# -*- coding: utf-8 -*-
"""Encode6BitBuf 双向实现（最终验证版）
来源: 游戏二进制 0x10004b4e4/0x10004b594 逐指令翻译
验证: pcap心跳帧 round-trip 100% 匹配
表: Encode6BitBuf_替换表.bin (前256B=ENC, 后256B=DEC)
"""
import os
import struct

_HERE = os.path.dirname(os.path.abspath(__file__))
_tables = open(os.path.join(_HERE, "Encode6BitBuf_替换表.bin"), "rb").read()
ENC_TABLE = _tables[:256]
INV_TABLE = [0] * 256
for _i, _v in enumerate(ENC_TABLE):
    INV_TABLE[_v] = _i


def encode6(src: bytes) -> bytes:
    dst = bytearray()
    w14 = 0
    w12 = 0
    for byte in src:
        w16 = (ENC_TABLE[byte] ^ 9) & 0xFFFF
        new_w12 = w12 + 2
        w17 = w16 >> new_w12
        w14 |= w17
        out6 = w14 & 0x3F
        w14 = ((w16 << ((6 - w12) & 0xFF)) & 0xFFFFFFFF) >> 2 & 0x3F
        dst.append((out6 + 0x3C) & 0xFF)
        if w12 >= 4:
            w12 = 0
            dst.append((w14 + 0x3C) & 0xFF)
            w14 = 0
        else:
            w12 = new_w12
    if w12 > 0:
        dst.append((w14 + 0x3C) & 0xFF)
    return bytes(dst)


def decode6(data: bytes) -> bytes:
    bits = 0
    nbits = 0
    raw = bytearray()
    for ch in data:
        v6 = ch - 0x3C
        if not (0 <= v6 <= 63):
            break
        bits = (bits << 6) | v6
        nbits += 6
        while nbits >= 8:
            nbits -= 8
            raw.append((bits >> nbits) & 0xFF)
    return bytes(INV_TABLE[b ^ 9] for b in raw)


def build_frame(msg_id: int, recog: int, p1: int, p2: int, p3: int, extra: bytes = b"\x00"*12) -> bytes:
    """构造发送帧: 48字符头(Encode6(36B)) + body"""
    head36 = struct.pack("<8i", 0, msg_id, recog, p1, p2, p3, 0, 0) + extra[:4]
    return encode6(head36)  # body由调用者拼接


if __name__ == "__main__":
    # self-test: 心跳帧
    plain = struct.pack("<8i", 0, 60000, 1789709744, 0, 0, 149, 0, 0) + bytes.fromhex("70000000")
    enc = encode6(plain)
    expected = bytes.fromhex("5d5452415d4c67445d545078495e55525d5452415d5452415d54507a5d5452415d5452415d5452415d54527b5d545241")
    assert enc == expected, "round-trip FAIL"
    print("✓ 心跳帧编码验证通过")
    dec = decode6(expected)
    assert dec == plain, "decode FAIL"
    print("✓ 解码验证通过")