taxonomy-images.php

<?php
/*
Plugin Name:          Taxonomy Images
Plugin URI:           http://wordpress.mfields.org/plugins/taxonomy-images/
Description:          Associate images from your media library to categories, tags and custom taxonomies.
Version:              0.7.3
Author:               Michael Fields
Author URI:           http://wordpress.mfields.org/
License:              GPLv2

Copyright 2010-2011  Michael Fields  michael@mfields.org

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License version 2 as published by
the Free Software Foundation.

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.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/


require_once( trailingslashit( dirname( __FILE__ ) ) . 'deprecated.php' );
require_once( trailingslashit( dirname( __FILE__ ) ) . 'public-filters.php' );


/**
 * Version Number.
 *
 * @return    string    The plugin's version number.
 * @access    private
 * @since     0.7
 * @alter     0.7.3
 */
function taxonomy_image_plugin_version() {
	return '0.7.3';
}


/**
 * Get a url to a file in this plugin.
 *
 * @return    string
 * @access    private
 * @since     0.7
 */
function taxonomy_image_plugin_url( $file = '' ) {
	static $path = '';
	if ( empty( $path ) ) {
		$path = plugin_dir_url( __FILE__ );
	}
	return $path . $file;
}


/**
 * Detail Image Size.
 *
 * @return    array     Configuration for the "detail" image size.
 * @access    private
 * @since     0.7
 */
function taxonomy_image_plugin_detail_image_size() {
	return array(
		'name' => 'detail',
		'size' => array( 75, 75, true )
		);
}


/**
 * Register custom image size with WordPress.
 *
 * @access    private
 * @since     2010-10-28
 */
function taxonomy_image_plugin_add_image_size() {
	$detail = taxonomy_image_plugin_detail_image_size();
	add_image_size(
		$detail['name'],
		$detail['size'][0],
		$detail['size'][1],
		$detail['size'][2]
		);
}
add_action( 'init', 'taxonomy_image_plugin_add_image_size' );


/**
 * Load Plugin Text Domain.
 *
 * @access    private
 * @since     0.7.3
 */
function taxonomy_image_plugin_text_domain() {
	load_plugin_textdomain( 'taxonomy-images', false, dirname( plugin_basename( __FILE__ ) ) . '/languages/' );
}
add_action( 'init', 'taxonomy_image_plugin_text_domain' );


/**
 * Modal Button.
 *
 * Create a button in the modal media window to associate the current image to the term.
 *
 * @param     array     Multidimensional array representing the images form.
 * @param     stdClass  WordPress post object.
 * @return    array     The image's form array with added button if modal window was accessed by this script.
 *
 * @access    private
 * @since     2010-10-28
 * @alter     0.7
 */
function taxonomy_image_plugin_modal_button( $fields, $post ) {
	if ( isset( $fields['image-size'] ) && isset( $post->ID ) ) {
		$image_id = (int) $post->ID;

		$o = '<div class="taxonomy-image-modal-control" id="' . esc_attr( 'taxonomy-image-modal-control-' . $image_id ) . '">';

		$o.= '<span class="button create-association">' . sprintf( esc_html__( 'Associate with %1$s', 'taxonomy-images' ), '<span class="term-name">' . esc_html__( 'this term', 'taxonomy-images' ) . '</span>' ) . '</span>';

		$o.= '<span class="remove-association">' . sprintf( esc_html__( 'Remove association with %1$s', 'taxonomy-images' ), '<span class="term-name">' . esc_html__( 'this term', 'taxonomy-images' ) . '</span>' ) . '</span>';

		$o.= '<input class="taxonomy-image-button-image-id" name="' . esc_attr( 'taxonomy-image-button-image-id-' . $image_id ) . '" type="hidden" value="' . esc_attr( $image_id ) . '" />';

		$o.= '<input class="taxonomy-image-button-nonce-create" name="' . esc_attr( 'taxonomy-image-button-nonce-create-' . $image_id ) . '" type="hidden" value="' . esc_attr( wp_create_nonce( 'taxonomy-image-plugin-create-association' ) ) . '" />';

		$o.= '<input class="taxonomy-image-button-nonce-remove" name="' . esc_attr( 'taxonomy-image-button-nonce-remove-' . $image_id ) . '" type="hidden" value="' . esc_attr( wp_create_nonce( 'taxonomy-image-plugin-remove-association' ) ) . '" />';

		$o.= '</div>';

		$fields['image-size']['extra_rows']['taxonomy-image-plugin-button']['html'] = $o;
	}
	return $fields;
}
add_filter( 'attachment_fields_to_edit', 'taxonomy_image_plugin_modal_button', 20, 2 );


/**
 * Get Image Source.
 *
 * Return a uri to a custom image size.
 *
 * If size doesn't exist, attempt to create a resized version.
 * The output of this function should be escaped before printing to the browser.
 *
 * @param     int       Image ID.
 * @return    string    URI of custom image on success; emtpy string otherwise.
 *
 * @access    private.
 * @since     2010-10-28
 */
function taxonomy_image_plugin_get_image_src( $id ) {
	$detail = taxonomy_image_plugin_detail_image_size();

