# -*- coding: utf-8 -*-
import time
import random
import struct
import base64
import hmac
import hashlib
import ctypes

class _RC4:
    """
    内部使用的 RC4 算法实现，还原了 Java 版本特殊的 Key Scheduling 逻辑
    """
    _RC4_PK = "QrMgt8GGYI6T52ZY5AnhtxkLzb8egpFn3j5JELI8H6wtACbUnZ5cc3aYTsTRbmkAkRJeYbtx92LPBWm7nBO9UIl7y5i5MQNmUZNf5QENurR5tGyo7yJ2G0MBjWvy6iAtlAbacKP0SwOUeUWx5dsBdyhxa7Id1APtybSdDgicBDuNjI0mlZFUzZSS9dmN8lBD0WTVOMz0pRZbR3cysomRXOO1ghqjJdTcyDIxzpNAEszN8RMGjrzyU7Hjbmwi6YNK"

    def __init__(self):
        self.state = list(range(256))
        self.x = 0
        self.y = 0
        self._prepare_key(self._RC4_PK)

    def _prepare_key(self, key_str):
        key_len = len(key_str)
        j = 0
        for i in range(256):
            c_char_at = ord(key_str[i % key_len])
            i13 = self.state[i]
            j = (c_char_at + i13 + j) % 256
            self.state[i], self.state[j] = self.state[j], self.state[i]
        self.x = 0
        self.y = 0

    def rc4(self, data):
        output = bytearray(len(data))
        x = self.x
        y = self.y
        state = list(self.state)
        for k in range(len(data)):
            x = (x + 1) % 256
            sx = state[x]
            y = (y + sx) % 256
            sy = state[y]
            state[x], state[y] = sy, sx
            idx = (state[x] + state[y]) % 256
            output[k] = data[k] ^ state[idx]
        return bytes(output)

class _JavaUtils:
    """
    内部工具类：处理 Python 与 Java 之间的数据类型差异（大端序、溢出处理）
    """
    @staticmethod
    def get_bytes(val):
        """Int -> 4 bytes (Big Endian)"""
        return struct.pack('>i', ctypes.c_int32(val).value)

    @staticmethod
    def string_hashcode(s):
        """模拟 Java String.hashCode 的溢出行为"""
        h = 0
        for c in s:
            h = (31 * h + ord(c)) & 0xFFFFFFFF
        return ctypes.c_int32(h).value

class UTDIDGenerator:
    """
    UTDID 生成器主类
    """
    def __init__(self):
        # 初始化配置与 HMAC Key
        self._init_hmac_key()

    def _init_hmac_key(self):
        MAX_POWER_OF_TWO = 64
        OP_LOAD = 24
        
        # 原始 Java 有符号 byte 数组
        raw_b_arr2_signed = [
            69, 114, 116, -33, 125, -54, -31, 86, -11, 11, -78, -96, -17, -99, 
            MAX_POWER_OF_TWO, 
            23, -95, -126, -82, -64, 113, 116, -16, -103, 
            OP_LOAD,          
            -30, 9, -39, 33, -80, -68, -78, -117, 53, 30, -122, 
            MAX_POWER_OF_TWO, 
            -104, 74, -49, 106, 85, -38, -93
        ]
        # 转换为无符号
        b_arr2 = bytearray([b + 256 if b < 0 else b for b in raw_b_arr2_signed])
        # 解密出 HMAC Key
        self.hmac_key = _RC4().rc4(b_arr2)

    def _calc_hmac(self, data):
        h = hmac.new(self.hmac_key, data, hashlib.sha1)
        signature = h.digest()
        return base64.b64encode(signature).decode('utf-8')

    def _generate_random_imei(self):
        """生成随机的 15 位数字 IMEI"""
        prefix = random.choice(['35', '86', '01', '99'])
        suffix = "".join([str(random.randint(0, 9)) for _ in range(15 - len(prefix))])
        return prefix + suffix

    def generate(self, imei=None):
        """
        生成一个 UTDID
        :param imei: 可选，指定 IMEI 字符串。如果不传则自动随机生成。
        :return: Base64 编码的 UTDID 字符串
        """
        buffer = bytearray()

        # 1. Timestamp (4 bytes)
        timestamp = int(time.time())
        buffer.extend(_JavaUtils.get_bytes(timestamp))

        # 2. Random Int (4 bytes)
        random_int = random.randint(-2147483648, 2147483647)
        buffer.extend(_JavaUtils.get_bytes(random_int))

        # 3. Version (1 byte) & Reserved (1 byte)
        buffer.append(3)
        buffer.append(0)

        # 4. IMEI Hash (4 bytes)
        real_imei = imei if imei else self._generate_random_imei()
        imei_hash = _JavaUtils.string_hashcode(real_imei)
        buffer.extend(_JavaUtils.get_bytes(imei_hash))

        # 5. Checksum (4 bytes)
        # 对应: hashCode(calcHmac(bytes[0:14]))
        data_14 = bytes(buffer)
        hmac_str = self._calc_hmac(data_14)
        hmac_hash = _JavaUtils.string_hashcode(hmac_str)
        buffer.extend(_JavaUtils.get_bytes(hmac_hash))

        # 6. Final Base64
        return base64.b64encode(buffer).decode('utf-8')

# --- 快捷单例导出 ---
# 实例化一个默认生成器，外部可以直接 import 这个对象或函数
_default_generator = UTDIDGenerator()

def generate_utdid(imei=None):
    """
    快捷函数：生成 UTDID
    """
    return _default_generator.generate(imei)

# if __name__ == "__main__":
#     # 测试代码
#     print("--- Testing UTDID Generator ---")
#     print(f"Random: {generate_utdid()}")
#     print(f"Fixed:  {generate_utdid('865100020000000')}")