WP-BookIt sample

/*
WP-BookIt is a WordPress plugin I developed for our internal use at the GAME-dept.

It provides a shortcode making any post an "asset" (staff, tech, rooms etc) that could be reserved directly from the site. It was fairly nifty, providing:

- LDAP-authentication
- iCalendar / Google Calendar integration
- SMS & email notifications
- realtime status updates
- dependencies (like; reserving room for meetings, deny if none available)

The plugin saw heavy use during a couple of years, but the code is my usual style
of horrible so I never released the plugin publicly. This function is fairly
representative and - to quote a famous developer - "it's the devils testicles". :)
*/

//returns associative array of dates[yyyy-mm-dd] => reason code
function wpbkt_get_fully_booked_dates($asset_id){
    $last_updated = wpbkt_get_asset_meta('cached_in_rev', $asset_id);
    if($last_updated == get_option('wpbkt_revision')){
        $cache = wpbkt_get_asset_meta('fully_booked_dates', $asset_id);
        return maybe_unserialize($cache);
    }
    global $wpdb;
    /*first, let's get all bookings that overlap the timespan*/
    $from = date('Y-m-d', strtotime(get_option('wpbkt_calendar_start'))); //H:i:s
    $to = date('Y-m-d', strtotime(get_option('wpbkt_calendar_end')));
    $full_dates = array();
    $table = WPBKT_TABLE;
    $wpdb->show_errors();
    $reservations = $wpdb->get_results("SELECT * FROM $table
            WHERE $table.asset_id = $asset_id
            AND ($table.status = ".WPBKT_PENDING." OR $table.status = ".WPBKT_CONFIRMED." OR $table.status = ".WPBKT_AWAITING_RETURN.")
            AND NOT(    ($table.to < CAST('$from' as DATETIME))
                        OR  ($table.from > CAST('$to' as DATETIME)))
            ORDER BY $table.from");

    /*now go through all reservations, and count the number of overlapping reservations per date*/
    $bookings_per_day = array();
    foreach($reservations as $reservation){
        $start = strtotime( date('Y-m-d', strtotime($reservation->from)) ); //throw away h:m:s
        $end = strtotime( date('Y-m-d', strtotime($reservation->to)) );
        for($i = $start; $i < $end; $i += WPBKT_A_DAY){
            $date = date("Y-m-d", $i);
            $bookings_per_day[$date] = !isset($bookings_per_day[$date]) ? 1 : $bookings_per_day[$date]+1;
        }
    }

    /*compare those numbers to our stock (or available timeslots)*/
    $meta = wpbkt_get_asset_meta('all', $asset_id);
    if($meta['by_daterange']){
        $total_stock = $meta['total_stock'];
        foreach($bookings_per_day as $date => $reservation_count){
            if($reservation_count >= $total_stock){
                $full_dates[$date] = WPBKT_OUT_OF_STOCK;
            }
        }
    }else{//else, timeslots
        foreach($bookings_per_day as $date => $reservation_count){
            $day = strtolower(date('D', strtotime($date)));
            $slots = explode(' ', $meta["$day_timeslots"]);
            if($reservation_count >= count($slots)){
                $full_dates[$date] = WPBKT_OUT_OF_STOCK;
            }
        }
    }

    /*next, lets find all invalid weekdays for the entire datespan */
    $start = strtotime( $from ); //throw away h:m:s
    $end = strtotime( $to );
    if($end < $start){ wp_die('get_fully_booked: invalid dates'); }
    $valid_days = $meta['weekdays'];
    for($i = $start; $i < $end; $i += WPBKT_A_DAY){
        $date = date("Y-m-d", $i);
        $day = date('D', strtotime($date));
        if(stripos($valid_days, $day) === false){
            $full_dates[$date] = WPBKT_BAD_DAY; //this day is unavailable
        }
    }

    /* now to find all days where *all* requirements are fully booked too */
    $required_resource = wpbkt_get_asset_meta('requires_resources', $asset_id);
    if($required_resource){
        $cats = wpbkt_get_subcategories_id($required_resource); //category id might be 'room' and you've got 'classrooms', 'office' etc. as subcats.
        $potential_assets = wpbkt_get_all_assets_ids($cats);//these are all assets that might satisfy out requirements
        $full = array();
        foreach($potential_assets as $resource_id){
            $fulldays = wpbkt_get_fully_booked_dates_between($resource_id, $from, $to);
            foreach($fulldays as $date){
                $full[$date] = !isset($full[$date]) ? 1 : $full[$date]+1; //count how many of these assets are fully booked on this date
            }
        }
        $max = count($potential_assets); //we have $max potential assets. if any date was fully booked more than max times, it's definetly unavailable.
        foreach($full as $date => $count){
            if($count >= $max){
                $full_dates[$date] = WPBKT_NO_RESOURCES; //ALL potential required resources are unavailable this date.
            }
        }
    }
    update_post_meta($asset_id, 'fully_booked_dates', $full_dates);
    update_post_meta($asset_id, 'cached_in_rev', get_option('wpbkt_revision'));
    return $full_dates;
}