package comics

import (
	"context"
	"database/sql"
	"fmt"
	"os"
	"path"
	"path/filepath"
	"strings"

	"github.com/mithral/vellum/internal/media"
)

func init() {
	media.RegisterCoverExtractor(Kind, ExtractCover)
}

// ExtractCover writes the first page of the archive into the cache and returns
// its path. A comic's first page is its cover by convention.
//
// Only zip-based archives are handled. A PDF in a comics library is a valid
// item but not a zip, so it returns no cover rather than logging an error on
// every request — the grid falls back to a placeholder.
func ExtractCover(ctx context.Context, db *sql.DB, item media.Item, absPath, cacheDir string) (string, error) {
	switch strings.ToLower(filepath.Ext(item.Path)) {
	case ".cbz", ".zip":
	default:
		return "", nil
	}

	pages, err := ListPages(absPath)
	if err != nil {
		return "", err
	}

	dir, err := media.CoverCacheDir(cacheDir, Kind)
	if err != nil {
		return "", err
	}

	ext := strings.ToLower(path.Ext(pages[0].Name))
	if ext == "" {
		ext = ".jpg"
	}
	outPath := filepath.Join(dir, fmt.Sprintf("%d%s", item.ID, ext))

	data, err := ReadPage(absPath, pages[0].Name)
	if err != nil {
		return "", err
	}

	tmp := outPath + ".tmp"
	if err := os.WriteFile(tmp, data, 0o640); err != nil {
		return "", fmt.Errorf("comics: write cover: %w", err)
	}
	if err := os.Rename(tmp, outPath); err != nil {
		_ = os.Remove(tmp)
		return "", err
	}
	return outPath, nil
}