SimpleSchema formly Mapping with walk

app.js

function formlyFieldsFromSchema(sschema) {
	var fields = [];
	var currentGroup = fields;
	var groupStack = [];
	
	var callbacks = {
		leaf: function (sschema, key) {
			var schema = sschema.schema(key);
			//SimpleSchema <-> formly mapping
			var mapping = {
				key: key,
				type: 'input',
				templateOptions: {
					label: sschema.label(key),
					required: !schema.optional
				}
			}
			currentGroup.push(mapping);
		},
		array: {
			prefix: function (sschema, key) { },
			intermed: function (sschema, key, i) { },
			sufix: function (sschema, key) { }
		},
		subSchema: {
			prefix: function (sschema, key) {
				if (key !== '') {
					//Not root
					//Create a fieldGroup
					var fieldGroup = {
						fieldGroup: []
					};
					groupStack.push(currentGroup);
					currentGroup = fieldGroup.fieldGroup;
				}
			},
			intermed: function (sschema, key, i) {
				//No-op
			},
			sufix: function (sschema, key) {
				//Close fieldGroup?
				currentGroup = groupStack.pop();
			}
		}
	};
	
	SimpleSchema.walk(sschema, '', callbacks);
	return fields;
}