#ifndef _AES_H_
#define _AES_H_

#include <stddef.h>
#include <stdint.h>

// #define the macros below to 1/0 to enable/disable the mode of operation.
//
// CBC enables AES encryption in CBC-mode of operation.
// CTR enables encryption in counter-mode.
// ECB enables the basic ECB 16-byte block algorithm. All can be enabled
// simultaneously.

// The #ifndef-guard allows it to be configured before #include'ing or at
// compile time.
#ifndef CBC
#define CBC 0
#endif

#ifndef ECB
#define ECB 0
#endif

#ifndef CTR
#define CTR 1
#endif

#define AES128 1
// #define AES192 1
// #define AES256 1

#define AES_BLOCKLEN 16 // Block length in bytes - AES is 128b block only

#if defined(AES256) && (AES256 == 1)
#define AES_KEYLEN 32
#define AES_keyExpSize 240
#elif defined(AES192) && (AES192 == 1)
#define AES_KEYLEN 24
#define AES_keyExpSize 208
#else
#define AES_KEYLEN 16 // Key length in bytes
#define AES_keyExpSize 176
#endif

struct AES_ctx {
  uint8_t RoundKey[AES_keyExpSize];
#if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1))
  uint8_t Iv[AES_BLOCKLEN];
#endif
};

void AES_init_ctx(struct AES_ctx *ctx, const uint8_t *key);
#if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1))
void AES_init_ctx_iv(struct AES_ctx *ctx, const uint8_t *key,
                     const uint8_t *iv);
void AES_ctx_set_iv(struct AES_ctx *ctx, const uint8_t *iv);
#endif

#if defined(ECB) && (ECB == 1)
// buffer size is exactly AES_BLOCKLEN bytes;
// you need only AES_init_ctx as IV is not used in ECB
// NB: ECB is considered insecure for most uses
void AES_ECB_encrypt(const struct AES_ctx *ctx, uint8_t *buf);
void AES_ECB_decrypt(const struct AES_ctx *ctx, uint8_t *buf);

#endif // #if defined(ECB) && (ECB == !)

#if defined(CBC) && (CBC == 1)
// buffer size MUST be mutile of AES_BLOCKLEN;
// Suggest https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7 for
// padding scheme NOTES: you need to set IV in ctx via AES_init_ctx_iv() or
// AES_ctx_set_iv()
//        no IV should ever be reused with the same key
void AES_CBC_encrypt_buffer(struct AES_ctx *ctx, uint8_t *buf, size_t length);
void AES_CBC_decrypt_buffer(struct AES_ctx *ctx, uint8_t *buf, size_t length);

#endif // #if defined(CBC) && (CBC == 1)

#if defined(CTR) && (CTR == 1)

// Same function for encrypting as for decrypting.
// IV is incremented for every block, and used after encryption as
// XOR-compliment for output Suggesting
// https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7 for padding scheme
// NOTES: you need to set IV in ctx with AES_init_ctx_iv() or AES_ctx_set_iv()
//        no IV should ever be reused with the same key
void AES_CTR_xcrypt_buffer(struct AES_ctx *ctx, uint8_t *buf, size_t length);

#endif // #if defined(CTR) && (CTR == 1)

#endif // _AES_H_
