import base64
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes

def decrypt(base64_input: str, secret: bytes) -> str | None:
    try:
        combined = base64.b64decode(base64_input)
        
        # IV length is 12 bytes in the Java implementation
        iv_length = 12
        if len(combined) <= iv_length + 16:
            return None
            
        iv = combined[:iv_length]
        
        # Java AES/GCM appends a 16-byte authentication tag at the end of cipherBytes
        # cryptography library expects it to be passed into the modes.GCM(iv, tag)
        cipher_bytes_with_tag = combined[iv_length:]
        actual_ciphertext = cipher_bytes_with_tag[:-16]
        tag = cipher_bytes_with_tag[-16:]
        
        cipher = Cipher(algorithms.AES(secret), modes.GCM(iv, tag))
        decryptor = cipher.decryptor()
        
        plain_bytes = decryptor.update(actual_ciphertext) + decryptor.finalize()
        return plain_bytes.decode('utf-8')
    except Exception:
        return None

def get_string_value(encrypted_id: str, secret: str, secret_key_internal: str) -> str | None:
    if not secret or not secret_key_internal:
        return None
    try:
        # Replicate Java's logic: (s + secretKeyInternal).substring(0, Math.min(..., 16))
        combined_str = secret + secret_key_internal
        combined_secret = combined_str[:16].encode('utf-8')
        return decrypt(encrypted_id, combined_secret)
    except Exception:
        return None