From 65bda681d52016749b3bb420736136e7001acfac Mon Sep 17 00:00:00 2001
From: Ivan Socolsky <jungans@gmail.com>
Date: Fri, 20 May 2016 12:27:45 -0300
Subject: [PATCH] allow a specific change address

---
 lib/errors/errordefinitions.js |  1 +
 lib/server.js                  | 23 +++++++++++++++++------
 test/integration/server.js     | 19 +++++++++++++++++++
 3 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/lib/errors/errordefinitions.js b/lib/errors/errordefinitions.js
index 62f0081..f5c8c2f 100644
--- a/lib/errors/errordefinitions.js
+++ b/lib/errors/errordefinitions.js
@@ -15,6 +15,7 @@ var errors = {
   INSUFFICIENT_FUNDS: 'Insufficient funds',
   INSUFFICIENT_FUNDS_FOR_FEE: 'Insufficient funds for fee',
   INVALID_ADDRESS: 'Invalid address',
+  INVALID_CHANGE_ADDRESS: 'Invalid change address',
   KEY_IN_COPAYER: 'Key already registered',
   LOCKED_FUNDS: 'Funds are locked by pending transaction proposals',
   HISTORY_LIMIT_EXCEEDED: 'Requested page limit is above allowed maximum',
diff --git a/lib/server.js b/lib/server.js
index 7c64ad3..185c963 100644
--- a/lib/server.js
+++ b/lib/server.js
@@ -1871,12 +1871,13 @@ WalletService.prototype._validateAndSanitizeTxOpts = function(wallet, opts, cb)
  * @param {number} opts.outputs[].amount - Amount to transfer in satoshi.
  * @param {string} opts.outputs[].message - A message to attach to this output.
  * @param {string} opts.message - A message to attach to this transaction.
- * @param {string} opts.feePerKb - Use an alternative fee per KB for this TX.
- * @param {string} opts.sendMax - Optional. Send maximum amount of funds that make sense under the specified fee/feePerKb conditions. (defaults to false).
+ * @param {number} opts.feePerKb - Use an alternative fee per KB for this TX.
+ * @param {string} opts.changeAddress - Optional. Use this address as the change address for the tx. The address should belong to the wallet.
+ * @param {Boolean} opts.sendMax - Optional. Send maximum amount of funds that make sense under the specified fee/feePerKb conditions. (defaults to false).
  * @param {string} opts.payProUrl - Optional. Paypro URL for peers to verify TX
- * @param {string} opts.excludeUnconfirmedUtxos[=false] - Optional. Do not use UTXOs of unconfirmed transactions as inputs
- * @param {string} opts.validateOutputs[=true] - Optional. Perform validation on outputs.
- * @param {string} opts.dryRun[=false] - Optional. Simulate the action but do not change server state.
+ * @param {Boolean} opts.excludeUnconfirmedUtxos[=false] - Optional. Do not use UTXOs of unconfirmed transactions as inputs
+ * @param {Boolean} opts.validateOutputs[=true] - Optional. Perform validation on outputs.
+ * @param {Boolean} opts.dryRun[=false] - Optional. Simulate the action but do not change server state.
  * @param {Array} opts.inputs - Optional. Inputs for this TX
  * @param {number} opts.fee - Optional. Use an fixed fee for this TX (only when opts.inputs is specified)
  * @param {Boolean} opts.noShuffleOutputs - Optional. If set, TX outputs won't be shuffled. Defaults to false
@@ -1909,9 +1910,19 @@ WalletService.prototype.createTx = function(opts, cb) {
         });
       },
       function(next) {
-        if (!opts.sendMax) {
+        if (opts.sendMax) return next();
+        if (opts.changeAddress) {
+          self.storage.fetchAddress(opts.changeAddress, function(err, address) {
+            if (err) return next(Errors.INVALID_CHANGE_ADDRESS);
+            changeAddress = address;
+            return next();
+          });
+        } else {
           changeAddress = wallet.createAddress(true);
+          return next();
         }
+      },
+      function(next) {
         var txOpts = {
           walletId: self.walletId,
           creatorId: self.copayerId,
diff --git a/test/integration/server.js b/test/integration/server.js
index 2e12885..c47b2b6 100644
--- a/test/integration/server.js
+++ b/test/integration/server.js
@@ -3138,6 +3138,25 @@ describe('Wallet service', function() {
           });
         });
       });
+      it('should be able to specify change address', function(done) {
+        helpers.stubUtxos(server, wallet, [1, 2], function(utxos) {
+          var txOpts = {
+            outputs: [{
+              toAddress: '18PzpUFkFZE8zKWUPvfykkTxmB9oMR8qP7',
+              amount: 0.8e8,
+            }],
+            feePerKb: 100e2,
+            changeAddress: utxos[0].address,
+          };
+          server.createTx(txOpts, function(err, tx) {
+            should.not.exist(err);
+            should.exist(tx);
+            var t = tx.getBitcoreTx();
+            t.getChangeOutput().script.toAddress().toString().should.equal(txOpts.changeAddress);
+            done();
+          });
+        });
+      });
       it('should be able to specify inputs & absolute fee', function(done) {
         helpers.stubUtxos(server, wallet, [1, 2], function(utxos) {
           var txOpts = {