	/* Return url to custom intermediate size if it exists. */
	$img = image_get_intermediate_size( $id, $detail['name'] );
	if ( isset( $img['url'] ) ) {
		return $img['url'];
	}

	/* Detail image does not exist, attempt to create it. */
	$wp_upload_dir = wp_upload_dir();
	if ( isset( $wp_upload_dir['basedir'] ) ) {

		/* Create path to original uploaded image. */
		$path = trailingslashit( $wp_upload_dir['basedir'] ) . get_post_meta( $id, '_wp_attached_file', true );
		if ( is_file( $path ) ) {

			/* Attempt to create a new downsized version of the original image. */
			$new = image_resize( $path,
				$detail['size'][0],
				$detail['size'][1],
				$detail['size'][2]
				);

			/* Image creation successful. Generate and cache image metadata. Return url. */
			if ( ! is_wp_error( $new ) ) {
				$meta = wp_generate_attachment_metadata( $id, $path );
				wp_update_attachment_metadata( $id, $meta );
				$img = image_get_intermediate_size( $id, $detail['name'] );
				if ( isset( $img['url'] ) ) {
					return $img['url'];
				}
			}
		}
	}

	/* Custom intermediate size cannot be created, try for thumbnail. */
	$img = image_get_intermediate_size( $id, 'thumbnail' );
	if ( isset( $img['url'] ) ) {
		return $img['url'];
	}

	/* Thumbnail cannot be found, try fullsize. */
	$url = wp_get_attachment_url( $id );
	if ( ! empty( $url ) ) {
		return $url;
	}

	/*
	 * No image can be found.
	 * This is most likely caused by a user deleting an attachment before deleting it's association with a taxonomy.
	 * If we are in the administration panels:
	 * - Delete the association.
	 * - Return uri to default.png.
	 */
	if ( is_admin() ) {
		$assoc = taxonomy_image_plugin_get_associations();
		foreach ( $assoc as $term => $img ) {
			if ( $img === $id ) {
				unset( $assoc[$term] );
			}
		}
		update_option( 'taxonomy_image_plugin', $assoc );
		return taxonomy_image_plugin_url( 'default.png' );
	}

	/*
	 * No image can be found.
	 * Return path to blank-image.png.
	 */
	return taxonomy_image_plugin_url( 'blank.png' );
}


/**
 * Sanitize Associations.
 *
 * Ensures that all key/value pairs are positive integers.
 * This filter will discard all zero and negative values.
 *
 * @param     array     An array of term_taxonomy_id/attachment_id pairs.
 * @return    array     Sanitized version of parameter.
 *
 * @access    private
 */
function taxonomy_image_plugin_sanitize_associations( $associations ) {
	$o = array();
	foreach ( (array) $associations as $tt_id => $im_id ) {
		$tt_id = absint( $tt_id );
		$im_id = absint( $im_id );
		if ( 0 < $tt_id && 0 < $im_id ) {
			$o[$tt_id] = $im_id;
		}
	}
	return $o;
}


/**
 * Sanitize Settings.
 *
 * This function is responsible for ensuring that
 * all values within the 'taxonomy_image_plugin_settings'
 * options are of the appropriate type.
 *
 * @param     array     Unknown.
 * @return    array     Multi-dimensional array of sanitized settings.
 *
 * @access    private
 * @since     0.7
 */
function taxonomy_image_plugin_settings_sanitize( $dirty ) {
	$clean = array();
	if ( isset( $dirty['taxonomies'] ) ) {
		$taxonomies = get_taxonomies();
		foreach ( (array) $dirty['taxonomies'] as $taxonomy ) {
			if ( in_array( $taxonomy, $taxonomies ) ) {
				$clean['taxonomies'][] = $taxonomy;
			}
		}
	}

	/* translators: Notice displayed on the custom administration page. */
	$message = __( 'Image support for taxonomies successfully updated', 'taxonomy-images' );
	if ( empty( $clean ) ) {
		/* translators: Notice displayed on the custom administration page. */
		$message = __( 'Image support has been disabled for all taxonomies.', 'taxonomy-images' );
	}

	add_settings_error( 'taxonomy_image_plugin_settings', 'taxonomies_updated', esc_html( $message ), 'updated' );

