#!/usr/bin/env python3
"""Reassemble a mission egg from a captured console->pod TCP stream.

Input: a hex dump of the concatenated console->pod TCP payloads, e.g.
  tshark -r cap.pcapng -Y 'ip.src==<console> && tcp.len>0' \
         -T fields -e tcp.payload | tr -d '\n' > c2p.hex

The console delivers the mission as a series of ReceiveEggFileMessage
packets (decoded from CODE/RP/MUNGA/NETWORK.HPP, wire is little-endian):
  NetworkPacketHeader (16B) + Receiver::Message hdr (12B: messageLength@+16,
  messageID@+20, flags@+24) + [egg body when messageLength==1024:
  sequenceNumber, notationFileLength, thisMessageLength, notationData[1000]].
StateQuery packets (messageLength=16) are interleaved and skipped.

Usage: python decode_egg.py c2p.hex out.egg
"""
import sys, struct

data = bytes.fromhex(open(sys.argv[1]).read())
out  = sys.argv[2] if len(sys.argv) > 2 else "reassembled.egg"

i, chunks, total = 0, {}, None
while i + 28 <= len(data):
    mlen, mid = struct.unpack("<ii", data[i+16:i+24])
    if mlen < 12 or mlen > 4000:
        break
    pkt = data[i:i+16+mlen]
    if len(pkt) < 16 + mlen:
        break
    if mlen == 1024:                       # ReceiveEggFileMessage
        seq, flen, tlen = struct.unpack("<iii", pkt[28:40])
        chunks[seq] = pkt[40:40+tlen]
        total = flen
    i += 16 + mlen

egg = b"".join(chunks[k] for k in sorted(chunks))
open(out, "wb").write(egg)
print(f"chunks={len(chunks)} reassembled={len(egg)}B declared={total} "
      f"complete={total is not None and len(egg) >= total} -> {out}")