"""
Helper module around the system's libssl library if available for IGE mode.
"""
import ctypes
import ctypes.util
import platform
import sys
try:
    import ctypes.macholib.dyld
except ImportError:
    pass
import logging
import os

__log__ = logging.getLogger(__name__)


def _find_ssl_lib():
    # macOS 10.15 segfaults on unversioned crypto libraries.
    # We therefore pin the current stable version here
    if sys.platform == 'darwin':
        release, _version_info, _machine = platform.mac_ver()
        ver, major, *_ = release.split('.')
        lib = None
        if int(ver) > 10 or int(ver) == 10 and int(major) > 14:
            lib = (
                ctypes.util.find_library('libssl.46') or
                ctypes.util.find_library('libssl.44') or
                ctypes.util.find_library('libssl.42')
            )
        if not lib:
            lib = ctypes.util.find_library('ssl')
        if lib:
            try:
                return ctypes.cdll.LoadLibrary(lib)
            except OSError:
                pass
        raise OSError('no library called "ssl" found on macOS')

    # Linux / other Unix systems
    lib = ctypes.util.find_library('ssl') or ctypes.util.find_library('crypto')
    if not lib:
        for fallback in ('libssl.so.3', 'libcrypto.so.3', 'libssl.so.1.1', 'libcrypto.so.1.1', 'libssl.so', 'libcrypto.so'):
            try:
                return ctypes.cdll.LoadLibrary(fallback)
            except OSError:
                continue
        raise OSError('no library called "ssl" or "crypto" found')

    try:
        return ctypes.cdll.LoadLibrary(lib)
    except OSError:
        for fallback in ('libssl.so.3', 'libcrypto.so.3', 'libssl.so.1.1', 'libcrypto.so.1.1', 'libssl.so', 'libcrypto.so'):
            try:
                return ctypes.cdll.LoadLibrary(fallback)
            except OSError:
                continue
        raise


try:
    _libssl = _find_ssl_lib()
except OSError as e:
    # See https://github.com/LonamiWebs/Telethon/issues/1167
    # Sometimes `find_library` returns improper filenames.
    __log__.info('Failed to load SSL library: %s (%s)', type(e), e)
    _libssl = None

if not _libssl:
    decrypt_ige = None
    encrypt_ige = None
else:
    # https://github.com/openssl/openssl/blob/master/include/openssl/aes.h
    AES_ENCRYPT = ctypes.c_int(1)
    AES_DECRYPT = ctypes.c_int(0)
    AES_MAXNR = 14

    class AES_KEY(ctypes.Structure):
        """Helper class representing an AES key"""
        _fields_ = [
            ('rd_key', ctypes.c_uint32 * (4 * (AES_MAXNR + 1))),
            ('rounds', ctypes.c_uint),
        ]

    def decrypt_ige(cipher_text, key, iv):
        aes_key = AES_KEY()
        key_len = ctypes.c_int(8 * len(key))
        key = (ctypes.c_ubyte * len(key))(*key)
        iv = (ctypes.c_ubyte * len(iv))(*iv)

        in_len = ctypes.c_size_t(len(cipher_text))
        in_ptr = (ctypes.c_ubyte * len(cipher_text))(*cipher_text)
        out_ptr = (ctypes.c_ubyte * len(cipher_text))()

        _libssl.AES_set_decrypt_key(key, key_len, ctypes.byref(aes_key))
        _libssl.AES_ige_encrypt(
            ctypes.byref(in_ptr),
            ctypes.byref(out_ptr),
            in_len,
            ctypes.byref(aes_key),
            ctypes.byref(iv),
            AES_DECRYPT
        )

        return bytes(out_ptr)

    def encrypt_ige(plain_text, key, iv):
        aes_key = AES_KEY()
        key_len = ctypes.c_int(8 * len(key))
        key = (ctypes.c_ubyte * len(key))(*key)
        iv = (ctypes.c_ubyte * len(iv))(*iv)

        in_len = ctypes.c_size_t(len(plain_text))
        in_ptr = (ctypes.c_ubyte * len(plain_text))(*plain_text)
        out_ptr = (ctypes.c_ubyte * len(plain_text))()

        _libssl.AES_set_encrypt_key(key, key_len, ctypes.byref(aes_key))
        _libssl.AES_ige_encrypt(
            ctypes.byref(in_ptr),
            ctypes.byref(out_ptr),
            in_len,
            ctypes.byref(aes_key),
            ctypes.byref(iv),
            AES_ENCRYPT
        )

        return bytes(out_ptr)