@specs-feup/lara/src-api/lara/util/Accumulator.ts

A js port of the popular framework for building source-to-source compilers

/**
 * Counts occurrences of tuples.
 */

export default class Accumulator {
  value = 0;
  accs: { [key: string]: Accumulator } = {};
  seenKeys = new Set<string>();

  /**
   * Adds the tuple to the accumulator. Each time a tuple is added, the corresponding value increments by 1.
   *
   * Alternatively, can also receive an array with the chain of values
   *
   * @returns the previous count of the added element
   */

  add(...args: any[]): number {
    let currentAcc: Accumulator = this;
    const argsParsed = this.parseArguments(args);

    // Travel chain of values
    for (const chainElement of argsParsed) {
      let nextAcc: Accumulator | undefined = currentAcc.accs[chainElement];

      // If no accumulator, create
      if (nextAcc === undefined) {
        nextAcc = new Accumulator();
        currentAcc.accs[chainElement] = nextAcc;
        currentAcc.seenKeys.add(chainElement);
      }

      // Update acc
      currentAcc = nextAcc;
    }

    // Store previous value
    const previousValue: number = currentAcc.value;

    // Increment acc value
    currentAcc.value++;

    return previousValue;
  }

  /**
   * Adds the value associated to the given tuple. If no value is defined for the given tuple, returns 0.
   * <p>
   * Alternatively, can also receive an array with the chain of values
   */
  get(...args: any) {
    const chainArray: string[] = this.parseArguments(arguments);

    let currentAcc: Accumulator = this;

    // Travel chain of values
    for (const chainElement of chainArray) {
      const nextAcc: Accumulator = currentAcc.accs[chainElement];

      // If no accumulator, return 0
      if (nextAcc === undefined) {
        return 0;
      }

      // Update acc
      currentAcc = nextAcc;
    }

    // Return acc value
    return currentAcc.value;
  }

  copy(...args: any) {
    let copy: Accumulator = new Accumulator();

    for (const key of this.keys()) {
      const value: number = this.get(key);

      // TODO: Not efficient, should have a method to internally set a value   ---OLD---
      for (let i = 0; i < value; i++) {
        copy.add(key);
      }
    }

    return copy;
  }

  /**
   * Returns an array of arrays with keys that have a value set.
   */
  keys() {
    const chains: Array<Array<string>> = [];
    const currentChain: Array<string> = [];

    this.keysPrivate(currentChain, chains);
    return chains;
  }

  private keysPrivate(
    currentChain: Array<string>,
    chains: Array<Array<string>>
  ) {
    // If this accumulator has a value, add current chain
    if (this.value > 0) {
      chains.push(currentChain);
    }

    for (const key of this.seenKeys) {
      const updatedChain = currentChain.concat(key);

      const nextAcc = this.accs[key];

      if (nextAcc === undefined) {
        continue;
      }
      nextAcc.keysPrivate(updatedChain, chains);
    }
  }

  /**
   * Receives an array with the arguments of the previous function.
   */
  private parseArguments(...args: any[]) {
    if (args.length !== 1) {
      throw "Accumulator._parseArguments: Expected arguments to have length 1";
    }

    let functionArguments = args[0];

    // If one argument and array, return it
    if (
      functionArguments.length === 1 &&
      functionArguments[0].constructor === Array
    ) {
      // Retrive the array in the previous arguments
      return functionArguments[0];
    }

    // Transform arguments into array
    return Array.from(functionArguments);
  }
}