
    algorithm: string;
    onEnd?: (result: {hash: string}) => any;
  };
};

/**
 * A transform that calculates Cryptographic Hash using Crypto JS library
 * @deprecated Warning, experimental class
 */
export class CryptoHash extends Hash {
  readonly name;

  options: CryptoHashOptions;
  /** Name of digest algorithm */
  private _algorithm;
  /** CryptoJS algorithm */
  private _algo;

  constructor(options: CryptoHashOptions) {
    super();
    this.options = options;
    registerJSModules(options?.modules);

    this._algorithm = this.options?.crypto?.algorithm;
    if (!this._algorithm) {
      throw new Error(this.name);
    }
    this.name = this._algorithm.toLowerCase();
  }

  async preload(): Promise<void> {
    const CryptoJS = getJSModule('CryptoJS', this.name);
    this._algo = CryptoJS.algo[this._algorithm];
  }

  /**
   * Atomic hash calculation
   * @returns base64 encoded hash
   */
  async hash(input: ArrayBuffer, encoding: 'hex' | 'base64'): Promise<string> {
    await this.preload();

    const hash = this._algo.create();
    if (!hash) {
      throw new Error(this.name);
    }

    const CryptoJS = getJSModule('CryptoJS', this.name);
    // arrayBuffer is accepted, even though types and docs say no
    // https://stackoverflow.com/questions/25567468/how-to-decrypt-an-arraybuffer
    const typedWordArray = CryptoJS.lib.WordArray.create(input);
    // Map our encoding constant to Crypto library
    const enc = encoding === 'base64' ? CryptoJS.enc.Base64 : CryptoJS.enc.Hex;
    return hash.update(typedWordArray).finalize().toString(enc);
  }

  async *hashBatches(
    asyncIterator: AsyncIterable<ArrayBuffer> | Iterable<ArrayBuffer>,
    encoding: 'hex' | 'base64' = 'base64'
  ): AsyncIterable<ArrayBuffer> {
    await this.preload();
    const CryptoJS = getJSModule('CryptoJS', this.name);

    const hash = this._algo.create();
    if (!hash) {
      throw new Error(this.name);
    }

    for await (const chunk of asyncIterator) {
      // arrayBuffer is accepted, even though types and docs say no
      // https://stackoverflow.com/questions/25567468/how-to-decrypt-an-arraybuffer
      const typedWordArray = CryptoJS.lib.WordArray.create(chunk);
      hash.update(typedWordArray);
      yield chunk;
    }

    // Map our encoding constant to Crypto library
    const enc = encoding === 'base64' ? CryptoJS.enc.Base64 : CryptoJS.enc.Hex;
    const digest = hash.finalize().toString(enc);
    this.options?.crypto?.onEnd?.({hash: digest});
  }
}