Refactor, read configuration from file

.gitignore

@@ -1 +1,2 @@
 matrix-alertmanager-receiver
+config.toml

config.toml.sample

@@ -0,0 +1,5 @@
+Homeserver = "https://staging.matrix.ungleich.cloud"
+TargetRoomID = "!jHFKHemgIAaDJekoxN:matrix-staging.ungleich.ch"
+MXID = "@fnux:matrix-staging.ungleich.ch"
+MXToken = "secret"
+HTTPPort = 9088

main.go

@@ -5,98 +5,127 @@ import (
 	"flag"
 	"fmt"
 	"log"
+	"io/ioutil"
 	"net/http"
 	"encoding/json"
 	"github.com/prometheus/alertmanager/template"
+	"github.com/BurntSushi/toml"
 	"github.com/matrix-org/gomatrix"
 )
 
+var logger *log.Logger
+
+type Configuration struct {
+	Homeserver string
+	TargetRoomID string
+
+	MXID string
+	MXToken string
+
+	HTTPPort int
+	HTTPToken string
+}
+
 func generateMatrixMessageBody(alert template.Alert) string {
 	return alert.Status + " // " + alert.Annotations["summary"]
 }
 
-func main() {
-	// Initialize logger.
-	var logger *log.Logger = log.New(os.Stdout, "", log.Flags())
-
-	// Handle command-line arguments.
-	var homeserver = flag.String("homeserver", "https://matrix.org", "Address of Matrix homeserver")
-	var user = flag.String("user", "", "Full MXID (e.g. @example.domain.tld) of Matrix user")
-	var token = flag.String("token", "", "Access Token of Matrix user")
-	var target = flag.String("target-room", "", "Matrix room to be notified of alerts.")
-	var port = flag.Int("port", 9088, "HTTP port to listen on (incoming alertmanager webhooks)")
-	flag.Parse()
-
-	if *user == "" {
-		logger.Fatal("Matrix user is required. See --help for usage.")
-	}
-	if *token == "" {
-		logger.Fatal("Matrix access token is required. See --help for usage.")
-	}
-	if *target== "" {
-		logger.Fatal("Matrix target room is required. See --help for usage.")
-	}
-
-	// Initialize Matrix client.
-	matrixClient, err := gomatrix.NewClient(*homeserver, *user, *token)
+func getMatrixClient(homeserver string, user string, token string, targetRoomID string) *gomatrix.Client {
+	logger.Printf("Connecting to Matrix Homserver %v as %v.", homeserver, user)
+	matrixClient, err := gomatrix.NewClient(homeserver, user, token)
 	if err != nil {
-		logger.Fatalf("Could not log in to Matrix (%v): %v", *homeserver, err)
+		logger.Fatalf("Could not log in to Matrix Homeserver (%v): %v", homeserver, err)
 	}
 
 	joinedRooms, err := matrixClient.JoinedRooms()
 	if err != nil {
-		logger.Fatalf("Could not fetch joined rooms: %v", err)
+		logger.Fatalf("Could not fetch Matrix rooms: %v", err)
 	}
 
 	alreadyJoinedTarget := false
 	for _, roomID := range joinedRooms.JoinedRooms {
-		// FIXME: will only work if target is a roomID, not an alias.
-		if *target == roomID {
+		if targetRoomID == roomID {
 			alreadyJoinedTarget = true
 		}
 	}
 
-	if !alreadyJoinedTarget {
-		logger.Printf("Trying to join %v...", *target)
-		_, err := matrixClient.JoinRoom(*target, "", nil)
+	if alreadyJoinedTarget {
+		logger.Printf("%v is already part of %v.", user, targetRoomID,)
+	} else {
+		logger.Printf("Joining %v.", targetRoomID)
+		_, err := matrixClient.JoinRoom(targetRoomID, "", nil)
 		if err != nil {
-			logger.Fatalf("Failed to join %v: %v", *target, err)
+			logger.Fatalf("Failed to join %v: %v", targetRoomID, err)
 		}
 	}
 
