pew-archive-filters.php

<?php
/*
Plugin Name: Pew Archive Filters
Description: Adds re-write rules and helper functions that make filtering archives by year and/or a taxonomy possible.
Version: 0.2
Author: Russell Heimlich
Author URI: http://www.russellheimlich.com
*/

function pew_archive_filter_rewrite_rules( $wp_rewrite ) {
	$taxonomy_by_year_rewrite_rules = array();
	$args = array(
		'public'   => true,
		'_builtin' => false 
	);
	$taxonomies = get_taxonomies($args);
	$taxonomies['category'] = 'category_name';
	$taxonomies['author'] = 'author_name';
	
	//Only PewResearch.org uses projects and needs these rewrite rules created. For the other projects we can skip the extra rewrite rules.
	$include_projects = false;
	if( get_template() == 'pewresearch' ) {
		$include_projects = true;
	}
	
	//Project taxonomy archives don't apply. 
	unset($taxonomies['projects']);
	
	$feed_regex = '(' . implode('|', $wp_rewrite->feeds) . ')';
	$pages_regex = '?([\d\-]+|all)';
	foreach( $taxonomies as $tax => $query_var ):
		
		$taxonomy_by_year_rewrite_rules = array_merge( array(
			//Just Year
			$tax . "/(.+?)/(\d\d\d\d)/pages/" . $pages_regex . "/feed/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&year=" . $wp_rewrite->preg_index(2) . "&pages=" . $wp_rewrite->preg_index(3) . "&feed=" . $wp_rewrite->preg_index(4),
			$tax . "/(.+?)/(\d\d\d\d)/page/?([0-9]{1,})/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&year=" . $wp_rewrite->preg_index(2) . "&paged=" . $wp_rewrite->preg_index(3) . "&feed=" . $wp_rewrite->preg_index(4),
			$tax . "/(.+?)/(\d\d\d\d)/page/?([0-9]{1,})/feed/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&year=" . $wp_rewrite->preg_index(2) . "&paged=" . $wp_rewrite->preg_index(3) . "&feed=" . $wp_rewrite->preg_index(4),
			$tax . "/(.+?)/(\d\d\d\d)/pages/" . $pages_regex . "/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&year=" . $wp_rewrite->preg_index(2) . "&pages=" . $wp_rewrite->preg_index(3) . "&feed=" . $wp_rewrite->preg_index(4),
			$tax . "/(.+?)/(\d\d\d\d)/page/?([0-9]{1,})/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&year=" . $wp_rewrite->preg_index(2) . "&paged=" . $wp_rewrite->preg_index(3) . "&feed=" . $wp_rewrite->preg_index(4),
			$tax . "/(.+?)/(\d\d\d\d)/feed/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&year=" . $wp_rewrite->preg_index(2) . "&feed=" . $wp_rewrite->preg_index(3),
    		$tax . "/(.+?)/(\d\d\d\d)/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&year=" . $wp_rewrite->preg_index(2) . "&feed=" . $wp_rewrite->preg_index(3),
    		$tax . "/(.+?)/(\d\d\d\d)/pages/" . $pages_regex . "/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&year=" . $wp_rewrite->preg_index(2) . "&pages=" . $wp_rewrite->preg_index(3),
			$tax . "/(.+?)/(\d\d\d\d)/page/?([0-9]{1,})/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&year=" . $wp_rewrite->preg_index(2) . "&paged=" . $wp_rewrite->preg_index(3),
			$tax . "/(.+?)/(\d\d\d\d)/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&year=" . $wp_rewrite->preg_index(2),
			
