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112package jsonp
import (
"bytes"
"encoding/json"
"fmt"
"net/http"
"strconv"
"strings"
)
func Handler(next http.Handler) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
callback := r.URL.Query().Get("callback")
if callback == "" {
callback = r.URL.Query().Get("jsonp")
}
if callback == "" {
next.ServeHTTP(w, r)
return
}
wb := NewResponseBuffer(w)
next.ServeHTTP(wb, r)
if strings.Index(wb.Header().Get("Content-Type"), "/json") >= 0 {
status := wb.Status
data := wb.Body.Bytes()
wb.Body.Reset()
resp := &jsonpResponse{
Meta: map[string]interface{}{"status": status},
Data: data,
}
for k, v := range wb.Header() {
resp.Meta[strings.ToLower(k)] = v[0]
}
resp.Meta["content-length"] = len(data)
body, err := json.Marshal(resp)
if err != nil {
panic(err.Error())
}
wb.Body.Write([]byte(callback + "("))
wb.Body.Write(body)
wb.Body.Write([]byte(")"))
wb.Header().Set("Content-Type", "application/javascript")
wb.Header().Set("Content-Length", strconv.Itoa(wb.Body.Len()))
}
wb.Flush()
}
return http.HandlerFunc(fn)
}
type jsonpResponse struct {
Meta map[string]interface{}
Data interface{}
}
func (j *jsonpResponse) MarshalJSON() ([]byte, error) {
meta, err := json.Marshal(j.Meta)
if err != nil {
return nil, err
}
b := fmt.Sprintf("{\"meta\":%s,\"data\":%s}", meta, j.Data)
return []byte(b), nil
}
type responseBuffer struct {
Response http.ResponseWriter // the actual ResponseWriter to flush to
Status int // the HTTP response code from WriteHeader
Body *bytes.Buffer // the response content body
Flushed bool
}
func NewResponseBuffer(w http.ResponseWriter) *responseBuffer {
return &responseBuffer{
Response: w, Status: 200, Body: &bytes.Buffer{},
}
}
func (w *responseBuffer) Header() http.Header {
return w.Response.Header() // use the actual response header
}
func (w *responseBuffer) Write(buf []byte) (int, error) {
w.Body.Write(buf)
return len(buf), nil
}
func (w *responseBuffer) WriteHeader(status int) {
w.Status = status
}
func (w *responseBuffer) Flush() {
if w.Flushed {
return
}
w.Response.WriteHeader(w.Status)
if w.Body.Len() > 0 {
_, err := w.Response.Write(w.Body.Bytes())
if err != nil {
panic(err)
}
w.Body.Reset()
}
w.Flushed = true
}