Config file logic

.gitignore

@@ -1 +1,2 @@
 guichet
+config.json

main.go

@@ -2,29 +2,92 @@ package main
 
 import (
 	"os"
+	"flag"
+	"fmt"
 	"log"
 	"net/http"
-	"fmt"
+	"io/ioutil"
+	"encoding/json"
+	"encoding/base64"
+	"crypto/rand"
 
 	"github.com/gorilla/sessions"
 )
 
-var store = sessions.NewCookieStore([]byte(os.Getenv("SESSION_KEY")))
-
-func handleHome(w http.ResponseWriter, r *http.Request) {
-	fmt.Fprintf(w, "Hello, world!")
+type ConfigFile struct {
+	HttpBindAddr   string `json:"http_bind_addr"`
+	SessionKey     string `json:"session_key"`
+	LdapServerAddr string `json:"ldap_server_addr"`
 }
 
+var configFlag = flag.String("config", "./config.json", "Configuration file path")
+
+func readConfig() ConfigFile {
+	key_bytes := make([]byte, 32)
+	n, err := rand.Read(key_bytes)
+	if err!= nil || n != 32 {
+		log.Fatal(err)
+	}
+
+	config_file := ConfigFile{
+		HttpBindAddr:   ":9991",
+		SessionKey:     base64.StdEncoding.EncodeToString(key_bytes),
+		LdapServerAddr: "127.0.0.1:389",
+	}
+
+	_, err = os.Stat(*configFlag)
+	if os.IsNotExist(err) {
+		// Generate default config file
+		log.Printf("Generating default config file as %s", *configFlag)
+
+		bytes, err := json.MarshalIndent(&config_file, "", "  ")
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		err = ioutil.WriteFile(*configFlag, bytes, 0644)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		return config_file
+	}
+
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	bytes, err := ioutil.ReadFile(*configFlag)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	err = json.Unmarshal(bytes, &config_file)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	return config_file
+}
+
+var store *sessions.CookieStore = nil
+
 func main() {
+	flag.Parse()
+
+	config := readConfig()
+	store = sessions.NewCookieStore([]byte(config.SessionKey))
+
 	http.HandleFunc("/", handleHome)
 
-	bind_addr := os.Getenv("HTTP_BIND_ADDR")
-	if bind_addr == "" {
-		bind_addr = ":9991"
-	}
-
-	err := http.ListenAndServe(bind_addr, nil)
+	err := http.ListenAndServe(config.HttpBindAddr, nil)
 	if err != nil {
 		log.Fatal("Cannot start http server: ", err)
 	}
 }
+
+// Page handlers ----
+
+func handleHome(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, "Hello, world!")
+}