-	// Initialize HTTP serve (= listen for incoming requests).
-	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		fmt.Fprintf(w, `Hi! I receive prometheus-alertmanager webhooks on /alert and forward them to Matrix.
-
-You will find more details on: http://git.sr.ht/~fnux/matrix-prometheus-alertmanager`)
-	})
-
-	http.HandleFunc("/alert", func(w http.ResponseWriter, r *http.Request) {
-		if r.Method != http.MethodPost {
-			w.WriteHeader(http.StatusMethodNotAllowed)
-			return
-		}
-
-		payload := template.Data{}
-		if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
-			w.WriteHeader(http.StatusBadRequest)
-		}
-
-		logger.Printf("Received valid hook from %v", r.RemoteAddr)
-
-		for _, alert := range payload.Alerts {
-			body := generateMatrixMessageBody(alert)
-			logger.Printf("> %v", body)
-			_, err := matrixClient.SendText(*target, body)
-			if err != nil {
-				logger.Fatalf("Could not forward to Matrix: %v", err)
-			}
-		}
-
-		w.WriteHeader(http.StatusOK)
-	})
-
-	var listenAddr = fmt.Sprintf(":%v", *port)
-	logger.Printf("Listening for HTTP requests (webhooks) on %v", listenAddr)
-	log.Fatal(http.ListenAndServe(listenAddr, nil))
+	return matrixClient
+}
+
+func handleIncomingHooks( w http.ResponseWriter, r *http.Request,
+	matrixClient *gomatrix.Client, targetRoomID string) {
+
+	if r.Method != http.MethodPost {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		return
+	}
+
+	payload := template.Data{}
+	if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+	}
+
+	logger.Printf("Received valid hook from %v", r.RemoteAddr)
+
+	for _, alert := range payload.Alerts {
+		body := generateMatrixMessageBody(alert)
+		logger.Printf("> %v", body)
+		_, err := matrixClient.SendText(targetRoomID, body)
+		if err != nil {
+			logger.Printf(">> Could not forward to Matrix: %v", err)
+		}
+	}
+
+	w.WriteHeader(http.StatusOK)
+}
+
+func main() {
+	// Initialize logger.
+	logger = log.New(os.Stdout, "", log.Flags())
+
+	// We use a configuration file since we need to specify secrets, and read
+	// everything else from it to keep things simple.
+	var configPath = flag.String("config", "/etc/matrix-alertmanager-receiver.toml", "Path to configuration file")
+	flag.Parse()
+
+	logger.Printf("Reading configuration from %v.", *configPath)
+	raw, err := ioutil.ReadFile(*configPath)
+	if err != nil {
+		logger.Fatalf("Could not read configuration file (%v): %v", *configPath, err)
+	}
+
+	var config Configuration
+	md, err := toml.Decode(string(raw), &config)
+	if err != nil {
+		logger.Fatalf("Could not parse configuration file (%v): %v", *configPath, err)
+	}
+
+	for _, field := range []string{"Homeserver", "MXID", "MXToken", "TargetRoomID", "HTTPPort"} {
+		if ! md.IsDefined(field) {
+			logger.Fatalf("Field %v is not set in config. Exiting.", field)
+		}
+	}
+
+	// Initialize Matrix client.
+	matrixClient := getMatrixClient(
+		config.Homeserver, config.MXID, config.MXToken, config.TargetRoomID)
+
+	// Initialize HTTP server.
+	http.HandleFunc("/alert", func(w http.ResponseWriter, r *http.Request) {
+		handleIncomingHooks(w, r, matrixClient, config.TargetRoomID)
+	})
+
+	var listenAddr = fmt.Sprintf(":%v", config.HTTPPort)
+	logger.Printf("Listening for HTTP requests (webhooks) on %v", listenAddr)
+	logger.Fatal(http.ListenAndServe(listenAddr, nil))
 }