#include <stdio.h>

int comprimi(FILE *fin, FILE *fout) {
    char lastChar = 0, currChar; // sono sicuro che il file non inizi con un null character
    int count = 0;

    int charCount = 0;

    while (!feof(fin))
    {
        currChar = fgetc(fin);

        if (feof(fin))
            break;
        

        if (currChar != lastChar || count == 10)   {
            if (count > 1) {
                fputc('$', fout);
                fputc('0'+count-1, fout);
                charCount += 2;
            }

            count = 1;
            lastChar = currChar;
            fputc(currChar, fout);
            charCount++;
        } else {
            count++;
        }
    }

    if (count > 1) { // Controllo se devo scrivere le ripetizioni dell'ultimo carattere
        fputc('$', fout);
        fputc('0'+count-1, fout);
        charCount += 2;
    }

    return charCount;
}

int decomprimi(FILE *fin, FILE *fout) {
    char lastChar, currChar;
    int count, i;

    int charCount = 0;
    while (!feof(fin))
    {
        currChar = fgetc(fin);

        if (feof(fin))
            break;

        if (currChar == '$') {
            count = fgetc(fin) - '0';

            for (i = 0; i < count; i++)
                fputc(lastChar, fout);

            charCount += count;
        } else {
            lastChar = currChar;
            fputc(currChar, fout);
            charCount++;
        }
    }

    return charCount;
}


int main()
{

    FILE *fp_read, *fp_write;
    char operation;

    puts("Inserisci 'c' per comprimere o qualsiasi altro carattere per decomprimere: ");
    scanf(" %c", &operation);

    if (operation == 'c') {
        fp_read = fopen("./sorgente.txt", "r");
        fp_write = fopen("./compresso.txt", "w");
    } else {
        fp_read = fopen("./compresso.txt", "r");
        fp_write = fopen("./decompresso.txt", "w");
    }

    if (fp_read == NULL)
    {
        printf("Error opening input file\n");
        return 1;
    }
    if (fp_write == NULL)
    {
        printf("Error opening output file\n");
        return 2;
    }

    if (operation == 'c') {
        comprimi(fp_read, fp_write);
    } else {
        decomprimi(fp_read, fp_write);
    }

    fclose(fp_read);
    fclose(fp_write);

    return 0;
}