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switchboard.go
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switchboard.go
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// Switchboard: link redirect server
// Copyright (C) 2013 the Authors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
package main
import (
"encoding/json"
"flag"
"fmt"
"io/ioutil"
"log"
"net/http"
"reflect"
"strconv"
"strings"
)
const (
DefaultConfigFilename string = "/etc/switchboard.conf"
DefaultPort uint16 = 80
)
type Switchboard map[string]interface{}
func (s Switchboard) handlePage(target string, w http.ResponseWriter,
r *http.Request, path string) {
var url string
if strings.Contains(target, "%s") {
url = fmt.Sprintf(target, path)
} else {
url = target
}
w.Header().Add("Location", url)
w.WriteHeader(http.StatusFound)
}
func (s Switchboard) handlePath(pathMap map[string]interface{},
w http.ResponseWriter, r *http.Request, path string) {
pathParts := strings.SplitN(path, "/", 2)
var pathHead, pathTail string
if len(pathParts) >= 1 {
pathHead = pathParts[0]
}
if len(pathParts) >= 2 {
pathTail = pathParts[1]
}
i, ok := pathMap[pathHead]
if ok {
s.handleBranch(i, w, r, pathTail)
} else {
i, ok = pathMap["*"]
if ok {
s.handleBranch(i, w, r, path)
} else {
s.handleDefault(w)
}
}
}
func (s Switchboard) handleBranch(i interface{}, w http.ResponseWriter,
r *http.Request, path string) {
switch v := i.(type) {
case string:
s.handlePage(v, w, r, path)
case map[string]interface{}:
s.handlePath(v, w, r, path)
default:
log.Fatalf("Unexpected type in path map: %s",
reflect.TypeOf(i).String())
}
}
func (s Switchboard) HandleHost(w http.ResponseWriter, r *http.Request) {
log.Printf("%s http://%s%s", r.Method, r.Host, r.URL.Path)
i, ok := s[r.Host]
if ok {
path := r.URL.Path
var p string
if len(path) > 0 && path[0] == '/' {
p = path[1:]
} else {
p = path
}
s.handleBranch(i, w, r, p)
} else {
s.handleDefault(w)
}
}
func (s Switchboard) handleDefault(w http.ResponseWriter) {
hostMapString, err := json.MarshalIndent(s, "", " ")
if err != nil {
log.Fatalf("Unexpected error marshaling host map: %s", err.Error())
}
w.Write([]byte(fmt.Sprintf(`<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml/" lang="en" xml:lang="en">
<head>
<meta charset="utf-8" />
<meta name="Switchboard" content="Switchboard summary" />
<title>Switchboard</title>
</head>
<body>
<h1>Welcome to Switchboard</h1>
<p>Here's what we've got:</p>
<pre>%s</pre>
</body>
</html>`, hostMapString)))
}
func main() {
// Read the configuration file
var configFilename string
flag.StringVar(&configFilename, "f", DefaultConfigFilename,
"configuration file")
flag.Parse()
configFile, err := ioutil.ReadFile(configFilename)
if err != nil {
log.Fatalf("Error reading configuration file %s: %s", configFilename,
err.Error())
}
var configBlob interface{}
err = json.Unmarshal(configFile, &configBlob)
if err != nil {
log.Fatalf("Error parsing configuration file %s: %s", configFilename,
err.Error())
}
config := configBlob.(map[string]interface{})
// Select the TCP address (interface and port) to listen on
var listenOn string
var port uint16
listenOnConfigBlob, ok := config["listen_on"]
if ok {
listenOn = listenOnConfigBlob.(string)
} else {
listenOn = ""
}
portConfigBlob, ok := config["port"]
if ok {
port = uint16(portConfigBlob.(float64))
} else {
port = DefaultPort
}
listenAddr := listenOn + ":" + strconv.FormatUint(uint64(port), 10)
// Read the host map
hostBlob, ok := config["hosts"]
if !ok {
log.Fatalf("Error parsing configuration file %s: Missing hosts",
configFilename)
}
hostMap := Switchboard(hostBlob.(map[string]interface{}))
// Start the server
http.HandleFunc("/", hostMap.HandleHost)
err = http.ListenAndServe(listenAddr, nil)
if err != nil {
log.Fatalf("ListenAndServe: %s", err.Error())
}
}