vendor/github.com/gin-contrib/sse/sse-encoder.go

   1 // Copyright 2014 Manu Martinez-Almeida.  All rights reserved.
   2 // Use of this source code is governed by a MIT style
   3 // license that can be found in the LICENSE file.
   4
   5 package sse
   6
   7 import (
   8         "encoding/json"
   9         "fmt"
  10         "io"
  11         "net/http"
  12         "reflect"
  13         "strconv"
  14         "strings"
  15 )
  16
  17 // Server-Sent Events
  18 // W3C Working Draft 29 October 2009
  19 // http://www.w3.org/TR/2009/WD-eventsource-20091029/
  20
  21 const ContentType = "text/event-stream"
  22
  23 var contentType = []string{ContentType}
  24 var noCache = []string{"no-cache"}
  25
  26 var fieldReplacer = strings.NewReplacer(
  27         "\n", "\\n",
  28         "\r", "\\r")
  29
  30 var dataReplacer = strings.NewReplacer(
  31         "\n", "\ndata:",
  32         "\r", "\\r")
  33
  34 type Event struct {
  35         Event string
  36         Id    string
  37         Retry uint
  38         Data  interface{}
  39 }
  40
  41 func Encode(writer io.Writer, event Event) error {
  42         w := checkWriter(writer)
  43         writeId(w, event.Id)
  44         writeEvent(w, event.Event)
  45         writeRetry(w, event.Retry)
  46         return writeData(w, event.Data)
  47 }
  48
  49 func writeId(w stringWriter, id string) {
  50         if len(id) > 0 {
  51                 w.WriteString("id:")
  52                 fieldReplacer.WriteString(w, id)
  53                 w.WriteString("\n")
  54         }
  55 }
  56
  57 func writeEvent(w stringWriter, event string) {
  58         if len(event) > 0 {
  59                 w.WriteString("event:")
  60                 fieldReplacer.WriteString(w, event)
  61                 w.WriteString("\n")
  62         }
  63 }
  64
  65 func writeRetry(w stringWriter, retry uint) {
  66         if retry > 0 {
  67                 w.WriteString("retry:")
  68                 w.WriteString(strconv.FormatUint(uint64(retry), 10))
  69                 w.WriteString("\n")
  70         }
  71 }
  72
  73 func writeData(w stringWriter, data interface{}) error {
  74         w.WriteString("data:")
  75         switch kindOfData(data) {
  76         case reflect.Struct, reflect.Slice, reflect.Map:
  77                 err := json.NewEncoder(w).Encode(data)
  78                 if err != nil {
  79                         return err
  80                 }
  81                 w.WriteString("\n")
  82         default:
  83                 dataReplacer.WriteString(w, fmt.Sprint(data))
  84                 w.WriteString("\n\n")
  85         }
  86         return nil
  87 }
  88
  89 func (r Event) Render(w http.ResponseWriter) error {
  90         r.WriteContentType(w)
  91         return Encode(w, r)
  92 }
  93
  94 func (r Event) WriteContentType(w http.ResponseWriter) {
  95         header := w.Header()
  96         header["Content-Type"] = contentType
  97
  98         if _, exist := header["Cache-Control"]; !exist {
  99                 header["Cache-Control"] = noCache
 100         }
 101 }
 102
 103 func kindOfData(data interface{}) reflect.Kind {
 104         value := reflect.ValueOf(data)
 105         valueType := value.Kind()
 106         if valueType == reflect.Ptr {
 107                 valueType = value.Elem().Kind()
 108         }
 109         return valueType
 110 }