<?php

require_once (dirname(__FILE__) . "/fetch.php");

// Move file pointer to the corresponding closing bracket of the current
// element.
function move_to_closing_bracket($fp, &$char)
{
   if ($char == CLOSE_ELEMENT_CHAR) return;

   $ii = 1;
   while (($char = fgetc($fp)) != NULL && !feof($fp))
   {
      if ($char == OPEN_ELEMENT_CHAR) $ii++;
      else
      {
         if ($char == CLOSE_ELEMENT_CHAR) $ii--;
         if ($ii == 0) break;
      }
   }
}

// Store the file contents as a string, replace the specified string with a new
// string, and re-write the file.
function replace_string_in_file($file_name, $old, $new="")
{
   $file_contents = file_get_contents($file_name);
   $file_contents = str_replace($old, $new, $file_contents);

   $fp = fopen($file_name, 'w');
   
   fwrite($fp, $file_contents);
}

// Erase file contents between and including element's brackets.
function read_raw_element_string($fp, &$char)
{
   $element_open_position = ftell($fp)-1;
   move_to_closing_bracket($fp, $char);
   $element_close_position = ftell($fp);

   if (char_is_white_space($char = fgetc($fp)))
   {
      skip_white_space($fp, $char);
      $element_close_position = ftell($fp)-1;
   }

   $byte_range = $element_close_position - $element_open_position;
   fseek($fp, $element_open_position);
   $element = fread($fp, $byte_range);

   return $element;
}

// If the submitted element points to an object, convert the element to its
// raw string representation.  Otherwise, leave the string unchanged.
function convert_element_to_raw($element)
{
   if (is_object($element))
   {
      $element = $element->convert_to_raw_string();
   }

   return $element;
}

// Replace in a file the element identified by specified ID w/ a new element.
// The new element can be an object, element string, or empty.  If empty, the
// old element will be removed and replaced with nothing.
function replace_element_by_id($file_name, $id, $element="")
{
   if (file_exists($file_name))
   {
      $fp = fopen($file_name, 'r+');
      move_to_element_by_id($fp, $char, $id);
      if (feof($fp)) return;
      $old_raw_element = read_raw_element_string($fp, $char, $id);
      $new_raw_element = convert_element_to_raw($element);
      fclose($fp);

      if ($old_raw_element != NULL)
      {
         replace_string_in_file(
            $file_name, $old_raw_element, $new_raw_element);
      }
      return $old_raw_element;
   }
}

// Replace an element with a new element.  If the new element is unspecified,
// the old element will be deleted.
function run_replace($file_name, $id, $element)
{
   if (!file_exists($file_name)) return;

   replace_element_by_id($file_name, $id, $element);
   $message = "!! Removing element $id... !!\n\n";
   if ($element != NULL)
   {
      $message .= "Replacing with\n--------------\n";
      $message .= convert_element_to_raw($element);
      $message .= "\n\n";
   }
   $message .= "New file\n--------\n";
   $message .= run_parse($file_name);

   return $message;
}

<?php

require_once (dirname(__FILE__) . "/fetch.php");
require_once (dirname(__FILE__) . "/replace.php");

// Insert a string into the file, leaving the current data intact.
function insert_string_at_cursor($fp, $string)
{
   $position = ftell($fp);
   $file_meta_data = fstat($fp);
   $length = $file_meta_data["size"] - $position;

   $tail = fread($fp, $length);
   fseek($fp, $position);
   $new_content = $string . $tail;

   ftruncate($fp, $position);
   fwrite($fp, $new_content);
}

// Insert the element data at the end of the file.
function insert_element_into_file($fp, $element)
{
   fwrite($fp, $element);
}

// Insert an element into the element referenced by id.  This will create a new
// child for the referenced element.
function insert_element_into_element($fp, $element, $id)
{
   move_to_element_by_id($fp, $char, $id);
   move_to_closing_bracket($fp, $char);
   fseek($fp, ftell($fp)-1);
   insert_string_at_cursor($fp, $element);
}

// Move to the position either before or after the element currently under the
// cursor.
function move_cursor_based_on_insertion_method($fp, $char, $before)
{
   if ($before == False)
   {
      move_to_closing_bracket($fp, $char);
   }
   else
   {
      fseek($fp, ftell($fp)-1);
   }
}

// Insert an element before or after the element referenced by id.
function insert_element_at_id($fp, $element, $id, $before=False)
{
   move_to_element_by_id($fp, $char, $id);
   move_cursor_based_on_insertion_method($fp, $char, $before);
   insert_string_at_cursor($fp, $element);
}

// Open file for writing or appending based on where the new element will be
// inserted.
function open_file_based_on_method($file_name, $id)
{
   if ($id != NULL)
   {
      $fp = fopen($file_name, 'r+');
   }
   else
   {
      $fp = fopen($file_name, 'a');
   }

   return $fp;
}

// Choose one of three methods for insertion based on the existence and values
// of the id and child parameters.
function apply_insertion_method($fp, $raw_element, $id, $child, $before)
{
   if ($child == True)
   {
      insert_element_into_element($fp, $raw_element, $id);
   }
   elseif ($id != NULL)
   {
      insert_element_at_id($fp, $raw_element, $id, $before);
   }
   else
   {
      insert_element_into_file($fp, $raw_element);
   }
}   

// Insert an element into the specified file.  The before parameter indicates
// whether or not the incoming element should be placed before the referenced
// element.
function insert_element(
   $file_name, $element, $id=NULL, $child=False, $before=False)
{
   $fp = open_file_based_on_method($file_name, $id);
   $raw_element = convert_element_to_raw($element);
   apply_insertion_method($fp, $raw_element, $id, $child, $before);
}

// Insert an element into the specified file.  Return relevant messages for
// verbose output.
function run_insert($file_name, $element, $id=NULL, $child=False, $before=False)
{
   $message = "Inserting\n---------\n";
   $message .= convert_element_to_raw($element) . "\n\n";

   $child = ($child && $child != '0') ? True : False;
   $before = ($before && $before != '0') ? True : False;
   insert_element($file_name, $element, $id, $child, $before);

   $message .= "New File\n--------\n";
   $message .= run_parse($file_name);

   return $message;
}