// Package logdaily 提供按天滚动的日志写入器（供 go-zero logx.SetWriter 使用）
package logdaily

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

type dailyWriter struct {
	mu       sync.Mutex
	dir      string
	base     string
	keepDays int
	date     string
	f        *os.File
}

// New 创建按天滚动的写入器：文件名 dir/base-2006-01-02.log，跨天自动切换，
// 超过 keepDays 天的旧日志在跨天时清理（keepDays<=0 表示永久保留）。
func New(dir, base string, keepDays int) io.WriteCloser {
	return &dailyWriter{dir: dir, base: base, keepDays: keepDays}
}

func (w *dailyWriter) filename(date string) string {
	return filepath.Join(w.dir, w.base+"-"+date+".log")
}

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

	today := time.Now().Format("2006-01-02")
	if w.f == nil || today != w.date {
		if w.f != nil {
			_ = w.f.Close()
		}
		if err := os.MkdirAll(w.dir, 0o755); err != nil {
			return 0, err
		}
		f, err := os.OpenFile(w.filename(today), os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o644)
		if err != nil {
			return 0, err
		}
		w.f = f
		w.date = today
		w.cleanup()
	}
	return w.f.Write(p)
}

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

func (w *dailyWriter) cleanup() {
	if w.keepDays <= 0 {
		return
	}
	entries, err := os.ReadDir(w.dir)
	if err != nil {
		return
	}
	cutoff := time.Now().AddDate(0, 0, -w.keepDays)
	for _, e := range entries {
		if e.IsDir() || !strings.HasPrefix(e.Name(), w.base+"-") || !strings.HasSuffix(e.Name(), ".log") {
			continue
		}
		datePart := strings.TrimSuffix(strings.TrimPrefix(e.Name(), w.base+"-"), ".log")
		t, err := time.ParseInLocation("2006-01-02", datePart, time.Local)
		if err != nil {
			continue
		}
		if t.Before(cutoff) {
			_ = os.Remove(filepath.Join(w.dir, e.Name()))
		}
	}
}

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