import os
try:
    from . import AES_KEY_SIZE
except ImportError:
    AES_KEY_SIZE = 32

SBOX = [
    0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
    0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
    0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
    0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
    0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
    0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
    0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
    0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
    0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
    0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
    0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
    0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
    0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
    0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
    0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
    0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16,
]

RCON = [0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80,0x1b,0x36]

def _xtime(a):
    return ((a << 1) ^ 0x1b) & 0xff if a & 0x80 else (a << 1) & 0xff

def _mix_single(a):
    t = a[0] ^ a[1] ^ a[2] ^ a[3]
    u = a[0]
    a[0] ^= _xtime(a[0] ^ a[1]) ^ t
    a[1] ^= _xtime(a[1] ^ a[2]) ^ t
    a[2] ^= _xtime(a[2] ^ a[3]) ^ t
    a[3] ^= _xtime(a[3] ^ u) ^ t

def _key_expansion(key):
    nk = len(key) // 4
    nr = nk + 6
    w = [key[4*i:4*i+4] for i in range(nk)]
    for i in range(nk, 4*(nr+1)):
        temp = list(w[i-1])
        if i % nk == 0:
            temp = [SBOX[temp[1]] ^ RCON[i//nk-1], SBOX[temp[2]], SBOX[temp[3]], SBOX[temp[0]]]
        elif nk > 6 and i % nk == 4:
            temp = [SBOX[b] for b in temp]
        w.append(bytes([a ^ b for a, b in zip(w[i-nk], temp)]))
    round_keys = []
    for r in range(nr + 1):
        rk = b''
        for i in range(4):
            rk += w[r*4 + i]
        round_keys.append(rk)
    return round_keys

def _encrypt_block(block, round_keys):
    nr = len(round_keys) - 1
    state = [list(block[i:i+4]) for i in range(0, 16, 4)]
    s = [[state[j][i] for j in range(4)] for i in range(4)]

    for i in range(4):
        for j in range(4):
            s[i][j] ^= round_keys[0][i*4+j]

    for rnd in range(1, nr + 1):
        for i in range(4):
            for j in range(4):
                s[i][j] = SBOX[s[i][j]]
        s[1] = s[1][1:] + s[1][:1]
        s[2] = s[2][2:] + s[2][:2]
        s[3] = s[3][3:] + s[3][:3]
        if rnd < nr:
            for j in range(4):
                col = [s[i][j] for i in range(4)]
                _mix_single(col)
                for i in range(4):
                    s[i][j] = col[i]
        for i in range(4):
            for j in range(4):
                s[i][j] ^= round_keys[rnd][i*4+j]

    result = bytearray(16)
    for i in range(4):
        for j in range(4):
            result[i*4+j] = s[i][j]
    return bytes(result)

def _pkcs7_pad(data, block_size=16):
    pad_len = block_size - (len(data) % block_size)
    return data + bytes([pad_len] * pad_len)

def _aes_cbc_encrypt(plaintext, key, iv):
    padded = _pkcs7_pad(plaintext)
    round_keys = _key_expansion(key)
    ciphertext = b''
    prev = iv
    for i in range(0, len(padded), 16):
        block = padded[i:i+16]
        xored = bytes([a ^ b for a, b in zip(block, prev)])
        encrypted = _encrypt_block(xored, round_keys)
        ciphertext += encrypted
        prev = encrypted
    return ciphertext

def _try_system_aes(data, key, iv):
    try:
        from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
        from cryptography.hazmat.primitives import padding
        from cryptography.hazmat.backends import default_backend
        padder = padding.PKCS7(128).padder()
        padded = padder.update(data) + padder.finalize()
        cipher = Cipher(algorithms.AES(key), modes.CBC(iv), backend=default_backend())
        enc = cipher.encryptor()
        return enc.update(padded) + enc.finalize()
    except ImportError:
        return None

def encrypt_payload(data, key, iv):
    result = _try_system_aes(data, key, iv)
    if result is not None:
        print("using system aes")
        return result
    print("using pure python aes (slow)")
    return _aes_cbc_encrypt(data, key, iv)