#include <stdio.h>
#include <string.h>

char romanian_numbers[7] = {'I', 'V', 'X', 'L', 'C', 'D', 'M'};
int arabic_numbers[7] = {1, 5, 10, 50, 100, 500, 1000};
char romanian_groups[14] = {'M', 'C', 'D', 'C', 'C', 'X', 'L', 'X', 'X', 'I', 'V', 'I', 'I'};
int arabic_groups[14] = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};

int romanian_number_validator(char number[]){
    int i, j, is_valid, k, l;
    i = 0;
    is_valid = 0;                              // counter of symbols being romanian symbols
    int counters[7] = {0,0,0,0,0,0,0};         // counter of the occurences of romanian symbols

    while (number[i] != (char)0 ){
        for (j=0; j < 7; j++){
            if(number[i] == romanian_numbers[j]){
                counters[j] += 1;
                is_valid += 1;
                if (j % 2 == 0 && counters[j] > 4){
                    return 2;                 // it means that there is more than 4 of I, X, C or M
                }
                if (j % 2 == 1 && counters[j] > 2){
                    return 3;                 // it means that there is more than 2 of V, L  or D
                }
                for (k=j-1; k > 0; k--){
                    if (counters[k] > 1){
                        return 4;             // it means that there is more than one number smaller than
                                              // number[i] before this number (e.g. CCD)
                    }
                }
            }
        }
        i++;
    }

    if (is_valid < i){                        // checks if romanian number contains only M,D,C,L,X,V,I
        return 1;
    }

    for (l=0; l < 15; l++){
        if(number[l-3] != (char)0 && number[l-2] != (char)0 && number[l-1] != (char)0){
            if (number[l-3] == number[l] && number[l-2] ==number[l] && number[l-1] == number[l]){
                return 5;
            }
        }
    }

    return 0;

}

void validation_messenger(char number[]){
    if (romanian_number_validator(number) == 1){
        printf("Your number contains some not romanian symbols.");
    }
    if (romanian_number_validator(number) == 2){
        printf("Your number contains more than 4 symbols from {I, X, C, M}.");
    }
    if (romanian_number_validator(number) == 3){
        printf("Your number contains more than 2 symbols from {V, L, D}.");
    }
    if (romanian_number_validator(number) == 4){
        printf("Before some number your input contains more than 1 smaller number. e.g. XXC");
    }
    if (romanian_number_validator(number) == 5){
        printf("Your number has 4 the same numbers in a row.");
    }
    else{
        if (romanian_to_arabic(number) == -1){
            printf("You have wrong order of the symbols. e.g. CMD or XCL");
        }
        if (romanian_to_arabic(number) == -2){
            printf("Before and after some number you have smaller one. e.g. XLX");
        }
        if (romanian_to_arabic(number) == -3){
            printf("You have wrong smaller number before greater one.");
        }
        if (romanian_to_arabic(number) == -4){
            printf("You have L, D or V before greater number.");
        }
    }
}

int romanian_to_arabic(char number[]){
    int i, j, k;
    int arabic;
    arabic = 0;
    k=0;
    int result[16];
    for (i=0; i<16; i++){          // returns table of int, each int is the value of proper romanian symbol
        for (j=0; j<7; j++){
            if (romanian_numbers[j] == number[i]){
                result[i] = arabic_numbers[j];
            }
        }
    result[i+1] = 0;
    }

    while(result[k] > 0){
        if (result[k] < result[k+1] && result[k+2] != 0){
            if (0.5*(-result[k] + result[k+1]) <= result[k+2]){
                return -1;
            }
            if (result[k] == result[k+2]){
                return -2;
            }
        }

        if (result[k] >= result[k+1]){
            arabic += result[k];
        }

        if (result[k] < result[k+1] && result[k+1] != 0 && result[k] != 0){
            if (result[k] != 5 && result[k] != 50 && result[k] != 500){
                if (result[k] == result[k+1] / 5 || result[k] == result[k+1]/10 ){
                    arabic -= result[k];
                }
                else {
                    return -3;
                }
            }
            else {
                return -4;
            }
        }
        k++;
    }
    return arabic;
}

void arabic_to_romanian(int arabic){
    int i, j;
    char result[20];
    j = 0;
    i = 0;

    for (i=0; i<13; i++){
        while(arabic >= arabic_groups[i]){
            if( i % 2 != 0 ){
                result[j] = romanian_groups[i];
                result[j+1] = romanian_groups[i-1];
                j += 1;
            }
            else{
                result[j] = romanian_groups[i];
            }
            arabic -= arabic_groups[i];
            j++;
        }
    }
    result[j] = (char)0;

    int k = 0;
    while (result[k]!= (char)0){
        printf("%c ", result[k]);
        k++;
    }
    return;
}

int main(int argc, char *argv[]){
    const int length = 15; // length of max romanian number (MMMDCCCLXXXVIII) + 1
    char number[length];
    char letter;
    int arabic;

    letter = 'X';

    printf ("This is converter from romanian numbers to arabic or otherwise.\n");

    if (argc == 1){
        printf("Please insert A if you want to convert from arabic to romanian or R otherwise\n");
        scanf("%c", &letter);
    }

    if((argc > 1 && strcmp(argv[1], "R")==0) || letter == 'R'){
        printf ("Please insert romanian number.");
        scanf("%s", number);

        if (romanian_number_validator(number) == 0 && romanian_to_arabic(number) > 0){
                printf("%d", romanian_to_arabic(number));
        }
        else{
            validation_messenger(number);
            printf ("\nTry again.");
        }
    }

    if((argc > 1 && strcmp(argv[1], "A")==0) || letter== 'A'){
        printf ("Please insert arabic number");
        scanf("%d", &arabic);
        if (arabic>3999){
            printf("Please insert number lower than 4000");
        }
        else{
            arabic_to_romanian(arabic);
        }
    }


    if ((argc > 1 && (strcmp(argv[1], "R")!=0) && (strcmp(argv[1], "A")!=0)) && letter == 'X') {
        printf("Please use command line to run program with correct letter: R or A");
    }

    return 0;
}