package logger

import (
	"io"
	"log/slog"
	"os"
	"strings"

	"server/internal/config"

	"gopkg.in/natefinch/lumberjack.v2"
)

// New 根据配置创建 slog.Logger，并将其设置为默认 logger。
// 日志会写入文件（自动按大小/时间滚动），并可选同时输出到控制台。
func New(cfg *config.Config) *slog.Logger {
	logCfg := cfg.Log

	// 文件滚动写入
	fileWriter := &lumberjack.Logger{
		Filename:   defaultStr(logCfg.Filename, "logs/app.log"),
		MaxSize:    defaultInt(logCfg.MaxSize, 100), // MB
		MaxBackups: defaultInt(logCfg.MaxBackups, 30),
		MaxAge:     defaultInt(logCfg.MaxAge, 30), // days
		Compress:   logCfg.Compress,
	}

	var writer io.Writer = fileWriter
	if logCfg.Console {
		writer = io.MultiWriter(os.Stdout, fileWriter)
	}

	opts := &slog.HandlerOptions{
		Level:     parseLevel(logCfg.Level),
		AddSource: false,
	}

	// 生产环境用 JSON，便于日志采集/检索；开发环境用文本更易读
	var handler slog.Handler
	if config.IsDev() {
		handler = slog.NewTextHandler(writer, opts)
	} else {
		handler = slog.NewJSONHandler(writer, opts)
	}

	l := slog.New(handler)
	slog.SetDefault(l) // 让全局 slog.Info/Error 也走同一套配置
	return l
}

func parseLevel(level string) slog.Level {
	switch strings.ToLower(level) {
	case "debug":
		return slog.LevelDebug
	case "warn", "warning":
		return slog.LevelWarn
	case "error":
		return slog.LevelError
	default:
		return slog.LevelInfo
	}
}

func defaultStr(v, def string) string {
	if v == "" {
		return def
	}
	return v
}

func defaultInt(v, def int) int {
	if v <= 0 {
		return def
	}
	return v
}