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mosaicUtilities.ts
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import clone from 'lodash/clone';
import get from 'lodash/get';
import { MosaicBranch, MosaicDirection, MosaicKey, MosaicNode, MosaicParent, MosaicPath } from '../types';
function alternateDirection<T extends MosaicKey>(
node: MosaicNode<T>,
direction: MosaicDirection = 'row',
): MosaicNode<T> {
if (isParent(node)) {
const nextDirection = getOtherDirection(direction);
return {
direction,
first: alternateDirection(node.first, nextDirection),
second: alternateDirection(node.second, nextDirection),
};
} else {
return node;
}
}
export enum Corner {
TOP_LEFT = 1,
TOP_RIGHT,
BOTTOM_LEFT,
BOTTOM_RIGHT,
}
/**
* Returns `true` if `node` is a MosaicParent
* @param node
* @returns {boolean}
*/
export function isParent<T extends MosaicKey>(node: MosaicNode<T>): node is MosaicParent<T> {
return (node as MosaicParent<T>).direction != null;
}
/**
* Creates a balanced binary tree from `leaves` with the goal of making them as equal area as possible
* @param leaves
* @param startDirection
* @returns {MosaicNode<T>}
*/
export function createBalancedTreeFromLeaves<T extends MosaicKey>(
leaves: MosaicNode<T>[],
startDirection: MosaicDirection = 'row',
): MosaicNode<T> | null {
if (leaves.length === 0) {
return null;
}
let current: MosaicNode<T>[] = clone(leaves);
let next: MosaicNode<T>[] = [];
while (current.length > 1) {
while (current.length > 0) {
if (current.length > 1) {
next.push({
direction: 'row',
first: current.shift()!,
second: current.shift()!,
});
} else {
next.unshift(current.shift()!);
}
}
current = next;
next = [];
}
return alternateDirection(current[0], startDirection);
}
/**
* Gets the sibling of `branch`
* @param branch
* @returns {any}
*/
export function getOtherBranch(branch: MosaicBranch): MosaicBranch {
if (branch === 'first') {
return 'second';
} else if (branch === 'second') {
return 'first';
} else {
throw new Error(`Branch '${branch}' not a valid branch`);
}
}
/**
* Gets the opposite of `direction`
* @param direction
* @returns {any}
*/
export function getOtherDirection(direction: MosaicDirection): MosaicDirection {
if (direction === 'row') {
return 'column';
} else {
return 'row';
}
}
/**
* Traverses `tree` to find the path to the specified `corner`
* @param tree
* @param corner
* @returns {MosaicPath}
*/
export function getPathToCorner(tree: MosaicNode<any>, corner: Corner): MosaicPath {
let currentNode: MosaicNode<any> = tree;
const currentPath: MosaicPath = [];
while (isParent(currentNode)) {
if (currentNode.direction === 'row' && (corner === Corner.TOP_LEFT || corner === Corner.BOTTOM_LEFT)) {
currentPath.push('first');
currentNode = currentNode.first;
} else if (currentNode.direction === 'column' && (corner === Corner.TOP_LEFT || corner === Corner.TOP_RIGHT)) {
currentPath.push('first');
currentNode = currentNode.first;
} else {
currentPath.push('second');
currentNode = currentNode.second;
}
}
return currentPath;
}
/**
* Gets all leaves of `tree`
* @param tree
* @returns {T[]}
*/
export function getLeaves<T extends MosaicKey>(tree: MosaicNode<T> | null): T[] {
if (tree == null) {
return [];
} else if (isParent(tree)) {
return getLeaves(tree.first).concat(getLeaves(tree.second));
} else {
return [tree];
}
}
/**
* Gets node at `path` from `tree`
* @param tree
* @param path
* @returns {MosaicNode<T>|null}
*/
export function getNodeAtPath<T extends MosaicKey>(tree: MosaicNode<T> | null, path: MosaicPath): MosaicNode<T> | null {
if (path.length > 0) {
return get(tree, path, null);
} else {
return tree;
}
}
/**
* Gets node at `path` from `tree` and verifies that neither `tree` nor the result are null
* @param tree
* @param path
* @returns {MosaicNode<T>}
*/
export function getAndAssertNodeAtPathExists<T extends MosaicKey>(
tree: MosaicNode<T> | null,
path: MosaicPath,
): MosaicNode<T> {
if (tree == null) {
throw new Error('Root is empty, cannot fetch path');
}
const node = getNodeAtPath(tree, path);
if (node == null) {
throw new Error(`Path [${path.join(', ')}] did not resolve to a node`);
}
return node;
}