import pytest

from smartthings_local.errors import MalformedMessageError
from smartthings_local.protocol.coap import (
    build_coap, parse_coap, encode_options, block_value, block_fields,
    fmt_code,
    TYPE_CON, METHOD_GET, URI_PATH, ACCEPT, CF_CBOR, BLOCK2,
)


def test_build_then_parse_roundtrip_no_payload():
    opts = [(URI_PATH, b'device'), (URI_PATH, b'0'), (ACCEPT, CF_CBOR)]
    datagram = build_coap(TYPE_CON, METHOD_GET, 0xABCD, b'\x01\x02', opts)
    mtype, code, mid, tok, parsed_opts, payload = parse_coap(datagram)
    assert mtype == TYPE_CON
    assert code == METHOD_GET
    assert mid == 0xABCD
    assert tok == b'\x01\x02'
    assert payload == b''
    assert sorted(parsed_opts) == sorted(opts)


def test_build_then_parse_roundtrip_with_payload():
    datagram = build_coap(TYPE_CON, 0x45, 1, b'\xff', [], payload=b'\xa1\x01\x02')
    _, code, _, _, _, payload = parse_coap(datagram)
    assert code == 0x45
    assert payload == b'\xa1\x01\x02'


def test_encode_options_orders_by_option_number():
    # ACCEPT (17) must be encoded after URI_PATH (11) regardless of input order
    encoded_in_order = encode_options([(URI_PATH, b'x'), (ACCEPT, CF_CBOR)])
    encoded_reversed = encode_options([(ACCEPT, CF_CBOR), (URI_PATH, b'x')])
    assert encoded_in_order == encoded_reversed


def test_block_value_encodes_num_more_szx():
    # num=2, more=1, szx=6 -> (2<<4)|(1<<3)|6 = 0x2E
    assert block_value(2, 1, 6) == bytes([0x2E])


def test_block_value_promotes_to_two_bytes_when_num_is_large():
    v = block_value(num=0xFFF, more=0, szx=0)
    assert len(v) == 2


@pytest.mark.parametrize('num, more, szx', [
    (0, 0, 0),
    (0, 1, 6),
    (2, 1, 6),
    (1, 0, 4),
    (0xFFF, 0, 0),
    (0xFFFFF, 1, 7),
])
def test_block_fields_inverts_block_value(num, more, szx):
    assert block_fields(block_value(num, more, szx)) == (num, more, szx)


def test_block_fields_treats_empty_value_as_block_zero():
    # RFC 7959 §2.2: a zero-length Block option means num=0, m=0, szx=0.
    assert block_fields(b'') == (0, 0, 0)


def test_fmt_code_formats_class_dot_detail():
    assert fmt_code(0x45) == '2.05'
    assert fmt_code(0x84) == '4.04'


@pytest.mark.parametrize('option_header', (b'\xf0', b'\x0f'))
def test_reserved_option_nibbles_raise_classified_value_error(option_header):
    datagram = b'\x40\x01\x00\x01' + option_header

    with pytest.raises(MalformedMessageError) as exc:
        parse_coap(datagram)

    assert isinstance(exc.value, ValueError)