/**
 * @copyright NHCarrigan
 * @license Naomi's Public License
 * @author Naomi Carrigan
 */

/**
 * Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
 * 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
 * By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
 * @param limit - The limit to find the Fibonacci sequence below.
 * @returns The sum of the even-valued terms in the Fibonacci sequence below the limit.
 * @see https://www.freecodecamp.org/learn/project-euler/project-euler-problems-1-to-100/problem-2-even-fibonacci-numbers
 */
export const fiboEvenSum = (limit: number): number => {
  let current = 3,
    previous = 2,
    sum = 2;

  while (current <= limit) {
    if (current % 2 === 0) {
      sum = sum + current;
    }
    const next = current + previous;
    previous = current;
    current = next;
  }
  return sum;
};