blockly/core/keyboard_nav/cursor.js

/**
 * @license
 * Copyright 2019 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @fileoverview The class representing a cursor.
 * Used primarily for keyboard navigation.
 */
'use strict';

/**
 * The class representing a cursor.
 * Used primarily for keyboard navigation.
 * @class
 */
goog.module('Blockly.Cursor');

const object = goog.require('Blockly.utils.object');
const registry = goog.require('Blockly.registry');
const {ASTNode} = goog.require('Blockly.ASTNode');
const {Marker} = goog.require('Blockly.Marker');

/**
 * Class for a cursor.
 * A cursor controls how a user navigates the Blockly AST.
 * @constructor
 * @extends {Marker}
 * @alias Blockly.Cursor
 */
const Cursor = function() {
  Cursor.superClass_.constructor.call(this);

  /**
   * @override
   */
  this.type = 'cursor';
};
object.inherits(Cursor, Marker);

/**
 * Find the next connection, field, or block.
 * @return {ASTNode} The next element, or null if the current node is
 *     not set or there is no next value.
 * @public
 */
Cursor.prototype.next = function() {
  const curNode = this.getCurNode();
  if (!curNode) {
    return null;
  }

  let newNode = curNode.next();
  while (newNode && newNode.next() &&
         (newNode.getType() === ASTNode.types.NEXT ||
          newNode.getType() === ASTNode.types.BLOCK)) {
    newNode = newNode.next();
  }

  if (newNode) {
    this.setCurNode(newNode);
  }
  return newNode;
};

/**
 * Find the in connection or field.
 * @return {ASTNode} The in element, or null if the current node is
 *     not set or there is no in value.
 * @public
 */
Cursor.prototype.in = function() {
  let curNode = this.getCurNode();
  if (!curNode) {
    return null;
  }
  // If we are on a previous or output connection, go to the block level before
  // performing next operation.
  if (curNode.getType() === ASTNode.types.PREVIOUS ||
      curNode.getType() === ASTNode.types.OUTPUT) {
    curNode = curNode.next();
  }
  const newNode = curNode.in();

  if (newNode) {
    this.setCurNode(newNode);
  }
  return newNode;
};

/**
 * Find the previous connection, field, or block.
 * @return {ASTNode} The previous element, or null if the current node
 *     is not set or there is no previous value.
 * @public
 */
Cursor.prototype.prev = function() {
  const curNode = this.getCurNode();
  if (!curNode) {
    return null;
  }
  let newNode = curNode.prev();

  while (newNode && newNode.prev() &&
         (newNode.getType() === ASTNode.types.NEXT ||
          newNode.getType() === ASTNode.types.BLOCK)) {
    newNode = newNode.prev();
  }

  if (newNode) {
    this.setCurNode(newNode);
  }
  return newNode;
};

/**
 * Find the out connection, field, or block.
 * @return {ASTNode} The out element, or null if the current node is
 *     not set or there is no out value.
 * @public
 */
Cursor.prototype.out = function() {
  const curNode = this.getCurNode();
  if (!curNode) {
    return null;
  }
  let newNode = curNode.out();

  if (newNode && newNode.getType() === ASTNode.types.BLOCK) {
    newNode = newNode.prev() || newNode;
  }

  if (newNode) {
    this.setCurNode(newNode);
  }
  return newNode;
};

registry.register(registry.Type.CURSOR, registry.DEFAULT, Cursor);

exports.Cursor = Cursor;