tree.ts

/**
 * Copyright 2019 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Node is the expected shape of input data.
 */
export interface Node {
  /**
   * id is optional but can be used to identify each node.
   * It should be unique among nodes at the same level.
   */
  id?: string;
  /** size should be >= the sum of the children's size. */
  size: number;
  /** children should be sorted by size in descending order. */
  children?: Node[];
  /** dom node will be created and associated with the data. */
  dom?: HTMLElement;
}

/**
 * treeify converts an array of [path, size] pairs into a tree.
 * Paths are /-delimited ids.
 */
export function treeify(data: Array<[string, number]>): Node {
  const tree: Node = {size: 0};
  for (const [path, size] of data) {
    const parts = path.replace(/\/$/, '').split('/');
    let t = tree;
    while (parts.length > 0) {
      const id = parts.shift();
      if (!t.children) t.children = [];
      let child = t.children.find(c => c.id === id);
      if (!child) {
        child = {id, size: 0};
        t.children.push(child);
      }
      if (parts.length === 0) {
        if (child.size !== 0) {
          throw new Error(`duplicate path ${path} ${child.size}`);
        }
        child.size = size;
      }
      t = child;
    }
  }
  return tree;
}

/**
 * flatten flattens nodes that have only one child.
 * @param join If given, a function that joins the names of the parent and
 * child.
 */
export function flatten(
  n: Node,
  join = (parent: string, child: string) => `${parent}/${child}`
) {
  if (n.children) {
    for (const c of n.children) {
      flatten(c, join);
    }
    if (n.children.length === 1) {
      const child = n.children[0];
      n.id += '/' + child.id;
      n.children = child.children;
    }
  }
}

/**
 * rollup fills in the size attribute for nodes by summing their children.
 *
 * Note that it's legal for input data to have a node with a size larger
 * than the sum of its children, perhaps because some data was left out.
 */
export function rollup(n: Node) {
  if (!n.children) return;
  let total = 0;
  for (const c of n.children) {
    rollup(c);
    total += c.size;
  }

  if (total > n.size) n.size = total;
}

/**
 * sort sorts a tree by size, descending.
 */
export function sort(n: Node) {
  if (!n.children) return;
  for (const c of n.children) {
    sort(c);
  }
  n.children.sort((a, b) => b.size - a.size);
}