add ansi color codes to logs (#12)

* add ansi color codes to logs

* make ResetColor a constant

* change if/else to switch

* fix go tests

* add terminal check

* addressing feedback about naming conventions

* fix test

* adjust constants and variables for clarity

* go mod tidy

* add go.sum file

* change message test to look for substring

* updates from PR feedback

* update variable names

go.mod

@@ -1,3 +1,10 @@
 module go.arcalot.io/log/v2
 
 go 1.21
+
+require (
+	go.arcalot.io/assert v1.8.0
+	golang.org/x/term v0.21.0
+)
+
+require golang.org/x/sys v0.21.0 // indirect

go.sum

@@ -0,0 +1,6 @@
+go.arcalot.io/assert v1.8.0 h1:hGcHMPncQXwQvjj7MbyOu2gg8VIBB00crUJZpeQOjxs=
+go.arcalot.io/assert v1.8.0/go.mod h1:nNmWPoNUHFyrPkNrD2aASm5yPuAfiWdB/4X7Lw3ykHk=
+golang.org/x/sys v0.21.0 h1:rF+pYz3DAGSQAxAu1CbC7catZg4ebC4UIeIhKxBZvws=
+golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/term v0.21.0 h1:WVXCp+/EBEHOj53Rvu+7KiT/iElMrO8ACK16SMZ3jaA=
+golang.org/x/term v0.21.0/go.mod h1:ooXLefLobQVslOqselCNF4SxFAaoS6KujMbsGzSDmX0=

message.go

@@ -2,9 +2,36 @@ package log
 
 import (
 	"fmt"
+	"os"
 	"time"
+
+	"golang.org/x/term"
+)
+
+const (
+	AnsiReset  = "\033[0m"
+	AnsiDim    = "\033[0;2m"
+	AnsiYellow = "\033[1;33m"
+	AnsiRed    = "\033[1;31m"
 )
 
+var (
+	SetColor = map[Level]string{
+		"debug":   AnsiDim,
+		"info":    AnsiReset,
+		"warning": AnsiYellow,
+		"error":   AnsiRed,
+	}
+	ResetColor = AnsiReset
+)
+
+func init() {
+	if !term.IsTerminal(int(os.Stderr.Fd())) {
+		SetColor = map[Level]string{}
+		ResetColor = ""
+	}
+}
+
 // Message is a single log message.
 type Message struct {
 	Timestamp time.Time `json:"timestamp"`
@@ -14,5 +41,13 @@ type Message struct {
 }
 
 func (m Message) String() string {
-	return fmt.Sprintf("%s\t%s\t%s\t%s", m.Timestamp.Format(time.RFC3339), m.Level, m.Labels, m.Message)
+	return fmt.Sprintf(
+		"%s%s\t%s\t%s\t%s%s",
+		SetColor[m.Level],
+		m.Timestamp.Format(time.RFC3339),
+		m.Level,
+		m.Labels,
+		m.Message,
+		ResetColor,
+	)
 }

message_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 	"time"
 
+	"go.arcalot.io/assert"
 	"go.arcalot.io/log/v2"
 )
 
@@ -19,7 +20,11 @@ func TestMessage(t *testing.T) {
 		Labels:    map[string]string{"source": "test"},
 		Message:   "Hello world!",
 	}
-	if m.String() != "2006-01-02T15:04:05Z\terror\tsource=test\tHello world!" {
-		t.Fatalf("Incorrect message string: %s", m.String())
-	}
+	assert.Equals(
+		t,
+		m.String(),
+		log.SetColor[m.Level]+
+			"2006-01-02T15:04:05Z\terror\tsource=test\tHello world!"+
+			log.ResetColor,
+	)
 }

writer_golog_test.go

@@ -23,7 +23,7 @@ func TestGoLogger(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if !strings.Contains(buf.String(), "Hello world!\n") {
+	if !strings.Contains(buf.String(), "Hello world!") {
 		t.Fatalf("failed to find written log message in output")
 	}
 }