from __future__ import annotations

import base64
import hashlib
import struct
import socket
import time

from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.primitives import padding as sym_padding


def verify_signature(token: str, timestamp: str, nonce: str, signature: str) -> bool:
    params = sorted([token, timestamp, nonce])
    sha1 = hashlib.sha1("".join(params).encode()).hexdigest()
    return sha1 == signature


def decrypt_message(
    encrypted_msg: str,
    encoding_aes_key: str,
) -> tuple[str, str]:
    key = base64.b64decode(encoding_aes_key + "=")
    ciphertext = base64.b64decode(encrypted_msg)

    cipher = Cipher(algorithms.AES(key), modes.CBC(key[:16]))
    decryptor = cipher.decryptor()
    plaintext = decryptor.update(ciphertext) + decryptor.finalize()

    pad = plaintext[-1]
    plaintext = plaintext[:-pad]

    content_len = socket.ntohl(struct.unpack("I", plaintext[16:20])[0])
    content = plaintext[20 : 20 + content_len].decode("utf-8")
    receive_id = plaintext[20 + content_len :].decode("utf-8")

    return content, receive_id


def encrypt_message(
    content: str,
    encoding_aes_key: str,
    app_id: str,
) -> str:
    key = base64.b64decode(encoding_aes_key + "=")

    random_bytes = struct.pack("I", int(time.time()))
    content_bytes = content.encode("utf-8")
    app_id_bytes = app_id.encode("utf-8")

    msg_len = struct.pack("!I", len(content_bytes))
    raw = random_bytes + msg_len + content_bytes + app_id_bytes

    padder = sym_padding.PKCS7(128).padder()
    padded = padder.update(raw) + padder.finalize()

    cipher = Cipher(algorithms.AES(key), modes.CBC(key[:16]))
    encryptor = cipher.encryptor()
    ciphertext = encryptor.update(padded) + encryptor.finalize()

    return base64.b64encode(ciphertext).decode()


def verify_url_signature(token: str, timestamp: str, nonce: str, echostr: str, signature: str) -> tuple[bool, str]:
    if not verify_signature(token, timestamp, nonce, signature):
        return False, ""

    key = base64.b64decode(echostr)
    return True, key.decode("utf-8")