			//Add /pages/ and /feed/ support to archive URLs.
			$tax . "/(.+?)/pages/" . $pages_regex . '/' . $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&pages=" . $wp_rewrite->preg_index(2) . "&feed=" . $wp_rewrite->preg_index(3),
			$tax . "/(.+?)/pages/" . $pages_regex . "/feed/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&pages=" . $wp_rewrite->preg_index(2) . "&feed=" . $wp_rewrite->preg_index(3)
		), $taxonomy_by_year_rewrite_rules);
		
		if( $include_projects ) {
			$taxonomy_by_year_rewrite_rules = array_merge( array(
				//Project and Year
				$tax . "/(.+?)/project/(.+?)/(\d\d\d\d)/feed/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&year=" . $wp_rewrite->preg_index(3) . "&feed=" . $wp_rewrite->preg_index(4),
				$tax . "/(.+?)/project/(.+?)/(\d\d\d\d)/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&year=" . $wp_rewrite->preg_index(3) . "&feed=" . $wp_rewrite->preg_index(4),
				$tax . "/(.+?)/project/(.+?)/(\d\d\d\d)/pages/" . $pages_regex . "/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&year=" . $wp_rewrite->preg_index(3) . "&pages=" . $wp_rewrite->preg_index(4),
				$tax . "/(.+?)/project/(.+?)/(\d\d\d\d)/page/?([0-9]{1,})/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&year=" . $wp_rewrite->preg_index(3) . "&paged=" . $wp_rewrite->preg_index(4),
				$tax . "/(.+?)/project/(.+?)/(\d\d\d\d)/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&year=" . $wp_rewrite->preg_index(3),
				
				//Just Project
				$tax . "/(.+?)/project/(.+?)/pages/" . $pages_regex . "/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&pages=" . $wp_rewrite->preg_index(3). "&feed=" . $wp_rewrite->preg_index(4),
				$tax . "/(.+?)/project/(.+?)/pages/" . $pages_regex . "/feed/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&pages=" . $wp_rewrite->preg_index(3). "&feed=" . $wp_rewrite->preg_index(4),
				$tax . "/(.+?)/project/(.+?)/page/?([0-9]{1,})/feed/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&paged=" . $wp_rewrite->preg_index(3). "&feed=" . $wp_rewrite->preg_index(4),
				$tax . "/(.+?)/project/(.+?)/pages/" . $pages_regex . "/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&pages=" . $wp_rewrite->preg_index(3). "&feed=" . $wp_rewrite->preg_index(4),
				$tax . "/(.+?)/project/(.+?)/page/?([0-9]{1,})/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&paged=" . $wp_rewrite->preg_index(3). "&feed=" . $wp_rewrite->preg_index(4),
				$tax . "/(.+?)/project/(.+?)/feed/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&feed=" . $wp_rewrite->preg_index(3),
				$tax . "/(.+?)/project/(.+?)/". $feed_regex ."/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&feed=" . $wp_rewrite->preg_index(3),
				$tax . "/(.+?)/project/(.+?)/pages/" . $pages_regex . "/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&pages=" . $wp_rewrite->preg_index(3),
				$tax . "/(.+?)/project/(.+?)/page/?([0-9]{1,})/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2) . "&paged=" . $wp_rewrite->preg_index(3),
				$tax . "/(.+?)/project/(.+?)/?$" => "index.php?" . $query_var . "=" . $wp_rewrite->preg_index(1) . "&projects=" . $wp_rewrite->preg_index(2)
			), $taxonomy_by_year_rewrite_rules);
		}
		
	endforeach;
	
    $wp_rewrite->rules = $taxonomy_by_year_rewrite_rules + $wp_rewrite->rules;
}
add_action('generate_rewrite_rules', 'pew_archive_filter_rewrite_rules');

function pew_archive_no_results_redirect() {
	global $wp_query;
	if( $wp_query->post_count > 0 || !is_archive() ) {
		return;
	}
	
	$year = get_query_var('year');
	$project = get_query_var('projects');
	$base_url = get_term_link( $wp_query->queried_object );
	$redirect_url = '';
	
	if( $year && $project ) {
		$redirect_url = $base_url . 'project/' . $project . '/';
	}
	
	if( $year && !$project ) {
		$redirect_url = $base_url;
	}
	
	if( $redirect_url ) {
		wp_redirect( $redirect_url, 301 );
	}
	
}
add_action('template_redirect', 'pew_archive_no_results_redirect');

function pew_archive_rejigger_the_loop() {
	global $wp_query;
	$year = get_query_var('year');
	$project = get_query_var('projects');
	
	if( $wp_query->post_count > 0 || !is_archive() ) {
		return;
	}
	
	if( $year || $project ) {
		$wp_query->found_posts = 1;
		$wp_query->is_404 = false;
	}
}
add_action( 'posts_selection', 'pew_archive_rejigger_the_loop' );

