import type { TRadian } from '../../typedefs';
import { halfPI } from '../../constants';

/**
 * Calculate the cos of an angle, avoiding returning floats for known results
 * This function is here just to avoid getting 0.999999999999999 when dealing
 * with numbers that are really 1 or 0.
 * @param {TRadian} angle the angle
 * @return {Number} the cosin value for angle.
 */
export const cos = (angle: TRadian): number => {
  if (angle === 0) {
    return 1;
  }
  const angleSlice = Math.abs(angle) / halfPI;
  switch (angleSlice) {
    case 1:
    case 3:
      return 0;
    case 2:
      return -1;
  }
  return Math.cos(angle);
};