// Copyright (c) 2019-2022 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
// Based off:   https://github.com/golang/go/blob/master/src/crypto/aes
// Last commit: https://github.com/golang/go/commit/691a2d457ab1bf03bd46d4b69e0f93b8993c0055
module aes

import crypto.cipher
import crypto.internal.subtle

pub const (
	// The AES block size in bytes.
	block_size = 16
)

// AesCipher represents an AES encryption using a particular key.
// It follows the API of golang's `cipher.Block` and is designed to
// handle only one block of data at a time. In most cases, you
// probably want to encrypt and decrypt using [[AesCbc](#AesCbc)]
struct AesCipher {
	block_size int = aes.block_size
mut:
	enc []u32
	dec []u32
}

// free the resources taken by the AesCipher `c`
[unsafe]
pub fn (mut c AesCipher) free() {
	$if prealloc {
		return
	}
	unsafe {
		c.enc.free()
		c.dec.free()
	}
}

// new_cipher creates and returns a new [[AesCipher](#AesCipher)].
// The key argument should be the AES key,
// either 16, 24, or 32 bytes to select
// AES-128, AES-192, or AES-256.
pub fn new_cipher(key []u8) cipher.Block {
	k := key.len
	match k {
		16, 24, 32 {
			// break
		}
		else {
			panic('crypto.aes: invalid key size ' + k.str())
			// return error('crypto.aes: invalid key size ' + k.str())
		}
	}
	// for now use generic version
	return new_cipher_generic(key)
}

// block_size returns the block size of the checksum in bytes.
pub fn (c &AesCipher) block_size() int {
	return aes.block_size
}

// encrypt encrypts the first block of data in `src` to `dst`.
// NOTE: `dst` and `src` are both mutable for performance reasons.
// NOTE: `dst` and `src` must both be pre-allocated to the correct length.
// NOTE: `dst` and `src` may be the same (overlapping entirely).
pub fn (c &AesCipher) encrypt(mut dst []u8, src []u8) {
	if src.len < aes.block_size {
		panic('crypto.aes: input not full block')
	}
	if dst.len < aes.block_size {
		panic('crypto.aes: output not full block')
	}
	// if subtle.inexact_overlap(dst[:block_size], src[:block_size]) {
	if subtle.inexact_overlap(dst[..aes.block_size], src[..aes.block_size]) {
		panic('crypto.aes: invalid buffer overlap')
	}
	// for now use generic version
	encrypt_block_generic(c.enc, mut dst, src)
}

// decrypt decrypts the first block of data in `src` to `dst`.
// NOTE: `dst` and `src` are both mutable for performance reasons.
// NOTE: `dst` and `src` must both be pre-allocated to the correct length.
// NOTE: `dst` and `src` may be the same (overlapping entirely).
pub fn (c &AesCipher) decrypt(mut dst []u8, src []u8) {
	if src.len < aes.block_size {
		panic('crypto.aes: input not full block')
	}
	if dst.len < aes.block_size {
		panic('crypto.aes: output not full block')
	}
	if subtle.inexact_overlap(dst[..aes.block_size], src[..aes.block_size]) {
		panic('crypto.aes: invalid buffer overlap')
	}
	// for now use generic version
	decrypt_block_generic(c.dec, mut dst, src)
}