/***
* Helper Functions
***/

function pew_get_archive_years() {
	global $wp_query, $wpdb;
	
	// Grab the main query WordPress used.
	$query = str_replace("\n", '', $wp_query->request);
	$query = preg_replace('/\s+/', ' ', $query);
	
	// Change a few things to get the distinct years found for the main query.
	$query = preg_replace('/SELECT .+ FROM/i', 'SELECT SQL_CALC_FOUND_ROWS DISTINCT YEAR(' . $wpdb->posts . '.post_date) FROM', $query);
	$query = preg_replace('/LIMIT \d+, \d+$/i', '', $query);
	// If there is a YEAR parameter in the main query, we need to take it out since it limits the number of years returned.
	$query = preg_replace('/AND \( YEAR\(.+\) = \d\d\d\d\)/im', '', $query);
	
	//$years = $wpdb->get_col("SELECT DISTINCT YEAR(post_date) FROM $wpdb->posts INNER JOIN $wpdb->term_relationships ON object_id = ID WHERE post_status = 'publish' AND post_type = 'post' " . implode('', $term_taxonomy_clause) . " ORDER BY post_date DESC");
	$years = $wpdb->get_col($query);
	$years = array_map('intval', $years);
	
	return $years;
}

function pew_archive_years( $base_url = FALSE ) {
	global $wp_query;
	if( !$base_url ) {
		$base_url = get_term_link( $wp_query->queried_object );
		if( $proj = get_query_var('projects') ) {
			$base_url .= 'project/' . $proj . '/';
		}
	}
	
	$years = pew_get_archive_years();
	
	// No point in showing the year filter if there is only one year to choose from.
	if( count( $years ) > 1 ):
		$current_year = get_query_var('year');
		
		$label = 'Filter by Year';
		// If a year is already set, show the filtered year and provide an option to remove the year filter completely (Show All Years).
		if( $current_year ) {
			?>
			<a href="<?=$base_url;?>" class="filtered-to" title="Show all years">Filtered to <?= $current_year; ?></a>
			<?php
			$label = 'Change Year Filter';
		}
		?>
		<h3><?=$label;?></h3>
		<ul class="years grid-filter">
		<?php
		foreach( $years as $year ):
			$classes = array();
			
			//If this is the first year in the list, we'll add a class of first for styling purposes. 
			if( $year == $years[0] ) {
				$classes[] = 'first';
			}
			
			//If this year is the current year we'll add a class of active for styling and use an <a> element without an href attribute. Helps keep styling consistent but it's not clickable.
			if( $year == $current_year ) {
				$classes[] = 'active';
			?>
				<li class="<?=implode(' ', $classes);?>"><a><?=$year;?></a></li>
			<?php } else { ?>
				<li class="<?=implode(' ', $classes);?>"><a href="<?=$base_url . $year . '/'?>"><?=$year;?></a></li>
			<?php
			}
		endforeach;
		?>
		</ul>
		<?php
	endif;
}

function pew_archive_projects() {
	global $wp_query;
	$current_project = get_query_var('projects');
	$base_url = get_term_link( $wp_query->queried_object );
	$year = get_query_var( 'year' );
	
	$label = 'Filter by Research Area';
	
	// If aproject is already set, show the filtered project and provide an option to remove the project filter completely (Show All Projects).
	if( $current_project ) {
		$current_project_obj = get_term_by( 'slug', $current_project, 'projects');
		
