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83// Copyright 2014 Manu Martinez-Almeida. All rights reserved.
// Use of this source code is governed by a MIT style
// license that can be found in the LICENSE file.
package main
import (
"fmt"
"io"
"net/http"
"strings"
)
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}
}
}
// Server-Sent Events
// W3C Working Draft 29 October 2009
// http://www.w3.org/TR/2009/WD-eventsource-20091029/
var contentType = []string{"text/event-stream"}
var noCache = []string{"no-cache"}
var fieldReplacer = strings.NewReplacer(
"\n", "\\n",
"\r", "\\r")
var dataReplacer = strings.NewReplacer(
"\n", "\ndata:",
"\r", "\\r")
type CustomEvent struct {
Event string
Id string
Retry uint
Data interface{}
}
func encode(writer io.Writer, event CustomEvent) error {
w := checkWriter(writer)
return writeData(w, event.Data)
}
func writeData(w stringWriter, data interface{}) error {
dataReplacer.WriteString(w, fmt.Sprint(data))
if strings.HasPrefix(data.(string), "data") {
w.writeString("\n\n")
}
return nil
}
func (r CustomEvent) Render(w http.ResponseWriter) error {
r.WriteContentType(w)
return encode(w, r)
}
func (r CustomEvent) WriteContentType(w http.ResponseWriter) {
header := w.Header()
header["Content-Type"] = contentType
if _, exist := header["Cache-Control"]; !exist {
header["Cache-Control"] = noCache
}
}