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

#define MAX_SIZE 256

void strip_newline(char* to_strip);
void encrypt_data(FILE* input_file, FILE* output_file, char *key);

int main(int argc, char* argv[])
{
        //Check for valid number of arguments
        if (argc != 3)
        {
                printf("Invalid number of arguments. %d arguments were supplied.\n", argc);
                printf("Usage: %s inputfile outputfile\n", argv[0]); //Usage: ./xortest inputfile outputfile
                exit(0);
        }
        
        FILE* input;
        FILE* output;

        //Open input and output files
        input = fopen(argv[1], "r");
        output = fopen(argv[2], "w");
                

        //Check input file
        if (input == NULL)
        {
                printf("Input file cannot be read.\n");
                exit(0);
        }
                
        //Check output file
        if (output == NULL)
        {
                printf("Output file cannot be written to.\n");
                exit(0);
        }

        //Key strings
        char *key = malloc(MAX_SIZE);

        //Prompt for key
        printf("Passphrase: ");

        //Read in key
        fgets(key, MAX_SIZE, stdin);

        printf("Encrypting %s\n", argv[1]);

        //strip newlines
        strip_newline(key);

        //XOR data and write it to file
        encrypt_data(input, output, key);
        
        printf("Encrypted data written to %s\n", argv[2]);

        //Release memory
        free(key);

        //Close files
        fclose(input);
        fclose(output);

        return 0;

}


void encrypt_data(FILE* input_file, FILE* output_file, char* key)
{
        int key_count = 0; //Used to restart key if strlen(key) < strlen(encrypt)
        int encrypt_byte;
        
        while( (encrypt_byte = fgetc(input_file)) != EOF) //Loop through each byte of file until EOF
        {
                //XOR the data and write it to a file
                fputc(encrypt_byte ^ key[key_count], output_file);

                //Increment key_count and start over if necessary
                key_count++;
                if(key_count == strlen(key))
                        key_count = 0;
        }
}

void strip_newline(char* to_strip)
{
        //remove newlines
        if (to_strip[strlen(to_strip) - 1] == '\n')
        {
                to_strip[strlen(to_strip) - 1] = '\0';
        }