	return $clean;
}


/**
 * Register settings with WordPress.
 *
 * This plugin will store to sets of settings in the
 * options table. The first is named 'taxonomy_image_plugin'
 * and stores the associations between terms and images. The
 * keys in this array represent the term_taxonomy_id of the
 * term while the value represents the ID of the image
 * attachment.
 *
 * The second setting is used to store everything else. As of
 * version 0.7 it has one key named 'taxonomies' whichi is a
 * flat array consisting of taxonomy names representing a
 * black-list of registered taxonomies. These taxonomies will
 * NOT be given an image UI.
 *
 * @access    private
 */
function taxonomy_image_plugin_register_settings() {
	register_setting(
		'taxonomy_image_plugin',
		'taxonomy_image_plugin',
		'taxonomy_image_plugin_sanitize_associations'
		);
	register_setting(
		'taxonomy_image_plugin_settings',
		'taxonomy_image_plugin_settings',
		'taxonomy_image_plugin_settings_sanitize'
		);
	add_settings_section(
		'taxonomy_image_plugin_settings',
		esc_html__( 'Settings', 'taxonomy-images' ),
		'__return_false',
		'taxonomy_image_plugin_settings'
		);
	add_settings_field(
		'taxonomy-images',
		esc_html__( 'Taxonomies', 'taxonomy-images' ),
		'taxonomy_image_plugin_control_taxonomies',
		'taxonomy_image_plugin_settings',
		'taxonomy_image_plugin_settings'
		);
}
add_action( 'admin_init', 'taxonomy_image_plugin_register_settings' );


/**
 * Admin Menu.
 *
 * Create the admin menu link for the settings page.
 *
 * @access    private
 * @since     0.7
 */
function taxonomy_images_settings_menu() {
	add_options_page(
		esc_html__( 'Taxonomy Images', 'taxonomy-images' ), /* HTML <title> tag. */
		esc_html__( 'Taxonomy Images', 'taxonomy-images' ), /* Link text in admin menu. */
		'manage_options',
		'taxonomy_image_plugin_settings',
		'taxonomy_image_plugin_settings_page'
		);
}
add_action( 'admin_menu', 'taxonomy_images_settings_menu' );


/**
 * Settings Page Template.
 *
 * This function in conjunction with others usei the WordPress
 * Settings API to create a settings page where users can adjust
 * the behaviour of this plugin. Please see the following functions
 * for more insight on the output generated by this function:
 *
 * taxonomy_image_plugin_control_taxonomies()
 *
 * @access    private
 * @since     0.7
 */
function taxonomy_image_plugin_settings_page() {
	print "\n" . '<div class="wrap">';
	screen_icon();

	/* translators: Heading of the custom administration page. */
	print "\n" . '<h2>' . esc_html__( 'Taxonomy Images Plugin Settings', 'taxonomy-images' ) . '</h2>';
	print "\n" . '<div id="taxonomy-images">';
	print "\n" . '<form action="options.php" method="post">';

	settings_fields( 'taxonomy_image_plugin_settings' );
	do_settings_sections( 'taxonomy_image_plugin_settings' );

	/* translators: Button on the custom administration page. */
	print "\n" . '<div class="button-holder"><input name="submit" type="submit" value="' . esc_attr__( 'Save Changes', 'taxonomy-images' ) . '" /></div>';
	print "\n" . '</div></form></div>';
}


/**
 * Taxonomy Checklist.
 *
 * @access    private
 */
function taxonomy_image_plugin_control_taxonomies() {
	$settings = get_option( 'taxonomy_image_plugin_settings' );
	$taxonomies = get_taxonomies( array(), 'objects' );
	foreach ( (array) $taxonomies as $taxonomy ) {
		if ( ! isset( $taxonomy->name ) ) {
			continue;
		}
		if ( ! isset( $taxonomy->label ) ) {
			continue;
		}
		if ( ! isset( $taxonomy->show_ui ) || empty( $taxonomy->show_ui ) ) {
			continue;
		}
		$id = 'taxonomy-images-' . $taxonomy->name;
		$checked = '';
		if ( isset( $settings['taxonomies'] ) && in_array( $taxonomy->name, (array) $settings['taxonomies'] ) ) {
			$checked = ' checked="checked"';
		}
		print "\n" . '<p><label for="' . esc_attr( $id ) . '">';
		print '<input' . $checked . ' id="' . esc_attr( $id ) . '" type="checkbox" name="taxonomy_image_plugin_settings[taxonomies][]" value="' . esc_attr( $taxonomy->name ) . '">';
		print ' ' . esc_html( $taxonomy->label ) . '</label></p>';
	}
}


/**
 * JSON Respose.
 * Terminates script execution.
 *
 * @param     array     Associative array of values to be encoded in JSON.
 *
 * @access    private
 */
function taxonomy_image_plugin_json_response( $args ) {
	/* translators: An ajax request has failed for an unknown reason. */
	$response = wp_parse_args( $args, array(
		'status' => 'bad',
		'why'    => esc_html__( 'Unknown error encountered', 'taxonomy-images' )
	) );
	header( 'Content-type: application/jsonrequest' );
	print json_encode( $response );
	exit;
}


/**
 * Get Term Info.
 *
 * Returns term info by term_taxonomy_id.
 *
 * @param     int       term_taxonomy_id
 * @return    array     Keys: term_id (int) and taxonomy (string).
 *
 * @access    private
 */
function taxonomy_image_plugin_get_term_info( $tt_id ) {
	static $cache = array();
	if ( isset( $cache[$tt_id] ) ) {
		return $cache[$tt_id];
	}
	global $wpdb;
	$data = $wpdb->get_results( $wpdb->prepare( "SELECT term_id, taxonomy FROM $wpdb->term_taxonomy WHERE term_taxonomy_id = %d LIMIT 1", $tt_id ) );
	if ( isset( $data[0]->term_id ) ) {
		$cache[$tt_id]['term_id'] = absint( $data[0]->term_id );
	}
	if ( isset( $data[0]->taxonomy ) ) {
		$cache[$tt_id]['taxonomy'] = sanitize_title_with_dashes( $data[0]->taxonomy );
	}
	if ( isset( $cache[$tt_id] ) ) {
		return $cache[$tt_id];
	}
	return array();
}


