import { formatDistanceToNow } from 'date-fns';

/**
 * Parse and optionally convert a date string to a Date object with timezone handling
 * @param dateString - The date string to parse
 * @param isUTC - Whether to convert from UTC to local timezone (default: true)
 * @returns Processed Date object or null if invalid
 */
function parseAndConvertDate(dateString: string, isUTC: boolean = true): Date | null {
  try {
    // If isUTC is true and the date string doesn't have timezone info, treat it as UTC
    let dateToProcess = dateString;
    if (isUTC && !dateString.endsWith('Z') && !dateString.includes('+') && !dateString.includes('-', 10)) {
      dateToProcess = `${dateString}Z`;
    }
    
    const date = new Date(dateToProcess);
    
    if (isNaN(date.getTime())) {
      return null;
    }

    if (!isUTC) {
      return date;
    }

    // Get timezone from localStorage, default to Europe/Paris
    const timezone = localStorage.getItem('timezone') || 'Europe/Paris';
    
    // Format the date in the target timezone
    const formatter = new Intl.DateTimeFormat('fr-FR', {
      timeZone: timezone,
      year: 'numeric',
      month: '2-digit',
      day: '2-digit',
      hour: '2-digit',
      minute: '2-digit',
      second: '2-digit',
      hour12: false
    });

    const parts = formatter.formatToParts(date);
    const partsObj = parts.reduce((acc, part) => {
      acc[part.type] = part.value;
      return acc;
    }, {} as Record<string, string>);

    // Create new date object in the target timezone
    return new Date(
      parseInt(partsObj.year),
      parseInt(partsObj.month) - 1, // Month is 0-indexed
      parseInt(partsObj.day),
      parseInt(partsObj.hour),
      parseInt(partsObj.minute),
      parseInt(partsObj.second)
    );
  } catch (error) {
    console.error('Error parsing date:', error);
    return null;
  }
}

/**
 * Format a date string to DD/MM/YYYY HH:MM:SS or DD/MM/YYYY
 * @param dateString - The date string to format
 * @param withTime - Whether to include time in the output (default: true)
 * @param isUTC - Whether to convert from UTC to local timezone (default: true)
 * @returns Formatted date string
 */
export function formatDate(
  dateString: string,
  withTime: boolean = true,
  isUTC: boolean = true
): string {
  const date = parseAndConvertDate(dateString, isUTC);
  
  if (!date) {
    return 'Invalid Date';
  }

  const day = date.getDate().toString().padStart(2, '0');
  const month = (date.getMonth() + 1).toString().padStart(2, '0');
  const year = date.getFullYear().toString();

  const dateFormatted = `${day}/${month}/${year}`;

  if (!withTime) {
    return dateFormatted;
  }

  const hours = date.getHours().toString().padStart(2, '0');
  const minutes = date.getMinutes().toString().padStart(2, '0');
  const seconds = date.getSeconds().toString().padStart(2, '0');

  return `${dateFormatted} ${hours}:${minutes}:${seconds}`;
}

/**
 * Format a date string to show distance to now (e.g., "2 hours ago", "3 days ago")
 * @param dateString - The date string to format
 * @param isUTC - Whether to convert from UTC to local timezone (default: true)
 * @returns Formatted distance string (e.g., "2 hours ago")
 */
export function formatDateDistanceToNow(
  dateString: string,
  isUTC: boolean = true
): string {
  const date = parseAndConvertDate(dateString, isUTC);
  
  if (!date) {
    return 'Invalid Date';
  }

  return formatDistanceToNow(date, { addSuffix: true });
}

/**
 * Format a date string with timezone consideration
 * @param dateString - The date string to format
 * @param timezone - The target timezone (default: 'UTC')
 * @returns Formatted date string with timezone
 */
export function formatDateTime(dateString: string, timezone: string = 'UTC'): string {
  try {
    const date = new Date(dateString)
    
    if (isNaN(date.getTime())) {
      return 'Invalid Date'
    }

    const formatter = new Intl.DateTimeFormat('fr-FR', {
      timeZone: timezone,
      year: 'numeric',
      month: '2-digit',
      day: '2-digit',
      hour: '2-digit',
      minute: '2-digit',
      hour12: false,
    })

    return formatter.format(date)
  } catch {
    return 'Invalid Date'
  }
}