frontend/src/utils/timezoneUtils.js

/**
 * Timezone utility functions for the frontend scheduling system.
 */

/**
 * Parse a timezone-prefixed schedule time string and extract the time part.
 * @param {string} scheduleTime - Schedule time in format "Day HH:MM::::timezone" or "Day HH:MM"
 * @returns {string} Time part without timezone
 */
export const parseScheduleTime = (scheduleTime) => {
  if (!scheduleTime) return scheduleTime;
  
  if (scheduleTime.includes('::::')) {
    return scheduleTime.split('::::')[0];
  }
  
  // Legacy format without timezone
  return scheduleTime;
};

/**
 * Get the user's timezone from the browser.
 * @returns {string} Timezone string (e.g., "America/New_York")
 */
export const getUserTimezone = () => {
  try {
    return Intl.DateTimeFormat().resolvedOptions().timeZone;
  } catch (error) {
    console.error('Error getting timezone:', error);
    return 'UTC'; // Fallback
  }
};

/**
 * Format a schedule time for display (day and time only, no timezone).
 * @param {string} scheduleTime - Schedule time string
 * @returns {string} Formatted time for display
 */
export const formatScheduleForDisplay = (scheduleTime) => {
  const parsedTime = parseScheduleTime(scheduleTime);
  if (!parsedTime) return '';
  
  // Split into day and time parts
  const parts = parsedTime.trim().split(' ');
  if (parts.length >= 2) {
    const day = parts[0];
    const time = parts[1];
    return `${day} ${time}`;
  }
  
  return parsedTime;
};

/**
 * Check if a schedule time has timezone information.
 * @param {string} scheduleTime - Schedule time string
 * @returns {boolean} True if timezone is included
 */
export const hasTimezone = (scheduleTime) => {
  return scheduleTime && scheduleTime.includes('::::');
};

/**
 * Extract timezone from a schedule time string.
 * @param {string} scheduleTime - Schedule time string
 * @returns {string|null} Timezone string or null if not present
 */
export const extractTimezone = (scheduleTime) => {
  if (!scheduleTime || !scheduleTime.includes('::::')) {
    return null;
  }
  
  return scheduleTime.split('::::')[1]?.trim() || null;
};