import struct

import pytest

import sys
from pathlib import Path

sys.path.insert(0, str(Path(__file__).parent.parent))

from protocol_parser import ProtocolParser


def build_packet(timestamp_ms: int, rms_db_x10: int, freq_hz: int) -> bytes:
    sof = bytes([ProtocolParser.SOF])
    header = bytes([ProtocolParser.TYPE_AUDIO_V1, ProtocolParser.PAYLOAD_LEN])
    payload = struct.pack("<IhH", timestamp_ms, rms_db_x10, freq_hz)

    crc_data = header + payload  # bytes 1..10 in the wire format
    crc = ProtocolParser._crc8_atm(crc_data)

    return sof + header + payload + bytes([crc])


def test_valid_packet():
    p = ProtocolParser()
    raw = build_packet(timestamp_ms=1234, rms_db_x10=-123, freq_hz=440)

    packets = p.feed(raw)

    assert len(packets) == 1
    pkt = packets[0]
    assert pkt.valid is True
    assert pkt.timestamp_ms == 1234
    assert pkt.rms_db == -12.3
    assert pkt.freq_hz == 440

    st = p.get_stats()
    assert st.packets_received == 1
    assert st.crc_errors == 0


def test_bad_crc_packet():
    p = ProtocolParser()
    raw = bytearray(build_packet(timestamp_ms=1, rms_db_x10=-10, freq_hz=1000))
    raw[-1] ^= 0xFF  # ломаем CRC

    packets = p.feed(bytes(raw))

    assert packets == []
    st = p.get_stats()
    assert st.packets_received == 0
    assert st.crc_errors == 1


def test_garbage_then_valid_packet_resync():
    p = ProtocolParser()

    garbage = b"\x00\xff\xaa\x01\x02\x03\x04"  # содержит ложный SOF и мусор
    raw = garbage + build_packet(timestamp_ms=777, rms_db_x10=-321, freq_hz=1234)

    packets = p.feed(raw)

    assert len(packets) == 1
    assert packets[0].timestamp_ms == 777
    assert packets[0].rms_db == -32.1
    assert packets[0].freq_hz == 1234
    assert p.get_stats().length_errors >= 1  # парсер должен "проглотить" мусор


def test_two_packets_in_one_chunk():
    p = ProtocolParser()

    raw = build_packet(timestamp_ms=10, rms_db_x10=-100, freq_hz=500) + build_packet(
        timestamp_ms=20, rms_db_x10=-200, freq_hz=600
    )

    packets = p.feed(raw)

    assert len(packets) == 2
    assert packets[0].timestamp_ms == 10
    assert packets[1].timestamp_ms == 20