const mts = 1000; // millis to seconds
const mtm = 1000 * 60; // millis to minutes
const mth = 1000 * 60 * 60; // millis to hours

export const timeFormat = 'HH:mm';
export const timeFormatSeconds = 'HH:mm:ss';
export const DAY_TO_MS = 86400000;

/**
 * @description Validates a time string
 * @param {string} string - time string "23:00:12"
 * @returns {boolean} string represents time
 */
export const isTimeString = (string) => {
  // ^                   # Start of string
  // (?:                 # Try to match...
  //  (?:                #  Try to match...
  //   ([01]?\d|2[0-3]): #   HH:
  //  )?                 #  (optionally).
  //  ([0-5]?\d):        #  MM: (required)
  // )?                  # (entire group optional, so either HH:MM:, MM: or nothing)
  // ([0-5]?\d)          # SS (required)
  // $                   # End of string

  const regex = /^(?:(?:([01]?\d|2[0-3])[:,.])?([0-5]?\d)[:,.])?([0-5]?\d)$/;
  return regex.test(string);
};

/**
 * @description Converts an excel date to milliseconds
 * @argument {string} date - excel string date
 * @returns {number} - time in milliseconds
 */
export const dateToMillis = (date) => {
  const h = date.getHours();
  const m = date.getMinutes();
  const s = date.getSeconds();

  return h * mth + m * mtm + s * mts;
};

/**
 * @description safe parse string to int, copied from client code
 * @param valueAsString
 * @return {number}
 */
const parse = (valueAsString) => {
  const parsed = parseInt(valueAsString, 10);
  if (isNaN(parsed)) {
    return 0;
  }
  return Math.abs(parsed);
};

/**
 * @description Parses a time string to millis, copied from client code
 * @param {string} value - time string
 * @param {boolean} fillLeft - autofill left = hours / right = seconds
 * @returns {number} - time string in millis
 */
export const forgivingStringToMillis = (value, fillLeft = true) => {
  let millis = 0;

  // split string at known separators    : , .
  const separatorRegex = /[\s,:.]+/;
  const [first, second, third] = value.split(separatorRegex);

  if (first != null && second != null && third != null) {
    // if string has three sections, treat as [hours] [minutes] [seconds]
    millis = parse(first) * mth;
    millis += parse(second) * mtm;
    millis += parse(third) * mts;
  } else if (first != null && second == null && third == null) {
    // if string has one section,
    // could be a complete string like 121010 - 12:10:10
    if (first.length === 6) {
      const hours = first.substring(0, 2);
      const minutes = first.substring(2, 4);
      const seconds = first.substring(4);
      millis = parse(hours) * mth;
      millis += parse(minutes) * mtm;
      millis += parse(seconds) * mts;
    } else {
      // otherwise lets treat as [minutes]
      millis = parse(first) * mtm;
    }
  }
  if (first != null && second != null && third == null) {
    // if string has two sections
    if (fillLeft) {
      // treat as [hours] [minutes]
      millis = parse(first) * mth;
      millis += parse(second) * mtm;
    } else {
      // treat as [minutes] [seconds]
      millis = parse(first) * mtm;
      millis += parse(second) * mts;
    }
  }
  return millis;
};

/**
 * @description Parses an excel date using the correct parser
 * @param {string} excelDate
 * @returns {number} - time in milliseconds

 */
export const parseExcelDate = (excelDate) => {
  // attempt converting to date object
  const date = new Date(excelDate);
  if (date instanceof Date && !isNaN(date)) {
    return dateToMillis(date);
  } else if (isTimeString(excelDate)) {
    return forgivingStringToMillis(excelDate);
  }
  return 0;
};