From a34f83e68466507d8a8f59db74483f916d16ebed Mon Sep 17 00:00:00 2001
From: Matthew Rich <matthewrich.conf@gmail.com>
Date: Thu, 3 Oct 2024 23:31:53 +0000
Subject: [PATCH] add close injector to allow auto-closing the wrapped writers

---
 internal/ext/addcloser.go      | 31 +++++++++++++++++++++++++++++++
 internal/ext/addcloser_test.go | 19 +++++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 internal/ext/addcloser.go
 create mode 100644 internal/ext/addcloser_test.go

diff --git a/internal/ext/addcloser.go b/internal/ext/addcloser.go
new file mode 100644
index 0000000..75a1e32
--- /dev/null
+++ b/internal/ext/addcloser.go
@@ -0,0 +1,31 @@
+// Copyright 2024 Matthew Rich <matthewrich.conf@gmail.com>. All rights reserved.
+
+package ext
+
+import (
+	"io"
+)
+
+type Closer func() error
+
+func WriteAddCloser(w io.WriteCloser, c Closer) io.WriteCloser {
+	a := writeAddCloser{ WriteCloser: w, AddClose: func() (err error) {
+		if err = w.Close(); err != nil {
+			return
+		}
+		if c != nil {
+			return c()
+		}
+		return
+	} }
+	return a
+}
+
+type writeAddCloser struct {
+	io.WriteCloser
+	AddClose Closer
+}
+
+func (w writeAddCloser) Close() error {
+	return w.AddClose()
+}
diff --git a/internal/ext/addcloser_test.go b/internal/ext/addcloser_test.go
new file mode 100644
index 0000000..cc53937
--- /dev/null
+++ b/internal/ext/addcloser_test.go
@@ -0,0 +1,19 @@
+// Copyright 2024 Matthew Rich <matthewrich.conf@gmail.com>. All rights reserved.
+
+package ext
+
+import (
+	"testing"
+	"github.com/stretchr/testify/assert"
+	"strings"
+_	"fmt"
+_	"log"
+)
+
+func TestNewWriteAddCloser(t *testing.T) {
+	var testWriter strings.Builder
+
+	closer := WriteAddCloser(WriteNopCloser(&testWriter), func() error { testWriter.Write([]byte("foo")); return nil })
+	closer.Close()
+	assert.Equal(t, "foo", testWriter.String())
+}