/* decrypt_file.c

      This function is part of the Polysqu program. It decrypts message input
      from the user and writes it to a file.

      Copyright (C) 2015, 2016, 2017  Scott C. MacCallum
      scm@ma.sdf.org

      This program is free software: you can redistribute it and/or modify
      it under the terms of the GNU Affero General Public License as published
      by the Free Software Foundation, either version 3 of the License, or
      (at your option) any later version.

      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.

      You should have received a copy of the GNU Affero General Public License
      along with this program.  If not, see <http://www.gnu.org/licenses/>. */

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

void decrypt_file(void)
{
	int choice;
	int index;
	int element_number = 1;
	int array_number[5];
	int element_letter = 97;
	int array_letter[25];
	int counter;

	char file_name[256];
	FILE *pointer_file;
	char *pointer_name = file_name;
	char *pointer_mode = "w";
	char letter;

	printf("\n");
	printf("File Name: ");

	scanf("%255s", file_name);

	printf("\n");
	printf("WARNING, if file exists, it will be overwritten.\n");
	printf("\n");

	printf("Do you want to proceed?\n");
	printf("\n");

	printf("1. Yes\n");
	printf("2. No\n");
	printf("\n");

	printf("Number: ");

	scanf("%d", &choice);

	switch (choice) {
	case 1:
		break;
	case 2:
		printf("\n");
		printf("Good bye!\n");
		printf("\n");

		exit(0);
	default:
		printf("\n");
		printf("Error! Bad input.\n");
		printf("\n");

		exit(1);
	}

	pointer_file = fopen(pointer_name, pointer_mode);

	fclose(pointer_file);

	pointer_mode = "a";

	printf("\n");
	printf("Your message will be encrypted using this\n");
	printf("Polybius Square.\n");

	/* At index zero, initialize the elements in the array of numbers
	   with values one through five */

	for (index = 0; element_number < 6; index++)
		array_number[index] = element_number++;

	printf("\n");
	printf("  ");

	/* At index zero, print the values of the elements in the array of
	   numbers */

	for (index = 0; index < 5; index++)
		printf("%d ", array_number[index]);

	printf("\n");

	/* At index zero, print the value of the element in the array of
	   numbers */

	printf("%d ", array_number[0]);

	/* At index zero, initialize the elements in the array of letters
	   with ASCII values ninety-seven through one hundred twenty-one */

	for (index = 0; element_letter < 122; index++)
		array_letter[index] = element_letter++;

	/* At index zero, print the five ASCII values of the elements in
	   the array of letters */

	for (index = 0; index < 5; index++)
		printf("%c ", array_letter[index]);

	printf("\n");

	/* At index one, print the ASCII value of the element in the
	   array of numbers */

	printf("%d ", array_number[1]);

	/* At index five, print the five ASCII values of the elements in
	   the array of letters */

	for (index = 5; index < 10; index++)
		printf("%c ", array_letter[index]);

	printf("\n");

	/* At index two, print the ASCII value of the element in the
	   array of numbers */

	printf("%d ", array_number[2]);

	/* At index ten, print the five ASCII values of the elements in
	   the array of letters */

	for (index = 10; index < 15; index++)
		printf("%c ", array_letter[index]);

	printf("\n");

	/* At index three, print the ASCII value of the element in the
	   number array */

	printf("%d ", array_number[3]);

	/* At index fifteen, print the five ASCII values of the elements
	   in the letter array */

	for (index = 15; index < 20; index++)
		printf("%c ", array_letter[index]);

	printf("\n");

	/* At index four, print the ASCII value of the element in the
	   number array */

	printf("%d ", array_number[4]);

	/* At index twenty, print the five ASCII values of the elements
	   in the letter array */

	for (index = 20; index < 25; index++)
		printf("%c ", array_letter[index]);

	printf("\n");
	printf("\n");
	printf("Limit your message to 75 letters and end it with\n");
	printf("an exclamation point.\n");

	printf("\n");
	printf("Message: ");

	for (counter = 0; counter < 77; counter++) {
		scanf("%c", &letter);

		letter = tolower(letter);

		/* a */

		if (letter == array_letter[0]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[0]);
			fprintf(pointer_file, "%d", array_number[0]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* b */

		if (letter == array_letter[1]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[0]);
			fprintf(pointer_file, "%d", array_number[1]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* c */

		if (letter == array_letter[2]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[0]);
			fprintf(pointer_file, "%d", array_number[2]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* d */

		if (letter == array_letter[3]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[0]);
			fprintf(pointer_file, "%d", array_number[3]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* e */

		if (letter == array_letter[4]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[0]);
			fprintf(pointer_file, "%d", array_number[4]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* f */

		if (letter == array_letter[5]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[1]);
			fprintf(pointer_file, "%d", array_number[0]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* g */

		if (letter == array_letter[6]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[1]);
			fprintf(pointer_file, "%d", array_number[1]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* h */

		if (letter == array_letter[7]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[1]);
			fprintf(pointer_file, "%d", array_number[2]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* i */

		if (letter == array_letter[8]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[1]);
			fprintf(pointer_file, "%d", array_number[3]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* j */

		if (letter == array_letter[9]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[1]);
			fprintf(pointer_file, "%d", array_number[4]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* k */

		if (letter == array_letter[10]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[2]);
			fprintf(pointer_file, "%d", array_number[0]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* l */

		if (letter == array_letter[11]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[2]);
			fprintf(pointer_file, "%d", array_number[1]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* m */

		if (letter == array_letter[12]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[2]);
			fprintf(pointer_file, "%d", array_number[2]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* n */

		if (letter == array_letter[13]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[2]);
			fprintf(pointer_file, "%d", array_number[3]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* o */

		if (letter == array_letter[14]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[2]);
			fprintf(pointer_file, "%d", array_number[4]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* p */

		if (letter == array_letter[15]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[3]);
			fprintf(pointer_file, "%d", array_number[0]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* q */

		if (letter == array_letter[16]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[3]);
			fprintf(pointer_file, "%d", array_number[1]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* r */

		if (letter == array_letter[17]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[3]);
			fprintf(pointer_file, "%d", array_number[2]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* s */

		if (letter == array_letter[18]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[3]);
			fprintf(pointer_file, "%d", array_number[3]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* t */

		if (letter == array_letter[19]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[3]);
			fprintf(pointer_file, "%d", array_number[4]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* u */

		if (letter == array_letter[20]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[4]);
			fprintf(pointer_file, "%d", array_number[0]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* v */

		if (letter == array_letter[21]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[4]);
			fprintf(pointer_file, "%d", array_number[1]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* w */

		if (letter == array_letter[22]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[4]);
			fprintf(pointer_file, "%d", array_number[2]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* x */

		if (letter == array_letter[23]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[4]);
			fprintf(pointer_file, "%d", array_number[3]);
			fprintf(pointer_file, " ");

			fclose(pointer_file);
		}

		/* y */

		if (letter == array_letter[24]) {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "%d", array_number[4]);
			fprintf(pointer_file, "%d", array_number[4]);
			fprintf(pointer_file, " ");


			fclose(pointer_file);
		}

		/* ! */

		if (letter == '!') {
			pointer_file = fopen(pointer_name, pointer_mode);

			fprintf(pointer_file, "\n");

			fclose(pointer_file);

			printf("\n");
			printf("Encrypted message written to file.");
			printf("\n");
			printf("\n");

			exit(0);
		}
		
		if (counter == 76) {
			printf("\n");
			printf("Error! Bad Input.");
			printf("\n");
			printf("\n");

			exit(1);
		}

	}
}