// This script demonstrates how to use GnuTLS to implement AEAD-AES128-GCM encryption and authentication in just a few lines of code.

#include <stdio.h>
#include <gnutls/gnutls.h>

int main(void) {
    // Initialize GnuTLS
    gnutls_init();
    
    // Set up the encryption context and load the key material
    gnutls_session_t session = gnutls_session_new();
    int ret = gnutls_handshake(session, GNUTLS_CLIENT);
    if (ret < 0) {
        printf("Handshake failed: %s\n", gnutls_strerror(ret));
        return 1;
    }
    
    // Generate some data to encrypt and authenticate
    const char *plaintext = "Hello, world! ";
    size_t plainlen = strlen(plaintext);
    unsigned int adatalen = 0;
    void *adataptr = NULL;
    gnutls_data_source_t *aes128gcm_src = gnutls_datasource_new();
    
    // Set up the encryption context and load the key material
    const char *key = "mysecretkey";
    size_t keymatlen = strlen(key);
    unsigned int ciphertextlen;
    void *ciphertextptr;
    gnutls_datasource_set_read_callback(aes128gcm_src, my_read_cb, NULL);
    
    // Encrypt and authenticate the data using AEAD-AES128-GCM
    ret = gnutls_cipher_write(session, aes128gcm_src, plaintext, plainlen, &adataptr, &adatalen);
    if (ret < 0) {
        printf("Encryption failed: %s\n", gnutls_strerror(ret));
        return 1;
    }
    
    // Read back the encrypted and authenticated data using AEAD-AES128-GCM
    ret = gnutls_cipher_read(session, aes128gcm_src, &adataptr, adatalen);
    if (ret < 0) {
        printf("Decryption failed: %s\n", gnutls_strerror(ret));
        return 1;
    }
    
    // Verify the authenticity of the data using AEAD-AES128-GCM
    ret = gnutls_cipher_verify(session, aes128gcm_src);
    if (ret < 0) {
        printf("Verification failed: %s\n", gnutls_strerror(ret));
        return 1;
    }
    
    // Clean up the resources and exit gracefully
    gnutls_session_deinit(session);
    gnutls_cleanup();
    
    printf("Encryption, decryption, and verification successful!\n");
    
    return 0;
}

// The script begins by initializing GnuTLS and setting up the encryption context. 
// It then generates some data to be encrypted and authenticated. 
// Next, it sets up the encryption context and loads the key material. 
// The data is then encrypted and authenticated using AEAD-AES128-GCM. 
// The encrypted data is then read back and decrypted. 
// Finally, the authenticity of the data is verified using AEAD-AES128-GCM. 
// The resources are then cleaned up and the script exits.