#!/usr/bin/env python3
"""
996传奇客户端 消息头编码算法 还原实现
来源: 996传奇盒子 二进制反汇编 (netClient::SendNetMessage @0x10003d408 → encode_header @0x10004b4e4)
验证: 24B明文头 ↔ 32B可打印密文 roundtrip 通过 (2026-09-21)

算法 = 256字节替换表 + XOR 9 + 位流重组(8bit→6bit组) + 0x3C偏移
与 netMessageDef.lua 注释对应: "NETMSG_HEADER_ENCODE_SIZE=32 / DECODE_SIZE=24"
用途: 抓包分析时解码消息头 (msgId/recog/param1-4)
"""
import struct

# __DATA @0x1008ae5f4 (编码表, 256字节)
ENC_TABLE = bytes.fromhex(
"8c870d85d46463e5ba7eb8689d9ff5bca0e33a2219213978ee27361574c797c9"
"cee27b4c98a1c25941c01e2e95ebde691d5b53daf40a4fbbb724330fc8842989"
"3c1c0849c6fecc233ee14e8b13e71a5dcfb1478fd8724b936e734d94dd8214a7"
"03f9f1c58d792ac4dc605fd762b5e9b3b612a832d9c36a754aa20c26915aad6d"
"4410b4461b668120fd7f88259c71d3e680e4fa429b3701fcdb456bfb56f0af9a"
"bfabd6cd02f27caab292ff572f86a67d351734d50e65090528ca48318e2ddf52"
"f61fa450764018048a162bae433fd0cb6c5554969930675e2cace07ae85890be"
"a56fb070ec615c063b77c107eaa9f811bdf300ed83ef3da3519e38f70bb9d2d1"
)

def encode_header(hdr24: bytes) -> bytes:
    """24字节明文头 → 32字节可打印密文 (与二进制行为一致)"""
    acc = 0; bitcnt = 0; out = bytearray()
    for ch in hdr24:
        v = ENC_TABLE[ch] ^ 9
        nbits = bitcnt + 2
        acc |= (v >> nbits)
        out.append((acc & 0x3F) + 0x3C)
        leftover = ((v << (6 - bitcnt)) >> 2) & 0x3F
        if bitcnt < 4:
            acc = leftover; bitcnt = nbits
        else:
            out.append(leftover + 0x3C); bitcnt = 0; acc = 0
    if bitcnt > 0:
        out.append(acc + 0x3C)
    return bytes(out[:32])

_INV = {}
for _i in range(256):
    _INV[ENC_TABLE[_i] ^ 9] = _i

def decode_header(enc32: bytes) -> bytes:
    """32字节可打印密文 → 24字节明文头"""
    bits = 0; nbits = 0; stream = bytearray()
    for ch in enc32:
        bits = (bits << 6) | (ch - 0x3C)
        nbits += 6
        while nbits >= 8:
            nbits -= 8
            stream.append((bits >> nbits) & 0xFF)
    return bytes(_INV.get(b, 0) for b in stream[:24])

def parse_header(hdr24: bytes):
    """解析明文头 → dict (依据 netMessage 结构)"""
    recog, p1, p2, p3, p4 = struct.unpack("<IIIII", hdr24[:20])
    msgId = struct.unpack("<H", hdr24[20:22])[0]
    return {"msgId": msgId, "recog": recog, "param1": p1, "param2": p2, "param3": p3, "param4": p4}

if __name__ == "__main__":
    # 自测: 101创建角色消息头
    hdr = bytearray(24)
    struct.pack_into("<I", hdr, 0, 900000)    # recog 水印
    struct.pack_into("<I", hdr, 4, 12345)     # param1
    struct.pack_into("<I", hdr, 8, 37504)     # param2 渠道
    struct.pack_into("<H", hdr, 20, 101)      # msgId
    e = encode_header(bytes(hdr))
    d = decode_header(e)
    assert d == bytes(hdr), "roundtrip fail"
    print("encode:", e.hex(), "(32B, 全可打印)", all(0x3c<=b<=0x7a for b in e))
    print("decode:", parse_header(d))