#include <stdio.h>
#include "linkedlist.h"

/* Defines the maximum length of each line read. */
#define Max 80

/* ReadFile takes a string representing a textfile, and returns the lines of
   it as seperate elements in a doubly-linked list. It will return a single
   element list, with the element being an error message, if there was an 
   error. */
node *readFile(char *fileName)
{
  /* Sets up a pointer to a doubly-linked list. */
  node *linkedList;

  /* Sets up listItem, used to store the current line from the textfile */
  char listItem[Max];

  /* Sets up a file pointer. */
  FILE *fp;
  
  /* Points the file pointer to the filename passed to ReadFile. Returns Null
     if the file does not exist. */
  if ((fp = fopen(fileName, "r")) == NULL) {
    linkedList = newList("File doesn't exist\n");
    return linkedList;
  }
  
  /* Creates a doubly-linked list with each node being a line from the 
     textfile. */
  
  /* Initialize list. */ 
  if ((fgets(listItem, Max, fp)) != NULL) {
    linkedList = newList(listItem);
  
  /* Fill list with data from textfile. */
    while ((fgets(listItem, Max, fp)) != NULL) {
      linkedList = addToEnd(linkedList, listItem);
    }
    return linkedList;
  }
  else {

    /* If the file is empty, return a list with "File is empty" as the data
       for its only node. */
    linkedList = newList("File is empty");
    return linkedList;
  }
}

/* writeFile takes a string representing a filename and a doubly-linked list.
   It writes the contents of the list to a textfile.  It returns 0 if 
   it is successful, and 1 if it is not. */

int writeFile(char * fileName, node *linkedList) {
  /* Sets up a file pointer. */ 
  FILE *fp;
  if ((fp = fopen(fileName, "w")) == NULL) {
    return 1;
  }
  else {
    linkedList = getFirst(linkedList);
    do {
      if (fputs(linkedList->data, fp) == NULL) {
        return 1;
      }
      linkedList = getNext(linkedList);
    }
    while (!atEnd(linkedList));
    return 0;
  }
}

/* listPrint takes a doubley linked list with at least one element.  It prints
   the contents of the list to the screen.  It assumes that if you want a list
   item to appear on the next line, you included a newline character in the 
   string. */

void listPrint(node *linkedList) {
  linkedList = getFirst(linkedList);
  do {
    printf("%s", linkedList->data);
    linkedList = getNext(linkedList);
  }
  while (!(atEnd(linkedList)));
  printf("%s", linkedList->data);
}