<?php	
#
# YEEEAAAAHHHH! IT'S ALIVE RIPPER!
#
# Alright, just in case you can't figure out what this does based on the class title, it provides 
# all the information required to show previous and next buttons while viewing search results 
# from page to page. At the heart of this class is the "calculate" member function. It 
# generates the numbers that are later parsed by the random_access() and new_limit() functions. 
# As a matter of fact, every member function in this class (save for the constructor, 
# which constructs absolutely nothing) is dependent up the calcuate() function. 
#

# 
# The variables that need to be passed to the class are
#
# 1) $howmany - represents the number of results returned from a query. I 
# get this information using the "your_sql_here"_num_rows() function. I know this 
# approach differs to some, but I feel this is the easiest. Less didling around 
# with the SQL statement.  Furthermore, some databases don't SEEM to have a 
# way of returning the number of rows returned by a SELECT statement. SESAM
# for example seems to be one of these (Someone correct me if I'm wrong).
# For those db's, I don't know what to say. 
#
# 2) $i_want - This is the number of results to show per page. This of course 
# can be based on user preference.
# 
# 3) $page - The present page number. I know that the class could've easily taken care 
# of such information, but my preference is to just have the page info passed 
# to the class then acted upon from there. Pass the page info as such....
#
# $pre_next->calculate($howmany, $i_want, $page+ or - 1);
#
# 4) $where - This is the file that the next an previous buttons point to.
#
# 5) $how - What method to use. Get or Post.
#
# 6) $SQL - To internalized first, then written out to the form second. This way, you don't have 
#	    to do it. 
#
# 7) $debug - Passed to the constructor, it controls debugging output.
#

# 
# The Variables in the calculate function (what and why)
# 
# $page - 				Explained above
# $next_views - 	Used mainly by the header() function, it is the high number
#									displayed. In this example, "Displaying 10 through 44 of 62...",
#									the number 44 is the variable $next_views.
# $first_view - 	Used by the limit() function. It is the first number telling the 
#									db where to fetch from in a result set (Based on my understanding
#									and use of SQL).
# $low_num - 			The exact opposite of $next_views and used by the same function.
# $left_overs -		Used in conjunction with $penultimate, it helps the class determine  
#									the last page.
# $penultimate - 	Ah yes,  I remember this one one well. You'll find it referenced in 
#									the header() and buttons() functions both. Used by both to help 
#									determine wether you are indeed on the page before the last, or on the 
#									last page if $left_overs equals 0. 
# $last_page -		Used by header() and buttons(), it represents the number of results to display
#									on the last page. If $last_page equals 0, then $i_want obviously 
#									divided up $howmany with no remainders making $penultimate the last
#									page.
# $howmany - 			Explained above.
# $i_want - 			Explained above.
# $total_pages - 	If you can't figure this one out, are you sure you should be programming? :)
#

class PreNext
{
# This is the heart of of the code controlling next and previous access
# to results returned from a database. 
# setup result listing controls

# Member vars. See above for description of each.
  var $page;
  var $next_views;
  var $first_view;
  var $low_num;
  var $left_overs;
  var $penultimate;
  var $last_page;
  var $howmany;
  var $i_want;
	var $total_pages;
  var $where;
  var $how;
	var $payload;

#########################################################################################
# PreNext()																				
#																						
# This is the obviously the constuctor. At this point in time, it requires a variable.	
# That being $debug. What is easiest is to call the class as such						
#																						
# $nav = new PreNext(yes);									
#																						
# Instead of adding the variable, we added the value we wanted passed. In this case, 	
# yes, in the interest of debugging. In the future, a second arg may be introduced to 
# to ascertain the database in use. There is no output.									
#########################################################################################
function PreNext($debug)
    {
    # Used for debugging. If yes, debugging is on.
    $this->debug = $debug;
    unset($debug);
    }
# End Constructor


#########################################################################################
# calculate()																			
#																						
# This function takes the information provided and calculates what is needed to 		
# continue showing results in the desired fashion. There is no ouptput.					
#########################################################################################
function calculate($howmany, $i_want, $page)
	{
  $this->page=$page;				// You're kidding right!?
  $this->next_views=$i_want * $page;
  $this->first_view=$this->next_views - $i_want;
  $this->low_num=$this->first_view + 1;
  $this->left_overs=$howmany - $this->next_views;
  $this->penultimate=floor($howmany / $i_want);
  $this->last_page=$howmany % $i_want;
  $this->howmany=$howmany;
  $this->i_want=$i_want;    

  # Get how many pages there are going to be. 
	$this->total_pages=ceil($this->howmany/$this->i_want);

  if($this->debug=='yes')
		{
		# Echo for debugging
		echo ("<h3>Output of the calculate() function </h3>\n");
   	echo ("\$this->page = $this->page\n");				echo "<br>";
    echo ("\$this->next_views = $this->next_views\n"); 		echo "<br>";
    echo ("\$this->first_view = $this->first_view\n"); 		echo "<br>";
		echo ("\$this->low_num = $this->low_num\n"); 			echo "<br>";
		echo ("\$this->left_overs = $this->left_overs\n"); 		echo "<br>";
    echo ("\$this->penulitmate = $this->penultimate\n"); 		echo "<br>";
		echo ("\$this->last_page = $this->last_page\n"); 		echo "<br>";
    echo ("\$this->howmany = $this->howmany\n"); 			echo "<br>";
		echo ("\$this->i_want = $this->i_want\n"); 			echo "<br>";   
		echo ("\$this->total_pages = $this->total_pages\n"); 			echo "<br>";   
		}
  }
# end calculate()
    

