export type Interval = [number, number];

/**
 * Uses a List of intervals to determine whether a number is in a set.
 * Intervals are [X, Y) (Start-inclusive, End-exclusive).
 */
export class Intervals {
    private _intervals: Interval[] = [];

    insert(n: Interval) {
        const newIntervals: Interval[] = [];
        for (let i of this._intervals) {
            if (!n || i[1] < n[0]) {
                newIntervals.push(i);
            } else if (i[0] > n[1]) {
                newIntervals.push(n, i);
                n = null;
            } else { // merge
                n[0] = Math.min(n[0], i[0]);
                n[1] = Math.max(n[1], i[1]);
            }
        }
        if (n && n[1] > n[0]) newIntervals.push(n);
        this._intervals = newIntervals;
        return this;
    }

    remove(n: Interval) {
        const newIntervals: Interval[] = [];
        for (let i of this._intervals) {
            if (i[0] >= n[0] && i[1] <= n[1]) {
                continue;
            } else {
                const trimEnd = (i[0] < n[0] && i[1] > n[0]);
                const trimStart = (i[1] > n[1] && i[0] < n[1]);
                if (trimEnd) {
                    newIntervals.push([i[0], n[0]]);
                }
                if (trimStart) {
                    newIntervals.push([n[1], i[1]]);
                }
                if (!trimEnd && !trimStart) newIntervals.push(i);
            }
        }
        this._intervals = newIntervals;
        return this;
    }

    contains(n: number | Interval) {
        for (let i of this._intervals) {
            if (typeof n == 'number') {
                if (i[0] <= n && n < i[1]) return true;
            } else {
                if (i[0] <= n[0] && n[1] <= i[1]) return true;
            }
        }
        return false;
    }

    breakup(n: Interval): Interval[] {
        const intervals: Interval[] = [];
        for (let i of this._intervals) {
            if (n[0] >= i[0] && n[1] <= i[1]) {
                return intervals;
            } else if (n[1] < n[0]) {
                return intervals;
            } else if (i[1] <= n[1] && i[1] >= n[0]) {
                if (i[0] > n[0]) {
                    intervals.push([n[0], i[0]]);
                }
                n[0] = i[1];
            } else if (i[0] >= n[0] && i[0] <= n[1]) {
                if (i[1] < n[1]) {
                    intervals.push([n[1], i[1]]);
                }
                n[1] = i[0];
            }
        }
        intervals.push(n);
        return intervals
    }
}