text: var assert = require('assert')
  var bigi = require('bigi')
  var bitcoin = require('../../')
  var helloblock = require('helloblock-js')({
    network: 'testnet'
  })
  
  describe('bitcoinjs-lib (advanced)', function() {
    it('can sign a Bitcoin message', function() {
      var key = bitcoin.ECKey.fromWIF('5KYZdUEo39z3FPrtuX2QbbwGnNP5zTd7yyr2SC1j299sBCnWjss')
      var message = 'This is an example of a signed message.'
  
      var signature = bitcoin.Message.sign(key, message)
      assert.equal(signature.toString('base64'), 'G9L5yLFjti0QTHhPyFrZCT1V/MMnBtXKmoiKDZ78NDBjERki6ZTQZdSMCtkgoNmp17By9ItJr8o7ChX0XxY91nk=')
    })
  
    it('can verify a Bitcoin message', function() {
      var address = '1HZwkjkeaoZfTSaJxDw6aKkxp45agDiEzN'
      var signature = 'HJLQlDWLyb1Ef8bQKEISzFbDAKctIlaqOpGbrk3YVtRsjmC61lpE5ErkPRUFtDKtx98vHFGUWlFhsh3DiW6N0rE'
      var message = 'This is an example of a signed message.'
  
      assert(bitcoin.Message.verify(address, signature, message))
    })
  
    it('can generate a single-key stealth address', function() {
      var receiver = bitcoin.ECKey.fromWIF('5KYZdUEo39z3FPrtuX2QbbwGnNP5zTd7yyr2SC1j299sBCnWjss')
  
      // XXX: ephemeral, must be random (and secret to sender) to preserve privacy
      var sender = bitcoin.ECKey.fromWIF('Kxr9tQED9H44gCmp6HAdmemAzU3n84H3dGkuWTKvE23JgHMW8gct')
  
      var G = bitcoin.ECKey.curve.G
      var d = receiver.d // secret (receiver only)
      var Q = receiver.pub.Q // shared
  
      var e = sender.d // secret (sender only)
      var P = sender.pub.Q // shared
  
      // derived shared secret
      var eQ = Q.multiply(e) // sender
      var dP = P.multiply(d) // receiver
      assert.deepEqual(eQ.getEncoded(), dP.getEncoded())
  
      var c = bigi.fromBuffer(bitcoin.crypto.sha256(eQ.getEncoded()))
      var cG = G.multiply(c)
  
      // derived public key
      var QprimeS = Q.add(cG)
      var QprimeR = G.multiply(d.add(c))
      assert.deepEqual(QprimeR.getEncoded(), QprimeS.getEncoded())
  
      // derived shared-secret address
      var address = new bitcoin.ECPubKey(QprimeS).getAddress().toString()
  
      assert.equal(address, '1EwCNJNZM5q58YPPTnjR1H5BvYRNeyZi47')
    })
  
    // TODO
    it.skip('can generate a dual-key stealth address', function() {})
  
    it('can create an OP_RETURN transaction', function(done) {
      this.timeout(20000)
  
      var key = bitcoin.ECKey.fromWIF("L1uyy5qTuGrVXrmrsvHWHgVzW9kKdrp27wBC7Vs6nZDTF2BRUVwy")
      var address = key.pub.getAddress(bitcoin.networks.testnet).toString()
  
      helloblock.faucet.withdraw(address, 2e4, function(err) {
        if (err) return done(err)
  
        helloblock.addresses.getUnspents(address, function(err, _, unspents) {
          if (err) return done(err)
  
          // filter small unspents
          unspents = unspents.filter(function(unspent) { return unspent.value > 1e4 })
  
          // use the oldest unspent
          var unspent = unspents.pop()
  
          var tx = new bitcoin.TransactionBuilder()
  
          var data = new Buffer('cafedeadbeef', 'hex')
          var dataScript = bitcoin.scripts.nullDataOutput(data)
  
          tx.addInput(unspent.txHash, unspent.index)
          tx.addOutput(dataScript, 1000)
          tx.sign(0, key)
  
          helloblock.transactions.propagate(tx.build().toHex(), function(err) {
            if (err) return done(err)
  
            // check that the message was propagated
            helloblock.addresses.getTransactions(address, function(err, res, transactions) {
              if (err) return done(err)
  
              var transaction = transactions[0]
              var output = transaction.outputs[0]
              var dataScript2 = bitcoin.Script.fromHex(output.scriptPubKey)
              var data2 = dataScript2.chunks[1]
  
              assert.deepEqual(dataScript, dataScript2)
              assert.deepEqual(data, data2)
  
              done()
            })
          })
        })
      })
    })
  })
  