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|
package middleware
import (
"net/http"
"strings"
"github.com/zenazn/goji/web"
)
type autoOptionsState int
const (
aosInit autoOptionsState = iota
aosHeaderWritten
aosProxying
)
// I originally used an httptest.ResponseRecorder here, but package httptest
// adds a flag which I'm not particularly eager to expose. This is essentially a
// ResponseRecorder that has been specialized for the purpose at hand to avoid
// the httptest dependency.
type autoOptionsProxy struct {
w http.ResponseWriter
c *web.C
state autoOptionsState
}
func (p *autoOptionsProxy) Header() http.Header {
return p.w.Header()
}
func (p *autoOptionsProxy) Write(buf []byte) (int, error) {
switch p.state {
case aosInit:
p.state = aosHeaderWritten
case aosProxying:
return len(buf), nil
}
return p.w.Write(buf)
}
func (p *autoOptionsProxy) WriteHeader(code int) {
methods := getValidMethods(*p.c)
switch p.state {
case aosInit:
if methods != nil && code == http.StatusNotFound {
p.state = aosProxying
break
}
p.state = aosHeaderWritten
fallthrough
default:
p.w.WriteHeader(code)
return
}
methods = addMethod(methods, "OPTIONS")
p.w.Header().Set("Allow", strings.Join(methods, ", "))
p.w.WriteHeader(http.StatusOK)
}
// AutomaticOptions automatically return an appropriate "Allow" header when the
// request method is OPTIONS and the request would have otherwise been 404'd.
func AutomaticOptions(c *web.C, h http.Handler) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
if r.Method == "OPTIONS" {
w = &autoOptionsProxy{c: c, w: w}
}
h.ServeHTTP(w, r)
}
return http.HandlerFunc(fn)
}
func getValidMethods(c web.C) []string {
if c.Env == nil {
return nil
}
v, ok := c.Env[web.ValidMethodsKey]
if !ok {
return nil
}
if methods, ok := v.([]string); ok {
return methods
}
return nil
}
func addMethod(methods []string, method string) []string {
for _, m := range methods {
if m == method {
return methods
}
}
return append(methods, method)
}
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