/*
   Copyright 2014 CoreOS, Inc.

   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 proxy

import (
	"net/http"
)

// GetProxyURLs is a function which should return the current set of URLs to
// which client requests should be proxied. This function will be queried
// periodically by the proxy Handler to refresh the set of available
// backends.
type GetProxyURLs func() []string

// NewHandler creates a new HTTP handler, listening on the given transport,
// which will proxy requests to an etcd cluster.
// The handler will periodically update its view of the cluster.
func NewHandler(t *http.Transport, urlsFunc GetProxyURLs) http.Handler {
	return &reverseProxy{
		director:  newDirector(urlsFunc),
		transport: t,
	}
}

// NewReadonlyHandler wraps the given HTTP handler to allow only GET requests
func NewReadonlyHandler(hdlr http.Handler) http.Handler {
	readonly := readonlyHandlerFunc(hdlr)
	return http.HandlerFunc(readonly)
}

func readonlyHandlerFunc(next http.Handler) func(http.ResponseWriter, *http.Request) {
	return func(w http.ResponseWriter, req *http.Request) {
		if req.Method != "GET" {
			w.WriteHeader(http.StatusNotImplemented)
			return
		}

		next.ServeHTTP(w, req)
	}
}