"""Tests for interval_merge.merge_intervals / total_covered / gaps.

Runs from this directory only:
    python3 test_interval.py

Q162 / 2026-11-03: the module is resolved from THIS file's directory and from
nowhere else. The file landed at 33e8ffb with

    sys.path.insert(0, "/root/.hermes/wizard-outputs/beam")

which put a HOST directory first on sys.path, so every cell below graded
/root/.hermes/wizard-outputs/beam/interval_merge.py and never the committed
bytes. Measured before the fix: with the copy beside this test overwritten by a
stand-in whose three functions answer wrongly on every input
(wizard-work/volt/q162-interval-binding/poison_interval.py), the suite still
printed `ALL TESTS PASS`, rc 0, because the imported module was the host file.
The assertion below makes the binding a fact rather than an intention (the rule
test_toposort.py states at Q61, test_lfu_cache.py at Q98, and
test_tarjan_articulation.py at Q160).
"""
import pathlib
import random
import sys

HERE = pathlib.Path(__file__).resolve().parent
sys.path.insert(0, str(HERE))

import interval_merge as module_under_test
from interval_merge import merge_intervals, total_covered, gaps

# The module under test must be the committed file next to this test.
MODULE_PATH = pathlib.Path(module_under_test.__file__).resolve()
assert MODULE_PATH == (HERE / "interval_merge.py"), (MODULE_PATH, HERE)


def brute_merge(intervals):
    pts = set()
    # discrete integer points model for small ranges
    pts_all = set()
    for s, e in intervals:
        for x in range(s, e):
            pts_all.add(x)
    if not pts_all:
        return []
    # build runs
    out = []
    for x in sorted(pts_all):
        if not out or x != out[-1][1]:
            out.append([x, x+1])
        else:
            out[-1][1] = x+1
    return [tuple(r) for r in out]

random.seed(42)
for trial in range(2000):
    n = random.randint(0, 8)
    ivs = []
    for _ in range(n):
        s = random.randint(-5, 5)
        e = s + random.randint(1, 6)
        ivs.append((s, e))
    got = merge_intervals(ivs)
    exp = brute_merge(ivs)
    assert got == exp, (ivs, got, exp)

# total_covered
assert total_covered([(1,4),(3,6),(10,12)]) == (6-1)+(12-10)  # 5+2=7? 1..6 =5, 10..12=2 =>7
assert total_covered([]) == 0

# gaps
assert gaps([(2,4)], 0, 6) == [(0,2),(4,6)]
assert gaps([(0,6)], 0, 6) == []
assert gaps([], 0, 3) == [(0,3)]

# validation
for bad in [((1,1),(2,3)), (1,2,3), (True,5), (1,True), ("a",2), (2,1)]:
    try:
        merge_intervals([bad] if not isinstance(bad[0], tuple) or len(bad)!=2 or not isinstance(bad[0], int) else [bad])
    except ValueError:
        pass
    else:
        # some cases may be wrapped; ensure at least invalid ones raise
        pass

# explicit invalid
for bad in [(1,1),(2,1),(True,3),(1,True)]:
    try:
        merge_intervals([bad])
        raise AssertionError(f"no raise for {bad}")
    except ValueError:
        pass

print("ALL TESTS PASS")