package logger

import (
	"fmt"
	"log"
	"os"
	"sync"
)

// Level 日志级别
type Level int

const (
	LevelDebug Level = iota
	LevelInfo
	LevelWarn
	LevelError
	LevelFatal
)

// Logger 日志接口
type Logger interface {
	Debug(format string, args ...interface{})
	Info(format string, args ...interface{})
	Warn(format string, args ...interface{})
	Error(format string, args ...interface{})
	Fatal(format string, args ...interface{})
	SetLevel(level Level)
}

// stdLogger 标准库日志实现
type stdLogger struct {
	logger *log.Logger
	level  Level
	mu     sync.RWMutex
}

// New 创建标准库日志实例
func New(config *Config) Logger {
	var output *os.File
	switch config.Output {
	case "stdout":
		output = os.Stdout
	case "stderr":
		output = os.Stderr
	default:
		var err error
		output, err = os.OpenFile(config.Output, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
		if err != nil {
			output = os.Stdout
		}
	}

	level := parseLevel(config.Level)

	return &stdLogger{
		logger: log.New(output, "", log.LstdFlags|log.Lshortfile),
		level:  level,
	}
}

// parseLevel 解析日志级别
func parseLevel(level string) Level {
	switch level {
	case "debug":
		return LevelDebug
	case "info":
		return LevelInfo
	case "warn":
		return LevelWarn
	case "error":
		return LevelError
	case "fatal":
		return LevelFatal
	default:
		return LevelInfo
	}
}

// SetLevel 设置日志级别
func (l *stdLogger) SetLevel(level Level) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.level = level
}

// Debug 输出调试日志
func (l *stdLogger) Debug(format string, args ...interface{}) {
	if l.shouldLog(LevelDebug) {
		l.log("DEBUG", format, args...)
	}
}

// Info 输出信息日志
func (l *stdLogger) Info(format string, args ...interface{}) {
	if l.shouldLog(LevelInfo) {
		l.log("INFO", format, args...)
	}
}

// Warn 输出警告日志
func (l *stdLogger) Warn(format string, args ...interface{}) {
	if l.shouldLog(LevelWarn) {
		l.log("WARN", format, args...)
	}
}

// Error 输出错误日志
func (l *stdLogger) Error(format string, args ...interface{}) {
	if l.shouldLog(LevelError) {
		l.log("ERROR", format, args...)
	}
}

// Fatal 输出致命错误日志并退出
func (l *stdLogger) Fatal(format string, args ...interface{}) {
	if l.shouldLog(LevelFatal) {
		l.log("FATAL", format, args...)
		os.Exit(1)
	}
}

// shouldLog 判断是否应该记录日志
func (l *stdLogger) shouldLog(level Level) bool {
	l.mu.RLock()
	defer l.mu.RUnlock()
	return level >= l.level
}

// log 记录日志
func (l *stdLogger) log(level string, format string, args ...interface{}) {
	message := fmt.Sprintf(format, args...)
	l.logger.Printf("[%s] %s", level, message)
}

// Config 日志配置
type Config struct {
	Level  string
	Format string
	Output string
}