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

void selection() {
    printf(" 1. Entering the natural number\n 2. Output the value of entered number in decimal, octal and hexadecimal form.\n 3. Output of a entered reversed natural number in decimal form.\n 4. Your natural number convertation to the number system with base n [2..16]. \n 5. Information about the version and author of the program. \n 6. Exit\n");
}

int enter_number() {
    int num;
    printf("Entering the natural number:\n");
    while (!(scanf_s("%d", &num)) || num <= 0) {
        rewind(stdin);
        printf("You entered wrong value.\nPlease, enter natural number.\n");
    }
    printf("You've entered number %d.  \n", num);
    return num;
}

void convert8(int number) {
    if (number >= 8)
    convert8(number / 8);
    printf("%d", number % 8);
}


void convert16 (int number) {
    int result;
    if (number >= 16) {
        result = number % 16;
        number /= 16;
        convert16(number);
        printf("%c", result > 9 ? result - 10 + 'A' : result + '0');
    } else {
        printf("%c", number > 9 ? number - 10 + 'A' : number + '0');
    }
}

void reversed_number (int number) {
    int result;
    while (number > 0) {
        result = number % 10;
        printf("%d", result);
        number /= 10;
    }
}

int radix_input() {
    int radix;
    printf("Enter the radix from 2 to 16: ");
    while (!(scanf_s("%d", &radix)) || radix < 2 || radix > 16) {
        rewind(stdin);
        printf("You entered wrong value.\nPlease, enter the radix from 2 to 16.\n");
    }
    return radix;
}

void convert_2_16(int number, int radix) {
    int result;
    if (number >= radix) {
        result = number % radix;
        number /= radix;
        convert_2_16(number, radix);
        printf("%c", result > 9 ? result - 10 + 'A' : result + '0');
    }
    else {
        printf("%c", number > 9 ? number - 10 + 'A' : number + '0');
    }
}

void output1_dec_oct_hex(int number) {
    printf("Your number was: ");
    printf("%d\n", number);
    printf("Your number in decimal form is: ");
    printf("%d\n", number);
    printf("Your number in octal form is: ");
    convert8(number);
    printf("\nYour number in hexadecimal form is: ");
    convert16(number);
}

void infotmation() {
    printf("Release version 1.0\nCopyright (c) 2018 Tonya-chan\n");
}

int main() {
    int number = 0, radix = 0;
    int switch_c;
    selection();
    do {
        printf("\n\nEnter 0 to get selection information.\n");
        printf("Enter from 0 to 6 to choose.\n");
        while (!(scanf_s("%d", &switch_c)) || switch_c < 0 || switch_c > 6) {
            rewind(stdin);
            printf("You entered wrong value.\nPlease, enter from 0 to 6.\n");
        }
        switch (switch_c) {
        case 0:
            system("CLS");
            selection();
                break;
        case 1:
            system("CLS");
            number = enter_number();
                break;
        case 2:
            system("CLS");
            output1_dec_oct_hex(number);
                break;
        case 3:
            system("CLS");
            reversed_number(number);
                break;
        case 4:
            system("CLS");
            radix = radix_input();
            convert_2_16(number, radix);
                break;
        case 5:
            system("CLS");
            infotmation();
                break;
        case 6:
            system("CLS");
            printf("Bye!\n");
            system("exit");
        }

    } while (switch_c != 6);
    return 0;
}