@davidosborn/crypto-tax-calculator/lib/trade-transactions-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} value       The value of the transaction, in Canadian dollars.
 * @property {number} time        The time of the transaction, as a UNIX timestamp.
 * @property {string} [feeAsset]  The asset of the transaction fee.
 * @property {number} [feeAmount] The amount of the transaction fee.
 * @property {number} feeValue    The value of the transaction fee, in Canadian dollars.
 */

/**
 * A stream that breaks up assets trades into currency transactions.
 */
class TradeTransactionsStream 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,
      value: chunk.value,
      time: chunk.time,
      feeValue: 0
    };
    let quoteChunk = {
      exchange: chunk.exchange,
      asset: chunk.quoteAsset,
      amount: chunk.quoteAmount,
      value: chunk.value,
      time: chunk.time,
      feeValue: 0
    };
    let chunks = [baseChunk, quoteChunk];

    if (chunk.sell) {
      chunks.reverse();
    }

    chunks[0].amount = -chunks[0].amount; // Drop the chunks that are empty.

    chunks = chunks.filter(function (chunk) {
      return chunk.amount;
    }); // Drop the chunks that represent fiat currencies.

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

    if (!chunks.length) {
      callback();
      return;
    } // Set the transaction fee of the disposed asset.


    chunks[0].feeValue = chunk.feeValue; // Set the transaction fee of the acquired asset.

    chunks[chunks.length - 1].feeAsset = chunk.feeAsset;
    chunks[chunks.length - 1].feeAmount = chunk.feeAmount;

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

    callback();
  }

}

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