CA Pageviews

ca-pageview.php

<?php
/**
 * Plugin Name: CodeAcademy Pageviews
 * Author: Arūnas Liuiza
 * Version: 0.3.0
 *
 * @package CA_Pageview
 * @version 0.3.0
 */

add_action( 'plugins_loaded', 'CA_Pageview' );

function CA_Pageview() {
	if ( false === CA_PageviewClass::$instance ) {
		CA_PageviewClass::$instance = new CA_PageviewClass();
	}
	return CA_PageviewClass::$instance;
}

class CA_PageviewClass {
	public static $instance = false;
	public $plugin_path = '';
	public function __construct() {
		$this->plugin_path = plugin_dir_path( __FILE__ );
		add_action( 'wp', array( $this, 'count' ) );
		add_filter( 'the_content', array( $this, 'display' ) );
		add_action( 'rest_api_init', array( $this, 'api_field' ) );
		add_action( 'rest_api_init', array( $this, 'api_endpoint' ) );
	}
	public function api_endpoint() {
		register_rest_route(
			'ca-pageview/v1',
			'/top',
			array(
				'methods' => 'GET',
				'callback' => array( $this, 'top' ),
			)
		);
	}
	public function top() {
		global $wpdb;
		$sql = "SELECT `post_id`, `meta_value` * 1 as `count`
		FROM {$wpdb->postmeta}
		WHERE `meta_key` = '_ca_pageview'
		ORDER BY `count` DESC";
		$result = $wpdb->get_results( $sql );
		return $result;
	}
	public function api_field() {
		register_rest_field(
			'post',
			'pageviews',
			array(
				'get_callback' => array( $this, 'get' ),
			)
		);
	}
	public function get( $post ) {
		$post_id = $post['id'];
		$count = get_post_meta( $post_id, '_ca_pageview', true );
		return (int) $count;
	}
	public function count() {
		if ( ! is_singular() ) {
			return false;
		}
		$post_id = get_the_id();
		$count = get_post_meta( $post_id, '_ca_pageview', true );
		++$count;
		update_post_meta( $post_id, '_ca_pageview', $count );
	}
	public function display( $content ) {
		if ( ! is_singular() ) {
			return $content;
		}
		$post_id = get_the_id();
		$count = get_post_meta( $post_id, '_ca_pageview', true );
		if ( ! $count ) {
			$count = 0;
		}
		$display = _n(
			'This post was viewed %s time.',
			'This post was viewed %s times.',
			$count,
			'ca-pageview'
		);
		$display = sprintf( $display, $count );
		$content .= PHP_EOL . PHP_EOL . $display;
		return $content;
	}
}