feat: add ctx ssevent; fix: superfluous response.WriteHeader

internal/sse/sse-encoder.go

@@ -0,0 +1,106 @@
+package sse
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+// Server-Sent Events
+// W3C Working Draft 29 October 2009
+// http://www.w3.org/TR/2009/WD-eventsource-20091029/
+
+const ContentType = "text/event-stream"
+
+var contentType = []string{ContentType}
+var noCache = []string{"no-cache"}
+
+var fieldReplacer = strings.NewReplacer(
+	"\n", "\\n",
+	"\r", "\\r")
+
+var dataReplacer = strings.NewReplacer(
+	"\n", "\ndata:",
+	"\r", "\\r")
+
+type Event struct {
+	Event string
+	Id    string
+	Retry uint
+	Data  interface{}
+}
+
+func Encode(writer io.Writer, event Event) error {
+	w := checkWriter(writer)
+	writeId(w, event.Id)
+	writeEvent(w, event.Event)
+	writeRetry(w, event.Retry)
+	return writeData(w, event.Data)
+}
+
+func writeId(w stringWriter, id string) {
+	if len(id) > 0 {
+		w.WriteString("id:")
+		fieldReplacer.WriteString(w, id)
+		w.WriteString("\n")
+	}
+}
+
+func writeEvent(w stringWriter, event string) {
+	if len(event) > 0 {
+		w.WriteString("event:")
+		fieldReplacer.WriteString(w, event)
+		w.WriteString("\n")
+	}
+}
+
+func writeRetry(w stringWriter, retry uint) {
+	if retry > 0 {
+		w.WriteString("retry:")
+		w.WriteString(strconv.FormatUint(uint64(retry), 10))
+		w.WriteString("\n")
+	}
+}
+
+func writeData(w stringWriter, data interface{}) error {
+	w.WriteString("data:")
+	switch kindOfData(data) {
+	case reflect.Struct, reflect.Slice, reflect.Map:
+		err := json.NewEncoder(w).Encode(data)
+		if err != nil {
+			return err
+		}
+		w.WriteString("\n")
+	default:
+		dataReplacer.WriteString(w, fmt.Sprint(data))
+		w.WriteString("\n\n")
+	}
+	return nil
+}
+
+func (r Event) Render(w http.ResponseWriter) error {
+	r.WriteContentType(w)
+	return Encode(w, r)
+}
+
+func (r Event) WriteContentType(w http.ResponseWriter) {
+	header := w.Header()
+	header["Content-Type"] = contentType
+
+	if _, exist := header["Cache-Control"]; !exist {
+		header["Cache-Control"] = noCache
+	}
+}
+
+func kindOfData(data interface{}) reflect.Kind {
+	value := reflect.ValueOf(data)
+	valueType := value.Kind()
+	if valueType == reflect.Ptr {
+		valueType = value.Elem().Kind()
+	}
+	return valueType
+}

internal/sse/writer.go

@@ -0,0 +1,24 @@
+package sse
+
+import "io"
+
+type stringWriter interface {
+	io.Writer
+	WriteString(string) (int, error)
+}
+
+type stringWrapper struct {
+	io.Writer
+}
+
+func (w stringWrapper) WriteString(str string) (int, error) {
+	return w.Writer.Write([]byte(str))
+}
+
+func checkWriter(writer io.Writer) stringWriter {
+	if w, ok := writer.(stringWriter); ok {
+		return w
+	} else {
+		return stringWrapper{writer}
+	}
+}