from Crypto.Cipher import AES
from Crypto.Util import Counter
from librespot.audio.storage.ChannelManager import ChannelManager
from librespot.audio.decrypt.AudioDecrypt import AudioDecrypt
import time


class AesAudioDecrypt(AudioDecrypt):
    audio_aes_iv = bytes([
        0x72, 0xe0, 0x67, 0xfb, 0xdd, 0xcb, 0xcf, 0x77, 0xeb, 0xe8, 0xbc, 0x64,
        0x3f, 0x63, 0x0d, 0x93
    ])
    iv_int = int.from_bytes(audio_aes_iv, "big")
    iv_diff = 0x100
    cipher = None
    decrypt_count = 0
    decrypt_total_time = 0
    key: bytes = None

    def __init__(self, key: bytes):
        self.key = key

    def decrypt_chunk(self, chunk_index: int, buffer: bytes):
        new_buffer = b""
        iv = self.iv_int + int(ChannelManager.CHUNK_SIZE * chunk_index / 16)
        start = time.time_ns()
        for i in range(0, len(buffer), 4096):
            cipher = AES.new(key=self.key,
                             mode=AES.MODE_CTR,
                             counter=Counter.new(128, initial_value=iv))

            count = min(4096, len(buffer) - i)
            decrypted_buffer = cipher.decrypt(buffer[i:i + count])
            new_buffer += decrypted_buffer
            if count != len(decrypted_buffer):
                raise RuntimeError(
                    "Couldn't process all data, actual: {}, expected: {}".
                    format(len(decrypted_buffer), count))

            iv += self.iv_diff

        self.decrypt_total_time += time.time_ns()
        self.decrypt_count += 1

        return new_buffer

    def decrypt_time_ms(self):
        return 0 if self.decrypt_count == 0 else int(
            (self.decrypt_total_time / self.decrypt_count) / 1000000)