package bookfile

import (
	"errors"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
)

func DirKey(id int64, hash string) string { return fmt.Sprintf("%d-%s", id, hash) }

func CoverDir(cacheDir, key string) string { return filepath.Join(cacheDir, "covers", key) }
func PagesDir(cacheDir, key string) string { return filepath.Join(cacheDir, "pages", key) }

func SweepStale(cacheDir string, live map[string]bool) (int, error) {
	removed := 0
	for _, kind := range []string{"covers", "pages"} {
		entries, err := os.ReadDir(filepath.Join(cacheDir, kind))
		if err != nil {
			if errors.Is(err, fs.ErrNotExist) {
				continue // 首次运行还没有该层目录,不算错
			}
			return removed, err
		}
		for _, e := range entries {
			if !e.IsDir() || live[e.Name()] {
				continue
			}
			if err := os.RemoveAll(filepath.Join(cacheDir, kind, e.Name())); err != nil {
				return removed, err
			}
			removed++
		}
	}
	return removed, nil
}