Initial commit

internal/log/main.go

@@ -0,0 +1,148 @@
+// Package log implements logging facility as golang slog module wrapper.
+package log
+
+import (
+	"fmt"
+	"log/slog"
+	"os"
+	"time"
+)
+
+var (
+	// Log contains *[os.File] pointing to log file descriptor.
+	Log *os.File
+)
+
+// Init sets up logger stuff.
+// level can be error, warn, info, debug; if something other is supplied, info level is selected.
+func Init(level, filename string) error {
+	var (
+		err      error
+		loglevel slog.Level
+	)
+
+	if filename != "" {
+		Log, err = os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0644)
+
+		if err != nil {
+			return fmt.Errorf("Unable to open log file: %w", err)
+		}
+	} else {
+		Log = os.Stderr
+	}
+
+	// no panic, no trace.
+	switch level {
+	case "error":
+		loglevel = slog.LevelError
+
+	case "warn":
+		loglevel = slog.LevelWarn
+
+	case "info":
+		loglevel = slog.LevelInfo
+
+	case "debug":
+		loglevel = slog.LevelDebug
+
+	default:
+		loglevel = slog.LevelInfo
+	}
+
+	opts := &slog.HandlerOptions{
+		// Use the ReplaceAttr function on the handler options
+		// to be able to replace any single attribute in the log output.
+		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr { //nolint: revive
+			// Check that we are handling the time key.
+			if a.Key != slog.TimeKey {
+				return a
+			}
+
+			t := a.Value.Time()
+
+			// Change the value from a time.Time to a String
+			// where the string has the correct time format.
+			a.Value = slog.StringValue(t.Format(time.DateTime))
+
+			return a
+		},
+
+		Level: loglevel,
+	}
+
+	slog.SetDefault(
+		slog.New(
+			slog.NewTextHandler(
+				Log,
+				opts,
+			),
+		),
+	)
+
+	return err
+}
+
+// Error passes message directly to [slog.Error()].
+func Error(message string) {
+	slog.Error(message)
+}
+
+// Errorf logs message on error log level and allows to supply arguments in printf() style.
+func Errorf(format string, a ...any) {
+	slog.Error(fmt.Sprintf(format, a...))
+}
+
+// Warn passes message directly to [slog.Warn()].
+func Warn(message string) {
+	slog.Warn(message)
+}
+
+// Warnf logs message on warn log level and allows to supply arguments in printf() style.
+func Warnf(format string, a ...any) {
+	slog.Warn(fmt.Sprintf(format, a...))
+}
+
+// Info passes message directly to [slog.Info()].
+func Info(message string) {
+	slog.Info(message)
+}
+
+// Infof logs message on info log level and allows to supply arguments in printf() style.
+func Infof(format string, a ...any) {
+	slog.Info(fmt.Sprintf(format, a...))
+}
+
+// Debug passes message directly to [slog.Debug()].
+func Debug(message string) {
+	slog.Debug(message)
+}
+
+// Debugf logs message on debug log level and allows to supply arguments in printf() style.
+func Debugf(format string, a ...any) {
+	slog.Debug(fmt.Sprintf(format, a...))
+}
+
+// Fatal passes message directly to [slog.Error()] and quits with status code 1.
+func Fatal(message string) {
+	slog.Error(message)
+	Close()
+	os.Exit(1)
+}
+
+// Fatalf logs message on error log level and allows to supply arguments in printf() style. After that it quits with
+// status code 1.
+func Fatalf(format string, a ...any) {
+	slog.Error(fmt.Sprintf(format, a...))
+	Close()
+	os.Exit(1)
+}
+
+// Close closes log file descriptor.
+func Close() {
+	if err := Log.Close(); err != nil {
+		msg := fmt.Sprintln("Failed to close log file:", err)
+		slog.Error(msg)
+	}
+}
+
+/* vim: setlocal ft=go noet ai ts=4 sw=4 sts=4: */