zippa/lib/walk.js

A Generic Zipper Library

'use strict';

Object.defineProperty(exports, "__esModule", {
    value: true
});
exports.walk = exports.preWalk = exports.postWalk = undefined;

var _curry = require('ramda/src/curry');

var _curry2 = _interopRequireDefault(_curry);

var _visit = require('./visit');

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

// @flow


var makeStatelessVisitor = function makeStatelessVisitor(fn) {
    return function (item, _) {
        return { item: fn(item) };
    };
};

/**
 * Walks the data structure in depth-first order, applying
 * the function after the item's subtree has been walked.
 *
 * Returns a new data structure of modified items, or the original
 * zipper if the structure wasn't modified.
 *
 * @param  {Function} fn - function applied to each item after it's subtree was walked
 * @param  {Zipper} zipper - A Zipper value to walk
 * @return {Zipper}
 */
var postWalk = exports.postWalk = (0, _curry2.default)(function (fn, zipper) {
    return (0, _visit.visit)([(0, _visit.onPost)(makeStatelessVisitor(fn))], undefined, zipper).zipper;
});

/**
 * Walks the data structure in depth-first order, applying
 * the function before the item's subtree has been walked.
 *
 * Returns a new data structure of modified items, or the original
 * zipper if the structure wasn't modified.
 *
 * @param  {Function} fn - function applied to each item before it's subtree is walked
 * @param  {Zipper} zipper - A Zipper value to walk
 * @return {Zipper}
 */
var preWalk = exports.preWalk = (0, _curry2.default)(function (fn, zipper) {
    return (0, _visit.visit)([(0, _visit.onPre)(makeStatelessVisitor(fn))], undefined, zipper).zipper;
});

/**
 * Walks the data structure in depth-first order,
 * applying inner and outer functions before and after (respectively) each
 * item's subtree is walked.
 *
 * Returns a new data structure from modified items, or the original
 * zipper if the structure wasn't modified.
 *
 * @param  {Function} inner - function applied to each item before it's subtree is walked
 * @param  {Function} outer  function applied to each item after it's subtree was walked
 * @param  {Zipper} zipper - A Zipper value to walk
 * @return {Zipper}
 */
var walk = exports.walk = (0, _curry2.default)(function (innerFn, outerFn, zipper) {
    return (0, _visit.visit)([(0, _visit.onPre)(makeStatelessVisitor(innerFn)), (0, _visit.onPost)(makeStatelessVisitor(outerFn))], undefined, zipper).zipper;
});

exports.default = {
    walk: walk,
    postWalk: postWalk,
    preWalk: preWalk
};