export const DEFAULT_COLOR: string = '#536dfe';

export function gcd(a: number, b: number): number {
  if (b == 0) return a;
  return gcd(b, a % b);
}

export function lcm(a: number, b: number): number {
  return a / gcd(a, b) * b;
}

/**
 * 将字符串中的 `{n}` 占位符替换为对应的参数值
 * @param str 目标字符串，若为 `null`/`undefined`/空字符串则返回原值或空串（根据需求）
 * @param args 用于替换的值列表
 * @returns 格式化后的字符串
 */
export function format(str: string, ...args: any[]): string {
  // 若 str 为假值（null/undefined/''），直接返回空字符串
  if (!str) return '';

  return str.replace(/\{(\d+)\}/g, (match, index) => {
    const idx = parseInt(index, 10);
    const value = args[idx];
    // 若参数存在且不为 null/undefined，则转为字符串，否则保留占位符
    return value != null ? String(value) : match;
  });
}

/**
 * Get Monday-first the day of week from given date instead of Sunday-first.
 * @param date The date for getting weekday.
 * @returns The zero-based weekday. 0 stands for Monday.
 */
export function getWeekday(date: Date): number {
  const day = date.getDay();
  if (day == 0) return 6;
  else return day - 1;
}

/**
 * Escape HTML special characters in the string and convert newlines to `<br />`
 * so it can be safely inserted via `v-html`. Port of the legacy jQuery-based
 * `LineBreaker2Br` (`$('<div>').text(strl).html().replace(/\n/g, '<br />')`).
 * @param strl The raw string to convert.
 * @returns The escaped, newline-broken HTML string.
 */
export function lineBreaker2Br(strl: string): string {
  return strl
    .replace(/&/g, '&amp;')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/\n/g, '<br />');
}