// In the context of merging the intervals Array, using the SOLID (OCP) principles by creating an IntervalMerger class that follows the (OCP) rules that suggests that software entities (classes, modules, functions, etc.) should be open for extension but closed for modification.

class IntervalMerger {
  merge(intervals) {
    if (intervals.length <= 1) return intervals;
    
    const mergedIntervals = [];
    intervals.sort((a, b) => a[0] - b[0]);
    
    intervals.forEach(function (currentInterval, i) {
      
      const previousInterval = //Conditional (ternary) operator
        i > 0 ? mergedIntervals[mergedIntervals.length - 1] : 0;
      
      if (currentInterval[0] <= previousInterval[1]) {
        previousInterval[1] = Math.max(previousInterval[1], currentInterval[1]);
      } else {
        mergedIntervals.push(currentInterval);
      }
      
    });
    
    return mergedIntervals;
  }
}

const intervals = [[1, 3],[2, 6],[8, 10],[15, 18]];
const intervalMerger = new IntervalMerger();
const updatedIntervals = intervalMerger.merge(intervals);

// output
console.log(updatedIntervals);
console.log(`Updated Intervals: ${JSON.stringify(updatedIntervals)}`);
document.getElementById("output").innerHTML = `Updated Intervals: ${JSON.stringify(updatedIntervals)}`;


// old version 

/*
class IntervalMerger {
    merge(intervals) {
        if (intervals.length <= 1) return intervals;

        intervals.sort((a, b) => a[0] - b[0]);

        const mergedIntervals = [intervals[0]];

        for (let i = 1; i < intervals.length; i++) {
            const currentInterval = intervals[i];
            const previousInterval = mergedIntervals[mergedIntervals.length - 1];

            if (currentInterval[0] <= previousInterval[1]) {
                previousInterval[1] = Math.max(previousInterval[1], currentInterval[1]);
            } else {
                mergedIntervals.push(currentInterval);
            }
        }

        return mergedIntervals;
    }
}
*/