package files

import (
	"archive/zip"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
)

var ErrZipTooLarge = errors.New("folder archive exceeds size limit")

// ZipDirectory writes dir into a temp .zip file and returns its path.
func ZipDirectory(dir string, maxBytes int64) (string, error) {
	info, err := os.Stat(dir)
	if err != nil {
		return "", err
	}
	if !info.IsDir() {
		return "", errors.New("path is not a directory")
	}

	tmp, err := os.CreateTemp("", "win64_mp-zip-*.zip")
	if err != nil {
		return "", err
	}
	path := tmp.Name()
	cleanup := func() { _ = os.Remove(path) }

	zw := zip.NewWriter(tmp)
	var written int64
	err = filepath.WalkDir(dir, func(current string, entry os.DirEntry, walkErr error) error {
		if walkErr != nil {
			return walkErr
		}
		if entry.Type()&os.ModeSymlink != 0 {
			return nil
		}
		if !isWithin(dir, current) {
			return ErrOutsideRoot
		}
		rel, err := filepath.Rel(dir, current)
		if err != nil {
			return err
		}
		if rel == "." {
			return nil
		}
		if entry.IsDir() {
			return nil
		}
		info, err := entry.Info()
		if err != nil {
			return err
		}
		if maxBytes > 0 && written+info.Size() > maxBytes {
			return ErrZipTooLarge
		}
		hdr, err := zip.FileInfoHeader(info)
		if err != nil {
			return err
		}
		hdr.Name = filepath.ToSlash(rel)
		hdr.Method = zip.Deflate
		w, err := zw.CreateHeader(hdr)
		if err != nil {
			return err
		}
		f, err := os.Open(current)
		if err != nil {
			return err
		}
		n, err := io.Copy(w, f)
		_ = f.Close()
		if err != nil {
			return err
		}
		written += n
		return nil
	})
	if err != nil {
		_ = zw.Close()
		_ = tmp.Close()
		cleanup()
		return "", err
	}
	if err := zw.Close(); err != nil {
		_ = tmp.Close()
		cleanup()
		return "", err
	}
	if err := tmp.Close(); err != nil {
		cleanup()
		return "", err
	}
	return path, nil
}

// ZipArchiveName returns a safe download filename for a directory path.
func ZipArchiveName(dir string) string {
	base := filepath.Base(dir)
	if base == "" || base == "." || base == string(os.PathSeparator) {
		return "folder.zip"
	}
	return fmt.Sprintf("%s.zip", base)
}