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// Copyright 2015 Light Code Labs, LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package header provides middleware that appends headers to
// requests based on a set of configuration rules that define
// which routes receive which headers.
package header
import (
"net/http"
"strings"
"github.com/caddyserver/caddy/caddyhttp/httpserver"
)
// Headers is middleware that adds headers to the responses
// for requests matching a certain path.
type Headers struct {
Next httpserver.Handler
Rules []Rule
}
// ServeHTTP implements the httpserver.Handler interface and serves requests,
// setting headers on the response according to the configured rules.
func (h Headers) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
replacer := httpserver.NewReplacer(r, nil, "")
rww := &responseWriterWrapper{
ResponseWriterWrapper: &httpserver.ResponseWriterWrapper{ResponseWriter: w},
}
for _, rule := range h.Rules {
if httpserver.Path(r.URL.Path).Matches(rule.Path) {
for name := range rule.Headers {
// One can either delete a header, add multiple values to a header, or simply
// set a header.
if strings.HasPrefix(name, "-") {
rww.delHeader(strings.TrimLeft(name, "-"))
} else if strings.HasPrefix(name, "+") {
for _, value := range rule.Headers[name] {
rww.Header().Add(strings.TrimLeft(name, "+"), replacer.Replace(value))
}
} else {
for _, value := range rule.Headers[name] {
rww.Header().Set(name, replacer.Replace(value))
}
}
}
}
}
return h.Next.ServeHTTP(rww, r)
}
type (
// Rule groups a slice of HTTP headers by a URL pattern.
Rule struct {
Path string
Headers http.Header
}
)
// headerOperation represents an operation on the header
type headerOperation func(http.Header)
// responseWriterWrapper wraps the real ResponseWriter.
// It defers header operations until writeHeader
type responseWriterWrapper struct {
*httpserver.ResponseWriterWrapper
ops []headerOperation
wroteHeader bool
}
func (rww *responseWriterWrapper) Header() http.Header {
return rww.ResponseWriterWrapper.Header()
}
func (rww *responseWriterWrapper) Write(d []byte) (int, error) {
if !rww.wroteHeader {
rww.WriteHeader(http.StatusOK)
}
return rww.ResponseWriterWrapper.Write(d)
}
func (rww *responseWriterWrapper) WriteHeader(status int) {
if rww.wroteHeader {
return
}
rww.wroteHeader = true
// capture the original headers
h := rww.Header()
// perform our revisions
for _, op := range rww.ops {
op(h)
}
rww.ResponseWriterWrapper.WriteHeader(status)
}
// delHeader deletes the existing header according to the key
// Also it will delete that header added later.
func (rww *responseWriterWrapper) delHeader(key string) {
// remove the existing one if any
rww.Header().Del(key)
// register a future deletion
rww.ops = append(rww.ops, func(h http.Header) {
h.Del(key)
})
}
// Interface guards
var _ httpserver.HTTPInterfaces = (*responseWriterWrapper)(nil)
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