From 5ecef0b787d0a2f5bddb9b07c42cb5d1abb07bab Mon Sep 17 00:00:00 2001
From: Christopher Schinnerl <chris@sia.tech>
Date: Fri, 26 Jan 2018 15:06:53 -0500
Subject: [PATCH 1/2] Wallet starts defragging implicitly when sending coins
 once it reaches a certain threshold of unspent outputs

---
 modules/wallet/consts.go             |  6 ++++
 modules/wallet/defrag_test.go        | 50 ++++++++++++++++++++++++++++
 modules/wallet/transactionbuilder.go | 18 ++++++++--
 3 files changed, 72 insertions(+), 2 deletions(-)

diff --git a/modules/wallet/consts.go b/modules/wallet/consts.go
index 4bdd51fb91..0e187174b0 100644
--- a/modules/wallet/consts.go
+++ b/modules/wallet/consts.go
@@ -15,6 +15,12 @@ const (
 	// defragThreshold is the number of outputs a wallet is allowed before it is
 	// defragmented.
 	defragThreshold = 50
+
+	// naturalDefragThreshold is the number of outputs a wallet is allowed
+	// before it starts defragging using its normal spending behavior. This
+	// threshold is a bit lower than the defragThreshold to avoid starting the
+	// thread.
+	naturalDefragThreshold = defragThreshold - 10
 )
 
 var (
diff --git a/modules/wallet/defrag_test.go b/modules/wallet/defrag_test.go
index 32e81c5bec..59161c5985 100644
--- a/modules/wallet/defrag_test.go
+++ b/modules/wallet/defrag_test.go
@@ -277,3 +277,53 @@ func TestDefragInterrupted(t *testing.T) {
 	}
 
 }
+
+// TestDefragWalletSendCoins mines many blocks and checks that the wallet's outputs are
+// consolidated after spending some coins.
+func TestDefragWalletSendCoins(t *testing.T) {
+	if testing.Short() {
+		t.SkipNow()
+	}
+	t.Parallel()
+	wt, err := createWalletTester(t.Name(), &ProductionDependencies{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer wt.closeWt()
+
+	// mine defragThreshold blocks, resulting in defragThreshold outputs
+	for i := 0; i < naturalDefragThreshold; i++ {
+		_, err := wt.miner.AddBlock()
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// send coins to trigger a defrag
+	uc, err := wt.wallet.NextAddress()
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = wt.wallet.SendSiacoins(types.SiacoinPrecision, uc.UnlockHash())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// allow some time for the defrag transaction to occur, then mine another block
+	time.Sleep(time.Second * 5)
+
+	_, err = wt.miner.AddBlock()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// defrag should keep the outputs below the threshold
+	wt.wallet.mu.Lock()
+	// force a sync because bucket stats may not be reliable until commit
+	wt.wallet.syncDB()
+	siacoinOutputs := wt.wallet.dbTx.Bucket(bucketSiacoinOutputs).Stats().KeyN
+	wt.wallet.mu.Unlock()
+	if siacoinOutputs > defragThreshold {
+		t.Fatalf("defrag should result in fewer than defragThreshold outputs, got %v wanted %v\n", siacoinOutputs, defragThreshold)
+	}
+}
diff --git a/modules/wallet/transactionbuilder.go b/modules/wallet/transactionbuilder.go
index c4e0d78cb6..6bfb9ced1c 100644
--- a/modules/wallet/transactionbuilder.go
+++ b/modules/wallet/transactionbuilder.go
@@ -149,7 +149,16 @@ func (tb *transactionBuilder) FundSiacoins(amount types.Currency) error {
 			so.outputs = append(so.outputs, sco)
 		}
 	}
-	sort.Sort(sort.Reverse(so))
+
+	// If we have too man unspent transactions we might as well do some
+	// defragging since we create a setup transaction anyway
+	defrag := tb.wallet.defragDisabled && len(so.ids) >= naturalDefragThreshold
+	if defrag {
+		// If we defrag we start with the smallest output
+		sort.Sort(so)
+	} else {
+		sort.Sort(sort.Reverse(so))
+	}
 
 	// Create and fund a parent transaction that will add the correct amount of
 	// siacoins to the transaction.
@@ -183,7 +192,12 @@ func (tb *transactionBuilder) FundSiacoins(amount types.Currency) error {
 		// Add the output to the total fund
 		fund = fund.Add(sco.Value)
 		potentialFund = potentialFund.Add(sco.Value)
-		if fund.Cmp(amount) >= 0 {
+		if defrag && len(spentScoids) >= defragBatchSize {
+			// If we defrag we don't stop once we have gathered enough money
+			// but if we reach the batch size.
+			break
+		} else if !defrag && fund.Cmp(amount) >= 0 {
+			// If we don't defrag we stop once we have gathered enough money.
 			break
 		}
 	}

From ff027784cd60ccd5cf82b71f197151c81970726d Mon Sep 17 00:00:00 2001
From: Christopher Schinnerl <chris@sia.tech>
Date: Mon, 5 Feb 2018 10:16:20 -0500
Subject: [PATCH 2/2] skip larget outputs and fix comment

---
 modules/wallet/transactionbuilder.go | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/modules/wallet/transactionbuilder.go b/modules/wallet/transactionbuilder.go
index 6bfb9ced1c..e382ec62d3 100644
--- a/modules/wallet/transactionbuilder.go
+++ b/modules/wallet/transactionbuilder.go
@@ -150,12 +150,16 @@ func (tb *transactionBuilder) FundSiacoins(amount types.Currency) error {
 		}
 	}
 
-	// If we have too man unspent transactions we might as well do some
+	// If we have too many unspent transactions we might as well do some
 	// defragging since we create a setup transaction anyway
 	defrag := tb.wallet.defragDisabled && len(so.ids) >= naturalDefragThreshold
 	if defrag {
-		// If we defrag we start with the smallest output
+		// If we defrag we start with the smallest output and skip the
+		// defragStartIndex last ones to make sure the wallet still has a
+		// minimum amount of large outputs to spend.
 		sort.Sort(so)
+		so.ids = so.ids[:len(so.ids)-defragStartIndex]
+		so.outputs = so.outputs[:len(so.outputs)-defragStartIndex]
 	} else {
 		sort.Sort(sort.Reverse(so))
 	}