From 92a2f3161d7858ef4b23beb8434f0fb106269fcc Mon Sep 17 00:00:00 2001
From: Adrian Lanzafame <adrianlanzafame92@gmail.com>
Date: Tue, 2 Oct 2018 12:10:15 +1000
Subject: [PATCH 1/2] batch: add functional opts to Batch

License: MIT
Signed-off-by: Adrian Lanzafame <adrianlanzafame92@gmail.com>
---
 batch.go      | 53 +++++++++++++++++++++++++++++++++++++++++----------
 batch_test.go | 16 ++++++++++++++++
 2 files changed, 59 insertions(+), 10 deletions(-)

diff --git a/batch.go b/batch.go
index 754490b..967a0fe 100644
--- a/batch.go
+++ b/batch.go
@@ -23,19 +23,18 @@ var ErrClosed = errors.New("error: batch closed")
 // to add or remove a lot of nodes all at once.
 //
 // If the passed context is canceled, any in-progress commits are aborted.
-func NewBatch(ctx context.Context, ds DAGService) *Batch {
+func NewBatch(ctx context.Context, ds DAGService, opts ...BatchOption) *Batch {
 	ctx, cancel := context.WithCancel(ctx)
+	bopts := defaultBatchOptions
+	for _, o := range opts {
+		o(&bopts)
+	}
 	return &Batch{
 		ds:            ds,
 		ctx:           ctx,
 		cancel:        cancel,
 		commitResults: make(chan error, ParallelBatchCommits),
-		MaxSize:       8 << 20,
-
-		// By default, only batch up to 128 nodes at a time.
-		// The current implementation of flatfs opens this many file
-		// descriptors at the same time for the optimized batch write.
-		MaxNodes: 128,
+		opts:          bopts,
 	}
 }
 
@@ -53,8 +52,7 @@ type Batch struct {
 	nodes []Node
 	size  int
 
-	MaxSize  int
-	MaxNodes int
+	opts batchOptions
 }
 
 func (t *Batch) processResults() {
@@ -120,7 +118,7 @@ func (t *Batch) Add(nd Node) error {
 	t.nodes = append(t.nodes, nd)
 	t.size += len(nd.RawData())
 
-	if t.size > t.MaxSize || len(t.nodes) > t.MaxNodes {
+	if t.size > t.opts.maxSize || len(t.nodes) > t.opts.maxNodes {
 		t.asyncCommit()
 	}
 	return t.err
@@ -175,3 +173,38 @@ loop:
 	t.size = 0
 	t.activeCommits = 0
 }
+
+// BatchOption provides a way of setting internal options of
+// a Batch.
+//
+// See this post about the "functional options" pattern:
+// http://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis
+type BatchOption func(o *batchOptions)
+
+type batchOptions struct {
+	maxSize  int
+	maxNodes int
+}
+
+var defaultBatchOptions = batchOptions{
+	maxSize: 8 << 20,
+
+	// By default, only batch up to 128 nodes at a time.
+	// The current implementation of flatfs opens this many file
+	// descriptors at the same time for the optimized batch write.
+	maxNodes: 128,
+}
+
+// MaxSizeBatchOption sets the maximum size of a Batch.
+func MaxSizeBatchOption(size int) BatchOption {
+	return func(o *batchOptions) {
+		o.maxSize = size
+	}
+}
+
+// MaxNodesBatchOption sets the maximum number of nodes in a Batch.
+func MaxNodesBatchOption(num int) func(o *batchOptions) {
+	return func(o *batchOptions) {
+		o.maxNodes = num
+	}
+}
diff --git a/batch_test.go b/batch_test.go
index 20b3e61..3ae6394 100644
--- a/batch_test.go
+++ b/batch_test.go
@@ -108,3 +108,19 @@ func TestBatch(t *testing.T) {
 		t.Fatal("should have one node")
 	}
 }
+
+func TestBatchOptions(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	wantMaxSize := 8 << 10
+	wantMaxNodes := 500
+	d := newTestDag()
+	b := NewBatch(ctx, d, MaxSizeBatchOption(wantMaxSize), MaxNodesBatchOption(wantMaxNodes))
+	if b.opts.maxSize != wantMaxSize {
+		t.Fatalf("maxSize incorrect, want: %d, got: %d", wantMaxSize, b.opts.maxSize)
+	}
+	if b.opts.maxNodes != wantMaxNodes {
+		t.Fatalf("maxNodes incorrect, want: %d, got: %d", wantMaxNodes, b.opts.maxNodes)
+	}
+}

From 434489e069bf62e78ae04b58a1d0851df6e40e43 Mon Sep 17 00:00:00 2001
From: Steven Allen <steven@stebalien.com>
Date: Tue, 2 Oct 2018 16:09:15 -0700
Subject: [PATCH 2/2] make MaxNodesBatchOption return a BatchOption

(address CR)
---
 batch.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/batch.go b/batch.go
index 967a0fe..662e1b8 100644
--- a/batch.go
+++ b/batch.go
@@ -203,7 +203,7 @@ func MaxSizeBatchOption(size int) BatchOption {
 }
 
 // MaxNodesBatchOption sets the maximum number of nodes in a Batch.
-func MaxNodesBatchOption(num int) func(o *batchOptions) {
+func MaxNodesBatchOption(num int) BatchOption {
 	return func(o *batchOptions) {
 		o.maxNodes = num
 	}