// TrieNode.js file:
--------------------
export class TrieNode {
  #map;
  #wordQuantity;
  constructor() {
    this.map = new Map();
    this.wordQuantity = 0;
  }

  get map() {
    return this.#map;
  }
  get wordQuantity() {
    return this.#wordQuantity;
  }

  set map(i_Map) {
    this.#map = i_Map;
  }
  set wordQuantity(i_WordQuantity) {
    this.#wordQuantity = i_WordQuantity;
  }
}

--------------------
// Trie.js file:
import { TrieNode } from "./TrieNode.js";

export class Trie {
  #root;
  constructor() {
    this.root = new TrieNode();
  }

  get root() {
    return this.#root;
  }
  set root(i_Root) {
    this.#root = i_Root;
  }

  insert(i_NewWord) {
    let current = this.root;

    for (const char of i_NewWord) {
      if (!current.map.has(char)) {
        current.map.set(char, new TrieNode());
      }
      current = current.map.get(char);
    }

    ++current.wordQuantity;
  }
}
--------------------
// index.js file
--------------------

import { Trie } from "./Trie.js";
import { TrieNode } from "./TrieNode.js";
const strings = ["aa", "a", "ab", "aab"];

// strings.sort(); // ["a", "aa", "aab", "ab"]

const countPrefixPairs = (root, wordsCount, totalPairs) => {
  if (!root) {
    return;
  }

  if (root.wordQuantity > 0) {
    wordsCount += root.wordQuantity;
    totalPairs.ctr += wordsCount - 1;
  }

  root.map.forEach((currentNode) =>
    countPrefixPairs(currentNode, wordsCount, totalPairs)
  );
};

let trie = new Trie();

for (const curStr of strings) {
  trie.insert(curStr);
}

let totalPairs = { ctr: 0 };
countPrefixPairs(trie.root, 0, totalPairs);
console.log(totalPairs);