#include<stdio.h>
#include<unistd.h>
#include<string.h>
/*
 * While no EOF
 * 	Encrypt block using key
 * 	Output ciphertext
 *	Might have a partial block
 */

/*
 * Password Length: 64 bits, but specified in ASCII
 * Block size:  64 bits
 */
__uint128_t ipow(int n, int e){
	__uint128_t retval = 1;
	for(int i = 0; i < e; i++)
		retval *= n;
	return retval;
}

size_t text_to_hex(char* password){
	char hex_password[8];
	__uint128_t pwd_so_far = 0;
	for(int i = 0; i < strlen(password); ++i){
		pwd_so_far += (password[i] - 32) * ipow(94, i);
	}
	size_t final_password = (size_t)pwd_so_far;
	printf("Final password:  %lx\n", final_password);
	return final_password;  
	// If we do it like this, we'll return a pointer to the stack!
}

int main(int argc, char ** argv){
	if(argc < 2){
		printf("Usage:  %s password [-d]\n", argv[0]);
		return 1;
	}
	char mode = 0;
	if(argc > 2 && argv[2][1] == 'd')
		mode = 1;
	
//	char pass_section[3];
//	pass_section[2] = 0;
	unsigned char password[8];
	*(size_t*)password = text_to_hex(argv[1]);
	unsigned result;
	/*
	for(int offset = 0; offset < 16; offset += 2){
		pass_section[0] = argv[1][offset];
		pass_section[1] = argv[1][offset+1];
		sscanf(pass_section, "%x", &result);
		password[offset/2] = result;
	}
	// This was from the old days, when the user had to type hex characters!
	*/

	unsigned char plaintext[8];
	unsigned char ciphertext[8];
	size_t readlen;
	do {
		readlen = read(0, plaintext, 8);
		for(int byte = 0; byte < readlen; byte++){
			if(!mode)
				ciphertext[byte] = plaintext[byte] + password[byte] % 256;
			else
				ciphertext[byte] = plaintext[byte] - password[byte] % 256;
		}
		write(1, ciphertext, readlen);
	} while (readlen == 8);

	return 0;
}