Keyboard Maestro macro for cycling numeric tag values in TaskPaper 3

TP3 Numeric Tag Cycle.js

// Cycle forward/back through numeric tags
// Brett Terpstra <http://brettterpstra.com>
// Credit: Rob Trew @complexpoint


(function () {
    'use strict';

    function TaskPaperContext(editor, options) {
        var selection = editor.selection,
            selectedItems = selection.selectedItems,

            strAttrib = 'data-' + options.tag,
            increment = options.offset,
            max = options.maxVal,
            min = options.minVal;
            
        function cyclePriority(val,inc) {
            var newVal;
            if (inc > 0) {
                if (val === 0) {
                    newVal = min;
                } else if (val + inc > max) {
                    newVal = null;
                } else {
                    newVal = val + inc;
                }
            } else {
                if (val === 0) {
                    newVal = max;
                } else if (val + inc < min) {
                    newVal = null;
                } else {
                    newVal = val + inc;
                }
            }
            return newVal;
        }

        editor.outline.groupUndoAndChanges(function () {
            selectedItems.forEach(function (item) {

                var currVal = item.getAttribute(strAttrib), 
                    newVal = null;

                if (currVal) {
                    currVal = parseInt(currVal,10);
                } else {
                    currVal = 0;
                }
                
                item.setAttribute(strAttrib, cyclePriority(currVal,increment));
            });
        });

        editor.moveSelectionToItems(selection);
    }

    function appIsInstalled(strBundleId) {
        ObjC.import('AppKit');

        return ObjC.unwrap(
            $.NSWorkspace.sharedWorkspace
            .URLForApplicationWithBundleIdentifier(
                strBundleId
            )
            .fileSystemRepresentation
        ) !== undefined;
    }

    var strKMEid = "com.stairways.keyboardmaestro.engine",
        kmVars = appIsInstalled(strKMEid) ? Application(strKMEid)
        .variables : {},
        varTag = kmVars.incTag,
        varOffset = kmVars.incVal,
        varMinVal = kmVars.minVal,
        varMaxVal = kmVars.maxVal;



    var ds = Application('TaskPaper').documents();
    

    if (ds.length) {
        return ds[0].evaluate({
            script: TaskPaperContext.toString(),
            withOptions: {
                tag: (varTag && varTag.value()) || 'priority',
                offset: (varOffset && parseInt(varOffset.value(),10)) || 1,
                maxVal: (varMaxVal && parseInt(varMaxVal.value(),10)) || 5,
                minVal: (varMinVal && parseInt(varMinVal.value(),10)) || 1
            }
        });
    }

})();