export interface FormatUnixTimestampResult {
  time: string;
  timezone: string;
}


export const formatUnixTimestamp = (
  timestamp: number,
  locale?: string | string[],
  options?: Intl.DateTimeFormatOptions
): FormatUnixTimestampResult => {
  const milliseconds = timestamp * 1000;
  
  const date = new Date(milliseconds);
  
  const formattedTime = date.toLocaleString(locale, options);

  // Calculate UTC offset in hours
  // getTimezoneOffset() returns offset in minutes (negative if ahead of UTC)
  const offsetMinutes = date.getTimezoneOffset();
  const offsetHours = -offsetMinutes / 60;
  const offsetSign = offsetHours >= 0 ? '+' : '-';
  const offsetAbs = Math.abs(offsetHours);
  
  // Format as UTC +2 or UTC -5 (with space and sign)
  let timezone: string;
  if (options?.timeZone) {
    // If a specific timezone is requested, calculate offset for that timezone
    try {
      // Get the offset for the specified timezone
      const formatter = new Intl.DateTimeFormat('en', {
        timeZone: options.timeZone,
        timeZoneName: 'shortOffset'
      });
      const parts = formatter.formatToParts(date);
      const offsetPart = parts.find(part => part.type === 'timeZoneName');
      
      if (offsetPart?.value) {
        // Format like "GMT+2" or "GMT-5"
        timezone = offsetPart.value.replace('GMT', 'UTC');
      } else {
        // Fallback: calculate offset manually
        const utcTime = date.getTime() + (date.getTimezoneOffset() * 60000);
        const tzDate = new Date(utcTime);
        const tzFormatter = new Intl.DateTimeFormat('en', {
          timeZone: options.timeZone,
          hour: '2-digit',
          hour12: false
        });
        const utcFormatter = new Intl.DateTimeFormat('en', {
          timeZone: 'UTC',
          hour: '2-digit',
          hour12: false
        });
        const tzHour = parseInt(tzFormatter.format(tzDate));
        const utcHour = parseInt(utcFormatter.format(tzDate));
        const tzOffset = tzHour - utcHour;
        const tzSign = tzOffset >= 0 ? '+' : '-';
        const tzAbs = Math.abs(tzOffset);
        timezone = `UTC ${tzSign}${tzAbs}`;
      }
    } catch {
      // Fallback to browser timezone
      timezone = `UTC ${offsetSign}${offsetAbs}`;
    }
  } else {
    // Use browser's timezone offset
    timezone = `UTC ${offsetSign}${offsetAbs}`;
  }
  
  return {
    time: formattedTime,
    timezone,
  };
};