<?php
/**
 * Plugin Name: Featured Image Column
 * Plugin URI: http://austinpassy.com/wordpress-plugins/featured-image-column
 * Description: Adds a column to the edit screen with the featured image if it exists.
 * Version: 0.2.0
 * Author: Austin Passy
 * Author URI: http://austinpassy.com
 *
 * @copyright 2009 - 2012
 * @author Austin Passy
 * @link http://frostywebdesigns.com/
 * @license http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * @package Featured_Image_Column
 */

if ( !class_exists( 'Featured_Image_Column' ) ) {
    class Featured_Image_Column {

        const domain  = 'featured-image-column';
        const version = '0.2.0';

        /**
         * Ensures that the rest of the code only runs on edit.php pages
         *
         * @since 0.1
         */
        function __construct() {
            global $pagenow;
            $is_on_edit_screen = is_admin() && $pagenow === 'edit.php';
            $is_doing_ajax = $pagenow === "admin-ajax.php";

            if($is_on_edit_screen || $is_doing_ajax) :
                add_action('init', array( $this, 'init' ) );
        endif;

        } // end constructor

        /**
         * Sets up the Featured_Image_Column plugin and loads files at the appropriate time.
         *
         * @since 0.1.6
         */
        function init() {
            if(isset($_GET['post_type'])) {
                $post_type = $_GET['post_type'];
            } else {
                $post_type = $_POST['post_type'];
            }

            if ( !post_type_supports( $post_type, 'thumbnail' ) )
                return;

            /* Print style */
            add_action( 'admin_enqueue_scripts',                    array( $this, 'style' ), 0 );

            /* Column manager */
            add_filter( "manage_{$post_type}_posts_columns",        array( $this, 'columns' ) );
            add_action( "manage_{$post_type}_posts_custom_column",  array( $this, 'column_data' ), 10, 2 );

            do_action( 'featured_image_column_loaded' );
        }

        /**
         * Enqueue stylesheaet
         * @since 0.1
         */
        function style() {
            wp_register_style( 'featured-image-column', apply_filters( 'featured_image_column_css', plugin_dir_url( __FILE__ ) . 'css/column.css' ), null, self::version );
            wp_enqueue_style( 'featured-image-column' );
        }

        /**
         * Filter the image in before the 'title'
         */
        function columns( $columns ) {
            if ( !is_array( $columns ) )
                $columns = array();

            $new = array();

            foreach( $columns as $key => $title ) {
                if ( $key == 'title' ) // Put the Thumbnail column before the Title column
                    $new['featured-image'] = __( 'Image', self::domain );

                $new[$key] = $title;
            }

            return $new;
        }

        /**
         * Output the image
         */
        function column_data( $column_name, $post_id ) {
            global $post;

            if ( 'featured-image' != $column_name )
                return;

            $image_src = self::get_the_image( $post->ID );

            if ( empty( $image_src ) ) {
                echo "&nbsp;"; // This helps prevent issues with empty cells
                return;
            }

            echo '<img alt="' . esc_attr( get_the_title() ) . '" src="' . esc_url( $image_src ) . '" />';
        }

        /**
         * Function to get the image
         *
         * @since   0.1
         * @updated 0.1.3 - Added wp_cache_set()
         * @updated 0.1.9 - fixed persistent cache per post_id
         *      @ref    http://www.ethitter.com/slides/wcmia-caching-scaling-2012-02-18/#slide-11
         */
        function get_the_image( $post_id ) {
            $post_id    = (int)$post_id;
            $cache_key  = 'featured_column_thumbnail';
            $image      = wp_cache_get( $cache_key, null );

            if ( !is_array( $image ) )
                $image = array();

            if ( !array_key_exists( $cache_key, $image ) ) {
                if ( empty( $image) || !is_string( $image ) ) {
                    $image = '';

                    if ( has_post_thumbnail( $post_id ) ) {
                        $image_array = wp_get_attachment_image_src( get_post_thumbnail_id( $post_id ), array( 36, 32 ) );

                        if ( is_array( $image_array ) && is_string( $image_array[0] ) )
                            $image = $image_array[0];
                    }

                    if ( empty( $image ) ) {
                        $image = plugins_url( 'images/default.png', __FILE__ );
                        $image = apply_filters( 'featured_image_column_default_image', $image );
                    }

                    $image = esc_url( $image );
                    $image[$cache_key] = $image;

                    wp_cache_set( $cache_key, $image, null, 60 * 60 * 24 /* 24 hours */ );
                }
            }

            return $image;
        }
    }
    $featured_image_column = new Featured_Image_Column();
};

?>