#include <stdio.h>
#include <string.h>

#include <openssl/evp.h>
#include <openssl/err.h>


#define ENCRYPT 1
#define DECRYPT 0
#define MAX_BUFFER 1024

void handle_errors(){
    ERR_print_errors_fp(stderr);
    abort();
}

int main(int argc, char **argv)
{

//  int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, const unsigned char *key, const unsigned char *iv, int enc);
//  int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl, const unsigned char *in, int inl);
//  int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);




    if(argc != 3){
        fprintf(stderr,"Invalid parameters. Usage: %s file_in ALGO-TO-USE\n",argv[0]);
        exit(1);
    }


    FILE *f_in;
    if((f_in = fopen(argv[1],"r")) == NULL) {
            fprintf(stderr,"Couldn't open the input file, try again\n");
            abort();
    }
    /*
    if(strlen(argv[2])!=32){
        fprintf(stderr,"Wrong key length\n");
        abort();
    }   
    if(strlen(argv[3])!=32){
        fprintf(stderr,"Wrong IV length\n");
        abort();
    }
    */
    /*FILE *f_out;
    if((f_out = fopen(argv[2],"wb")) == NULL) {
            fprintf(stderr,"Couldn't open the output file, try again\n");
            abort();
    }*/
    unsigned char key[] = "0123456789ABCDEF";
    unsigned char iv[] = "0123456789ABCDEF";
    /*unsigned char key[strlen(argv[2])/2];
    for(int i = 0; i < strlen(argv[2])/2;i++){
        sscanf(&argv[2][2*i],"%2hhx", &key[i]);
    }

    unsigned char iv[strlen(argv[3])/2];
    for(int i = 0; i < strlen(argv[3])/2;i++){
        sscanf(&argv[3][2*i],"%2hhx", &iv[i]);
    }
    */
    /* Load the human readable error strings for libcrypto */
    ERR_load_crypto_strings();
    /* Load all digest and cipher algorithms */
    OpenSSL_add_all_algorithms(); // deprecated since version 1.1.1



    // pedantic mode: check NULL
    EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();

    if(!EVP_CipherInit(ctx,EVP_get_cipherbyname(argv[2]), key, iv, DECRYPT))
        handle_errors();
    EVP_CIPHER_CTX_set_padding(ctx,0);
    int length;
    unsigned char ciphertext[MAX_BUFFER+16];

    int n_read;
    unsigned char buffer[MAX_BUFFER];

    while((n_read = fread(buffer,1,MAX_BUFFER,f_in)) > 0){
        //printf("n_Read=%d-",n_read);
        if(!EVP_CipherUpdate(ctx,ciphertext,&length,buffer,n_read))
            handle_errors();
        //printf("length=%d\n",length);

        /*if(fwrite(ciphertext, 1, length,f_out) < length){
            fprintf(stderr,"Error writing the output file\n");
            abort();
        }*/
    }
            
    if(!EVP_CipherFinal_ex(ctx,ciphertext,&length))
        handle_errors();

    //printf("lenght=%d\n",length);
    printf("ALGORITHM:%s, Output: %s\n", argv[2], ciphertext);
    /*if(fwrite(ciphertext,1, length, f_out) < length){
        fprintf(stderr,"Error writing in the output file\n");
        abort();
    }
    */
    EVP_CIPHER_CTX_free(ctx);

    fclose(f_in);
//    fclose(f_out);

    //printf("File decrypted!\n");


    // completely free all the cipher data
    CRYPTO_cleanup_all_ex_data();
    /* Remove error strings */
    ERR_free_strings();

    return 0;
}