package files

import (
	"errors"
	"os"
	"path/filepath"
	"strings"
)

const (
	PartFileName      = ".download.part"
	JobFileName       = ".job.json"
	temporaryPrefix   = ".ddc-tmp-"
	temporaryWildcard = temporaryPrefix + "*"
)

func IsInternal(name string) bool {
	return name == PartFileName || name == JobFileName || strings.HasPrefix(name, temporaryPrefix)
}

func WriteAtomically(path string, data []byte) error {
	temporary, err := os.CreateTemp(filepath.Dir(path), temporaryWildcard)
	if err != nil {
		return err
	}
	_, writeErr := temporary.Write(data)
	closeErr := temporary.Close()
	if writeErr != nil || closeErr != nil {
		os.Remove(temporary.Name())
		return errors.Join(writeErr, closeErr)
	}
	if err := os.Chmod(temporary.Name(), 0o644); err != nil {
		os.Remove(temporary.Name())
		return err
	}
	if err := os.Rename(temporary.Name(), path); err != nil {
		os.Remove(temporary.Name())
		return err
	}
	return nil
}