@kazeblockchain/kazejs/src/transactions/strategy.js

Javascript libraries for Kaze wallet

import { Fixed8 } from '../utils'

/**
 * Select the coins in order of value, smallest first.
 * @param {AssetBalance} assetBalance
 * @param {Fixed8} requiredAmt
 * @return {Coin[]}
 */
export const smallestFirst = (assetBalance, requiredAmt) => {
  // Ascending order sort
  assetBalance.unspent.sort((a, b) => a.value.sub(b.value).toNumber())
  return fillFromLeft(requiredAmt, assetBalance.unspent)
}

/**
 * Select the coins in order of value, biggest first.
 * @param {AssetBalance} assetBalance
 * @param {Fixed8} requiredAmt
 * @return {Coin[]}
 */
export const biggestFirst = (assetBalance, requiredAmt) => {
  // Descending order sort
  assetBalance.unspent.sort((a, b) => b.value.sub(a.value).toNumber())
  return fillFromLeft(requiredAmt, assetBalance.unspent)
}

/**
 * Use a balanced approach by selecting a coin that
 * @param {AssetBalance} assetBalance
 * @param {Fixed8} requiredAmt
 * @return {Coin[]}
 */
export const balancedApproach = (assetBalance, requiredAmt) => {
  // Ascending sort first
  assetBalance.unspent.sort((a, b) => a.value.sub(b.value).toNumber())
  // Trim off coins larger than requiredAmt
  const smallCoins = assetBalance.unspent.filter((c) => c.value.lte(requiredAmt))
  if (smallCoins.length === 0) return [assetBalance.unspent[0]]
  // Check for naive solution
  const i = smallCoins.findIndex((c) => requiredAmt.eq(c.value))
  if (i >= 0) return [smallCoins[i]]
  // Take the largest coin available and fill it up with little pieces
  const bigCoins = assetBalance.unspent.slice(smallCoins.length)
  const selectedInputs = []
  if (smallCoins.length > 0) selectedInputs.push(smallCoins.pop())
  const remainderAmt = requiredAmt.minus(selectedInputs.length > 0 ? selectedInputs[0].value : 0)
  const remainderInputs = fillFromLeft(remainderAmt, smallCoins.concat(bigCoins))
  return selectedInputs.concat(remainderInputs)
}

/**
 * Selects inputs from left of array till sum of inputs is equal or larger than requiredAmt.
 * @param {Fixed8} requiredAmt
 * @param {Coin[]} availableInputs
 * @return {Coin[]}
 */
const fillFromLeft = (requiredAmt, availableInputs) => {
  let selectPointer = 0
  let selectedAmt = new Fixed8(0)
  // Selected min inputs to satisfy outputs
  while (selectedAmt.lt(requiredAmt)) {
    selectPointer += 1
    if (selectPointer > availableInputs.length) throw new Error(`Insufficient assets! Reached end of unspent coins! ${availableInputs.length}`)
    selectedAmt = selectedAmt.add(availableInputs[selectPointer - 1].value)
  }
  return availableInputs.slice(0, selectPointer)
}