"""Merge overlapping intervals.

merge_intervals(intervals) -> list of [start, end] (inclusive endpoints).
Accepts any iterable of (start, end) pairs. Sorts by start then end.
Handles empty, single, touching (adjacent) intervals per `merge_touching`.
"""
from __future__ import annotations
from typing import Iterable, Tuple, List


def merge_intervals(intervals: Iterable[Tuple[int, int]], *, merge_touching: bool = False) -> List[List[int]]:
    items = sorted((tuple(x) for x in intervals), key=lambda p: (p[0], p[1]))
    if not items:
        return []
    out: List[List[int]] = [list(items[0])]
    for s, e in items[1:]:
        last = out[-1]
        threshold = last[1] + (1 if merge_touching else 0)
        if s <= threshold:
            if e > last[1]:
                last[1] = e
        else:
            out.append([s, e])
    return out