import type { NumberArray } from 'cheminfo-types';

export interface XIsEquallySpacedOptions {
  /**
   * The tolerance define what is the allowed difference in percent
   * @default: 0.05
   */
  tolerance?: number;
}

/**
 * Check if the values are separated always by the same difference
 * @param array - Monotone growing array of number
 * @param options
 */
export function xIsEquallySpaced(
  array: NumberArray,
  options: XIsEquallySpacedOptions = {},
): boolean {
  if (array.length < 3) return true;
  const { tolerance = 0.05 } = options;
  let maxDx = 0;
  let minDx = Number.MAX_SAFE_INTEGER;
  for (let i = 0; i < array.length - 1; ++i) {
    const absoluteDifference = array[i + 1] - array[i];
    if (absoluteDifference < minDx) {
      minDx = absoluteDifference;
    }
    if (absoluteDifference > maxDx) {
      maxDx = absoluteDifference;
    }
  }
  return (maxDx - minDx) / maxDx < tolerance;
}