/***************************************************************************
                                shuffler.c
                          -------------------
    begin                : Fri Mar 21 01:05:09 CST 2003
    copyright            : (C) 2003 by Andy Ruder
    email                : aeruder@yahoo.com
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
#include<stdio.h>
#include<stdlib.h>
#include<time.h>

const long int MaxStringLength = 3000;

struct item_list
  {
   struct item_list *previous;
   struct item_list *next;
   char *item_name;
  };

typedef struct item_list item_list;

int isspace(char x)
  {
   if (x == ' ' || x == '\n') return 1;
   if (x == '\r' || x == '\t') return 1;
   return 0;
  }

int file_exists(char *string)
  {
   FILE *x;
   x = fopen(string, "r");
   if (x == NULL)
     {
      return 0;
     }
   fclose(x);
   return 1;
  }

int load_items(item_list **playlist, char *playlist_file_name)
  {
   FILE *playlist_file;
   item_list *temp;
   long int buffer_position = 0;
   char buffer[MaxStringLength];
   char x;
   int uncasted_x;
   long int abort_flag = 0;
   long int number_items = 0;

   playlist_file = fopen(playlist_file_name, "r");

   while (!abort_flag)
     {
      buffer_position = 0;
      buffer[0] = 0;
      do
        {
         x = 0;
         uncasted_x = fgetc(playlist_file);
         if (uncasted_x == EOF)
           {
            abort_flag = 1;
            break;
           }
         x = (char) uncasted_x;
        } while(isspace(x));
      while (!isspace(x))
        {
         buffer[buffer_position] = x;
         uncasted_x = fgetc(playlist_file);
         x = 0;
         if (uncasted_x == EOF)
           {
            abort_flag = 1;
            break;
           }
         x = (char) uncasted_x;
         buffer_position++;
         if (buffer_position == MaxStringLength - 1) buffer_position --;
        }
      buffer[buffer_position] = 0;
      temp = malloc(sizeof(item_list));
      temp->item_name = malloc(strlen(buffer) + 1);
      strcpy(temp->item_name, buffer);
      temp->next = *playlist;
      //temp->previous = NULL;
      //(*playlist)->previous = temp;

      *playlist = temp;
      number_items++;
     }
   fclose(playlist_file);
   return number_items-1;
  }

void swap_item(item_list **list, long int x, long int y, long int items)
  {
   long int z;
   item_list *temp;
   item_list *x_list;
   item_list *y_list;   
   char *temp_string;
   
   if (x > items) return;
   if (y > items) return;
   
   for (temp = *list, z = 0; temp != NULL && z != x; z++, temp = temp->next);
   x_list = temp;

   for (temp = *list, z = 0; temp != NULL && z != y; z++, temp = temp->next);
   y_list = temp;
   
   if (x_list == NULL || y_list == NULL) return;
   if (x_list == y_list) return;

   temp_string = x_list->item_name;
   x_list->item_name = y_list->item_name;
   y_list->item_name = temp_string;
   
  }       
         
   
int main(int argc, char *argv[])
  {
   item_list *playlist = NULL;
   long int number_of_items;
   item_list *temp_list = NULL;
   item_list *temp_list2 = NULL;
   long int x;
   
   if (argc == 1)
     {
      printf("Syntax : shuffler <playlist>\n");
      return 1;
     }

   if (!file_exists(argv[1]))
     {
      printf("File does not exist!\n");
      return 2;
     }

   number_of_items = load_items(&playlist, argv[1]);

   srand(time(NULL));

/*   for (temp_list = playlist; temp_list != NULL; temp_list = temp_list->next)
     {
      printf("%s ", temp_list->item_name);
     }*/

   for (x = 1; x <= number_of_items; x++)
     {
      swap_item(&playlist, x, rand() % number_of_items + 1, number_of_items);
     }

   for (temp_list = playlist; temp_list != NULL; temp_list = temp_list->next)
     {
      printf("%s\n", temp_list->item_name);
     }

   for (temp_list = playlist; temp_list != NULL; )
     {
      temp_list2 = temp_list->next;
      free(temp_list->item_name);
      free(temp_list);
      temp_list = temp_list2;
     }
   playlist = NULL;
   return 0;
  }