		$filtered_url = $base_url;
		if( $year ) {
			$filtered_url .= $year . '/';
		}
		?>
		<a href="<?=$filtered_url;?>" title="Show all projects" class="filtered-to">Filtered to <?= $current_project_obj->name; ?></a>
		<?php
		$label = 'Change Research Area Filter';
	}
	
	$args = array(
		'orderby' => 'count',
		'order' => 'DESC'
	);
	$projects = get_terms( 'projects', $args );
	if( $projects ) :
	?>
		<h3><?=$label;?></h3>
		<ul class="projects">
		<?php
		foreach( $projects as $project ):
			if( $project->slug == $current_project ) { ?>
				<li class="active"><a><?=$project->name;?></a></li>
			<?php } else {
					$url = $base_url . 'project/' . $project->slug . '/';
					if( $year ) {
						$url .=  $year . '/';
					}
				?>
				<li><a href="<?=$url;?>"><?=$project->name;?></a></li>
			<?php }	
		endforeach;
		?>
		</ul>
	<?php
	endif;
}

function pew_archive_categories( $args = NULL ) {
	$defaults = array(
		// for get_terms
		'term_ids' => false,
		'term_id' => false,
		'taxonomy' => 'category',
		'label' => 'Publication Type',
		'orderby' => 'count',
		'order' => 'DESC',
		// Just for this function
		'show_all' => false
	);
	$args = wp_parse_args( $args, $defaults );
	extract( $args, EXTR_SKIP );
	
	if( !is_taxonomy($taxonomy) ) {
		return false;
	}
	
	$query_var_key = $taxonomy;
	if( $query_var_key == 'category' ) {
		$query_var_key .= '_name';
	}
	$current_term_slug = get_query_var($query_var_key);
	$current_term_obj = get_term_by( 'slug', $current_term_slug, $taxonomy );
	$top_level_term_obj = $current_term_obj;
	if( !$top_level_term_obj ) {
		return false;
	}
	
	if ($show_all == false) {
		$count = 0;
		// Find a top-level category; display that and its children
		while( $top_level_term_obj->parent != "0" ) {
			$top_level_term_obj = get_term_by( 'id', $top_level_term_obj->parent, $taxonomy );
			$count++;
			if( $count > 10 ) {
				//Something has gone wrong, let's bail and not create an infinite loop...
				return false;
			}
		}
		$args['child_of'] = $top_level_term_obj->term_id;
	} 
	
	$terms = get_terms( $taxonomy, $args );
	
	$year = get_query_var( 'year' );
	$base_url = get_term_link( $current_term_obj, $taxonomy );
	
	if( $top_level_term_obj->slug == 'interactives') {
		$label = 'Interactive Type';
	} 
	$full_label = 'Filter By ' . $label;
	// If a category is already set, show the filtered category and provide an option to remove filter (Show All Categories).
	if( $current_term_slug != $top_level_term_obj->slug ) {
		$filtered_url = get_term_link( $top_level_term_obj, $taxonomy );
		if( $year ) {
			$filtered_url .= $year . '/';
		}
	
	?>
		<a href="<?=$filtered_url;?>" title="Show all types" class="filtered-to">Filtered to <?= $current_term_obj->name; ?></a>
		<? $full_label = 'Change ' . $label . ' Filter';
	}
	
	if( $terms ):
		$project = '';
		if( $project = get_query_var('projects') ) {
			$project = 'project/' . $project . '/';
		}
	?>
		<h3><?=$full_label;?></h3>
		<ul class="types">
			<?php
			foreach( $terms as $term ):
				$url = get_term_link($term, $taxonomy) . $project;
				if( $year ) {
					$url .= $year . '/';
				}
				if( $term->slug == $current_term_slug ) { ?>
					<li class="active"><a><?=$term->name;?></a></li>
                <? } else { ?>
					<li><a href="<?= $url; ?>"><?=$term->name;?></a></li>
			<?php }
			endforeach; ?>
		</ul>
	<?php endif;
}

Helpful plugin https://wordpress.org/plugins/rewrite-rules-inspector/ Use it to inspect rewrite rules for basic built-in taxonomies and use that to build your own.