/**
 * Check Taxonomy Permissions.
 *
 * Allows a permission check to be performed on a term
 * when all you know is the term_taxonomy_id.
 *
 * @param     int       term_taxonomy_id
 * @return    bool      True if user can edit terms, False if not.
 *
 * @access    private
 */
function taxonomy_image_plugin_check_permissions( $tt_id ) {
	$data = taxonomy_image_plugin_get_term_info( $tt_id );
	if ( ! isset( $data['taxonomy'] ) ) {
		return false;
	}

	$taxonomy = get_taxonomy( $data['taxonomy'] );
	if ( ! isset( $taxonomy->cap->edit_terms ) ) {
		return false;
	}

	return current_user_can( $taxonomy->cap->edit_terms );
}


/**
 * Create an association.
 *
 * Callback for the wp_ajax_{$_GET['action']} hook.
 *
 * @access    private
 */
function taxonomy_image_plugin_create_association() {
	if ( ! isset( $_POST['tt_id'] ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'tt_id not sent', 'taxonomy-images' ),
		) );
	}

	$tt_id = absint( $_POST['tt_id'] );
	if ( empty( $tt_id ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'tt_id is empty', 'taxonomy-images' ),
		) );
	}

	if ( ! taxonomy_image_plugin_check_permissions( $tt_id ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'You do not have the correct capability to manage this term', 'taxonomy-images' ),
		) );
	}

	if ( ! isset( $_POST['wp_nonce'] ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'No nonce included.', 'taxonomy-images' ),
		) );
	}

	if ( ! wp_verify_nonce( $_POST['wp_nonce'], 'taxonomy-image-plugin-create-association' ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'Nonce did not match', 'taxonomy-images' ),
		) );
	}

	if ( ! isset( $_POST['attachment_id'] ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'Image id not sent', 'taxonomy-images' )
		) );
	}

	$image_id = absint( $_POST['attachment_id'] );
	if ( empty( $image_id ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'Image id is not a positive integer', 'taxonomy-images' )
		) );
	}

	$assoc = taxonomy_image_plugin_get_associations();
	$assoc[$tt_id] = $image_id;
	if ( update_option( 'taxonomy_image_plugin', taxonomy_image_plugin_sanitize_associations( $assoc ) ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'good',
			'why'    => esc_html__( 'Image successfully associated', 'taxonomy-images' ),
			'attachment_thumb_src' => taxonomy_image_plugin_get_image_src( $image_id )
		) );
	}
	else {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'Association could not be created', 'taxonomy-images' )
		) );
	}

	/* Don't know why, but something didn't work. */
	taxonomy_image_plugin_json_response();
}
add_action( 'wp_ajax_taxonomy_image_create_association', 'taxonomy_image_plugin_create_association' );


/**
 * Remove an association.
 *
 * Removes an association from the setting stored in the database.
 * Print json encoded message and terminates script execution.
 *
 * @access    private
 */
function taxonomy_image_plugin_remove_association() {
	if ( ! isset( $_POST['tt_id'] ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'tt_id not sent', 'taxonomy-images' ),
		) );
	}

	$tt_id = absint( $_POST['tt_id'] );
	if ( empty( $tt_id ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'tt_id is empty', 'taxonomy-images' ),
		) );
	}

	if ( ! taxonomy_image_plugin_check_permissions( $tt_id ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'You do not have the correct capability to manage this term', 'taxonomy-images' ),
		) );
	}

	if ( ! isset( $_POST['wp_nonce'] ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'No nonce included', 'taxonomy-images' ),
		) );
	}

	if ( ! wp_verify_nonce( $_POST['wp_nonce'], 'taxonomy-image-plugin-remove-association') ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'Nonce did not match', 'taxonomy-images' ),
		) );
	}

	$assoc = taxonomy_image_plugin_get_associations();
	if ( ! isset( $assoc[$tt_id] ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'good',
			'why'    => esc_html__( 'Nothing to remove', 'taxonomy-images' )
		) );
	}

	unset( $assoc[$tt_id] );

	if ( update_option( 'taxonomy_image_plugin', $assoc ) ) {
		taxonomy_image_plugin_json_response( array(
			'status' => 'good',
			'why'    => esc_html__( 'Association successfully removed', 'taxonomy-images' )
		) );
	}
	else {
		taxonomy_image_plugin_json_response( array(
			'status' => 'bad',
			'why'    => esc_html__( 'Association could not be removed', 'taxonomy-images' )
		) );
	}

