// Setup creates a conf file with list of kernel modules required by given snap,
// writes it in /etc/modules-load.d/ directory and immediately loads the modules
// using /sbin/modprobe. The devMode is ignored.
//
// If the method fails it should be re-tried (with a sensible strategy) by the caller.
func (b *Backend) Setup(snapInfo *snap.Info, confinement interfaces.ConfinementOptions, repo *interfaces.Repository) error {
	snapName := snapInfo.Name()
	// Get the snippets that apply to this snap
	snippets, err := repo.SecuritySnippetsForSnap(snapInfo.Name(), interfaces.SecurityKMod)
	if err != nil {
		return fmt.Errorf("cannot obtain kmod security snippets for snap %q: %s", snapName, err)
	}

	// Get the files that this snap should have
	glob := interfaces.SecurityTagGlob(snapName)
	content, modules, err := b.combineSnippets(snapInfo, snippets)
	if err != nil {
		return fmt.Errorf("cannot obtain expected security files for snap %q: %s", snapName, err)
	}

	dir := dirs.SnapKModModulesDir
	if err := os.MkdirAll(dir, 0755); err != nil {
		return fmt.Errorf("cannot create directory for kmod files %q: %s", dir, err)
	}

	changed, _, err := osutil.EnsureDirState(dirs.SnapKModModulesDir, glob, content)
	if err != nil {
		return err
	}

	if len(changed) > 0 {
		return loadModules(modules)
	}
	return nil
}

// Setup creates udev rules specific to a given snap.
// If any of the rules are changed or removed then udev database is reloaded.
//
// Since udev has no concept of a complain mode, devMode is ignored.
//
// If the method fails it should be re-tried (with a sensible strategy) by the caller.
func (b *Backend) Setup(snapInfo *snap.Info, devMode bool, repo *interfaces.Repository) error {
	snapName := snapInfo.Name()
	snippets, err := repo.SecuritySnippetsForSnap(snapInfo.Name(), interfaces.SecurityUDev)
	if err != nil {
		return fmt.Errorf("cannot obtain udev security snippets for snap %q: %s", snapName, err)
	}
	content, err := b.combineSnippets(snapInfo, snippets)
	if err != nil {
		return fmt.Errorf("cannot obtain expected udev rules for snap %q: %s", snapName, err)
	}
	dir := dirs.SnapUdevRulesDir
	if err := os.MkdirAll(dir, 0755); err != nil {
		return fmt.Errorf("cannot create directory for udev rules %q: %s", dir, err)
	}

	rulesFilePath := snapRulesFilePath(snapInfo.Name())

	if len(content) == 0 {
		// Make sure that the rules file gets removed when we don't have any
		// content and exists.
		err = os.Remove(rulesFilePath)
		if err != nil && !os.IsNotExist(err) {
			return err
		} else if err == nil {
			return ReloadRules()
		}
		return nil
	}

	var buffer bytes.Buffer
	buffer.WriteString("# This file is automatically generated.\n")
	for _, snippet := range content {
		buffer.Write(snippet)
		buffer.WriteByte('\n')
	}

	rulesFileState := &osutil.FileState{
		Content: buffer.Bytes(),
		Mode:    0644,
	}

	// EnsureFileState will make sure the file will be only updated when its content
	// has changed and will otherwise return an error which prevents us from reloading
	// udev rules when not needed.
	err = osutil.EnsureFileState(rulesFilePath, rulesFileState)
	if err == osutil.ErrSameState {
		return nil
	} else if err != nil {
		return err
	}

	return ReloadRules()
}