Switch on debug logs via env var flag (#260)

Co-authored-by: makeworld

amfora.go

@@ -10,6 +10,7 @@ import (
 	"github.com/makeworld-the-better-one/amfora/client"
 	"github.com/makeworld-the-better-one/amfora/config"
 	"github.com/makeworld-the-better-one/amfora/display"
+	"github.com/makeworld-the-better-one/amfora/logger"
 	"github.com/makeworld-the-better-one/amfora/subscriptions"
 )
 
@@ -20,10 +21,15 @@ var (
 )
 
 func main() {
-	// err := logger.Init()
-	// if err != nil {
-	// 	panic(err)
-	// }
+	log, err := logger.GetLogger()
+	if err != nil {
+		panic(err)
+	}
+
+	debugModeEnabled := os.Getenv("AMFORA_DEBUG") == "1"
+	if debugModeEnabled {
+		log.Println("Debug mode enabled")
+	}
 
 	if len(os.Args) > 1 {
 		if os.Args[1] == "--version" || os.Args[1] == "-v" {
@@ -42,7 +48,7 @@ func main() {
 		}
 	}
 
-	err := config.Init()
+	err = config.Init()
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Config error: %v\n", err)
 		os.Exit(1)

logger/logger.go

@@ -3,18 +3,42 @@ package logger
 // For debugging
 
 import (
+	"io"
+	"io/ioutil"
 	"log"
 	"os"
 )
 
-var Log *log.Logger
+var logger *log.Logger
 
-func Init() error {
-	f, err := os.Create("debug.log")
+func GetLogger() (*log.Logger, error) {
+	if logger != nil {
+		return logger, nil
+	}
+
+	var writer io.Writer
+	var err error
+
+	debugModeEnabled := os.Getenv("AMFORA_DEBUG") == "1"
+	if debugModeEnabled {
+		writer, err = os.Create("debug.log")
 		if err != nil {
-		return err
+			return nil, err
 		}
-	Log = log.New(f, "", log.LstdFlags)
-	Log.Println("Started Log")
-	return nil
+	} else {
+		// Suppress all logging output if debug mode is disabled
+		writer = ioutil.Discard
+	}
+
+	logger = log.New(writer, "", log.LstdFlags)
+
+	if !debugModeEnabled {
+		// Clear all flags to skip log output formatting step to increase
+		// performance somewhat if we're not logging anything
+		logger.SetFlags(0)
+	}
+
+	logger.Println("Started logger")
+
+	return logger, nil
 }