# All files / src/operations utils.js

97.5% Statements 78/80
93.1% Branches 27/29
100% Functions 22/22
97.26% Lines 71/73

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     /* @flow */

    import bitcoinjs from 'bitcoinjs-lib'
    import RIPEMD160 from 'ripemd160'
    import bigi from 'bigi'

    import { NotEnoughFundsError } from '../errors'
    import { TransactionSigner } from './signers'

    export const DUST_MINIMUM = 5500

    export function hash160(buff: Buffer) {
      const sha256 = bitcoinjs.crypto.sha256(buff)
      return (new RIPEMD160()).update(sha256).digest()
    }

    export function hash128(buff: Buffer) {
      return Buffer.from(bitcoinjs.crypto.sha256(buff).slice(0, 16))
    }

    // COPIED FROM coinselect, because 1 byte matters sometimes.
    // baseline estimates, used to improve performance
    const TX_EMPTY_SIZE = 4 + 1 + 1 + 4
    const TX_INPUT_BASE = 32 + 4 + 1 + 4
    const TX_INPUT_PUBKEYHASH = 107
    const TX_OUTPUT_BASE = 8 + 1
    const TX_OUTPUT_PUBKEYHASH = 25

    type txPoint = {
      script: { length: number }
    }

    function inputBytes(input: txPoint | null) {
      Iif (input && input.script && input.script.length > 0) {
        return TX_INPUT_BASE + input.script.length
      } else {
        return TX_INPUT_BASE + TX_INPUT_PUBKEYHASH
      }
    }

    function outputBytes(output: txPoint | null) {
      if (output && output.script && output.script.length > 0) {
        return TX_OUTPUT_BASE + output.script.length
      } else {
        return TX_OUTPUT_BASE + TX_OUTPUT_PUBKEYHASH
      }
    }

    function transactionBytes(inputs: Array<txPoint | null>, outputs: Array<txPoint | null>) {
      return TX_EMPTY_SIZE
        + inputs.reduce((a: number, x: txPoint | null) => (a + inputBytes(x)), 0)
        + outputs.reduce((a: number, x: txPoint | null) => (a + outputBytes(x)), 0)
    }

    //

    export function estimateTXBytes(txIn: bitcoinjs.Transaction | bitcoinjs.TransactionBuilder,
                                    additionalInputs: number,
                                    additionalOutputs: number) {
      let innerTx = txIn
      if (txIn instanceof bitcoinjs.TransactionBuilder) {
        innerTx = txIn.__tx
      }
      const dummyInputs: Array<null> = new Array(additionalInputs)
      dummyInputs.fill(null)
      const dummyOutputs: Array<null> = new Array(additionalOutputs)
      dummyOutputs.fill(null)

      const inputs: Array<null | txPoint> = [].concat(innerTx.ins, dummyInputs)
      const outputs: Array<null | txPoint> = [].concat(innerTx.outs, dummyOutputs)

      return transactionBytes(inputs, outputs)
    }

    export function sumOutputValues(txIn : bitcoinjs.Transaction | bitcoinjs.TransactionBuilder) {
      let innerTx = txIn
      if (txIn instanceof bitcoinjs.TransactionBuilder) {
        innerTx = txIn.__tx
      }

      return innerTx.outs.reduce((agg, x) => agg + x.value, 0)
    }

    export function decodeB40(input: string) {
      // treat input as a base40 integer, and output a hex encoding
      // of that integer.
      //
      //   for each digit of the string, find its location in `characters`
      //    to get the value of the digit, then multiply by 40^(-index in input)
      // e.g.,
      // the 'right-most' character has value: (digit-value) * 40^0
      //  the next character has value: (digit-value) * 40^1
      //
      // hence, we reverse the characters first, and use the index
      //  to compute the value of each digit, then sum
      const characters = '0123456789abcdefghijklmnopqrstuvwxyz-_.+'
      const base = bigi.valueOf(40)
      const inputDigits = input.split('').reverse()
      const digitValues = inputDigits.map(
        ((character: string, exponent: number) => bigi.valueOf(characters.indexOf(character))
          .multiply(base.pow(bigi.valueOf(exponent))))
      )
      const sum = digitValues.reduce(
        (agg: bigi.BigInteger, cur: bigi.BigInteger) => agg.add(cur),
        bigi.ZERO
      )
      return sum.toHex()
    }

    /**
     * Adds UTXOs to fund a transaction
     * @param {TransactionBuilder} txBuilderIn - a transaction builder object to add the inputs to. this
     *    object is _always_ mutated. If not enough UTXOs exist to fund, the tx builder object
     *    will still contain as many inputs as could be found.
     * @param {Array<{value: number, tx_hash: string, tx_output_n}>} utxos - the utxo set for the
     *    payer's address.
     * @param {number} amountToFund - the amount of satoshis to fund in the transaction. the payer's
     *    utxos will be included to fund up to this amount of *output* and the corresponding *fees*
     *    for those additional inputs
     * @param {number} feeRate - the satoshis/byte fee rate to use for fee calculation
     * @param {boolean} fundNewFees - if true, this function will fund `amountToFund` and any new fees
     *    associated with including the new inputs.
     *    if false, this function will fund _at most_ `amountToFund`
     * @returns {number} - the amount of leftover change (in satoshis)
     * @private
     */
    export function addUTXOsToFund(txBuilderIn: bitcoinjs.TransactionBuilder,
                                   utxos: Array<{value: number, tx_hash: string, tx_output_n: number}>,
                                   amountToFund: number, feeRate: number,
                                   fundNewFees: ?boolean = true) {
      if (utxos.length === 0) {
        throw new NotEnoughFundsError(amountToFund)
      }

      // how much are we increasing fees by adding an input ?
      const newFees = feeRate * (estimateTXBytes(txBuilderIn, 1, 0)
                                 - estimateTXBytes(txBuilderIn, 0, 0))
      let utxoThreshhold = amountToFund
      if (fundNewFees) {
        utxoThreshhold += newFees
      }

      const goodUtxos = utxos.filter(utxo => utxo.value >= utxoThreshhold)
      if (goodUtxos.length > 0) {
        goodUtxos.sort((a, b) => a.value - b.value)
        const selected = goodUtxos[0]
        let change = selected.value - amountToFund
        if (fundNewFees) {
          change -= newFees
        }

        txBuilderIn.addInput(selected.tx_hash, selected.tx_output_n)
        return change
      } else {
        utxos.sort((a, b) => b.value - a.value)
        const largest = utxos[0]

        Iif (newFees >= largest.value) {
          throw new NotEnoughFundsError(amountToFund)
        }

        txBuilderIn.addInput(largest.tx_hash, largest.tx_output_n)

        let remainToFund = amountToFund - largest.value
        if (fundNewFees) {
          remainToFund += newFees
        }

        return addUTXOsToFund(txBuilderIn, utxos.slice(1),
                              remainToFund, feeRate, fundNewFees)
      }
    }

    export function signInputs(txB: bitcoinjs.TransactionBuilder,
                               defaultSigner: TransactionSigner,
                               otherSigners?: Array<{index: number, signer: TransactionSigner}>) {
      const signerArray = txB.__tx.ins.map(() => defaultSigner)
      if (otherSigners) {
        otherSigners.forEach((signerPair) => {
          signerArray[signerPair.index] = signerPair.signer
        })
      }
      let signingPromise = Promise.resolve()
      for (let i = 0; i < txB.__tx.ins.length; i++) {
        signingPromise = signingPromise.then(
          () => signerArray[i].signTransaction(txB, i)
        )
      }
      return signingPromise.then(() => txB)
    }