ExchangeLedger

a class for creating ledgers to manage exchange trading of currencies and other arbitrary exchangeable entities

:star: Getting Started

Install as a dependency:

$ npm install exchange-ledger

Initialize a ledger with a starting balance:

var ExchangeLedger = require('exchange-ledger')

var ledger = new ExchangeLedger({
    balance: {
      'usd': 100,
      'cny': 100
    }
})

---

:money_with_wings: Trading

Commit a trade from one currency to another, specifying the conversion rate and the amount to be converted:

ledger.trade({
  from: 'usd',
  to: 'cny',
  rate: 7,
  amount: 50 // trading 50 USD for 350 CNY
})

(Optional) Apply a percent-based transaction fee to the trade, taken out of the currency being traded to:

ledger.trade({
  from: 'usd',
  to: 'cny',
  fee: .25, // woah, 25% is alot!
  rate: 7,
  amount: 50
})

Trades can safely be made to currencies not yet specified on the balance:

ledger.trade({
  from: 'cny',
  to: 'jpy', // an entry be auto generated on the balance
  rate: 16.4,
  amount: 100
})

The trade history will be stored on the ledger as an array:

ledger.trades
// [ { from: 'usd', to: 'cny', rate: 7, amount: 50},
// { from: 'cny', to: 'jpy', rate: 16.4, amount: 100 } ]

There's also easy access to the last trade committed:

ledger.lastTrade()
// { from: 'cny', to: 'jpy', rate: 16.4, amount: 100 }

---

:book: Balance and Liquidation

Check what the current balance for all specified currencies:

ledger.balance
// { 'usd': 0, 'cny': 512.5, 'jpy': 1640 }

ledger.balance.usd
// 0

Use getLiquidatedTo to check the liquidated value of the balance for a specific currency, by specifying the associated conversion rate(s) (and optionally the transaction fee(s)):

var currentUSD = ledger.getLiquidatedTo('usd', {
    'cny': {rate: 1},
    'jpy': {rate: 1, fee: .5}
})
// currentUSD == 1332.5
// NOTE: This command will not affect the ledger.

Similarly, use liquidateTo to actually convert the balance on the ledger to a specific currency:

ledger.liquidateTo('usd', {
    'cny': {rate: 1},
    'jpy': {rate: 1, fee: .5}
})

var currentUSD = ledger.balance.usd
// currentUSD == 1332.5

Testing

mocha is used for unit-testing in test.js. To run these test, simply:

$ npm test