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

# define SIZE 500

int strlen(char * str);
int isDelimiter(char c);
void checkRegister(char * buffer);
void showСorrectText(char * buffer, FILE * result);

int main() {

    int i = 0;
    char buffer[SIZE];

    FILE * text, *result;
    text = fopen("text.txt", "r");
    result = fopen("newtext.txt", "w");

    if (text == NULL || result == NULL) {
        printf("Error occured!\n");
        system("pause");
        exit(1);
    }

    fgets(buffer, SIZE, text);

    checkRegister(buffer);
    showСorrectText(buffer, result);

    fclose(text);
    fclose(result);
    system("pause");
    return 1;
}

int strlen(char * str) {
    int len = 0;
    while (str[len++]);
    return len - 1;
}

int isDelimiter(char c) {
    int i;
    char delimiters[] = {
        '.',
        '!',
        '?'
    };
    for (i = 0; i < 3; i++)
        if (c == delimiters[i])
            return 1;
    return 0;
}

void checkRegister(char * buffer) {
    for (int j = 0; buffer[j] != '\0'; j++) {

        if (isDelimiter(buffer[j])) {
            if (toupper(buffer[j + 1]))
                buffer[j + 1] = toupper(buffer[j + 1]);
        }

        if (isDelimiter(buffer[j]) && (buffer[j + 1] == ' ')) {
            if (toupper(buffer[j + 2])) {
                buffer[j + 2] = toupper(buffer[j + 2]);
                j += 2;
            }
        }
        else if (tolower(buffer[j]) && !isDelimiter(buffer[j - 1]))
            buffer[j] = tolower(buffer[j]);

        if (toupper(buffer[0]))
            buffer[0] = toupper(buffer[0]);

    }
}

void showСorrectText(char * buffer, FILE * result) {
    int j, i;
    char temp[SIZE];

    for (j = 0, i = 0; buffer[j] != '\0';) {
        if (buffer[i] == ' ' && buffer[i + 1] == ' ') {
            temp[j] = ' ';
            i++;
            continue;
        }

        if ((isDelimiter(buffer[i]) || buffer[i] == ',') && (buffer[i + 1] != ' ')) {
            temp[j] = buffer[i];
            temp[j + 1] = ' ';
            j += 2;
            i++;
            continue;
        }

        temp[j] = buffer[i];
        i++;
        j++;
    }
    temp[j] = '\0';

    for (i = 0; temp[i] != '\0'; i++) {
        printf("%c", temp[i]);
    }

    fputs(temp, result);
}