#!/usr/bin/env python3
"""Конвертер дампа USBPcap (pcapng) → лог control-трансферов SET/GET_REPORT.

Использование: ./analyze_pcap.py <capture.pcapng> [out.txt]
"""
import struct
import sys

# тип блока Enhanced Packet в pcapng
BLOCK_ENHANCED_PACKET = 6
# тип transfer'а control в USBPcap
XFER_CONTROL = 2
# биты направления в endpoint
EP_DIR_IN = 0x80  # device → host; иначе host → device


def read_packet_blocks(data: bytes) -> list[bytes]:
    """Извлечь данные всех Enhanced Packet-блоков из pcapng-файла."""
    records = []
    off = 0
    while off + 12 <= len(data):
        block_type, block_len = struct.unpack_from("<II", data, off)
        if block_len < 12 or off + block_len > len(data):
            break
        if block_type == BLOCK_ENHANCED_PACKET:
            caplen = struct.unpack_from("<I", data, off + 20)[0]
            records.append(data[off + 28:off + 28 + caplen])
        off += block_len
    return records


def parse_usb_header(packet: bytes):
    """Разобрать заголовок USBPcap: → (irpid, endpoint, transfer, payload)."""
    header_len = struct.unpack_from("<H", packet, 0)[0]
    irpid = struct.unpack_from("<Q", packet, 2)[0]
    endpoint = packet[21]
    transfer = packet[22]
    data_len = struct.unpack_from("<I", packet, 23)[0]
    payload = packet[header_len:header_len + data_len]
    return irpid, endpoint, transfer, payload


def parse_events(records: list[bytes]) -> list[tuple]:
    """Собрать события SET/GET_REPORT, склеивая setup+data GET-ов по irpid."""
    events = []
    pending_get = {}  # irpid → (iface, request_type, report_id)
    for packet in records:
        irpid, endpoint, transfer, data = parse_usb_header(packet)
        if transfer != XFER_CONTROL or not data:
            continue
        if (not endpoint & EP_DIR_IN and len(data) >= 8
                and data[0] == 0x21 and data[1] == 0x09):
            # merged SET_REPORT: setup(8 байт) + payload
            wValue = struct.unpack("<H", data[2:4])[0]
            wIndex = struct.unpack("<H", data[4:6])[0]
            events.append(("SET", wIndex, wValue >> 8, wValue & 0xFF, data[8:]))
        elif (endpoint & EP_DIR_IN and len(data) == 8
                and data[0] == 0xA1 and data[1] == 0x01):
            # setup-часть GET_REPORT: данные придут отдельным пакетом с тем же irpid
            wValue = struct.unpack("<H", data[2:4])[0]
            wIndex = struct.unpack("<H", data[4:6])[0]
            pending_get[irpid] = (wIndex, wValue >> 8, wValue & 0xFF)
        elif endpoint & EP_DIR_IN and irpid in pending_get:
            iface, request_type, report_id = pending_get.pop(irpid)
            events.append(("GET", iface, request_type, report_id, data))
    return events


def main():
    if len(sys.argv) < 2:
        raise SystemExit(__doc__)
    src = sys.argv[1]
    dst = sys.argv[2] if len(sys.argv) > 2 else "/tmp/tx_log.txt"

    with open(src, "rb") as f:
        data = f.read()
    events = parse_events(read_packet_blocks(data))

    with open(dst, "w") as f:
        for num, (kind, iface, rtype, rid, payload) in enumerate(events, 1):
            f.write(f"{kind} #{num:4d} if={iface} t={rtype} rid={rid:02x} "
                    f"len={len(payload)}: {payload.hex(' ')}\n")
    print("events:", len(events))


if __name__ == "__main__":
    main()