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package headers
import (
"net/http"
"strings"
"bitbucket.org/lightcodelabs/caddy2"
"bitbucket.org/lightcodelabs/caddy2/modules/caddyhttp"
)
func init() {
caddy2.RegisterModule(caddy2.Module{
Name: "http.middleware.headers",
New: func() interface{} { return new(Headers) },
})
}
// Headers is a middleware which can mutate HTTP headers.
type Headers struct {
Request HeaderOps `json:"request"`
Response RespHeaderOps `json:"response"`
}
// HeaderOps defines some operations to
// perform on HTTP headers.
type HeaderOps struct {
Add http.Header `json:"add"`
Set http.Header `json:"set"`
Delete []string `json:"delete"`
}
// RespHeaderOps is like HeaderOps, but
// optionally deferred until response time.
type RespHeaderOps struct {
HeaderOps
Deferred bool `json:"deferred"`
}
func (h Headers) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
repl := r.Context().Value(caddy2.ReplacerCtxKey).(caddy2.Replacer)
apply(h.Request, r.Header, repl)
if h.Response.Deferred {
w = &responseWriterWrapper{
ResponseWriterWrapper: &caddyhttp.ResponseWriterWrapper{ResponseWriter: w},
replacer: repl,
headerOps: h.Response.HeaderOps,
}
} else {
apply(h.Response.HeaderOps, w.Header(), repl)
}
return next.ServeHTTP(w, r)
}
func apply(ops HeaderOps, hdr http.Header, repl caddy2.Replacer) {
for fieldName, vals := range ops.Add {
fieldName = repl.ReplaceAll(fieldName, "")
for _, v := range vals {
hdr.Add(fieldName, repl.ReplaceAll(v, ""))
}
}
for fieldName, vals := range ops.Set {
fieldName = repl.ReplaceAll(fieldName, "")
for i := range vals {
vals[i] = repl.ReplaceAll(vals[i], "")
}
hdr.Set(fieldName, strings.Join(vals, ","))
}
for _, fieldName := range ops.Delete {
hdr.Del(repl.ReplaceAll(fieldName, ""))
}
}
// responseWriterWrapper defers response header
// operations until WriteHeader is called.
type responseWriterWrapper struct {
*caddyhttp.ResponseWriterWrapper
replacer caddy2.Replacer
headerOps HeaderOps
wroteHeader bool
}
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
apply(rww.headerOps, rww.ResponseWriterWrapper.Header(), rww.replacer)
rww.ResponseWriterWrapper.WriteHeader(status)
}
// Interface guards
var (
_ caddyhttp.MiddlewareHandler = (*Headers)(nil)
_ caddyhttp.HTTPInterfaces = (*responseWriterWrapper)(nil)
)
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