Add configuration wizard. (#2)

* Add configuration wizard.

internal/logger/logger.go

@@ -0,0 +1,159 @@
+package logger
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"time"
+)
+
+type Level int
+
+const (
+	LevelDebug Level = iota
+	LevelInfo
+	LevelWarn
+	LevelError
+)
+
+type Format int
+
+const (
+	FormatText Format = iota
+	FormatJSON
+)
+
+type Logger struct {
+	level  Level
+	format Format
+	output io.Writer
+}
+
+type logEntry struct {
+	Time    string                 `json:"time"`
+	Level   string                 `json:"level"`
+	Message string                 `json:"message"`
+	Fields  map[string]interface{} `json:"fields,omitempty"`
+}
+
+func New(level Level, format Format, output io.Writer) *Logger {
+	if output == nil {
+		output = os.Stderr
+	}
+	return &Logger{
+		level:  level,
+		format: format,
+		output: output,
+	}
+}
+
+func (l *Logger) log(level Level, msg string, fields map[string]interface{}) {
+	if level < l.level {
+		return
+	}
+
+	levelStr := levelToString(level)
+
+	if l.format == FormatJSON {
+		entry := logEntry{
+			Time:    time.Now().Format(time.RFC3339),
+			Level:   levelStr,
+			Message: msg,
+			Fields:  fields,
+		}
+		data, _ := json.Marshal(entry)
+		fmt.Fprintln(l.output, string(data))
+	} else {
+		// Text format
+		if len(fields) > 0 {
+			fmt.Fprintf(l.output, "[%s] %s %v\n", levelStr, msg, fields)
+		} else {
+			fmt.Fprintf(l.output, "[%s] %s\n", levelStr, msg)
+		}
+	}
+}
+
+func (l *Logger) Debug(msg string, fields ...map[string]interface{}) {
+	f := make(map[string]interface{})
+	if len(fields) > 0 {
+		f = fields[0]
+	}
+	l.log(LevelDebug, msg, f)
+}
+
+func (l *Logger) Info(msg string, fields ...map[string]interface{}) {
+	f := make(map[string]interface{})
+	if len(fields) > 0 {
+		f = fields[0]
+	}
+	l.log(LevelInfo, msg, f)
+}
+
+func (l *Logger) Warn(msg string, fields ...map[string]interface{}) {
+	f := make(map[string]interface{})
+	if len(fields) > 0 {
+		f = fields[0]
+	}
+	l.log(LevelWarn, msg, f)
+}
+
+func (l *Logger) Error(msg string, fields ...map[string]interface{}) {
+	f := make(map[string]interface{})
+	if len(fields) > 0 {
+		f = fields[0]
+	}
+	l.log(LevelError, msg, f)
+}
+
+func levelToString(level Level) string {
+	switch level {
+	case LevelDebug:
+		return "DEBUG"
+	case LevelInfo:
+		return "INFO"
+	case LevelWarn:
+		return "WARN"
+	case LevelError:
+		return "ERROR"
+	default:
+		return "UNKNOWN"
+	}
+}
+
+// Global logger for backward compatibility
+var globalLogger *Logger
+
+func Init(level Level, format Format, output ...io.Writer) {
+	var out io.Writer
+	if len(output) > 0 && output[0] != nil {
+		out = output[0]
+	} else {
+		out = os.Stderr
+	}
+	globalLogger = New(level, format, out)
+}
+
+func Debug(msg string, fields ...map[string]interface{}) {
+	if globalLogger != nil {
+		globalLogger.Debug(msg, fields...)
+	}
+}
+
+func Info(msg string, fields ...map[string]interface{}) {
+	if globalLogger != nil {
+		globalLogger.Info(msg, fields...)
+	}
+}
+
+func Warn(msg string, fields ...map[string]interface{}) {
+	if globalLogger != nil {
+		globalLogger.Warn(msg, fields...)
+	}
+}
+
+func Error(msg string, fields ...map[string]interface{}) {
+	if globalLogger != nil {
+		globalLogger.Error(msg, fields...)
+	}
+}