	/* Don't know why, but something didn't work. */
	taxonomy_image_plugin_json_response();
}
add_action( 'wp_ajax_taxonomy_image_plugin_remove_association', 'taxonomy_image_plugin_remove_association' );


/**
 * Get a list of user-defined associations.
 * Associations are stored in the WordPress options table.
 *
 * @param     bool      Should WordPress query the database for the results
 * @return    array     List of associations. Key => taxonomy_term_id; Value => image_id
 *
 * @access    private
 */
function taxonomy_image_plugin_get_associations( $refresh = false ) {
	static $associations = array();
	if ( empty( $associations ) || $refresh ) {
		$associations = taxonomy_image_plugin_sanitize_associations( get_option( 'taxonomy_image_plugin' ) );
	}
	return $associations;
}
add_action( 'init', 'taxonomy_image_plugin_get_associations' );


/**
 * Dynamically create hooks for each taxonomy.
 *
 * Adds hooks for each taxonomy that the user has given
 * an image interface to via settings page. These hooks
 * enable the image interface on wp-admin/edit-tags.php.
 *
 * @access    private
 * @since     0.4.3
 * @alter     0.7
 */
function taxonomy_image_plugin_add_dynamic_hooks() {
	$settings = get_option( 'taxonomy_image_plugin_settings' );
	if ( ! isset( $settings['taxonomies'] ) ) {
		return;
	}
	foreach ( $settings['taxonomies'] as $taxonomy ) {
		add_filter( 'manage_' . $taxonomy . '_custom_column', 'taxonomy_image_plugin_taxonomy_rows', 15, 3 );
		add_filter( 'manage_edit-' . $taxonomy . '_columns',  'taxonomy_image_plugin_taxonomy_columns' );
		add_action( $taxonomy . '_edit_form_fields',          'taxonomy_image_plugin_edit_tag_form', 10, 2 );
	}
}
add_action( 'admin_init', 'taxonomy_image_plugin_add_dynamic_hooks' );


/**
 * Edit Term Columns.
 *
 * Insert a new column on wp-admin/edit-tags.php.
 *
 * @see taxonomy_image_plugin_add_dynamic_hooks()
 *
 * @param     array     A list of columns.
 * @return    array     List of columns with "Images" inserted after the checkbox.
 *
 * @access    private
 * @since     0.4.3
 */
function taxonomy_image_plugin_taxonomy_columns( $original_columns ) {
	$new_columns = $original_columns;
	array_splice( $new_columns, 1 );
	$new_columns['taxonomy_image_plugin'] = esc_html__( 'Image', 'taxonomy-images' );
	return array_merge( $new_columns, $original_columns );
}


/**
 * Edit Term Rows.
 *
 * Create image control for each term row of wp-admin/edit-tags.php.
 *
 * @see taxonomy_image_plugin_add_dynamic_hooks()
 *
 * @param     string    Row.
 * @param     string    Name of the current column.
 * @param     int       Term ID.
 * @return    string    @see taxonomy_image_plugin_control_image()
 *
 * @access    private
 * @since     2010-11-08
 */
function taxonomy_image_plugin_taxonomy_rows( $row, $column_name, $term_id ) {
	if ( 'taxonomy_image_plugin' === $column_name ) {
		global $taxonomy;
		return $row . taxonomy_image_plugin_control_image( $term_id, $taxonomy );
	}
	return $row;
}


/**
 * Edit Term Control.
 *
 * Create image control for wp-admin/edit-tag-form.php.
 * Hooked into the '{$taxonomy}_edit_form_fields' action.
 *
 * @param     stdClass  Term object.
 * @param     string    Taxonomy slug.
 *
 * @access    private
 * @since     2010-11-08
 */
function taxonomy_image_plugin_edit_tag_form( $term, $taxonomy ) {
	$taxonomy = get_taxonomy( $taxonomy );
	$name = __( 'term', 'taxonomy-images' );
	if ( isset( $taxonomy->labels->singular_name ) ) {
		$name = strtolower( $taxonomy->labels->singular_name );
	}
	?>
	<tr class="form-field hide-if-no-js">
		<th scope="row" valign="top"><label for="description"><?php print esc_html__( 'Image', 'taxonomy-images' ) ?></label></th>
		<td>
			<?php print taxonomy_image_plugin_control_image( $term->term_id, $taxonomy->name ); ?>
			<div class="clear"></div>
			<span class="description"><?php printf( esc_html__( 'Associate an image from your media library to this %1$s.', 'taxonomy-images' ), esc_html( $name ) ); ?></span>
		</td>
	</tr>
	<?php
}

/**
 * Image Control.
 *
 * Creates all image controls on edit-tags.php.
 *
 * @todo      Remove rel tag from link... will need to adjust js to accomodate.
 * @since     0.7
 * @access    private
 */
function taxonomy_image_plugin_control_image( $term_id, $taxonomy ) {

	$term = get_term( $term_id, $taxonomy );

	$tt_id = 0;
	if ( isset( $term->term_taxonomy_id ) ) {
		$tt_id = (int) $term->term_taxonomy_id;
	}

	$taxonomy = get_taxonomy( $taxonomy );

