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// Copyright 2013 The Gorilla Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package handlers
import (
"bufio"
"fmt"
"net"
"net/http"
"sort"
"strings"
)
// MethodHandler is an http.Handler that dispatches to a handler whose key in the
// MethodHandler's map matches the name of the HTTP request's method, eg: GET
//
// If the request's method is OPTIONS and OPTIONS is not a key in the map then
// the handler responds with a status of 200 and sets the Allow header to a
// comma-separated list of available methods.
//
// If the request's method doesn't match any of its keys the handler responds
// with a status of HTTP 405 "Method Not Allowed" and sets the Allow header to a
// comma-separated list of available methods.
type MethodHandler map[string]http.Handler
func (h MethodHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
if handler, ok := h[req.Method]; ok {
handler.ServeHTTP(w, req)
} else {
allow := []string{}
for k := range h {
allow = append(allow, k)
}
sort.Strings(allow)
w.Header().Set("Allow", strings.Join(allow, ", "))
if req.Method == http.MethodOptions {
w.WriteHeader(http.StatusOK)
} else {
http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
}
}
}
// responseLogger is wrapper of http.ResponseWriter that keeps track of its HTTP
// status code and body size.
type responseLogger struct {
w http.ResponseWriter
status int
size int
}
func (l *responseLogger) Write(b []byte) (int, error) {
size, err := l.w.Write(b)
l.size += size
return size, err
}
func (l *responseLogger) WriteHeader(s int) {
l.w.WriteHeader(s)
l.status = s
}
func (l *responseLogger) Status() int {
return l.status
}
func (l *responseLogger) Size() int {
return l.size
}
func (l *responseLogger) Hijack() (net.Conn, *bufio.ReadWriter, error) {
conn, rw, err := l.w.(http.Hijacker).Hijack()
if err == nil && l.status == 0 {
// The status will be StatusSwitchingProtocols if there was no error and
// WriteHeader has not been called yet
l.status = http.StatusSwitchingProtocols
}
return conn, rw, err
}
// isContentType validates the Content-Type header matches the supplied
// contentType. That is, its type and subtype match.
func isContentType(h http.Header, contentType string) bool {
ct := h.Get("Content-Type")
if i := strings.IndexRune(ct, ';'); i != -1 {
ct = ct[0:i]
}
return ct == contentType
}
// ContentTypeHandler wraps and returns a http.Handler, validating the request
// content type is compatible with the contentTypes list. It writes a HTTP 415
// error if that fails.
//
// Only PUT, POST, and PATCH requests are considered.
func ContentTypeHandler(h http.Handler, contentTypes ...string) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if !(r.Method == http.MethodPut || r.Method == http.MethodPost || r.Method == http.MethodPatch) {
h.ServeHTTP(w, r)
return
}
for _, ct := range contentTypes {
if isContentType(r.Header, ct) {
h.ServeHTTP(w, r)
return
}
}
http.Error(w, fmt.Sprintf("Unsupported content type %q; expected one of %q",
r.Header.Get("Content-Type"),
contentTypes),
http.StatusUnsupportedMediaType)
})
}
const (
// HTTPMethodOverrideHeader is a commonly used
// http header to override a request method.
HTTPMethodOverrideHeader = "X-HTTP-Method-Override"
// HTTPMethodOverrideFormKey is a commonly used
// HTML form key to override a request method.
HTTPMethodOverrideFormKey = "_method"
)
// HTTPMethodOverrideHandler wraps and returns a http.Handler which checks for
// the X-HTTP-Method-Override header or the _method form key, and overrides (if
// valid) request.Method with its value.
//
// This is especially useful for HTTP clients that don't support many http verbs.
// It isn't secure to override e.g a GET to a POST, so only POST requests are
// considered. Likewise, the override method can only be a "write" method: PUT,
// PATCH or DELETE.
//
// Form method takes precedence over header method.
func HTTPMethodOverrideHandler(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r.Method == http.MethodPost {
om := r.FormValue(HTTPMethodOverrideFormKey)
if om == "" {
om = r.Header.Get(HTTPMethodOverrideHeader)
}
if om == http.MethodPut || om == http.MethodPatch || om == http.MethodDelete {
r.Method = om
}
}
h.ServeHTTP(w, r)
})
}
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