@davidosborn/crypto-tax-calculator/lib/trade-separate-stream.js

A tool to calculate the capital gains of cryptocurrency assets for Canadian taxes

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = _default;

var _stream = _interopRequireDefault(require("stream"));

var _assets = _interopRequireDefault(require("./assets"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

/**
 * A transaction.
 * @typedef {object} Transaction
 * @property {string} exchange The exchange on which the transaction was executed.
 * @property {string} asset    The asset.
 * @property {number} amount   The amount of assets.
 * @property {number} time     The time of the transaction, as a UNIX timestamp.
 * @property {number} value    The value of the transaction, in Canadian dollars.
 * @property {number} fee      The transaction fee, in Canadian dollars.
 */

/**
 * A stream that breaks up assets trades into currency transactions.
 */
class TradeSeparateStream extends _stream.default.Transform {
  constructor() {
    super({
      objectMode: true
    });
  }
  /**
   * Breaks up an asset trade into currency transactions.
   * @param {Trade}    chunk    The trade.
   * @param {string}   encoding The encoding type (always 'Buffer').
   * @param {function} callback A callback for when the transformation is complete.
   */


  async _transform(chunk, encoding, callback) {
    let baseChunk = {
      exchange: chunk.exchange,
      asset: chunk.baseAsset,
      amount: chunk.baseAmount,
      time: chunk.time,
      value: chunk.value,
      fee: 0
    };
    let quoteChunk = {
      exchange: chunk.exchange,
      asset: chunk.quoteAsset,
      amount: chunk.quoteAmount,
      time: chunk.time,
      value: chunk.value,
      fee: 0
    };
    let chunks = [baseChunk, quoteChunk];

    if (chunk.sell) {
      quoteChunk.amount = -quoteChunk.amount;
      quoteChunk.fee = chunk.fee;
      chunks.reverse();
    } else {
      baseChunk.amount = -baseChunk.amount;
      baseChunk.fee = chunk.fee;
    } // Drop the chunks that represent fiat currencies.
    // TODO: This is questionable.


    for (let i = 0; i < chunks.length; ++i) if (_assets.default.getPriority(chunks[i].asset) === 0) chunks.splice(i--, 1);

    for (let chunk of chunks) this.push(chunk);

    callback();
  }

}

function _default(...args) {
  return new TradeSeparateStream(...args);
}