openpublish/src/opentip.js

var bitcoin = require('bitcoinjs-lib')

var headerHex = 'e299a5' // ♥

var signFromTransactionHex = function (signTransactionHex) {
  if (!signTransactionHex) {
    return false
  }
  return function (tx, callback) {
    var txHex = tx.tx.toHex()
    signTransactionHex(txHex, function (error, signedTxHex) {
      var signedTx = bitcoin.TransactionBuilder.fromTransaction(bitcoin.Transaction.fromHex(signedTxHex))
      callback(error, signedTx)
    })
  }
}

var create = function (options, callback) {
  var commonWallet = options.commonWallet
  var commonBlockchain = options.commonBlockchain
  var openpublishSha1 = options.openpublishSha1
  var tipDestinationAddress = options.tipDestinationAddress
  var tipAmount = options.tipAmount || 10000
  var data = new Buffer(headerHex + openpublishSha1, 'hex')
  var signTransaction = signFromTransactionHex(commonWallet.signRawTransaction)
  options.signTransaction = signTransaction
  var address = commonWallet.address
  var fee = options.fee || 1000
  var payloadScript = bitcoin.Script.fromChunks([bitcoin.opcodes.OP_RETURN, data])
  var tx = new bitcoin.TransactionBuilder()
  commonBlockchain.Addresses.Unspents([address], function (err, addresses_unspents) {
    if (err || addresses_unspents.length === 0) {
      callback('error: possibly no unspents associated with address', null)
    } else {
      var unspentOutputs = addresses_unspents[0]
      var compare = function (a, b) {
        if (a.value < b.value) {
          return -1
        }
        if (a.value > b.value) {
          return 1
        }
        return 0
      }
      unspentOutputs.sort(compare)
      var unspentValue = 0
      for (var i = unspentOutputs.length - 1; i >= 0; i--) {
        var unspentOutput = unspentOutputs[i]
        if (unspentOutput.value === 0) {
          continue
        }
        unspentValue += unspentOutput.value
        tx.addInput(unspentOutput.txid, unspentOutput.vout)
        if (unspentValue - fee - tipAmount >= 0) {
          break
        }
      }
      tx.addOutput(payloadScript, 0)
      tx.addOutput(tipDestinationAddress, tipAmount)

      if (unspentValue - fee - tipAmount > 0) {
        tx.addOutput(address, unspentValue - fee - tipAmount)
      }

      signTransaction(tx, function (err, signedTx) {
        if (err) { } // TODO
        var signedTxBuilt = signedTx.build()
        var signedTxHex = signedTxBuilt.toHex()
        var txid = signedTxBuilt.getId()
        callback(false, signedTxHex, txid)
      })
    }
  })
}

var scanSingle = function (options, callback) {
  if (options.tx) {
    return scan({transactions: [options.tx]}, function (err, tips) {
      if (err) { } // TODO
      callback(err, tips[0])
    })
  } else {
    var txid = options.txid
    var commonBlockchain = options.commonBlockchain
    return commonBlockchain.Transactions.Get([txid], function (err, txs) {
      if (err) { } // TODO
      var tx = txs[0]
      scan({transactions: [tx]}, function (err, tips) {
        callback(err, tips[0])
      })
    })
  }
}

var scan = function (options, callback) {
  var transactions = options.transactions
  var tips = []
  transactions.forEach(function (tx) {
    if (!tx) {
      return
    }
    var tip = {}
    var sources = []
    var value
    var tipDestinationAddresses = []
    var tipAmount = 0
    tx.vin.forEach(function (input) {
      var sourceAddress = input.addresses[0]
      if (sourceAddress) {
        sources.push(sourceAddress)
      }
    })
    tx.vout.forEach(function (output) {
      if (output.scriptPubKey.type === 'nulldata') {
        var scriptPubKey = output.scriptPubKey.hex
        if (scriptPubKey.slice(0, 2) === '6a') {
          var data = scriptPubKey.slice(4, 84)
          if (data.slice(0, 6) === headerHex && data.length === 46) {
            tip.openpublishSha1 = data.slice(6, 46)
          }
        }
      } else if (output.scriptPubKey.type === 'pubkeyhash') {
        var destinationAddress = output.scriptPubKey.addresses[0]
        if (!value || output.value < value) {
          value = output.value
        }
        if (sources.indexOf(destinationAddress) < 0) {
          tipAmount += output.value
          tipDestinationAddresses.push(destinationAddress)
        }
      }
    })
    tip.tipDestinationAddresses = tipDestinationAddresses
    tip.tipAmount = tipAmount
    tip.tipSourceAddresses = []
    tip.txid = tx.txid
    sources.forEach(function (source) {
      if (tipDestinationAddresses.indexOf(source) === -1) {
        tip.tipSourceAddresses.push(source)
      }
    })
    if (tip.tipDestinationAddresses.length === 0 && typeof (value) !== 'undefined') {
      tip.tipDestinationAddresses = [sources]
      tip.tipAmount = value
    }
    if (tip.openpublishSha1 && tip.tipDestinationAddresses && tip.tipAmount) {
      tips.push(tip)
    }
  })
  callback(false, tips)
}

var opentip = {
  create: create,
  scan: scan,
  scanSingle: scanSingle
}

module.exports = opentip