// main.c

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

#include "students.h"

#define OUTPUT_FILE_NAME "output.txt"

// gcc -o main main.c students.c

int main() {
    int *students = NULL;
    // KEY is a mark, VALUE is count of students who get that mark
    int map[] = {0, 0, 0, 0, 0, 0};

    int currIndex = 0;
    int mark;
    do
    {
        printf("\nEnter a mark for %d student(0 - to exit): ", currIndex + 1);
        scanf("%d", &mark);
        if(mark != 0 && (mark < 2 || mark > 5)) printf("\nMark only can be in range (2, 5)");
        else {
            if(mark == 0) break;
            students = (int*)realloc(students, (currIndex + 1) * sizeof(int));
            students[currIndex++] = mark;
            map[mark] = map[mark] + 1;
        }
    } while (mark != 0);

    int countOfStudents = 0;
    calculate_and_print_metadata_about_students(students, map, &countOfStudents);
    print_students_to_file(OUTPUT_FILE_NAME, students, &countOfStudents);
    print_ith_student_mark_or_exit(students, &countOfStudents);

    free(students);
    return 0;
}

// students.h

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

#define EXCELLENT_MARK 5
#define NEGATIVE_MARK 2

void print_students_to_file(char *file_name, int *students, int *countOfStudents);
void print_ith_student_mark_or_exit(int *students, int *countOfStudents);

void calculate_and_print_metadata_about_students(int *students, const int map[], int *countOfStudents);

void fill_students_manually(int **students, int *map);
void fill_students_via_random(int **students, int *map, unsigned long count);

// students.c

#include "students.h"

void calculate_and_print_metadata_about_students(int *students, const int map[], int *countOfStudents) {
    double averageMark = 0.0;
    double sumOfMarks = 0;

    for(int mark = 2; mark <= 5; mark++) {
        sumOfMarks += mark * map[mark];
        *countOfStudents += map[mark];
    }

    for(int i = 0; i < *countOfStudents; i++) {
        printf("\n%5d'th student's mark is %d", i + 1, students[i]);
    }

    averageMark = sumOfMarks / *countOfStudents;
    printf("\n\nAverage mark is %.3lf", averageMark);

    printf("\n\nCount of students who get excellent mark %d", map[EXCELLENT_MARK]);
    printf("\n\nCount of students who get negative mark %d", map[NEGATIVE_MARK]);
}

void print_students_to_file(char *file_name, int *students, int *countOfStudents) {
    FILE *output = fopen(file_name, "w");
    if(output != NULL) {
        for(int i = 0; i < *countOfStudents; i++) {
            fprintf(output, "\n%5d'th student's mark is %d", i + 1, students[i]);
            fputs("\n", output);
        }
    } else {
        printf("printToFile Error: file does not exist yet");
    }
    fclose(output);
}

void print_ith_student_mark_or_exit(int *students, int *countOfStudents) {
    int numberOfStudent = 0;
    do
    {
        printf("\nEnter a number of student who mark you want to see(0 - to exit): ");
        scanf("%d", &numberOfStudent);

        if(numberOfStudent < 0 || numberOfStudent > *countOfStudents) {
            printf("\nUser by %d number cannot be find...", numberOfStudent);
        } else {
            if(numberOfStudent > 0) {
                printf("%d'th student's mark is %d", numberOfStudent, students[numberOfStudent - 1]);
            }
        }
    } while (numberOfStudent != 0);
}

void fill_students_manually(int **students, int *map) {
    int currIndex = 0;
    int mark;
    do
    {
        printf("\nEnter a mark for %d student(0 - to exit): ", currIndex + 1);
        scanf("%d", &mark);
        if(mark != 0 && (mark < 2 || mark > 5)) printf("\nMark only can be in range (2, 5)");
        else {
            if(mark == 0) break;
            *students = realloc(*students, (currIndex + 1) * sizeof(int));
            *students[currIndex++] = mark;
            map[mark] = map[mark] + 1;
        }
    } while (mark != 0);
}
void fill_students_using_random(int **students, int *map, unsigned long count) {
    int currIndex = 0;
    for(int i = 0; i < count; i++) {
        int mark = rand() % (EXCELLENT_MARK - NEGATIVE_MARK + 1) + NEGATIVE_MARK;
        *students = (int*)realloc(*students, (currIndex + 1) * sizeof(int));
        *students[currIndex++] = mark;
        map[mark] = map[mark] + 1;
    }
}