package logx

import (
	"io"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

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

// dailyWriter 按天滚动的日志写入器：文件名 base-2006-01-02.log，跨天自动切换；
// 超过 MaxAge 天的日志文件在跨天时清理。
type dailyWriter struct {
	mu   sync.Mutex
	conf LogConf
	date string
	lj   *lumberjack.Logger
}

func newDailyWriter(conf LogConf) *dailyWriter {
	return &dailyWriter{conf: conf}
}

func (w *dailyWriter) filename(date string) string {
	ext := filepath.Ext(w.conf.Filename)
	base := strings.TrimSuffix(w.conf.Filename, ext)
	return base + "-" + date + ext
}

func (w *dailyWriter) Write(p []byte) (int, error) {
	w.mu.Lock()
	defer w.mu.Unlock()

	today := time.Now().Format("2006-01-02")
	if w.lj == nil || today != w.date {
		if w.lj != nil {
			_ = w.lj.Close()
		}
		w.date = today
		w.lj = &lumberjack.Logger{
			Filename:   w.filename(today),
			MaxSize:    w.conf.MaxSize,
			MaxBackups: w.conf.MaxBackups,
			MaxAge:     w.conf.MaxAge,
			Compress:   w.conf.Compress,
		}
		w.cleanup()
	}
	return w.lj.Write(p)
}

func (w *dailyWriter) Close() error {
	w.mu.Lock()
	defer w.mu.Unlock()
	if w.lj != nil {
		return w.lj.Close()
	}
	return nil
}

// cleanup 清理超过 MaxAge 天的按天日志文件
func (w *dailyWriter) cleanup() {
	if w.conf.MaxAge <= 0 {
		return
	}
	dir := filepath.Dir(w.conf.Filename)
	ext := filepath.Ext(w.conf.Filename)
	base := strings.TrimSuffix(filepath.Base(w.conf.Filename), ext)
	entries, err := os.ReadDir(dir)
	if err != nil {
		return
	}
	cutoff := time.Now().AddDate(0, 0, -w.conf.MaxAge)
	for _, e := range entries {
		if e.IsDir() || !strings.HasPrefix(e.Name(), base+"-") || !strings.HasSuffix(e.Name(), ext) {
			continue
		}
		datePart := strings.TrimSuffix(strings.TrimPrefix(e.Name(), base+"-"), ext)
		t, err := time.ParseInLocation("2006-01-02", datePart, time.Local)
		if err != nil {
			continue
		}
		if t.Before(cutoff) {
			_ = os.Remove(filepath.Join(dir, e.Name()))
		}
	}
}

var (
	_ io.WriteCloser = (*dailyWriter)(nil)
	_ io.Writer      = (*dailyWriter)(nil)
)