sweep.js

var BitcoinTools = require('bitcoin-tools')
, debug = require('debug')('snow:bitcoin-sweep')
, BitcoinLib = require('bitcoinjs-lib')
, blockchaininfo = require('./blockchaininfo.js')

function reverseHex(hash) {
    var res = ''
    for (var i = 0; i < hash.length; i++) {
        res = hash.substr(i * 2, 2) + res
    }
    return res
}

var SIGHASH_ALL = 1

// See https://github.com/kyledrake/coinpunk/blob/master/public/js/coinpunk/models/wallet.js
module.exports  = function(privKeys, destAddr, feeSatoshis, cb) {
    var sourceAddrs = privKeys.map(BitcoinTools.addressFromPrivateKey)
    , tx = new BitcoinLib.Transaction()

    debug('gathering unspent outputs from blockchain.info...')

    // Retrieve the unspent outputs for the source address
    blockchaininfo.unspent(sourceAddrs, function(err, unspent) {
        debug('found %s unspent outputs', unspent.length)

        if (!unspent.length) return cb()

        // Sum the unspent values
        var value = unspent.reduce(function(p, c) {
            return p + c.value
        }, 0)

        value = value - feeSatoshis

        debug('will sweep %s BTC from the private key', value / 1e8)

        tx.addOutput(destAddr, value)

        // Add inputs
        unspent.forEach(function(unspentOutput) {
            // For some reason blockchain.info returns the unspent transaction
            // hashes reversed. ABCDEF is returned EFCDAB
            var hashReversed = reverseHex(unspentOutput.tx_hash)

            // Add the input
            tx.addInput({ hash: hashReversed }, unspentOutput.tx_output_n)
        })

        unspent.forEach(function(unspentOutput, i) {
            // Sign the input
            var unspentOutScript = new BitcoinLib.Script(BitcoinLib.convert.hexToBytes(unspentOutput.script))

            // Determine which private key will need to sign the input
            var pubKeyHash = unspentOutScript.simpleOutHash()
            , pubKeyHashHex = BitcoinLib.convert.bytesToHex(pubKeyHash)
            , key

            privKeys.some(function(privKey) {
                var privKeyEc = new BitcoinLib.Key(privKey)
                , addr = privKeyEc.getBitcoinAddress()
                , addrHashHex = BitcoinLib.convert.bytesToHex(addr.hash)
                if (addrHashHex != pubKeyHashHex) return
                key = privKeyEc
                return true
            })

            if (!key) {
                return cb(new Error('No private key found for public key with hash ' + pubKeyHashHex))
            }

            debug('signing input %s with priv key %s', i, key.toString('base58').substr(0, 6))

            var hash = tx.hashTransactionForSignature(unspentOutScript, i, SIGHASH_ALL)
            , signature = key.sign(hash)

            // Push the signature type
            signature.push(SIGHASH_ALL)

            tx.ins[i].script = BitcoinLib.Script.createInputScript(signature, key.getPub())
        })

        // Serialize the transaction, convert to hex and push
        var hex = BitcoinLib.convert.bytesToHex(tx.serialize())

        debug('transaction (hex):\n%s', hex)

        debug('pushing transaction...')

        blockchaininfo.pushtx(hex, cb)
    })
}