#include <stdio.h>
#include <opensslevp.h>

unsigned char key[16]   = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
                                  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f};

unsigned char nonce[13] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
                                  0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c};

unsigned char test[16]  = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
                                  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f};

unsigned char AAD[1]    = {0x01};


void encrypt()
{

    unsigned char output[16];
    unsigned char tag[4];
    int ciphertext_len = 0;
    int len = 0;

    // Create Cipher
    EVP_CIPHER_CTX *ctx;

    // Create and Initialize context
    if (!(ctx = EVP_CIPHER_CTX_new())) {
        printf("Problem creating Cipher");
    }

    // Initialize Encryption Operation
    if (1 != EVP_EncryptInit_ex(ctx, EVP_aes_128_ccm(), NULL, NULL, NULL)) {
        printf("Error Initializing Encryption");
    }

    // Set nonce length (setting to 13 bytes)
    if (1 != EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, 13, NULL)) {
        printf("Error setting IV length");
    }

    // Set tag length to 4 bytes
    if (1 != EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, 4, NULL)) {
        printf("Error setting tag size");
    }

    // Initialize Key and IV (nonce)
    if (1 != EVP_EncryptInit_ex(ctx, NULL, NULL, key, nonce)) {
        printf("Error initializing Key and IV");
    }

// THIS IS WHERE THE ISSUE IS //
    // Provide AAD Data
    if (1 != EVP_EncryptUpdate(ctx, NULL, &len, AAD, sizeof(AAD))) {
        printf("Error providing Additional Authenticated Data");
    }
// END ISSUE

    // Provide message to be encrypted and obtain encrypted output
    if (1 != EVP_EncryptUpdate(ctx, output, &len, test, sizeof(test))) {
        printf("Error obtaining encrypted output");
    }

    ciphertext_len = len;

    // Finalize encryption
    if (1 != EVP_EncryptFinal(ctx, output + len, &len)) {
        printf("Failed to finalize encryption");
    }

    // Get the tag
    if (1 != EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, 4, tag)) {
        printf("Error collecting tag");
    }

    // Clean up
    EVP_CIPHER_CTX_free(ctx);

    printf("nCiphertext Length = %i", ciphertext_len);

    for (int i = 0; i < ciphertext_len; i++) {
        printf("nByte [%i] = %i", i, output[i]);
    }

    for (int i = 0; i < sizeof(tag); i++) {
        printf("nMAC [%i] = %i", i, tag[i]);
    }
}