export const amSuffix = ' AM';
export const pmSuffix = ' PM';

export const makeTimeOptions = (
  stepMinutes: number,
  hour12: boolean,
  delimiter: string,
  minTime: string,
  maxTime: string,
  includeSeconds: boolean
) => {
  const res = [];
  const iter = new Date(new Date().setHours(0, 0, 0, 0));
  const iterDay = iter.getDay();
  while (iter.getDay() === iterDay) {
    let hour: string | number = iter.getHours();
    let suffix = amSuffix;
    if (hour12) {
      if (hour === 0) {
        hour = 12; // 12am
      } else if (hour >= 12) {
        suffix = pmSuffix;
      }
      if (hour > 12) {
        hour %= 12;
      }
    }
    hour = hour12 ? hour.toString() : hour.toString().padStart(2, '0');
    const minutes = iter.getMinutes().toString().padStart(2, '0');
    const timeOption = `${hour}${delimiter}${minutes}${hour12 ? suffix : ''}`;
    // time option is valid if within min/max constraints
    if (isWithinMinMax(minTime, maxTime, timeOption, delimiter, includeSeconds)) {
      res.push(timeOption);
    }
    iter.setMinutes(iter.getMinutes() + stepMinutes);
  }
  return res;
};

export const parseTime = (
  time: string | Date,
  timeRegex: RegExp,
  delimiter: string,
  is12Hour: boolean,
  includeSeconds: boolean
): string => {
  const date = new Date(time);

  // if default time is a ISO 8601 formatted date string, we parse it to hh:mm(am/pm) format
  if (!isNaN(date.getDate()) && (time instanceof Date || time.includes('T'))) {
    const hours = is12Hour
      ? `${date.getHours() > 12 ? date.getHours() - 12 : date.getHours()}`
      : `${date.getHours()}`.padStart(2, '0');
    const minutes = `${date.getMinutes()}`.padStart(2, '0');
    const seconds = includeSeconds ? `${date.getSeconds()}`.padStart(2, '0') : '';
    const secondsWithDelimiter = seconds ? `${delimiter}${seconds}` : '';
    let ampm = '';

    if (is12Hour && date.getHours() > 11) {
      ampm = pmSuffix;
    } else if (is12Hour) {
      ampm = amSuffix;
    }

    return `${hours}${delimiter}${minutes}${secondsWithDelimiter}${ampm}`;
  } else if (typeof time === 'string') {
    time = time.trim();
    if (time !== '' && validateTime(time, timeRegex, delimiter, is12Hour)) {
      const [, hours, minutes, seconds, suffix = ''] = timeRegex.exec(time);
      const secondsWithDelimiter = includeSeconds ? `${delimiter}${seconds ?? '00'}` : '';
      let ampm = '';

      // Format AM/PM according to design
      if (is12Hour) {
        const uppercaseSuffix = suffix.toUpperCase();

        if (uppercaseSuffix === amSuffix.toUpperCase().trim()) {
          ampm = amSuffix;
        } else if (uppercaseSuffix === pmSuffix.toUpperCase().trim()) {
          ampm = pmSuffix;
        } else {
          // if this 12 hour time is missing am/pm but otherwise valid,
          // append am/pm depending on time of day
          ampm = new Date().getHours() > 11 ? pmSuffix : amSuffix;
        }
      }

      return `${hours}${delimiter}${minutes}${secondsWithDelimiter}${ampm}`;
    }
  }
  return time.toString();
};

export const validateTime = (time: string, timeRegex: RegExp, delimiter: string, is12Hour: boolean) => {
  // ISO 8601 format is valid
  const date = new Date(time);
  if (!isNaN(date.getDate()) && time.includes('T')) {
    return true;
  }
  // hours only valid if they are [0-23] or [1-12]
  const hours = parseInt(time.split(delimiter)[0]);
  const validHours = hours >= (is12Hour ? 1 : 0) && hours <= (is12Hour ? 12 : 23);
  // minutes verified by timeRegex

  // empty string is valid
  return time === '' || (timeRegex.test(time) && validHours);
};

export const getHours = (time: string, timeRegex: RegExp) => {
  const parts = time.match(timeRegex);
  if (parts && parts.length) {
    if (/pm/i.test(parts[4])) {
      return parseInt(parts[1]) === 12 ? parseInt(parts[1]) : parseInt(parts[1]) + 12;
    }
    if (/am/i.test(parts[4])) {
      return parseInt(parts[1]) === 12 ? 0 : parseInt(parts[1]);
    }
    return parseInt(parts[1]);
  }
  return null;
};

export const getMinutes = (time: string, timeRegex: RegExp) => {
  const parts = time.match(timeRegex);
  return parts && parts.length ? parseInt(parts[2]) : null;
};

export const getSeconds = (time: string, timeRegex: RegExp) => {
  const seconds = time.match(timeRegex)?.[3];

  return seconds ? parseInt(seconds) : null;
};

export const isWithinMinMax = (
  minTime: string,
  maxTime: string,
  time: string,
  delimiter: string,
  includeSeconds?: boolean
) => {
  // do not throw error if empty string
  if (time.trim() === '') {
    return true;
  }

  // correctly format as 24hr times (12:30AM => 00:30, 1:15 => 01:15)
  const min24HourTime = convertTo24Hour(minTime, delimiter, includeSeconds);
  const selected24HourTime = convertTo24Hour(time, delimiter, includeSeconds);
  const max24HourTime = convertTo24Hour(maxTime, delimiter, includeSeconds);

  // simple string comparison for 24hr times
  return min24HourTime <= selected24HourTime && selected24HourTime <= max24HourTime;
};

const convertTo24Hour = (time: string, delimiter: string, includeSeconds: boolean): string => {
  const timeReg = new RegExp(`^\\s*(\\d\\d?)${delimiter}([0-5]\\d)${delimiter}?([0-5]\\d)?\\s*([AaPp][Mm])?\\s*$`);
  const regMatches = timeReg.exec(time);
  if (!regMatches || !regMatches.length) {
    return;
  }
  let hours = regMatches[1].padStart(2, '0');
  const minutes = regMatches[2];
  let seconds = regMatches[3] ? `${delimiter}${regMatches[3]}` : '';

  // When seconds is empty and 'includeSeconds' is enabled, append 0 seconds.
  if (!seconds && includeSeconds) {
    seconds = `${delimiter}00`;
  }

  const suffix = regMatches[4] || '';
  if (suffix.toUpperCase() === 'PM' && hours !== '12') {
    hours = `${parseInt(hours) + 12}`;
  } else if (suffix.toUpperCase() === 'AM' && hours === '12') {
    hours = '00';
  }

  return `${hours}${delimiter}${minutes}${seconds}`;
};