Overriding default calendar to show posts from a category

Question

I'm trying to modify the default WP calendar (get_calendar()) so that it shows posts from a specific category and then use that as a shortcode.

Here's what I've done:

Copied across the get_calendar() function from the core (from wp-includes) into my child theme's functions.php file. In order to make it an 'independent' calendar, I changed the name of the get_calendar() function to osu_get_calendar() and have successfully hardcoded the calendar into my template using osu_get_calendar();

Now I'm trying to get my hands a bit dirtier and do the following:

1) Restrict the posts shown in the calendar to a specific category (while maintaining the previous and next navigation so visitors can search through those posts by month)

2) Make it into a shortcode so my client can essentially embed a calendar with posts from a category they choose at the bottom of their posts.

I'm stuck on 1) at the moment as it looks like I need to modify the SQL queries so that it pulls posts from a specific category. Looking at the code below from the get_calendar() function, how would I filter the posts pulled from the database so that they are from a specific category? There are other SQL queries in there, but hopefully someone can help me with this one for now:

$previous = $wpdb->get_row("SELECT DISTINCT MONTH(post_date) AS month, YEAR(post_date) AS year
        FROM $wpdb->posts
        WHERE post_date < '$thisyear-$thismonth-01'
        AND post_type = 'post' AND post_status = 'publish'
            ORDER BY post_date DESC
            LIMIT 1");
    $next = $wpdb->get_row("SELECT  DISTINCT MONTH(post_date) AS month, YEAR(post_date) AS year
        FROM $wpdb->posts
        WHERE post_date >   '$thisyear-$thismonth-01'
        AND MONTH( post_date ) != MONTH( '$thisyear-$thismonth-01' )
        AND post_type = 'post' AND post_status = 'publish'
            ORDER   BY post_date ASC
            LIMIT 1");

Thanks,

osu

Answer 1

You were starting on the right track but you had several bits of WordPress hookage you still needed to add. An approach I like to use is to encapsulate a call to get_calendar() in a class so we can use the low-level 'query' hook but only use for it for the one call.

So I wrote up an example which you can drop into your theme's functions.php file (or in a .php file for a plugin you might be writing) using a class I named YourSite_Category_Calendar(), and here is how you'd call it in place of your call to get_calendar():

$cc = new YourSite_Category_Calendar('your-category');
echo $cc->get_calendar();

And here's the code for the class:

<?php 

class YourSite_CategoryCalendar {
  var $category;
  var $initial;
  var $echo;
  static function on_load() {
    add_shortcode('category-calendar',array(__CLASS__,'shortcode'));
    add_action('init',array(__CLASS__,'init'));
    global $wp_rewrite;
    $wp_rewrite->add_rule('^events/([0-9]{4})/([0-9]{1,2})/([0-9]{1,2})/([^/]+)/?$',
      'index.php?post_type=event&year=$matches[1]&monthnum=$matches[2]&day=$matches[3]&category_name=$matches[4]',
      'top');
    $wp_rewrite->flush_rules(false);  // Remove this after you've got it working
  }
  static function shortcode($attributes) {
    $attributes = wp_parse_args($attributes,array(
      'category' => false,
    ));
    $cc = new YourSite_CategoryCalendar($attributes['category']);
    echo $cc->get_calendar();
  }
  static function init() {
    register_post_type('event',array(
      'hierarchical'    => true,
      'label'          => 'Events',
      'public'          => true,
      'show_ui'         => true,
      'query_var'       => 'event',
      'rewrite'         => array('slug' => 'events'),
      'supports'        => array('title','editor','custom-fields'),
      'taxonomies'      => array('category'),
    ));
  }
  function __construct($category,$initial=true,$echo=true) {
    $this->category = $category;
    $this->initial = $initial;
    $this->echo = $echo;
  }
  function get_calendar() {
    add_filter('query',array(&$this,'query'));
    ob_start();
    get_calendar($this->category,$this->initial,$this->echo);
    $calendar = ob_get_clean();
    remove_filter('query',array(&$this,'query'));
    list($header,$body) = explode('<tbody>',$calendar);
    $find = '#(href="http://[^/]+)(/[0-9]{4}/[0-9]{1,2}/[0-9]{1,2}/)#';
    $replace = '$1/events$2'.$this->category.'/"';
    $body = preg_replace($find,$replace,$body);
    return "{$header}<tbody>{$body}";
  }
  function query($query) {
    if ($this->category) {
      global $wpdb;
      $find = "FROM {$wpdb->posts}\\s+WHERE";
      $add =<<<SQL
INNER JOIN {$wpdb->term_relationships} calendar_term_relationship ON calendar_term_relationship.object_id={$wpdb->posts}.ID
INNER JOIN {$wpdb->term_taxonomy} calendar_term_taxonomy ON calendar_term_taxonomy.term_taxonomy_id=calendar_term_relationship.term_taxonomy_id
INNER JOIN {$wpdb->terms} calendar_term ON calendar_term.term_id=calendar_term_taxonomy.term_id
WHERE calendar_term_taxonomy.taxonomy='category' AND calendar_term.slug='%s' AND
SQL;
      $replace = "FROM {$wpdb->posts} {$add} ";
      $query = preg_replace("#{$find}#Us",$replace,$query);
      $query = preg_replace("#post_type\s*=\s*'post'#","post_type='event'",$query);
      $query = $wpdb->prepare($query,$this->category);
    }
    return $query;
  }
}
YourSite_CategoryCalendar::on_load();

UPDATE

Based on the comments I've added the URLs rewriting needed as well as a shortcode you'd call like this:

[category-calendar category="party"]