@triply/yasqe/src/trie.ts

Yet Another SPARQL Query Editor

export default class Trie {
  private words = 0;
  private prefixes = 0;
  private children: { [char: string]: Trie } = {};

  /*
   * Insert a word into the dictionary.
   * Recursively traverse through the trie nodes, and create new node if does not already exist.
   *
   * @method insert
   * @param {String} str Word to insert in the dictionary
   * @param {Integer} pos Current index of the string to be inserted
   * @return {Void}
   */
  insert(str: string, pos?: number) {
    if (str.length == 0) {
      //blank string cannot be inserted
      return;
    }

    var T = this,
      k,
      child;

    if (pos === undefined) {
      pos = 0;
    }
    if (pos === str.length) {
      T.words++;
      return;
    }
    T.prefixes++;
    k = str[pos];
    if (T.children[k] === undefined) {
      //if node for this char doesn't exist, create one
      T.children[k] = new Trie();
    }
    child = T.children[k];
    child.insert(str, pos + 1);
  }
  /*
   * Remove a word from the dictionary.
   *
   * @method remove
   * @param {String} str Word to be removed
   * @param {Integer} pos Current index of the string to be removed
   * @return {Void}
   */
  remove(str: string, pos?: number) {
    if (str.length == 0) {
      return;
    }
    var T = this,
      k,
      child;

    if (pos === undefined) {
      pos = 0;
    }
    if (T === undefined) {
      return;
    }
    if (pos === str.length) {
      T.words--;
      return;
    }
    T.prefixes--;
    k = str[pos];
    child = T.children[k];
    child.remove(str, pos + 1);
  }

  /*
   * Update an existing word in the dictionary.
   * This method removes the old word from the dictionary and inserts the new word.
   *
   * @method update
   * @param {String} strOld The old word to be replaced
   * @param {String} strNew The new word to be inserted
   * @return {Void}
   */
  update(strOld: string, strNew: string) {
    if (strOld.length == 0 || strNew.length == 0) {
      return;
    }
    this.remove(strOld);
    this.insert(strNew);
  }

  /*
   * Count the number of times a given word has been inserted into the dictionary
   *
   * @method countWord
   * @param {String} str Word to get count of
   * @param {Integer} pos Current index of the given word
   * @return {Integer} The number of times a given word exists in the dictionary
   */
  countWord(str: string, pos?: number) {
    if (str.length == 0) {
      return 0;
    }

    var T = this,
      k,
      child,
      ret = 0;

    if (pos === undefined) {
      pos = 0;
    }
    if (pos === str.length) {
      return T.words;
    }
    k = str[pos];
    child = T.children[k];
    if (child !== undefined) {
      //node exists
      ret = child.countWord(str, pos + 1);
    }
    return ret;
  }

  /*
   * Count the number of times a given prefix exists in the dictionary
   *
   * @method countPrefix
   * @param {String} str Prefix to get count of
   * @param {Integer} pos Current index of the given prefix
   * @return {Integer} The number of times a given prefix exists in the dictionary
   */
  countPrefix(str: string, pos: number) {
    if (str.length == 0) {
      return 0;
    }

    var T = this,
      k: string,
      child,
      ret = 0;

    if (pos === undefined) {
      pos = 0;
    }
    if (pos === str.length) {
      return T.prefixes;
    }
    var k = str[pos];
    child = T.children[k];
    if (child !== undefined) {
      //node exists
      ret = child.countPrefix(str, pos + 1);
    }
    return ret;
  }

  /*
   * Find a word in the dictionary
   *
   * @method find
   * @param {String} str The word to find in the dictionary
   * @return {Boolean} True if the word exists in the dictionary, else false
   */
  find(str: string) {
    if (str.length == 0) {
      return false;
    }

    if (this.countWord(str) > 0) {
      return true;
    } else {
      return false;
    }
  }

  /*
   * Get all words in the dictionary
   *
   * @method getAllWords
   * @param {String} str Prefix of current word
   * @return {Array} Array of words in the dictionary
   */
  getAllWords(str: string): string[] {
    var T = this,
      k,
      child,
      ret = [];
    if (str === undefined) {
      str = "";
    }
    if (T === undefined) {
      return [];
    }
    if (T.words > 0) {
      ret.push(str);
    }
    for (k in T.children) {
      if (T.children.hasOwnProperty(k)) {
        child = T.children[k];
        ret = ret.concat(child.getAllWords(str + k));
      }
    }
    return ret;
  }

  /*
   * Autocomplete a given prefix
   *
   * @method autoComplete
   * @param {String} str Prefix to be completed based on dictionary entries
   * @param {Integer} pos Current index of the prefix
   * @return {Array} Array of possible suggestions
   */
  autoComplete(str: string, pos?: number): string[] {
    var T = this,
      k,
      child;
    if (str.length == 0) {
      if (pos === undefined) {
        return T.getAllWords(str);
      } else {
        return [];
      }
    }
    if (pos === undefined) {
      pos = 0;
    }
    k = str[pos];
    child = T.children[k];
    if (child === undefined) {
      //node doesn't exist
      return [];
    }
    if (pos === str.length - 1) {
      return child.getAllWords(str);
    }
    return child.autoComplete(str, pos + 1);
  }
}