Recently a friend of mine asked about showing random facts on his blog. He found a nice website with a few facts, but it hadn’t been updated in a while so the search was on.

Fortunately, there’s a blog at tumblr called nerdy-facts which has plenty of content. This plugin simply scrapes that site, downloads the images and then shows a random one each day in a widget.

The code is a bit rough, assumes you have pre-seeded the storage folder and isn’t fully tested. But it works.

<?php
/*
Plugin Name: Nerdy Facts
Plugin URI: https://eliottrobson.me
Description: Adds a "nerdy facts" widget from tumblr.
Version: 1.0
Author: Eliott Robson
Author URI: https://eliottrobson.me
*/

define('NERDY_FACTS_FOLDER', trailingslashit(WP_CONTENT_DIR) . 'nerdy-facts/');
define('NERDY_FACTS_URL', trailingslashit(content_url()) . 'nerdy-facts/');

/**
 * Called when the plugin activates, setup once
 */
function nerdyfacts_activate()
{
    // Create the storage folder
    wp_mkdir_p(NERDY_FACTS_FOLDER);

    // Schedule update
    if (!wp_next_scheduled('nerdyfacts_seed')) {
        wp_schedule_event(strtotime('23:00:00'), 'daily', 'nerdyfacts_seed');
    }

    if (!wp_next_scheduled('nerdyfacts_select')) {
        wp_schedule_event(strtotime('00:00:00'), 'daily', 'nerdyfacts_select');
    }

    // Check for updated images
    nerdyfacts_seed();

    // Select a new images
    nerdyfacts_select();
}

/**
 * Called when the plugin is deactivated
 */
function nerdyfacts_deactivate()
{
    wp_clear_scheduled_hook('nerdyfacts_update');
}

/**
 * Seed the folder with any new facts
 */
function nerdyfacts_seed()
{
    // Only seed on mondays
    if (date('l') !== 'Monday') return;

    $blog = 'nerdyfacts';
    $start = 0;
    $perPage = 50;
    $posts = [];

    // The folder has been "pre-seeded" in order to improve performance
    $lastId = (int) get_option('nerdy_facts_last_id', 161179905143);

    do {
        // Grab the next posts
        $url = 'http://' . $blog . '.tumblr.com/api/read/?start=' . $start . '&num=' . $perPage . '&type=photo';
        $file = file_get_contents($url);
        $feed = new SimpleXMLElement($file);

        // We only want new posts
        $newPosts = array_filter($feed->xpath('posts//post'), function ($post) use ($lastId) {
            return ((int) $post->attributes()->id) > $lastId;
        });
        $posts = array_merge($posts, $newPosts);

        // Get ready for the next posts
        $start = (int) $feed->posts->attributes()->start + $perPage;
    } while ($start <= (int) $feed->posts["total"] && count($newPosts) > 0);

    // If we don't have any new posts, bail
    if (count($posts) == 0) return;

    $newFiles = [];

    // We have all the data now, let's download the images
    foreach ($posts as $post) {
        $post_array = (array) $post;
        $id = $post_array["@attributes"]["id"];
        if ($lastId < $id) {
            $lastId = $id;
        }

        // Let's not assume it'll always be the same
        $ext = pathinfo($post_array["photo-url"][0], PATHINFO_EXTENSION);

        // Store each fact image as a file on the server
        $newFile = $id . '.' . $ext;
        copy($post_array["photo-url"][0], NERDY_FACTS_FOLDER . $newFile);

        $newFiles[] = $newFile;
    }

    // Update last id
    update_option('nerdy_facts_last_id', $lastId);

    // Add new files into the list
    $allFacts = array_merge(_nerdyfacts_get_stored(), $newFiles);

    // Re-shuffle
    shuffle($allFacts);

    // Update the list
    update_option('nerdy_facts_all', json_encode($allFacts));
}

/**
 * Get a shuffled array of all the stores facts
 */
function _nerdyfacts_get_stored() {
    $allFacts = get_option('nerdy_facts_all', false);
    if ($allFacts === false) {
        $allFacts = [];
    } else {
        $allFacts = json_decode($data);
    }

    if (count($allFacts) == 0) {
        // We only want the files, ignore all folders
        $allFacts = array_filter(scandir(NERDY_FACTS_FOLDER), function($item) {
            return !is_dir(NERDY_FACTS_FOLDER . $item);
        });

        // Shuffle the facts
        shuffle($allFacts);
    }

    return $allFacts;
}

/**
 * Select an image from those already seeded
 */
function nerdyfacts_select()
{
    // Get the current list of facts
    $allFacts = _nerdyfacts_get_stored();

    // Take the first one
    update_option('nerdy_facts_current', array_shift($allFacts));

    // Update the list
    update_option('nerdy_facts_all', json_encode($allFacts));
}

/**
 * Build the widget for rendering
 */
class NerdyFacts_Widget_Class extends WP_Widget
{
    public function __construct()
    {
        parent::__construct(false, $name = 'Nerdy Facts');
    }

    public function widget($args, $instance)
    {
        $fact = get_option('nerdy_facts_current', false);

        if ($fact === false) return;

        $title = apply_filters('widget_title', $instance['title']);

        echo $args['before_widget'];

        if (!empty($title))
            echo $args['before_title'] . $title . $args['after_title'];

        echo '<img src="' . NERDY_FACTS_URL . $fact . '" style="max-width: 100%; display: block; height: auto;" />';

        echo $args['after_widget'];
    }

    public function form($instance)
    {
        if (isset($instance['title'])) {
            $title = $instance['title'];
        } else {
            $title = 'Nerdy Facts';
        }
        ?>
        <p>
            <label for="<?php echo $this->get_field_id('title'); ?>"><?php _e('Title:'); ?></label>
            <input class="widefat" id="<?php echo $this->get_field_id('title'); ?>" name="<?php echo $this->get_field_name('title'); ?>" type="text" value="<?php echo esc_attr($title); ?>" />
        </p>
        <?php
    }

    public function update($new_instance, $old_instance)
    {
        $instance = array();
        $instance['title'] = !empty($new_instance['title']) ? strip_tags($new_instance['title']) : '';
        return $instance;
    }
}

/**
 * Called when widgets are initialised, so we can setup our own
 */
function nerdyfacts_widget()
{
    register_widget("NerdyFacts_Widget_Class");
}

register_activation_hook(__FILE__, 'nerdyfacts_activate');
register_deactivation_hook(__FILE__, 'nerdyfacts_deactivate');
add_action('widgets_init', 'nerdyfacts_widget');
add_action('nerdyfacts_seed', 'nerdyfacts_seed');
add_action('nerdyfacts_select', 'nerdyfacts_select');