	$name = esc_html__( 'term', 'taxonomy-images' );
	if ( isset( $taxonomy->labels->singular_name ) ) {
		$name = strtolower( $taxonomy->labels->singular_name );
	}

	$hide = ' hide';
	$attachment_id = 0;
	$associations = taxonomy_image_plugin_get_associations();
	if ( isset( $associations[ $tt_id ] ) ) {
		$attachment_id = (int) $associations[ $tt_id ];
		$hide = '';
	}

	$img = taxonomy_image_plugin_get_image_src( $attachment_id );

	$term = get_term( $term_id, $taxonomy->name );

	$o = "\n" . '<div id="' . esc_attr( 'taxonomy-image-control-' . $tt_id ) . '" class="taxonomy-image-control hide-if-no-js">';
	$o.= "\n" . '<a class="thickbox taxonomy-image-thumbnail" href="' . esc_url( admin_url( 'media-upload.php' ) . '?type=image&tab=library&post_id=0&TB_iframe=true' ) . '" title="' . esc_attr( sprintf( __( 'Associate an image with the %1$s named &#8220;%2$s&#8221;.', 'taxonomy-images' ), $name, $term->name ) ) . '"><img id="' . esc_attr( 'taxonomy_image_plugin_' . $tt_id ) . '" src="' . esc_url( $img ) . '" alt="" /></a>';
	$o.= "\n" . '<a class="control upload thickbox" href="' . esc_url( admin_url( 'media-upload.php' ) . '?type=image&tab=type&post_id=0&TB_iframe=true' ) . '" title="' . esc_attr( sprintf( __( 'Upload a new image for this %s.', 'taxonomy-images' ), $name ) ) . '">' . esc_html__( 'Upload.', 'taxonomy-images' ) . '</a>';
	$o.= "\n" . '<a class="control remove' . $hide . '" href="#" id="' . esc_attr( 'remove-' . $tt_id ) . '" rel="' . esc_attr( $tt_id ) . '" title="' . esc_attr( sprintf( __( 'Remove image from this %s.', 'taxonomy-images' ), $name ) ) . '">' . esc_html__( 'Delete', 'taxonomy-images' ) . '</a>';
	$o.= "\n" . '<input type="hidden" class="tt_id" name="' . esc_attr( 'tt_id-' . $tt_id ) . '" value="' . esc_attr( $tt_id ) . '" />';

	$o.= "\n" . '<input type="hidden" class="image_id" name="' . esc_attr( 'image_id-' . $tt_id ) . '" value="' . esc_attr( $attachment_id ) . '" />';

	if ( isset( $term->name ) && isset( $term->slug ) ) {
		$o.= "\n" . '<input type="hidden" class="term_name" name="' . esc_attr( 'term_name-' . $term->slug ) . '" value="' . esc_attr( $term->name ) . '" />';
	}

	$o.= "\n" . '</div>';
	return $o;
}


/**
 * Custom javascript for modal media box.
 *
 * This script need to be added to all instance of the media upload box.
 *
 * @access    private
 */
function taxonomy_image_plugin_media_upload_popup_js() {
	wp_enqueue_script(
		'taxonomy-images-media-upload-popup',
		taxonomy_image_plugin_url( 'media-upload-popup.js' ),
		array( 'jquery' ),
		taxonomy_image_plugin_version()
		);
	wp_localize_script( 'taxonomy-images-media-upload-popup', 'TaxonomyImagesModal', array (
		'termBefore'  => esc_html__( '&#8220;', 'taxonomy-images' ),
		'termAfter'   => esc_html__( '&#8221;', 'taxonomy-images' ),
		'associating' => esc_html__( 'Associating &#8230;', 'taxonomy-images' ),
		'success'     => esc_html__( 'Successfully Associated', 'taxonomy-images' ),
		'removing'    => esc_html__( 'Removing &#8230;', 'taxonomy-images' ),
		'removed'     => esc_html__( 'Successfully Removed', 'taxonomy-images' )
		) );
}
add_action( 'admin_print_scripts-media-upload-popup', 'taxonomy_image_plugin_media_upload_popup_js' );


/**
 * Custom javascript for wp-admin/edit-tags.php.
 *
 * @access    private
 */
function taxonomy_image_plugin_edit_tags_js() {
	if ( false == taxonomy_image_plugin_is_screen_active() ) {
		return;
	}
	wp_enqueue_script(
		'taxonomy-image-plugin-edit-tags',
		taxonomy_image_plugin_url( 'edit-tags.js' ),
		array( 'jquery', 'thickbox' ),
		taxonomy_image_plugin_version()
		);
	wp_localize_script( 'taxonomy-image-plugin-edit-tags', 'taxonomyImagesPlugin', array (
		'nonce'    => wp_create_nonce( 'taxonomy-image-plugin-remove-association' ),
		'img_src'  => taxonomy_image_plugin_url( 'default.png' ),
		'tt_id'    => 0,
		'image_id' => 0,
		) );
}
add_action( 'admin_print_scripts-edit-tags.php', 'taxonomy_image_plugin_edit_tags_js' );


