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

#define CORRECT_ENDING 0
#define WRONG_ARGUMENTS_NUMBER -1
#define FILE_NOT_FOUND -2
#define EMPTY_FILE -3
#define UNKNOWN_ARGUMENT -4
#define FILE_OVERRUN -5

#define fd FILE
#define END -1

int get_number_by_pos(fd *f, int pos)
{
    int number;

    fseek(f, (pos + 1) * sizeof(int), SEEK_SET);
    fread(&number, sizeof(int), 1, f);

    return number;
}

void put_number_by_pos(fd *f, int pos, int val)
{
    fseek(f, (pos + 1) * sizeof(int), SEEK_SET);
    fwrite(&val, sizeof(int), 1, f);
}

void quicksort_file(fd *f, size_t start, size_t finish)
{
    int mid, temp;

    size_t i = start;
    size_t j = finish;

    if (finish == END)
    {
        fread(&finish, sizeof(int), 1, f);
    }

    mid = get_number_by_pos(f, finish/2);

    do
    {
        while (get_number_by_pos(f, i) < mid)
        {
            i++;
        }
        while (get_number_by_pos(f, j) > mid)
        {
            j--;
        }

        if (i <= j)
        {
            if (get_number_by_pos(f, i) > get_number_by_pos(f, j))
            {
                temp = get_number_by_pos(f, i);
                put_number_by_pos(f, i, get_number_by_pos(f, j));
                put_number_by_pos(f, j, temp);
            }
            i++;
            if (j > 0)
            {
                j--;
            }
        }
    }
    while (i <= j);

    if (i < finish)
    {
        quicksort_file(f, i, finish);
    }

    if (j > start)
    {
        quicksort_file(f, start, j);
    }

    fclose(f);
}

int generate_file(char *filename)
{
    fd *f;
    int number;
    int n;

    setbuf(stdout, NULL);
    f = fopen(filename, "wb");

    if (!f)
    {
        fprintf(stderr, "Error occured while opening file.\n");
        return FILE_NOT_FOUND;
    }

    printf("Enter the number of integers:\n");
    scanf("%d", &n);

    srand(time(0));

    fwrite(&n, sizeof(int), 1, f);

    for (int i = 0; i < n; i++)
    {
        number = rand() % 100;
        fwrite(&number, sizeof(int), 1, f);
    }

    fclose(f);

    return CORRECT_ENDING;
}

int output_file(char *filename)
{
    fd *f;
    int number;
    int rc = CORRECT_ENDING;

    setbuf(stdout, NULL);

    f = fopen(filename, "rb");

    if (!f)
    {
        fprintf(stderr, "Matching file not found.\n");
        rc = FILE_NOT_FOUND;
    }

    while (fread(&number, sizeof(int), 1, f))
    {
        printf("%d ", number);
    }

    fclose(f);

    return rc;
}

int main(int argc, char** argv)
{
    int rc;

    if (argc != 3)
    {
        fprintf(stderr, "Wrong number of arguments.\n");
        return WRONG_ARGUMENTS_NUMBER;
    }


    if (strcmp(argv[1], "g") == 0)
    {
        rc = generate_file(argv[2]);
    }

    else if (strcmp(argv[1], "p") == 0)
    {
        rc = output_file(argv[2]);
    }

    else if (strcmp(argv[1], "s") == 0)
    {
        fd *f;

        f = fopen(argv[2], "wb");

        if (f == NULL)
        {
            return FILE_NOT_FOUND;
        }

        quicksort_file(f, 0, END);
        rc = CORRECT_ENDING;
    }

    else
    {
        rc = UNKNOWN_ARGUMENT;
    }


    if (rc != CORRECT_ENDING)
      switch (rc)
      {

      case FILE_NOT_FOUND:
      {
          fprintf(stderr, "File is not found.\n");
          break;
      }

      case EMPTY_FILE:
      {
          fprintf(stderr, "Executed file is empty.\n");
          break;
      }

      case UNKNOWN_ARGUMENT:
      {
         fprintf(stderr, "Unknown argument.\n");
         break;
      }

      }
    return rc;
}