From f836e90345a8a1c2c62f888787137e312997746a Mon Sep 17 00:00:00 2001
From: Charles Iliya Krempeaux <iamreiver@gmail.com>
Date: Wed, 11 Sep 2019 12:36:02 -0700
Subject: [PATCH] utf8s.RuneWriter

---
 runewriter.go      |  26 +++++++++++
 runewriter_test.go | 110 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 136 insertions(+)
 create mode 100644 runewriter.go
 create mode 100644 runewriter_test.go

diff --git a/runewriter.go b/runewriter.go
new file mode 100644
index 0000000..b63b8fa
--- /dev/null
+++ b/runewriter.go
@@ -0,0 +1,26 @@
+package utf8s
+
+import (
+	"io"
+)
+
+// RuneWriter writes a single UTF-8 encoded Unicode characters.
+type RuneWriter struct {
+	writer io.Writer
+}
+
+// NewRuneWriter wraps an io.Writer and returns a RuneWriter.
+func NewRuneWriter(writer io.Writer) *RuneWriter {
+	return &RuneWriter{
+		writer: writer,
+	}
+}
+
+// WriteRune writes a single UTF-8 encoded Unicode character and returns the number of bytes written.
+func (receiver *RuneWriter) WriteRune(r rune) (int, error) {
+	if nil == receiver {
+		return 0, errNilReceiver
+	}
+
+	return WriteRune(receiver.writer, r)
+}
diff --git a/runewriter_test.go b/runewriter_test.go
new file mode 100644
index 0000000..90e2251
--- /dev/null
+++ b/runewriter_test.go
@@ -0,0 +1,110 @@
+package utf8s_test
+
+import (
+	"github.com/reiver/go-utf8s"
+
+	"strings"
+
+	"testing"
+)
+
+func TestRuneWriter(t *testing.T) {
+
+	tests := []struct{
+		Runes []rune
+		Expected string
+	}{
+		{
+			Runes: []rune{},
+			Expected: "",
+		},
+
+
+
+		{
+			Runes: []rune{'a','p','p','l','e'},
+			Expected: "apple",
+		},
+		{
+			Runes: []rune{'B','A','N','A','N','A'},
+			Expected: "BANANA",
+		},
+		{
+			Runes: []rune{'C','h','e','r','r','y'},
+			Expected: "Cherry",
+		},
+		{
+			Runes: []rune{'d','A','T','E'},
+			Expected: "dATE",
+		},
+
+
+
+		{
+			Runes: []rune{'😀','😁','😂','😃','😄','😅','😆','😇','😈','😉','😊','😋','😌','😍','😎','😏'},
+			Expected: "😀😁😂😃😄😅😆😇😈😉😊😋😌😍😎😏",
+		},
+
+
+
+		{
+			Runes: []rune{'H','i','!','\u2029','👾','\u2029','S','e','e',' ','y','a','\u2029'},
+			Expected: "Hi!\u2029👾\u2029See ya\u2029",
+		},
+	}
+
+	TestLoop: for testNumber, test := range tests {
+
+		var buffer strings.Builder
+		var total int
+
+		runeWriter := utf8s.NewRuneWriter(&buffer)
+
+		for runeNumber, r := range test.Runes {
+
+			n, err := runeWriter.WriteRune(r)
+			if nil != err {
+				t.Errorf("For test #%d and rune #%d, did not expect an error, but actually got one.", testNumber, runeNumber)
+				for i, rr := range test.Runes {
+					t.Logf("\t[%d] %q (%d)", i, string(rr), rr)
+				}
+				t.Logf("ERROR TYPE: %T", err)
+				t.Logf("ERROR: %q", err)
+				continue TestLoop
+			}
+
+			if expected, actual := n, utf8s.Len(r); expected != actual {
+				t.Errorf("For test #%d and rune #%d, expected a certain number of bytes to be written, but actually wasn't.", testNumber, runeNumber)
+				for i, rr := range test.Runes {
+					t.Logf("\t[%d] %q (%d)", i, string(rr), rr)
+				}
+				t.Logf("RUNE: %q (%d)", string(r), r)
+				t.Logf("EXPECTED: %d", expected)
+				t.Logf("ACTUAL:   %d", actual)
+				continue TestLoop
+			}
+
+			total += n
+		}
+
+		if expected, actual := len(test.Expected), total; expected != actual {
+			t.Errorf("For test #%d, expected the total number of bytes to be written to be something, but actually wasn't.", testNumber)
+			for i, rr := range test.Runes {
+				t.Logf("\t[%d] %q (%d)", i, string(rr), rr)
+			}
+			t.Logf("EXPECTED: %d", expected)
+			t.Logf("ACTUAL:   %d", actual)
+			continue TestLoop
+		}
+
+		if expected, actual := test.Expected, buffer.String(); expected != actual {
+			t.Errorf("For test #%d, what what expected to be written, is not what was actually written.", testNumber)
+			for i, rr := range test.Runes {
+				t.Logf("\t[%d] %q (%d)", i, string(rr), rr)
+			}
+			t.Logf("EXPECTED: %q", expected)
+			t.Logf("ACTUAL:   %q", actual)
+			continue TestLoop
+		}
+	}
+}