/**
 * Custom styles.
 *
 * @since     0.7
 * @access    private
 */
function taxonomy_image_plugin_css_admin() {
	if ( false == taxonomy_image_plugin_is_screen_active() && 'admin_print_styles-media-upload-popup' != current_filter() ) {
		return;
	}
	wp_enqueue_style(
		'taxonomy-image-plugin-edit-tags',
		taxonomy_image_plugin_url( 'admin.css' ),
		array(),
		taxonomy_image_plugin_version(),
		'screen'
		);
}
add_action( 'admin_print_styles-edit-tags.php', 'taxonomy_image_plugin_css_admin' );
add_action( 'admin_print_styles-media-upload-popup', 'taxonomy_image_plugin_css_admin' );


/**
 * Thickbox styles.
 *
 * @since     0.7
 * @access    private
 */
function taxonomy_image_plugin_css_thickbox() {
	if ( false == taxonomy_image_plugin_is_screen_active() ) {
		return;
	}
	wp_enqueue_style( 'thickbox' );
}
add_action( 'admin_print_styles-edit-tags.php', 'taxonomy_image_plugin_css_thickbox' );


/**
 * Public Styles.
 *
 * Prints custom css to all public pages. If you do not
 * wish to have these styles included for you, please
 * insert the following code into your theme's functions.php
 * file:
 *
 * add_filter( 'taxonomy-images-disable-public-css', '__return_true' );
 *
 * @since     0.7
 * @access    private
 */
function taxonomy_image_plugin_css_public() {
	if ( apply_filters( 'taxonomy-images-disable-public-css', false ) ) {
		return;
	}
	wp_enqueue_style(
		'taxonomy-image-plugin-public',
		taxonomy_image_plugin_url( 'style.css' ),
		array(),
		taxonomy_image_plugin_version(),
		'screen'
		);
}
add_action( 'wp_print_styles', 'taxonomy_image_plugin_css_public' );


/**
 * Activation.
 *
 * Two entries in the options table will created when this
 * plugin is activated in the event that they do not exist.
 *
 * 'taxonomy_image_plugin' (array) A flat list of all assocaitions
 * made by this plugin. Keys are integers representing the
 * term_taxonomy_id of terms. Values are integers representing the
 * ID property of an image attachment.
 *
 * 'taxonomy_image_plugin_settings' (array) A multi-dimensional array
 * of user-defined settings. As of version 0.7, only one key is used:
 * 'taxonomies' which is a whitelist of registered taxonomies having ui
 * that support the custom image ui provided by this plugin.
 *
 * @access    private
 * @alter     0.7
 */
function taxonomy_image_plugin_activate() {
	$associations = get_option( 'taxonomy_image_plugin' );
	if ( false === $associations ) {
		add_option( 'taxonomy_image_plugin', array() );
	}
	$settings = get_option( 'taxonomy_image_plugin_settings' );
	if ( false === $settings ) {
		add_option( 'taxonomy_image_plugin_settings', array(
			'taxonomies' => array()
			) );
	}
}
register_activation_hook( __FILE__, 'taxonomy_image_plugin_activate' );


/**
 * Is Screen Active?
 *
 * @return    bool
 *
 * @access    private
 * @since     0.7
 */
function taxonomy_image_plugin_is_screen_active() {
	$screen = get_current_screen();
	if ( ! isset( $screen->taxonomy ) ) {
		return false;
	}

	$settings = get_option( 'taxonomy_image_plugin_settings' );
	if ( ! isset( $settings['taxonomies'] ) ) {
		return false;
	}

	if ( in_array( $screen->taxonomy, $settings['taxonomies'] ) ) {
		return true;
	}
	return false;
}


/**
 * Cache Images
 *
 * Sets the WordPress object cache for all term images
 * associated to the posts in the provided array. This
 * function has been created to minimize queries when
 * using this plugins get_the_terms() style function.
 *
 * @param     array          Post objects.
 *
 * @access    private
 * @since     1.1
 */
function taxonomy_image_plugin_cache_images( $posts ) {
	$assoc = taxonomy_image_plugin_get_associations();
	if ( empty( $assoc ) ) {
		return;
	}

	$tt_ids = array();
	foreach ( (array) $posts as $post ) {
		if ( ! isset( $post->ID ) || ! isset( $post->post_type ) ) {
			continue;
		}

		$taxonomies = get_object_taxonomies( $post->post_type );
		if ( empty( $taxonomies ) ) {
			continue;
		}

		foreach ( $taxonomies as $taxonomy ) {
			$the_terms = get_the_terms( $post->ID, $taxonomy );
			foreach ( (array) $the_terms as $term ) {
				if ( ! isset( $term->term_taxonomy_id ) ) {
					continue;
				}
				$tt_ids[] = $term->term_taxonomy_id;
			}
		}
	}
	$tt_ids = array_filter( array_unique( $tt_ids ) );

