/* 
 * CMPE 311
 * F19 Discussion 5
 * Created: 9/27/2019 1:17:11 PM
 */ 

#include "U0_UART.h"
#include <string.h>
#include <avr/io.h>

extern FILE uart_stream; /* declare uart_stream indicating that it is defined within project scope */

// constant char arrays transmitted via serial
const char promptEncrypt[] = "Enter a password (U,D,L,R) [25 characters max]: \n";
const char promptCompare[] = "Enter the password: \n";
const char secretMessage[] = "Get started on Homework 2!!\n";

#define MAX_PASS_LENGTH 25 /* maximum length of user defined password */

// basic encryption function
char* encrypt(char input[]){
	int i = 0;
	while(input[i] != '\0'){
		input[i] += 3;
		i++;
	}
	return input;
}

// basic decryption function
char* decrypt(char stored[]){
	int i = 0;
	while(stored[i] != '\0'){
		stored[i] -= 3;
		i++;
	}
	return stored;
}


int main(void)
{
	stderr = stdin = stdout = &uart_stream; /* re-map standard output, input, error */
	
	UARTInit(); /* initialize the UART (set hardware specific configuration registers) */
	
	printf(promptEncrypt);
	
	char input[MAX_PASS_LENGTH]; /* char array to store user defined password */
	char guess[MAX_PASS_LENGTH]; /* char array to store user's password guess */
	char* encrypted; /* char array to store encrypted user defined password */
	char* decrypted; /* char array to store decrypted user defined password */
	
	fgets(input, MAX_PASS_LENGTH, &uart_stream); /* user sets password */
	
	encrypted = encrypt(input); /* encrypt password */

	printf(promptCompare);
	fgets(guess, MAX_PASS_LENGTH, &uart_stream); /* user attempts to enter correct password */
	
	decrypted = decrypt(encrypted); /* decrypt stored password */
	
	/* [INSTRUCTIONS]: compare the decrypted password to the user's 
	   input using function strcmp(const char* str1, const char* str2)
	   
	   strcmp returns: 
	   (int = 0): strings are identical
	   (int > 0): first non-matching char in str1 > str2
	   (int < 0): first non-matching char in str1 < str2
	   
	   loop and re-prompt the user to enter a password while
	   their entry does not match the decrypted password, when 
	   the passwords match the loop should exit and the secret 
	   message will be transmitted
	*/
	
	// transmits secret message 
	printf("Secret Message: ");
	printf(secretMessage);
	
	return 0;
}