use crypto::Error;
use crypto::ciphers::{
    aes_gcm::Aes256Gcm,
    traits::Aead,
};
use crypto::utils::rand;

/// A nonce used for encrypting the gallery's index, as well as all full images
pub const NONCE_A: [u8; 12] = [0xd0, 0xc3, 0x75, 0x56, 0x58, 0xc1, 0x7e, 0x5f, 0xd6, 0xcc, 0xb6, 0x76];

/// A nonce used for encrypting all thumbnails
pub const NONCE_B: [u8; 12] = [0x77, 0xe7, 0xf7, 0x64, 0x33, 0x80, 0x25, 0x49, 0xec, 0xef, 0x57, 0x3f];

pub fn encrypt(key: &[u8; 32], nonce: &[u8; 12], plaintext: &[u8]) -> Vec<u8> {
	let mut result = vec![0; plaintext.len() + 16];
	let (cyphertext, tag) = result.split_at_mut(plaintext.len());
	Aes256Gcm::try_encrypt(
		key,
		nonce,
		&[],
		plaintext,
		cyphertext,
		tag).expect("Unexpected cryptography error");
	result
}

pub fn decrypt<'p>(key: &[u8; 32], nonce: &[u8; 12], encrypted: &[u8], plaintext_dest: &'p mut Vec<u8>) -> Option<&'p mut Vec<u8>> {
	let (cyphertext, tag) = encrypted.split_at(encrypted.len() - 16);
	plaintext_dest.resize(cyphertext.len(), 0);
	let e = Aes256Gcm::try_decrypt(
		key,
		nonce,
		&[],
		plaintext_dest,
		cyphertext,
		tag);
	match e {
		Ok(_) => Some(plaintext_dest),
		Err(Error::CipherError { alg: "AES-256-GCM" }) => None, // Invalid key or tag
		Err(e) => panic!("Unexpected decryption return value:  {e:?}"),
	}
}

pub fn make_key() -> [u8; 32] {
	let mut result = [0; 32];
	rand::fill(&mut result).expect("Unexpected error generating random data");
	result
}