from meshbot.messages import trim_to_bytes


def test_short_ascii_passthrough():
    assert trim_to_bytes("hello", 184) == "hello"


def test_exact_fit_passthrough():
    s = "a" * 184
    assert trim_to_bytes(s, 184) == s


def test_long_ascii_clean_cut():
    s = "x" * 200
    out = trim_to_bytes(s, 184)
    assert len(out.encode("utf-8")) == 184
    assert out == "x" * 184


def test_emoji_does_not_split():
    # Each 🎉 is 4 UTF-8 bytes. Limit of 5 must keep just one emoji (4 bytes), not 5.
    out = trim_to_bytes("🎉🎉", 5)
    assert out == "🎉"
    assert len(out.encode("utf-8")) == 4


def test_multibyte_at_boundary():
    # "ä" is 2 bytes in UTF-8. With a 3-byte budget for "aä" (3 bytes total), we keep both.
    assert trim_to_bytes("aä", 3) == "aä"
    # With a 2-byte budget we can only keep the leading "a".
    assert trim_to_bytes("aä", 2) == "a"


def test_zero_or_negative_max_bytes():
    assert trim_to_bytes("anything", 0) == ""
    assert trim_to_bytes("anything", -1) == ""


def test_empty_input():
    assert trim_to_bytes("", 184) == ""