A relatively functional v0.1

main.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/acaloiaro/roam-location/receiver"
+	"github.com/acaloiaro/roam-location/service"
+)
+
+var dbPath string
+
+func init() {
+	var ok bool
+	if dbPath, ok = os.LookupEnv("ROAM_LOCATION_DB_PATH"); !ok {
+		log.Fatalf("ROAM_LOCATION_DB_PATH environment variable not set. Please set it before running")
+	}
+}
+
+func main() {
+	modePtr := flag.String("mode", "listener", "set application mode to either 'listener' (listening for NMEA sentences) or 'service' (providing current coordinates)")
+
+	flag.Parse()
+
+	switch *modePtr {
+	case "listener":
+		fmt.Println("Listener mode")
+		receiver.Receive(dbPath)
+
+	case "service":
+		fmt.Println("Service mode")
+		service.Listen(dbPath)
+	}
+
+}

receiver/nmea_receiver.go

@@ -1,4 +1,4 @@
-package main
+package receiver
 
 import (
 	"fmt"
@@ -10,13 +10,19 @@ import (
 	"github.com/adrianmo/go-nmea"
 )
 
-func main() {
-	listen()
-}
+var dbFile *os.File
+var err error
 
-func listen() {
+// Receive receives NMEA sentences from the Sierra Wireless RV55 router and writes parsed sentences to
+// ROAM_LOCATION_DB_PATH
+func Receive(dbPath string) {
 	addr, _ := net.ResolveUDPAddr("udp", ":22335")
 	sock, _ := net.ListenUDP("udp", addr)
+	dbFile, err = os.OpenFile(dbPath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+	if err != nil {
+		log.Fatalf("unable to open DB file: '%v'", err)
+	}
+	defer dbFile.Close()
 
 	for {
 		buf := make([]byte, 2048)
@@ -51,16 +57,8 @@ func handlePacket(buf []byte, rlen int) {
 }
 
 func appendLog(lat, lon float64, nmeaSentence string) {
-	dbPath := os.Getenv("ROAM_LOCATION_DB_PATH")
-
-	f, err := os.OpenFile(dbPath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-	if err != nil {
-		log.Println(err)
-	}
-	defer f.Close()
-
 	row := fmt.Sprintf("%f,%f,%s\n", lat, lon, nmeaSentence)
-	if _, err := f.WriteString(row); err != nil {
-		log.Println(err)
+	if _, err := dbFile.WriteString(row); err != nil {
+		log.Println("unable to write to database:", err)
 	}
 }

service/current_location.go

@@ -1,4 +1,4 @@
-package main
+package service
 
 import (
 	"encoding/json"
@@ -10,29 +10,39 @@ import (
 	"strings"
 )
 
+var port = 22495
+
+// Listen listens for location requests from clients and return my current coordinates from the db located at dbPath
+// my last known location is always the tail end of the file
+func Listen(dbPath string) {
+	http.HandleFunc("/current_location", listenHandler(dbPath))
+	log.Printf("Listening: 0.0.0.0:%d", port)
+	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", port), nil))
+}
+
 type Location struct {
 	Lat float64 `json:"lat"`
 	Lon float64 `json:"lon"`
 }
 
-func handler(w http.ResponseWriter, r *http.Request) {
-	location := currentLocation()
-	byteArray, err := json.MarshalIndent(location, "", "  ")
-	if err != nil {
-		log.Fatalf("error providing current location: %v", err)
-	}
+func listenHandler(dbPath string) (handler func(http.ResponseWriter, *http.Request)) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		location := currentLocation(dbPath)
+		byteArray, err := json.MarshalIndent(location, "", "  ")
+		if err != nil {
+			log.Fatalf("error providing current location: %v", err)
+		}
 
-	w.Header().Set("Content-Type", "application/json")
-	fmt.Fprintf(w, string(byteArray))
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprintf(w, string(byteArray))
+	}
 }
 
-func currentLocation() (location Location) {
-	dbPath := os.Getenv("ROAM_LOCATION_DB_PATH")
-
+func currentLocation(dbPath string) (location Location) {
+	var err error
 	fileHandle, err := os.Open(dbPath)
-
 	if err != nil {
-		panic("Cannot open file")
+		log.Fatalf("unable to open db file: %v", err)
 	}
 	defer fileHandle.Close()
 
@@ -71,6 +81,4 @@ func currentLocation() (location Location) {
 }
 
 func main() {
-	http.HandleFunc("/current_location", handler)
-	log.Fatal(http.ListenAndServe(":22495", nil))
 }