#########################################################################################
# header()																				
#																						
# In the even that you wish to see something say "display n through n results", this is 
# is the member function to do it. Will be extended in time to allow the developer to 	
# the ability to add his own text. But that's later.									
#########################################################################################
function header()
    {
    # Check to see if this is the last page or only page
    if ($this->page > $this->penultimate)
      {
			if($this->last_page == 1)
				{ $header='Displaying the last result'; }
			elseif($this->howmany < $this->i_want)
				{ $header='Displaying '.$this->howmany.' results'; }
			else
       	{ $header='Displaying the last '.$this->last_page.' results'; }
			}       
    # Check for the first page
    elseif(($this->page==$this->penultimate) && ($this->left_overs=0))
			{
			if($this->howmany==$this->i_want)
		    { $header="Display $this->howmany results"; }	
			}
    # If it is not the last page
    else
        { $header="Displaying $this->low_num through $this->next_views of $this->howmany results"; }
    return $header;
    }
# end header()
    

#########################################################################################    
# new_limit()																			
# 																						
# This is where the limit portion of the SQL statement is generated. Have this function 
# return the statement as a variable ($limit = $pre_next->limit()) then tack it onto    
# end of SQL statement and resend the query. 											
#########################################################################################    
function new_limit()
  { 
	$limit='LIMIT '.$this->first_view.', '.$this->i_want;
  return $limit;
	}
# end new_limit()

#########################################################################################
# action()																				
#																						
# Some of this is information that is moved to the next page. Some if it is used in 	
# existing page. $where and $how are used to build the buttons at the bottom of page. 
# $payload is tweaked and passed onto the next page. This member function has no output.	
# It's really just a way of internalizing certain bits of information.					
#																						
# As can be seen below, it requires  three arguments be passed. 						
# 1) $where is what page the information is being sent to. 								
# 2) $how is POST or GET.																
# 3) $SQL should be obvious. It's the SQL statement. Es no sorpresa grande.				
#########################################################################################
function action($where, $how, $payload)
  {
  $this->where=$where;
  $this->how=$how;
  $this->payload=$payload;
  }
# End action()

#########################################################################################
# random_access()																		
#																						
# After thinking a little about it, this should be pretty easy. Of course, after 		
# setting out in WRONG direction, I got it figured out. What does this function do in a 
# nutshell? Well...																		
# 1) Finds out howmany pages will be needed to show all results	(Stored as $x)			
# 2) Prints out those numbers and creates links at the same time while providing all 	
#    of the information needed for the recieving page to process the request.			
#																						
# What don't I like about this way of doing it? Everything is seen in the URL. 			
# Therefore, I'm still game to a different way of doing things. 						
#########################################################################################
function random_access()
	{
  # Tweaking this thing is turning out to be harder than I thought. However, I have an 
  # idea that I think is going to work. What we do is create sets. We take the number 
  # of results, the number of links to show, and the number of results to show per page. 
  # With this information, we create a movable "glass" that highlights and displays 
  # only the information we need.  
    
  # This is the nunber of links to show
  if($this->i_want>$this->total_pages)
		{ $links_shown=$this->total_pages; }    
  else
		{ $links_shown=$this->i_want; }

	# Set the window_position vars
	$window_position=$this->page;
	$window_position_max=(1+($this->total_pages-$links_shown));

	# Here goes nothing
	if($this->page<$window_position_max)
  	{ 
  	$window_position_counter=$this->page; 
  	$prev_arrow=$this->page;
  	}
	else
  	{ $prev_arrow=$window_position_counter=$window_position_max; }

	# Check to see if the number of links to show is greater than the total number pages
	if( ($links_shown*$this->i_want) >= $this->last_page )
		{
		# If on the first page, do not show the "|<--" and "<<<<" arrows. 
		if($this->page>1 && ($this->total_pages>$this->i_want)) 
			{
			?><a href="<?=$this->where ?>?page=1&i_want=<?=$this->i_want?>&howmany=<?=$this->howmany?>&payload=<?=$this->payload?>" title="First page">
			|&lt;--&nbsp;&nbsp;&nbsp;</a><?php
			echo "<a href=\"$this->where?page=";
			echo $prev_arrow-1;
			echo "&i_want=$this->i_want&howmany=$this->howmany&payload=$this->payload\" title=\"Previous\">\n";
			echo "<<<<</a> &nbsp;&nbsp;"; 
			}

		# Now loop through showing the links
		$counted=(($window_position_counter+$links_shown)-1);		
  	for( ; $window_position_counter<=($counted); ++$window_position_counter)
			{
			# This line builds the anchor tag (link).
			echo "<a href=\"$this->where?page=$window_position_counter&i_want=$this->i_want&howmany=$this->howmany&payload=$this->payload\" title=\"Page $window_position_counter\">\n";
		
			# Make it obvious what page we are on.
			if($window_position_counter==$this->page)
		    { ?><font color="yellow"><?=$window_position_counter ?></font><? }
			else
		    { echo $window_position_counter; }
			?></a>
			<!--- Now for some spacing between the numbers --->
			&nbsp;<?php
			}
		
		# Test for the need of the next and last page arrows
		if($window_position<$window_position_max)
			{ 
			echo "&nbsp; &nbsp;<a href=\"$this->where?page=";
			echo $window_position_counter;
			echo "&i_want=$this->i_want&howmany=$this->howmany&payload=$this->payload\" title=\"Next\">\n";
			?>>>>></a>
			<a href="<?=$this->where ?>?page=<?=$this->total_pages?>&i_want=<?=$this->i_want?>&howmany=<?=$this->howmany?>&payload=<?=$this->payload?>" title="Last page">
			&nbsp;&nbsp;&nbsp;--&gt;|</a><?php
			}
		}
	else
		{ /* We are not getting beyond this page anyways */ }
	}
# end random_access()

}
# end class PreNext

?>