import os, sys
sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
from lcs import lcs_length, lcs, lcs_diff


def test_empty():
    assert lcs_length([], []) == 0
    assert lcs([], [1,2]) == []
    assert lcs([1,2], []) == []


def test_identical():
    s = [1,2,3,4]
    assert lcs_length(s, s) == 4
    assert lcs(s, s) == s


def test_classic():
    a = "ABCBDAB"
    b = "BDCAB"
    assert lcs_length(a, b) == 4
    seq = lcs(a, b)
    assert len(seq) == 4
    # verify it's a subsequence of both
    def subseq(x, y):
        it = iter(y)
        return all(c in it for c in x)
    assert subseq(seq, a) and subseq(seq, b)


def test_no_common():
    assert lcs_length("abc", "xyz") == 0
    assert lcs("abc", "xyz") == []


def test_diff_roundtrip():
    a = [1, 2, 3, 4, 5]
    b = [2, 4, 6]
    ops = lcs_diff(a, b)
    # reconstruct b from a applying ops
    out = []
    for op, item in ops:
        if op in ("keep", "insert"):
            out.append(item)
        # delete: skip
    assert out == b
    # deletes+keeps should cover a
    covered = [item for op, item in ops if op in ("keep", "delete")]
    assert covered == a


def test_strings():
    assert lcs("kitten", "sitting") == list("ittn") or len(lcs("kitten","sitting"))==4
    assert lcs_length("kitten", "sitting") == 4


def test_type_error():
    try:
        lcs_length(5, [1])
        assert False, "expected TypeError"
    except TypeError:
        pass