function setLangMode(lang: string) {
    ace.acequire('ace/ext/language_tools');
    codeEditor.setOptions({
      enableBasicAutocompletion: true,
      enableLiveAutocompletion: true,
      enableSnippets: snippetsEnabled,
    });

    if (scope.getCompleter()) {
      // make copy of array as ace seems to share completers array between instances
      const anyEditor = codeEditor as any;
      anyEditor.completers = anyEditor.completers.slice();
      anyEditor.completers.push(scope.getCompleter());
    }

    const aceModeName = `ace/mode/${lang}`;
    editorSession.setMode(aceModeName);
  }

export default function previewPanelDirective($interval: ng.IIntervalService, $timeout: ng.ITimeoutService) {
    let animation = {editor: null, stage: 0, start: 0, stop: 0};
    let prevContent = [];

    const Range = ace.acequire('ace/range').Range;

    const _clearSelection = (editor) => {
        _.forEach(editor.session.getMarkers(false), (marker) => {
            editor.session.removeMarker(marker.id);
        });
    };

    /**
     * Switch to next stage of animation.
     */
    const _animate = () => {
        animation.stage += animation.step;

        const stage = animation.stage;
        const editor = animation.editor;

        _clearSelection(editor);

        animation.selections.forEach((selection) => {
            editor.session.addMarker(new Range(selection.start, 0, selection.stop, 0),
                'preview-highlight-' + stage, 'line', false);
        });

        if (stage === animation.finalStage) {
            editor.animatePromise = null;

            if (animation.clearOnFinal)
                _clearSelection(editor);
        }
    };

    /**
     * Selection with animation.
     *
     * @param editor Editor to show selection animation.
     * @param selections Array of selection intervals.
     * @param step Step of animation (1 or -1).
     * @param stage Start stage of animation.
     * @param finalStage Final stage of animation.
     * @param clearOnFinal Boolean flat to clear selection on animation finish.
     */
    const _fade = (editor, selections, step, stage, finalStage, clearOnFinal) => {
        const promise = editor.animatePromise;

        if (promise) {
            $interval.cancel(promise);

            _clearSelection(editor);
        }

        animation = {editor, selections, step, stage, finalStage, clearOnFinal};

        editor.animatePromise = $interval(_animate, 100, 10, false);
    };

    /**
     * Show selections with animation.
     *
     * @param editor Editor to show selection.
     * @param selections Array of selection intervals.
     */
    const _fadeIn = (editor, selections) => {
        _fade(editor, selections, 1, 0, 10, false);
    };

    /**
     * Hide selections with animation.
     *
     * @param editor Editor to show selection.
     * @param selections Array of selection intervals.
     */
    const _fadeOut = (editor, selections) => {
        _fade(editor, selections, -1, 10, 0, true);
    };

    const onChange = ([content, editor]) => {
        const {clearPromise} = editor;
        const {lines} = content;

        if (content.action === 'remove')
            prevContent = lines;
        else if (prevContent.length > 0 && lines.length > 0 && editor.attractAttention) {
            if (clearPromise) {
                $timeout.cancel(clearPromise);

                _clearSelection(editor);
            }

            const selections = [];

            let newIx = 0;
            let prevIx = 0;

            let prevLen = prevContent.length - (prevContent[prevContent.length - 1] === '' ? 1 : 0);
            let newLen = lines.length - (lines[lines.length - 1] === '' ? 1 : 0);
//.........这里部分代码省略.........