// The source code refers to the go standard library, which will be combined with AES in the future.

module cipher

// A Block represents an implementation of block cipher
// using a given key. It provides the capability to encrypt
// or decrypt individual blocks. The mode implementations
// extend that capability to streams of blocks.
pub interface Block {
	block_size int // block_size returns the cipher's block size.
	encrypt(mut dst []u8, src []u8) // Encrypt encrypts the first block in src into dst.
	// Dst and src must overlap entirely or not at all.
	decrypt(mut dst []u8, src []u8) // Decrypt decrypts the first block in src into dst.
	// Dst and src must overlap entirely or not at all.
}

// A Stream represents a stream cipher.
pub interface Stream {
mut:
	// xor_key_stream XORs each byte in the given slice with a byte from the
	// cipher's key stream. Dst and src must overlap entirely or not at all.
	//
	// If len(dst) < len(src), xor_key_stream should panic. It is acceptable
	// to pass a dst bigger than src, and in that case, xor_key_stream will
	// only update dst[:len(src)] and will not touch the rest of dst.
	//
	// Multiple calls to xor_key_stream behave as if the concatenation of
	// the src buffers was passed in a single run. That is, Stream
	// maintains state and does not reset at each xor_key_stream call.
	xor_key_stream(mut dst []u8, src []u8)
}

// A BlockMode represents a block cipher running in a block-based mode (CBC,
// ECB etc).
pub interface BlockMode {
	block_size int // block_size returns the mode's block size.
	crypt_blocks(mut dst []u8, src []u8) // crypt_blocks encrypts or decrypts a number of blocks. The length of
	// src must be a multiple of the block size. Dst and src must overlap
	// entirely or not at all.
	//
	// If len(dst) < len(src), crypt_blocks should panic. It is acceptable
	// to pass a dst bigger than src, and in that case, crypt_blocks will
	// only update dst[:len(src)] and will not touch the rest of dst.
	//
	// Multiple calls to crypt_blocks behave as if the concatenation of
	// the src buffers was passed in a single run. That is, BlockMode
	// maintains state and does not reset at each crypt_blocks call.
}

// AEAD provides an authenticated encryption with associated data for encryption (decryption).
pub interface AEAD {
	// nonce_size returns the size of nonce (in bytes) used by this AEAD that must be
	// passed to `.encrypt` or `.decrypt`.
	nonce_size() int
	// overhead returns the maximum difference between the lengths of a plaintext and its ciphertext.
	overhead() int
	// encrypt encrypts and authenticates the provided plaintext along with the nonce and
	// additional data in `ad`. The nonce must be `nonce_size()` bytes long and unique
	// for all time, for a given key. It returns encrypted (and authenticated) ciphertext bytes
	// where its encoded form is up to implementation and not dictated by the interfaces.
	// Commonly, its contains encrypted text plus some authentication tag, and maybe some other bytes.
	encrypt(plaintext []u8, nonce []u8, ad []u8) ![]u8
	// decrypt decrypts and authenticates (verifies) the provided ciphertext along with a nonce, and
	// additional data. The nonce must be `nonce_size()` bytes long and both it and the additional data
	// must match the value passed to `encrypt`.
	// Its returns the verified plaintext on success, or errors on fails.
	decrypt(ciphertext []u8, nonce []u8, ad []u8) ![]u8
}

// Utility routines

// fn dup(p []u8) []u8 {
// 	q := make([]u8, p.len)
// 	copy(mut q, p)
// 	return q
// }