<?php
/*
The "Categoryfinder" class takes a list of articles, creates an internal representation of all their parent
categories (as well as parents of parents etc.). From this representation, it determines which of these articles
are in one or all of a given subset of categories.

Example use :

	# Determines wether the article with the page_id 12345 is in both
	# "Category 1" and "Category 2" or their subcategories, respectively
	
	$cf = new Categoryfinder ;
	$cf->seed (
		array ( 12345 ) ,
		array ( "Category 1","Category 2" ) ,
		"AND"
	) ;
	$a = $cf->run() ;
	print implode ( "," , $a ) ;

*/


class Categoryfinder {

	var $articles = array () ; # The original article IDs passed to the seed function
	var $deadend = array () ; # Array of DBKEY category names for categories that don't have a page
	var $parents = array () ; # Array of [ID => array()]
	var $next = array () ; # Array of article/category IDs
	var $targets = array () ; # Array of DBKEY category names
	var $name2id = array () ;
	var $mode ; # "AND" or "OR"
	var $dbr ; # Read-DB slave

	/**
	 * Constructor (currently empty).
	*/
	function Categoryfinder () {
	}

	/**
	 * Initializes the instance. Do this prior to calling run().
	 @param $article_ids Array of article IDs
	*/
	function seed ( $article_ids , $categories , $mode = "AND" ) {
		$this->articles = $article_ids ;
		$this->next = $article_ids ;
		$this->mode = $mode ;

		# Set the list of target categories; convert them to DBKEY form first
		$this->targets = array () ;
		foreach ( $categories AS $c ) {
			$ct = Title::newFromText ( $c , NS_CATEGORY ) ;
			$c = $ct->getDBkey () ;
			$this->targets[$c] = $c ;
		}
	}

	/**
	 * Iterates through the parent tree starting with the seed values,
	 * then checks the articles if they match the conditions
	 @return array of page_ids (those given to seed() that match the conditions)
	*/
	function run () {
		$this->dbr =& wfGetDB( DB_SLAVE );
		while ( count ( $this->next ) > 0 ) {
			$this->scan_next_layer () ;
		}

		# Now check if this applies to the individual articles
		$ret = array () ;
		foreach ( $this->articles AS $article ) {
			$conds = $this->targets ;
			if ( $this->check ( $article , $conds ) ) {
				# Matches the conditions
				$ret[] = $article ;
			}
		}
		return $ret ;
	}

	/**
	 * This functions recurses through the parent representation, trying to match the conditions
	 @param $id The article/category to check
	 @param $conds The array of categories to match
	 @return bool Does this match the conditions?
	*/
	function check ( $id , &$conds ) {
		# Shortcut (runtime paranoia): No contitions=all matched
		if ( count ( $conds ) == 0 ) return true ;
		
		if ( !isset ( $this->parents[$id] ) ) return false ;

		# iterate through the parents
		foreach ( $this->parents[$id] AS $p ) {
			$pname = $p->cl_to ;
			
			# Is this a condition?
			if ( isset ( $conds[$pname] ) ) {
				# This key is in the category list!
				if ( $this->mode == "OR" ) {
					# One found, that's enough!
					$conds = array () ;
					return true ;
				} else {
					# Assuming "AND" as default
					unset ( $conds[$pname] ) ;
					if ( count ( $conds ) == 0 ) {
						# All conditions met, done
						return true ;
					}
				}
			}
			
			# Not done yet, try sub-parents
			if ( !isset ( $this->name2id[$pname] ) ) {
				# No sub-parent
				continue ;
			}
			$done = $this->check ( $this->name2id[$pname] , $conds ) ;
			if ( $done OR count ( $conds ) == 0 ) {
				# Subparents have done it!
				return true ;
			}
		}
		return false ;
	}

	/**
	 * Scans a "parent layer" of the articles/categories in $this->next
	*/
	function scan_next_layer () {
		$fname = "Categoryfinder::scan_next_layer" ;
	
		# Find all parents of the article currently in $this->next
		$layer = array () ;
		$res = $this->dbr->select(
				/* FROM   */ 'categorylinks',
				/* SELECT */ '*',
				/* WHERE  */ array( 'cl_from' => $this->next ),
				$fname."-1"
		);
		while ( $o = $this->dbr->fetchObject( $res ) ) {
			$k = $o->cl_to ;

			# Update parent tree
			if ( !isset ( $this->parents[$o->cl_from] ) ) {
				$this->parents[$o->cl_from] = array () ;
			}
			$this->parents[$o->cl_from][$k] = $o ;

			# Ignore those we already have
			if ( in_array ( $k , $this->deadend ) ) continue ;
			if ( isset ( $this->name2id[$k] ) ) continue ;

			# Hey, new category!
			$layer[$k] = $k ;
		}
		$this->dbr->freeResult( $res ) ;

		$this->next = array() ;
		
		# Find the IDs of all category pages in $layer, if they exist
		if ( count ( $layer ) > 0 ) {
			$res = $this->dbr->select(
					/* FROM   */ 'page',
					/* SELECT */ 'page_id,page_title',
					/* WHERE  */ array( 'page_namespace' => NS_CATEGORY , 'page_title' => $layer ),
					$fname."-2"
			);
			while ( $o = $this->dbr->fetchObject( $res ) ) {
				$id = $o->page_id ;
				$name = $o->page_title ;
				$this->name2id[$name] = $id ;
				$this->next[] = $id ;
				unset ( $layer[$name] ) ;
			}
			$this->dbr->freeResult( $res ) ;
			}

		# Mark dead ends
		foreach ( $layer AS $v ) {
			$this->deadend[$v] = $v ;
		}
	}

} # END OF CLASS "Categoryfinder"

?>
