WIP: Initial release

eth-amp-analytics-wp.php

+<?php
+/*
+Plugin Name: Google Analytics for AMP
+Plugin URI: https://ethitter.com/plugins/
+Description: Enable Google Analytics support for Automattic's AMP plugin
+Author: Erick Hitter
+Version: 0.2
+Author URI: https://ethitter.com/
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+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
+*/
+
+class ETH_AMP_Analytics_WP {
+	/**
+	 * PLUGIN SETUP
+	 */
+
+	/**
+	 * Singleton
+	 */
+	private static $instance = null;
+
+	/**
+	 * Instantiate singleton
+	 */
+	public static function get_instance() {
+		if ( ! is_a( self::$instance, __CLASS__ ) ) {
+			self::$instance = new self;
+		}
+
+		return self::$instance;
+	}
+
+	/**
+	 * Dummy magic methods
+	 */
+	public function __clone() {_doing_it_wrong( __FUNCTION__, __( 'Cheatin&#8217; huh?', 'eth-amp-analytics-wp' ), '0.1' ); }
+	public function __wakeup() { _doing_it_wrong( __FUNCTION__, __( 'Cheatin&#8217; huh?', 'eth-amp-analytics-wp' ), '0.1' ); }
+	public function __call( $name = '', $args = array() ) { unset( $name, $args ); return null; }
+
+	/**
+	 * Class properties
+	 */
+	private $plugin_option_name = 'eth_amp_analytics_wp';
+	private $plugin_option_defaults = array(
+		'property_id' => null,
+	);
+
+	private $options = null;
+
+	/**
+	 * Defer plugin action loading until all plugins are loaded
+	 *
+	 * @return null
+	 */
+	private function __construct() {
+		add_action( 'plugins_loaded', array( $this, 'action_plugins_loaded' ) );
+	}
+
+	/**
+	 * Register actions and filters
+	 */
+	public function action_plugins_loaded() {
+		if ( ! defined( 'AMP__FILE__' ) ) {
+			return;
+		}
+
+		// Front-end
+		add_action( 'wp_loaded', array( $this, 'action_wp_loaded' ) );
+
+		// Admin UI
+		add_action( 'admin_init', array( $this, 'action_admin_init' ) );
+		register_uninstall_hook( __FILE__, array( 'ETH_AMP_Analytics_WP', 'uninstall' ) );
+	}
+
+	/**
+	 * Clean up plugin data when it's removed
+	 */
+	public static function uninstall() {
+		delete_option( 'eth_amp_analytics_wp' );
+	}
+
+	/**
+	 * Conditionally load front-end hooks
+	 */
+	public function action_wp_loaded() {
+		if ( ! empty( $this->get_option( 'property_id' ) ) ) {
+			add_filter( 'amp_post_template_analytics', array( $this, 'filter_amp_post_template_analytics' ) );
+		}
+	}
+
+	/**
+	 * TEMPLATING
+	 */
+
+	/**
+	 * Set analytics properties
+	 */
+	public function filter_amp_post_template_analytics( $analytics ) {
+		if ( ! is_array( $analytics ) ) {
+			$analytics = array();
+		}
+
+		// Don't track logged-in/known users visits
+		if ( is_user_logged_in() && apply_filters( 'eth_amp_do_not_track_known_user', is_user_logged_in() ) ) {
+			return $analytics;
+		}
+
+		$analytics['eth-amp-googleanalytics'] = array(
+			'type' => 'googleanalytics',
+			'attributes' => array(
+				// 'data-credentials' => 'include',
+			),
+			'config_data' => array(
+				'vars' => array(
+					'account' => $this->get_option( 'property_id' ),
+				),
+				'triggers' => array(
+					'trackPageview' => array(
+						'on' => 'visible',
+						'request' => 'pageview',
+					),
+				),
+			),
+		);
+
+		return $analytics;
+	}
+
+	/**
+	 * ADMIN UI
+	 */
+
+	/**
+	 * Register admin additions
+	 */
+	public function action_admin_init() {
+		register_setting( 'reading', $this->plugin_option_name, array( $this, 'sanitize_options' ) );
+
+		add_settings_section( 'eth-amp-analytics-wp', __( 'Google Analytics for AMP', 'eth-amp-analytics-wp' ), '__return_false', 'reading' );
+		add_settings_field( 'eth-amp-analytics-wp-property-id', __( 'Property ID:', 'eth-amp-analytics-wp' ), array( $this, 'settings_field_property_id' ), 'reading', 'eth-amp-analytics-wp' );
+	}
+
+	/**
+	 * Render Property ID input field
+	 */
+	public function settings_field_property_id() {
+		?>
+		<input type="text" name="<?php echo esc_attr( $this->plugin_option_name ); ?>[property_id]" value="<?php echo esc_attr( $this->get_option( 'property_id' ) ); ?>" class="medium-text" />
+
+		<p class="description"><?php printf( __( 'Google Analytics property ID, in the format %s.', 'eth-amp-analytics-wp' ), '<strong>UA-XXXXX-Y</strong>' ); ?></p>
+
+		<p class="description"><?php printf( __( 'Google recommends using a property ID specific to AMP, rather than re-using the site&#8217;s existing ID. See %s.', 'eth-amp-analytics-wp' ), '<a href="https://developers.google.com/analytics/devguides/collection/amp-analytics/" target="_blank">https://developers.google.com/analytics/devguides/collection/amp-analytics/</a>' ); ?></p>
+		<?php
+	}
+
+	/**
+	 * Sanitize options
+	 */
+	public function sanitize_options( $options ) {
+		$sanitized_options = $this->plugin_option_defaults;
+
+		foreach ( $options as $key => $value ) {
+			switch( $key ) {
+				case 'property_id' :
+					$value = trim( $value );
+
+					if ( preg_match( '#^UA-([\d]+)-([\d]+)$#i', $value ) ) {
+						$sanitized_options[ $key ] = $value;
+					}
+					break;
+
+				default :
+					// Do nothing, this is unexpected. :)
+					break;
+			}
+		}
+
+		return $sanitized_options;
+	}
+
+	/**
+	 * UTILITY FUNCTIONS
+	 */
+
+	/**
+	 * Retrieve one of the plugin's options
+	 */
+	private function get_option( $name ) {
+		// Prepare options if this is the first request
+		if ( is_null( $this->options ) ) {
+			$ga_options = get_option( $this->plugin_option_name );
+
+			if ( is_array( $ga_options ) ) {
+				$this->options = wp_parse_args( $ga_options, $this->plugin_option_defaults );
+			} else {
+				return false;
+			}
+
+			unset( $ga_options );
+		}
+
+		// Does the key exist?
+		if ( isset( $this->options[ $name ] ) ) {
+			return $this->options[ $name ];
+		} else {
+			return false;
+		}
+	}
+}
+
+ETH_AMP_Analytics_WP::get_instance();