fix: make encoder split the event data into several data events per line

pkg/encoder/encoder.go

@@ -1,10 +1,13 @@
 package encoder
 
 import (
+	"bufio"
 	"bytes"
 	"io"
 	"strconv"
+	"strings"
 
+	"github.com/alevinval/sse/internal"
 	"github.com/alevinval/sse/pkg/base"
 )
 
@@ -41,9 +44,18 @@ func (e *Encoder) WriteEvent(event base.MessageEventGetter) (int, error) {
 	}
 
 	if event.GetData() != "" {
-		e.buf.WriteString("data: ")
-		e.buf.WriteString(event.GetData())
-		e.buf.WriteByte('\n')
+		input := strings.NewReader(event.GetData())
+		scanner := bufio.NewScanner(input)
+		scanner.Split(internal.ScanLinesCR)
+		for scanner.Scan() {
+			line := scanner.Text()
+			if len(line) == 0 {
+				break
+			}
+			e.buf.WriteString("data: ")
+			e.buf.WriteString(line)
+			e.buf.WriteByte('\n')
+		}
 	}
 
 	e.buf.WriteByte('\n')

pkg/encoder/encoder_test.go

@@ -54,6 +54,16 @@ func TestEncoder_WriteEvent_EncodesData(t *testing.T) {
 	assert.Equal(t, "data: event-data\n\n", out.String())
 }
 
+func TestEncoder_WriteEvent_EncodesMultiLineInput(t *testing.T) {
+	sut, out := getEncoder()
+	sut.WriteEvent(&base.MessageEvent{
+		ID:   "abc",
+		Name: "test",
+		Data: "line1\nline2",
+	})
+	assert.Equal(t, "id: abc\nevent: test\ndata: line1\ndata: line2\n\n", out.String())
+}
+
 func TestEncoder_WriteEvent_EncodesFullEvent(t *testing.T) {
 	event := &base.MessageEvent{ID: "event-id", Name: "event-name", Data: "event-data"}
 	sut, out := getEncoder()