divvy-lib-transactionparser/src/balancechanges.js

Parses transaction objects to a higher-level view

'use strict'

var _ = require('lodash')
var BigNumber = require('bignumber.js')
var normalizeNodes = require('./utils').normalizeNodes
var dropsToXDV = require('./utils').dropsToXDV

function groupByAddress(balanceChanges) {
  var grouped = _.groupBy(balanceChanges, function(node) {
    return node.address
  })
  return _.mapValues(grouped, function(group) {
    return _.map(group, function(node) {
      return node.balance
    })
  })
}

function parseValue(value) {
  return new BigNumber(value.value || value)
}

function computeBalanceChange(node) {
  var value = null
  if (node.newFields.Balance) {
    value = parseValue(node.newFields.Balance)
  } else if (node.previousFields.Balance && node.finalFields.Balance) {
    value = parseValue(node.finalFields.Balance).minus(
      parseValue(node.previousFields.Balance))
  }
  return value === null ? null : value.isZero() ? null : value
}

function parseFinalBalance(node) {
  if (node.newFields.Balance) {
    return parseValue(node.newFields.Balance)
  } else if (node.finalFields.Balance) {
    return parseValue(node.finalFields.Balance)
  }
  return null
}


function parseXDVQuantity(node, valueParser) {
  var value = valueParser(node)

  if (value === null) {
    return null
  }

  return {
    address: node.finalFields.Account || node.newFields.Account,
    balance: {
      counterparty: '',
      currency: 'XDV',
      value: dropsToXDV(value).toString()
    }
  }
}

function flipTrustlinePerspective(quantity) {
  var negatedBalance = (new BigNumber(quantity.balance.value)).negated()
  return {
    address: quantity.balance.counterparty,
    balance: {
      counterparty: quantity.address,
      currency: quantity.balance.currency,
      value: negatedBalance.toString()
    }
  }
}

function parseTrustlineQuantity(node, valueParser) {
  var value = valueParser(node)

  if (value === null) {
    return null
  }

  /*
   * A trustline can be created with a non-zero starting balance
   * If an offer is placed to acquire an asset with no existing trustline,
   * the trustline can be created when the ofer is taken.
   */
  var fields = _.isEmpty(node.newFields) ? node.finalFields : node.newFields

  // the balance is always from low node's perspective
  var result = {
    address: fields.LowLimit.issuer,
    balance: {
      counterparty: fields.HighLimit.issuer,
      currency: fields.Balance.currency,
      value: value.toString()
    }
  }
  return [result, flipTrustlinePerspective(result)]
}

function parseQuantities(metadata, valueParser) {
  var values = normalizeNodes(metadata).map(function(node) {
    if (node.entryType === 'AccountRoot') {
      return [parseXDVQuantity(node, valueParser)]
    } else if (node.entryType === 'DivvyState') {
      return parseTrustlineQuantity(node, valueParser)
    }
    return []
  })
  return groupByAddress(_.compact(_.flatten(values)))
}

/**
 *  Computes the complete list of every balance that changed in the ledger
 *  as a result of the given transaction.
 *
 *  @param {Object} metadata Transaction metada
 *  @returns {Object} parsed balance changes
 */
function parseBalanceChanges(metadata) {
  return parseQuantities(metadata, computeBalanceChange)
}


/**
 *  Computes the complete list of every final balance in the ledger
 *  as a result of the given transaction.
 *
 *  @param {Object} metadata Transaction metada
 *  @returns {Object} parsed balances
 */
function parseFinalBalances(metadata) {
  return parseQuantities(metadata, parseFinalBalance)
}

module.exports.parseBalanceChanges = parseBalanceChanges
module.exports.parseFinalBalances = parseFinalBalances