import parseTimeToMinutes from './parseTimeToMinutes.js'
/**
 * Merges overlapping intervals in an array of time intervals.
 *
 * This function takes an array of time intervals, where each interval is represented as a tuple of
 * start and end times in "HH:MM" format or as a single number in hours. It merges any overlapping
 * intervals to produce a minimal set of intervals.
 *
 * @param {Array<Array<string>>} intervals - An array of tuples representing the time intervals.
 * @returns {Array<Array<string>>} A new array of tuples with merged intervals in "HH:MM" format.
 */
const mergeIntervals = (intervals) => {
  // Convert all intervals to minutes for easier comparison and sorting.
  const parsedIntervals = intervals.map(([
    start,
    end,
  ]) => [
    parseTimeToMinutes(start),
    parseTimeToMinutes(end),
  ])

  // Sort intervals based on the start time to prepare for merging.
  parsedIntervals.sort((
    a, b,
  ) => a[0] - b[0])

  const merged = [] // This array will hold the merged intervals.
  let currentInterval = parsedIntervals[0] // Start with the first interval.

  // for (let i = 1; i < parsedIntervals.length; i++) {
  parsedIntervals.forEach((interval) => {
    const [
      currentStart,
      currentEnd,
    ] = currentInterval
    const [
      nextStart,
      nextEnd,
    ] = interval

    if (currentEnd >= nextStart) {
      // If the current and next intervals overlap, merge them.
      currentInterval = [
        currentStart,
        Math.max(
          currentEnd, nextEnd,
        ),
      ]
    } else {
      // If they don't overlap, push the current interval to the result and move to the next.
      merged.push(currentInterval)
      currentInterval = interval
    }
  })

  // Don't forget to add the last interval to the result.
  merged.push(currentInterval)

  // Convert the merged intervals back to "HH:MM" format.
  return merged.map(([
    start,
    end,
  ]) => [
    `${Math.floor(start / 60)
      .toString()
      .padStart(
        2, '0',
      )}:${(start % 60).toString().padStart(
      2, '0',
    )}`,
    `${Math.floor(end / 60)
      .toString()
      .padStart(
        2, '0',
      )}:${(end % 60).toString().padStart(
      2, '0',
    )}`,
  ])
}

/**
 * Example usage:
 * const intervals = [["04:04", "15:01"], ["8:00", "10:30"], ...];
 * const mergedIntervals = mergeIntervals(intervals);
 * console.log(mergedIntervals); // Prints the merged intervals
 */

export default mergeIntervals