/**
 * Date Utilities - Core Module
 *
 * Framework-agnostic date manipulation and formatting functions.
 * Can be used in any project (NestJS, Express, Frontend, etc.)
 *
 * @module @shared/utils/date
 * @version 1.0.0
 */

/**
 * Format date to ISO string
 */
export const formatToISO = (date: Date): string => {
  return date.toISOString();
};

/**
 * Format date to readable string (YYYY-MM-DD)
 */
export const formatToDate = (date: Date): string => {
  return date.toISOString().split('T')[0];
};

/**
 * Format date to datetime string (YYYY-MM-DD HH:mm:ss)
 */
export const formatToDateTime = (date: Date): string => {
  return date.toISOString().replace('T', ' ').split('.')[0];
};

/**
 * Format date with custom pattern
 * @param date - Date to format
 * @param pattern - Pattern (YYYY, MM, DD, HH, mm, ss)
 */
export const formatDate = (date: Date, pattern: string): string => {
  const pad = (n: number): string => n.toString().padStart(2, '0');

  return pattern
    .replace('YYYY', date.getFullYear().toString())
    .replace('MM', pad(date.getMonth() + 1))
    .replace('DD', pad(date.getDate()))
    .replace('HH', pad(date.getHours()))
    .replace('mm', pad(date.getMinutes()))
    .replace('ss', pad(date.getSeconds()));
};

/**
 * Add days to a date
 */
export const addDays = (date: Date, days: number): Date => {
  const result = new Date(date);
  result.setDate(result.getDate() + days);
  return result;
};

/**
 * Add hours to a date
 */
export const addHours = (date: Date, hours: number): Date => {
  const result = new Date(date);
  result.setHours(result.getHours() + hours);
  return result;
};

/**
 * Add minutes to a date
 */
export const addMinutes = (date: Date, minutes: number): Date => {
  const result = new Date(date);
  result.setMinutes(result.getMinutes() + minutes);
  return result;
};

/**
 * Add months to a date
 */
export const addMonths = (date: Date, months: number): Date => {
  const result = new Date(date);
  result.setMonth(result.getMonth() + months);
  return result;
};

/**
 * Check if date is in the past
 */
export const isPast = (date: Date): boolean => {
  return date < new Date();
};

/**
 * Check if date is in the future
 */
export const isFuture = (date: Date): boolean => {
  return date > new Date();
};

/**
 * Get start of day (00:00:00.000)
 */
export const startOfDay = (date: Date): Date => {
  const result = new Date(date);
  result.setHours(0, 0, 0, 0);
  return result;
};

/**
 * Get end of day (23:59:59.999)
 */
export const endOfDay = (date: Date): Date => {
  const result = new Date(date);
  result.setHours(23, 59, 59, 999);
  return result;
};

/**
 * Get start of month
 */
export const startOfMonth = (date: Date): Date => {
  const result = new Date(date);
  result.setDate(1);
  result.setHours(0, 0, 0, 0);
  return result;
};

/**
 * Get end of month
 */
export const endOfMonth = (date: Date): Date => {
  const result = new Date(date);
  result.setMonth(result.getMonth() + 1, 0);
  result.setHours(23, 59, 59, 999);
  return result;
};

/**
 * Get difference in days between two dates
 */
export const diffInDays = (date1: Date, date2: Date): number => {
  const diff = Math.abs(date1.getTime() - date2.getTime());
  return Math.ceil(diff / (1000 * 60 * 60 * 24));
};

/**
 * Get difference in hours between two dates
 */
export const diffInHours = (date1: Date, date2: Date): number => {
  const diff = Math.abs(date1.getTime() - date2.getTime());
  return Math.ceil(diff / (1000 * 60 * 60));
};

/**
 * Get difference in minutes between two dates
 */
export const diffInMinutes = (date1: Date, date2: Date): number => {
  const diff = Math.abs(date1.getTime() - date2.getTime());
  return Math.ceil(diff / (1000 * 60));
};

/**
 * Check if two dates are the same day
 */
export const isSameDay = (date1: Date, date2: Date): boolean => {
  return (
    date1.getFullYear() === date2.getFullYear() &&
    date1.getMonth() === date2.getMonth() &&
    date1.getDate() === date2.getDate()
  );
};

/**
 * Parse ISO string to Date
 */
export const parseISO = (isoString: string): Date => {
  return new Date(isoString);
};

/**
 * Check if string is valid date
 */
export const isValidDate = (dateString: string): boolean => {
  const date = new Date(dateString);
  return !isNaN(date.getTime());
};

/**
 * Get relative time description (e.g., "2 hours ago")
 */
export const getRelativeTime = (date: Date): string => {
  const now = new Date();
  const diffMs = now.getTime() - date.getTime();
  const diffSec = Math.floor(diffMs / 1000);
  const diffMin = Math.floor(diffSec / 60);
  const diffHour = Math.floor(diffMin / 60);
  const diffDay = Math.floor(diffHour / 24);

  if (diffSec < 60) return 'just now';
  if (diffMin < 60) return `${diffMin} minute${diffMin > 1 ? 's' : ''} ago`;
  if (diffHour < 24) return `${diffHour} hour${diffHour > 1 ? 's' : ''} ago`;
  if (diffDay < 30) return `${diffDay} day${diffDay > 1 ? 's' : ''} ago`;

  return formatToDate(date);
};

/**
 * Get Unix timestamp (seconds since epoch)
 */
export const toUnixTimestamp = (date: Date): number => {
  return Math.floor(date.getTime() / 1000);
};

/**
 * Create date from Unix timestamp
 */
export const fromUnixTimestamp = (timestamp: number): Date => {
  return new Date(timestamp * 1000);
};

/**
 * Check if date is today
 */
export const isToday = (date: Date): boolean => {
  return isSameDay(date, new Date());
};

/**
 * Check if date is yesterday
 */
export const isYesterday = (date: Date): boolean => {
  const yesterday = addDays(new Date(), -1);
  return isSameDay(date, yesterday);
};

/**
 * Get age from birthdate
 */
export const getAge = (birthDate: Date): number => {
  const today = new Date();
  let age = today.getFullYear() - birthDate.getFullYear();
  const monthDiff = today.getMonth() - birthDate.getMonth();

  if (monthDiff < 0 || (monthDiff === 0 && today.getDate() < birthDate.getDate())) {
    age--;
  }

  return age;
};