from connection.message_codec import BYTE_ORDER, MESSAGE_SIZE_BYTES, MESSAGE_TYPE_BYTES, encode_message


class TestEncodeMessage:
    def test_encodes_empty_payload(self):
        result = encode_message(message_type=1, message=b"")

        expected_size = MESSAGE_TYPE_BYTES.to_bytes(MESSAGE_SIZE_BYTES, byteorder=BYTE_ORDER)
        expected_type = (1).to_bytes(MESSAGE_TYPE_BYTES, byteorder=BYTE_ORDER)
        assert result == expected_size + expected_type

    def test_encodes_payload(self):
        payload = b"\x0a\x0b\x0c"
        result = encode_message(message_type=42, message=payload)

        expected_size = (MESSAGE_TYPE_BYTES + len(payload)).to_bytes(MESSAGE_SIZE_BYTES, byteorder=BYTE_ORDER)
        expected_type = (42).to_bytes(MESSAGE_TYPE_BYTES, byteorder=BYTE_ORDER)
        assert result == expected_size + expected_type + payload

    def test_size_field_excludes_itself(self):
        payload = b"\xff"
        result = encode_message(message_type=0, message=payload)

        size_field = int.from_bytes(result[:MESSAGE_SIZE_BYTES], byteorder=BYTE_ORDER)
        assert size_field == MESSAGE_TYPE_BYTES + len(payload)