/*Verifiers.c
 * By: Adrien Kwok
 * This code is licensed under the General Public License Version 2.
 * Year: 2008
 * Easter Egg: dropped on Windows version as it heavily depends on UNIX.
 */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void initSIN(){
	char SIN[10];
	int intArray[9];
	int intArray2[4];
	int intCount;

	while(1) {
		printf("\nFor security reasons, your SIN will be wiped from memory after each verification.\n\n");
		while(1) {	
			printf("Please enter your SIN (Type 0 to menu): ");
			scanf ("%s", SIN);
			int error = 0; // no error 
                        for (intCount = 0; intCount<9; intCount++) {
				if(SIN[intCount] < '0' || SIN[intCount] > '9') {
					error = 1; // error
				}
	                        intArray[intCount] = (int)(SIN[intCount] - '0');
                        }
			if (error == 1 || intArray[0]){
				system ("cls");
				intCount = 0;
				break;
			}
		}
		if (intArray[0] == 0 || SIN[0] == '0') break;  // exit the program if user enters '0'
		intCount = 0;
		// step 1
		intArray2[0] = intArray[1] * 2;
		intArray2[1] = intArray[3] * 2;
		intArray2[2] = intArray[5] * 2;
		intArray2[3] = intArray[7] * 2;

		// step 2
		int intSum = 0;
		if (intArray2[0] < 10) intSum += intArray2[0]; else intSum += intArray2[0] - 9;
		if (intArray2[1] < 10) intSum += intArray2[1]; else intSum += intArray2[1] - 9;
		if (intArray2[2] < 10) intSum += intArray2[2]; else intSum += intArray2[2] - 9;
		if (intArray2[3] < 10) intSum += intArray2[3]; else intSum += intArray2[3] - 9;

		// step 3
		int intOrig = intArray[0] + intArray [2] + intArray[4] + intArray[6];

		// step 4
		int intFinal = intSum + intOrig;

		// step 5
		int intRound = ((intFinal - 1) / 10 + 1) * 10;  // round up to the nearest 10
		int intDiff = intRound - intFinal;
		if (intDiff == intArray[8]) {
			for (intCount = 0; intCount<9; intCount++){
				intArray[intCount] == 0;
			}
			printf("Your SIN number is valid.\n");
		} else {
			for (intCount = 0; intCount<9; intCount++){
				intArray[intCount] == 0;
			}
			printf("Your SIN number is invalid.\n");
		}
	}
}

void initISBN(){
	while(1){
		printf("Please enter your 10-digit ISBN Number (Type 0 to menu): ");
		long long ISBN;
		scanf("%lld", &ISBN);
		if (ISBN <= 0) {
			system ("cls");
			break;
		}
		long long ISBNSum=(ISBN/1000000000LL)*10 + ((ISBN/100000000LL)%10)*9 + ((ISBN/10000000LL)%10)*8
			 + ((ISBN/1000000LL)%10)*7 + ((ISBN/100000LL)%10)*6 + ((ISBN/10000)%10)*5
			 + ((ISBN/1000)%10)*4 + ((ISBN/100)%10)*3 + ((ISBN/10)%10)*2 + (ISBN%10*1);
		if (ISBNSum % 11 == 0 && ISBN != 0) {
			printf("Congratulations, your ISBN is valid!\n");
		} else {
			printf("Sorry, your ISBN is invalid!\n");	
		}
	}
}

void initUPC(){
	while(1) {
		printf("Please enter your 12 digit UPC Code (Type 0 to menu): ");
		long long UPC;
		scanf("%lld", &UPC);
		if(UPC == 0) {
			system ("cls");
			break;
		}
		long long UPCSum = (UPC/100000000000LL) + ((UPC/1000000000LL)%10) + ((UPC/10000000LL)%10) 
                                   + ((UPC/100000LL)%10) + ((UPC/1000)%10) + ((UPC/10)%10);
		UPCSum = UPCSum * 3;
		long long UPCSum2 = ((UPC/10000000000LL)%10) + ((UPC/100000000LL)%10) + ((UPC/1000000LL)%10) + ((UPC/10000)%10) + ((UPC/100)%10);
		long long UPCTotal = UPCSum + UPCSum2;
		if ((UPCTotal + (UPC % 10)) % 10 == 0) {
			printf("Your UPC Code is Valid!\n");
			long long UPCCom = UPC / 1000000;
			long long UPCProd = UPC % 1000000;
			UPCProd /= 10;
			if((UPCCom/100000 == 0)){
				printf("Your company code: 0%lld\n", UPCCom);
			}else{
				printf("Your company code: %lld\n", UPCCom);
			}
			printf("Your product code: ");
			if((UPCProd%100000 < 10000)){
				printf("0");
			}
			if((UPCProd%100000 < 1000)){
				printf("0");
			}
			if((UPCProd%100000 < 100)){
				printf("0");
			}
			if((UPCProd%100000 < 10)){
				printf("0");
			}
			if((UPCProd%100000 < 1)){
				printf("0");
			}
			printf("%lld\n", UPCProd);
		}else{
			printf("Your UPC Code is Invalid!\n");
		}
	}
}

void initClr(){
	system("cls");
}

main(){
	system ("cls");
	printf("Welcome to the Verification Centre!\n\n");
	while(1){
		printf("Main Menu\n");
		printf("[1] Social Insurance Number Verifier\n");
		printf("[2] ISBN Verifier\n");
		printf("[3] UPC Verifier\n");
		printf("[4] Reset Screen\n");
		printf("[0] Exit\n");
		printf("Please make a selection: ");
		int intSelection;
		scanf("%d", &intSelection);
		int flagExit = 0;
		switch (intSelection) {
			case 1: initSIN(); break;
			case 2: initISBN(); break;
			case 3: initUPC(); break;
			case 4: initClr(); break;
			case 0: {
				flagExit = 1;
				system ("cls");
				break;
			}
			default: {
				system ("cls");
				printf("Invalid input!\n\n");
			}
		}
		if (flagExit) break;
	}
}