example of messing with binance/coinbase apis to calculate cross exchange value

cross-exchange-value.js

var fs = require('fs')
var _ = require('lodash')

var USD_CONVERSIONS = ["ETH", "BTC"]

// Array of Arrays where inner Array is SYMBOL(str), SHARES(num)
var portfolio_data_file = "portfolio.json"
// Example dump of coinbase API
var coinbase_data_file = "coinbase.json"
// Example dump of binance API
var binance_data_file = "binance.json"
var portfolio_data = JSON.parse(fs.readFileSync(portfolio_data_file, 'utf8'))
var coinbase_data = JSON.parse(fs.readFileSync(coinbase_data_file, 'utf8'))
var binance_data = JSON.parse(fs.readFileSync(binance_data_file, 'utf8'))

var binance_map = binance_data_to_map(binance_data)

var portfolio = _.map(portfolio_data, function(equity) {
    var currency = equity[0]
    var shares = equity[1]
    var entry = { currency: currency, shares: shares }
    set_rates(entry)
    calculate_value(entry)
    return entry
})

console.log(portfolio)

function calculate_value(entry) {
    if (entry.rate_per_usd) {
        entry.primary_value_symbol = 'USD'
        entry.primary_value = entry.shares * entry.rate_per_usd
        entry.secondary_value_symbol = 'BTC'
        entry.secondary_value = entry.shares * entry.rate_per_btc
    } else {
        entry.primary_value_symbol = 'BTC'
        entry.primary_value = entry.shares * entry.rate_per_btc
        entry.secondary_value_symbol = 'ETH'
        entry.secondary_value = entry.shares * entry.rate_per_eth
    }
}

function set_rates(entry) {
    if ( _.includes(USD_CONVERSIONS, entry.currency) ) {
        entry.rate_per_usd = coinbase_data.data.rates[entry.currency]
    } else {
        entry.rate_per_eth = binance_map[entry.currency + 'ETH']
    }
    entry.rate_per_btc = entry.currency != 'BTC' ? binance_map[entry.currency + 'BTC'] : 1
}

function binance_data_to_map(data) {
    return _.chain(data).keyBy(function(i) {
        return i.symbol
    }).mapValues('price').value()
}