pmg-cdn.php

<?php
/**
 * Plugin Name: PMG CDN
 * Plugin URI: https://github.com/AgencyPMG/pmg-cdn
 * Description: A simple origin-pull CDN for yoru WordPress site.
 * Version: 1.0
 * Text Domain: pmgcdn
 * Author: Christopher Davis
 * Author URI: http://christopherdavis.me
 * License: MIT
 *
 * Copyright (c) 2015 PMG <https://www.pmg.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * @category    WordPress
 * @author      Christopher Davis <http://christopherdavis.me>
 * @copyright   2015 MIT
 * @license     http://opensource.org/licenses/MIT MIT
 */


!defined('ABSPATH') && exit;

PMG_CDN::init();

class PMG_CDN
{
    // option name
    const SETTING = 'pmg_cdn_settings';

    // page on which the options reside
    const PAGE = 'media';

    // container for the instance
    private static $ins = null;

    // extension urls to change
    private $ext = array();

    // Only user uploads or everything?
    private $uploads = false;

    // site url
    private $site_url;

    // CDN url
    private $cdn_url;

    public static function instance()
    {
        is_null(self::$ins) && self::$ins = new self;
        return self::$ins;
    }

    public static function init()
    {
        add_action('plugins_loaded', array(self::instance(), '_setup'));
    }

    public static function opt($key, $default='')
    {
        $opts = get_option(self::SETTING, array());
        return isset($opts[$key]) ? $opts[$key] : $default;
    }

    private static function opt_name($k)
    {
        return sprintf('%s[%s]', self::SETTING, $k);
    }

    public function _setup()
    {
        $this->ext = apply_filters(
            'pmg_cdn_extensions',
            array('jpe?g', 'gif', 'png', 'css', 'bmp', 'js', 'ico',)
        );

        $this->uploads = apply_filters(
            'pmg_cdn_uploads_only',
            defined('CDN_UPLOADS_ONLY') ?
                CDN_UPLOADS_ONLY : static::opt('uploads', 'on') == 'on'
        );

        $this->site_url = parse_url(home_url(), PHP_URL_HOST);
        $this->cdn_url = defined('CDN_HOST') ? CDN_HOST : self::opt('cdn_host', false);

        add_action('admin_init', array($this, 'settings'));

        // make sure we can do this
        if(
            (defined('CDN_DISABLE') && CDN_DISABLE) ||
            !$this->cdn_url ||
            !$this->ext
        ) return;

        add_action('template_redirect', array($this, 'start_ob'));

        if($this->uploads)
            add_filter('cdn_filter', array($this, 'filter_uploads'));
        else
            add_filter('cdn_filter', array($this, 'filter_all'));
    }

    /********** Hooks **********/

    /**
     * Hooked into `admin_init` registers settinsgs for this plugins.
     *
     * @since   1.0
     * @access  public
     * @uses    register_setting
     * @uses    add_settings_section
     * @uses    add_settings_field
     * @return  void
     */
    public function settings()
    {
        register_setting(
            self::PAGE,
            self::SETTING,
            array($this, 'validate')
        );

        add_settings_section(
            'cdn-settings',
            __('CDN Settings', 'pmgcdn'),
            array($this, 'help_cb'),
            self::PAGE
        );

        add_settings_field(
            'cdn-host',
            __('CDN Host', 'pmgcdn'),
            array($this, 'host_cb'),
            self::PAGE,
            'cdn-settings',
            array('label_for' => self::opt_name('cdn_host'), 'key' => 'cdn_host')
        );

        add_settings_field(
            'cdn-uploads',
            __('Uploads Only?', 'pmgcdn'),
            array($this, 'uploads_cb'),
            self::PAGE,
            'cdn-settings',
            array('label_for' => self::opt_name('uploads'), 'key' => 'uploads')
        );
    }

    /**
     * Hooked into `tempalte_redirect`.  Starts an output buffer for this plugin.
     *
     * @since   1.0
     * @access  public
     * @return  void
     */
    public function start_ob()
    {
        ob_start(array($this, 'ob'));
    }

    /**
     * Hooked into `cdn_filter`.  Switches out all URLs that end in one of
     * $this->ext with their CDN equivilents.
     *
     * @since   1.0
     * @access  public
     * @param   string $output
     * @return  string
     */
    public function filter_all($output)
    {
        return preg_replace(
            "#=(['\"])" // open equal sign and opening quote
            . "((?:https?:)?//{$this->site_url})/" // domain (optional)
            . "((?:(?!\\1).)+)" // look for anything that's not our opening quote
            . "\.(" . implode('|', $this->ext) . ")" // extensions
            . "(\?((?:(?!\\1).))+)?" // match query strings
            . "\\1#", // closing quote
            '=$1//' . $this->cdn_url . '/$3.$4$5$1',
            $output
        );
    }

    /**
     * Hooked into `cdn_filter`.  Switches user uploads with their CDN
     * domain equivilent.
     *
     * @since   1.0
     * @access  public
     * @param   string $output;
     * @return  string
     */
    public function filter_uploads($output)
    {
        $uploads = wp_upload_dir();

        // deal with protocol relative urls
        if(preg_match('#^//#', $uploads['baseurl']))
        {
            $uploads['baseurl'] = 'http://' . ltrim($uploads['baseurl'], '/');
        }

        $domain = preg_quote(parse_url($uploads['baseurl'], PHP_URL_HOST), '#');
        $path = preg_quote(parse_url($uploads['baseurl'], PHP_URL_PATH), '#');

        return preg_replace(
            "#=(['\"])" // open equal sign and opening quote
            . "((?:https?:)?//{$domain})?{$path}/" // domain (optional) and upload path
            . "((?:(?!\\1).)+)" // look for anything that's not our opening quote
            . "\.(" . implode('|', $this->ext) . ")" // extensions
            . "(\?((?:(?!\\1).))+)?" // match query strings
            . "\\1#u", // closing quote
            '=$1//' . $this->cdn_url . $path . '/$3.$4$5$1',
            $output
        );
    }

    /**
     * Output buffer callback.  Nothing existing, just an apply filters call.
     *
     * @since   1.0
     * @access  public
     * @uses    apply_filters
     * @param   string $output The output buffer string
     * @return  string
     */
    public function ob($output)
    {
        return apply_filters('cdn_filter', $output);
    }

    /********** Settings Callbacks **********/

    public function validate($dirty)
    {
        $c = array();

        $c['cdn_host'] = isset($dirty['cdn_host']) ? $dirty['cdn_host'] : '';
        $c['uploads'] = !empty($dirty['uploads']) ? 'on' : 'off';

        return $c;
    }

    public function help_cb()
    {
        echo '<p class="description">';
        esc_html_e('Settings for your origin pull CDN. CDN Host should be ' .
            'the CDN hostname -- no http. Checking "uploads only" will force ' .
            'this plugin to only swap out user uploads with CDN urls.',
            'pmgcdn'
        );
        echo '</p>';
    }

    public function host_cb($args)
    {
        printf(
            '<input type="text" class="regular-text" name="%1$s" id="%1$s" value="%2$s" />',
            esc_attr($args['label_for']),
            esc_attr(self::opt($args['key']))
        );
    }

    public function uploads_cb($args)
    {
        printf(
            '<input type="checkbox" name="%1$s" id="%1$s" value="on" %2$s />',
            esc_attr($args['label_for']),
            checked('on', self::opt($args['key'], 'off'), false)
        );
    }
}