	$image_ids = array();
	foreach ( $tt_ids as $tt_id ) {
		if ( ! isset( $assoc[$tt_id] ) ) {
			continue;
		}
		if ( in_array( $assoc[$tt_id], $image_ids ) ) {
			continue;
		}
		$image_ids[] = $assoc[$tt_id];
	}

	if ( empty( $image_ids ) ) {
		return;
	}

	get_posts( array(
		'include'   => $image_ids,
		'post_type' => 'attachment'
		) );
}


/**
 * Cache Images
 *
 * Cache all term images associated with posts in
 * the main WordPress query.
 *
 * @param     array          Post objects.
 *
 * @access    private
 * @since     0.7
 */
function taxonomy_image_plugin_cache_queried_images() {
	global $posts;
	taxonomy_image_plugin_cache_images( $posts );
}
add_action( 'template_redirect', 'taxonomy_image_plugin_cache_queried_images' );


/**
 * Check Taxonomy
 *
 * Wrapper for WordPress core functions taxonomy_exists().
 * In the event that an unregistered taxonomy is passed a
 * E_USER_NOTICE will be generated.
 *
 * @param     string         Taxonomy name as registered with WordPress.
 * @param     string         Name of the current function or filter.
 * @return    bool           True if taxonomy exists, False if not.
 *
 * @access    private
 * @since     0.7
 */
function taxonomy_image_plugin_check_taxonomy( $taxonomy, $filter ) {
	if ( ! taxonomy_exists( $taxonomy ) ) {
		trigger_error( sprintf( esc_html__( 'The %1$s argument for %2$s is set to %3$s which is not a registered taxonomy. Please check the spelling and update the argument.', 'taxonomy-images' ),
		'<var>' . esc_html__( 'taxonomy', 'taxonomy-images' ) . '</var>',
		'<code>' . esc_html( $filter ) . '</code>',
		'<strong>' . esc_html( $taxonomy ) . '</strong>'
		) );
		return false;
	}

	$settings = get_option( 'taxonomy_image_plugin_settings' );

	if ( ! isset( $settings['taxonomies'] ) ) {
		trigger_error( sprintf( esc_html__( 'No taxonomies have image support. %1$s', 'taxonomy-images' ), taxonomy_images_plugin_settings_page_link() ) );
		return false;
	}

	if ( ! in_array( $taxonomy, (array) $settings['taxonomies'] ) ) {
		trigger_error( sprintf( esc_html__( 'The %1$s taxonomy does not have image support. %2$s', 'taxonomy-images' ),
		'<strong>' . esc_html( $taxonomy ) . '</strong>',
		taxonomy_images_plugin_settings_page_link()
		) );
		return false;
	}

	return true;
}


/**
 * Please Use Filter.
 *
 * Report to user that they are directly calling a function
 * instead of using supported filters. A E_USER_NOTICE will
 * be generated.
 *
 * @param     string         Name of function called.
 * @param     string         Name of filter to use instead.
 *
 * @access    private
 * @since     0.7
 */
function taxonomy_image_plugin_please_use_filter( $function, $filter ) {
	trigger_error( sprintf( esc_html__( 'The %1$s has been called directly. Please use the %2$s filter instead.', 'taxonomy-images' ),
	'<code>' . esc_html( $function . '()' ) . '</code>',
	'<code>' . esc_html( $filter ) . '</code>'
	) );
}


/**
 * Plugin Meta Links.
 *
 * Add a link to this plugin's setting page when it
 * displays in the table on wp-admin/plugins.php.
 *
 * @param     array          List of links.
 * @param     string         Current plugin being displayed in plugins.php.
 * @return    array          Potentially modified list of links.
 *
 * @access    private
 * @since     0.7
 */
function taxonomy_images_plugin_row_meta( $links, $file ) {
	static $plugin_name = '';

	if ( empty( $plugin_name ) ) {
		$plugin_name = plugin_basename( __FILE__ );
	}

	if ( $plugin_name != $file ) {
		return $links;
	}

	$link = taxonomy_images_plugin_settings_page_link( __( 'Settings', 'taxonomy-images' ) );
	if ( ! empty( $link ) ) {
		$links[] = $link;
	}

	$links[] = '<a href="http://wordpress.mfields.org/donate/">' . __( 'Donate', 'taxonomy-images' ) . '</a>';

	return $links;
}
add_filter( 'plugin_row_meta', 'taxonomy_images_plugin_row_meta', 10, 2 );


/**
 * Settings Page Link.
 *
 * @param     array     Localized link text.
 * @return    string    HTML link to settings page.
 *
 * @access    private
 * @since     0.7
 */
function taxonomy_images_plugin_settings_page_link( $link_text = '' ) {
	if ( empty( $link_text ) ) {
		$link_text = __( 'Manage Settings', 'taxonomy-images' );
	}

	$link = '';
	if ( current_user_can( 'manage_options' ) ) {
		$link = '<a href="' . esc_url( add_query_arg( array( 'page' => 'taxonomy_image_plugin_settings' ), admin_url( 'options-general.php' ) ) ) . '">' . esc_html( $link_text ) . '</a>';
	}

	return $link;
}