<?php
/**
 * Cookie free page view counting.
 *
 * @package ACSSEO
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Counts views per entry and exposes the totals to the admin screens.
 *
 * Nothing leaves the site: there is no third party service, no cookie and no
 * stored IP address. Repeat views within the same day are recognised through a
 * short lived one way hash held in the object cache.
 */
class ACSSEO_Stats {

	/**
	 * Meta key prefix for the per day counters.
	 */
	const DAY_PREFIX = '_acsseo_views_day_';

	/**
	 * Meta key holding the lifetime total.
	 */
	const TOTAL_KEY = '_acsseo_views_total';

	/**
	 * Singleton instance.
	 *
	 * @var ACSSEO_Stats|null
	 */
	private static $instance = null;

	/**
	 * Return the shared instance.
	 *
	 * @return ACSSEO_Stats
	 */
	public static function instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}

		return self::$instance;
	}

	/**
	 * Hook counting and the admin column.
	 */
	private function __construct() {
		add_action( 'template_redirect', array( $this, 'maybe_count' ) );
		add_action( 'admin_init', array( $this, 'register_columns' ) );
		add_action( 'add_meta_boxes', array( $this, 'add_meta_box' ) );
		add_action( 'acsseo_daily_rollup', array( $this, 'prune_old_days' ) );
	}

	/**
	 * Count one view when the request qualifies.
	 *
	 * @return void
	 */
	public function maybe_count() {
		if ( ! ACSSEO_Settings::get( 'stats_enabled' ) ) {
			return;
		}

		if ( is_admin() || ! is_singular() || is_attachment() || is_preview() || is_feed() || is_robots() ) {
			return;
		}

		if ( is_user_logged_in() && current_user_can( 'edit_posts' ) ) {
			return;
		}

		if ( $this->looks_like_a_bot() ) {
			return;
		}

		$post_id = get_queried_object_id();
		if ( ! $post_id ) {
			return;
		}

		$today       = current_time( 'Y-m-d' );
		$visitor_key = 'acsseo_seen_' . md5( $post_id . '|' . $today . '|' . $this->visitor_fingerprint() );

		if ( false !== get_transient( $visitor_key ) ) {
			return;
		}

		set_transient( $visitor_key, 1, DAY_IN_SECONDS );

		$day_key = self::DAY_PREFIX . $today;
		$current = (int) get_post_meta( $post_id, $day_key, true );
		update_post_meta( $post_id, $day_key, $current + 1 );

		$total = (int) get_post_meta( $post_id, self::TOTAL_KEY, true );
		update_post_meta( $post_id, self::TOTAL_KEY, $total + 1 );
	}

	/**
	 * One way fingerprint of the current visitor.
	 *
	 * The raw address and browser string are hashed immediately and never
	 * written to the database; only the hash reaches the transient key.
	 *
	 * @return string
	 */
	private function visitor_fingerprint() {
		$address = isset( $_SERVER['REMOTE_ADDR'] )
			? sanitize_text_field( wp_unslash( $_SERVER['REMOTE_ADDR'] ) )
			: '';
		$agent   = isset( $_SERVER['HTTP_USER_AGENT'] )
			? sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) )
			: '';

		return wp_hash( $address . '|' . $agent );
	}

	/**
	 * Cheap user agent test so obvious crawlers are not counted.
	 *
	 * @return bool
	 */
	private function looks_like_a_bot() {
		$agent = isset( $_SERVER['HTTP_USER_AGENT'] )
			? sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) )
			: '';

		if ( '' === $agent ) {
			return true;
		}

		return (bool) preg_match( '/bot|crawl|spider|slurp|scrape|curl|wget|monitor|preview|headless/i', $agent );
	}

	/**
	 * Read the counters for one entry.
	 *
	 * @param int $post_id Post ID.
	 * @return array{today:int,yesterday:int,month:int,total:int}
	 */
	public static function summary( $post_id ) {
		$all = get_post_meta( $post_id );

		$today     = current_time( 'Y-m-d' );
		$yesterday = gmdate( 'Y-m-d', strtotime( $today . ' -1 day' ) );
		$month     = substr( $today, 0, 7 );

		$read = static function ( $key ) use ( $all ) {
			return isset( $all[ $key ][0] ) ? (int) $all[ $key ][0] : 0;
		};

		$month_total = 0;
		foreach ( $all as $key => $value ) {
			if ( 0 !== strpos( $key, self::DAY_PREFIX ) ) {
				continue;
			}
			if ( 0 === strpos( substr( $key, strlen( self::DAY_PREFIX ) ), $month ) ) {
				$month_total += isset( $value[0] ) ? (int) $value[0] : 0;
			}
		}

		return array(
			'today'     => $read( self::DAY_PREFIX . $today ),
			'yesterday' => $read( self::DAY_PREFIX . $yesterday ),
			'month'     => $month_total,
			'total'     => $read( self::TOTAL_KEY ),
		);
	}

	/**
	 * Add the views column to the supported list tables.
	 *
	 * @return void
	 */
	public function register_columns() {
		if ( ! ACSSEO_Settings::get( 'stats_enabled' ) || ! ACSSEO_Settings::get( 'stats_column' ) ) {
			return;
		}

		foreach ( ACSSEO_Meta::supported_post_types() as $post_type ) {
			add_filter( "manage_{$post_type}_posts_columns", array( $this, 'add_column' ) );
			add_action( "manage_{$post_type}_posts_custom_column", array( $this, 'render_column' ), 10, 2 );
		}
	}

	/**
	 * Append the views column.
	 *
	 * @param array<string,string> $columns Existing columns.
	 * @return array<string,string>
	 */
	public function add_column( $columns ) {
		$columns['acsseo_views'] = __( 'Views', 'acs-seo-plus' );

		return $columns;
	}

	/**
	 * Print one cell of the views column.
	 *
	 * @param string $column  Column key.
	 * @param int    $post_id Post ID.
	 * @return void
	 */
	public function render_column( $column, $post_id ) {
		if ( 'acsseo_views' !== $column ) {
			return;
		}

		$summary = self::summary( $post_id );

		printf(
			'<span class="acsseo-views">%1$s<br /><span class="acsseo-views-sub">%2$s</span></span>',
			esc_html(
				sprintf(
					/* translators: %s: number of views today. */
					__( 'Today: %s', 'acs-seo-plus' ),
					number_format_i18n( $summary['today'] )
				)
			),
			esc_html(
				sprintf(
					/* translators: %s: total number of views. */
					__( 'Total: %s', 'acs-seo-plus' ),
					number_format_i18n( $summary['total'] )
				)
			)
		);
	}

	/**
	 * Add the statistics meta box to the editor.
	 *
	 * @return void
	 */
	public function add_meta_box() {
		if ( ! ACSSEO_Settings::get( 'stats_enabled' ) ) {
			return;
		}

		foreach ( ACSSEO_Meta::supported_post_types() as $post_type ) {
			add_meta_box(
				'acsseo_stats_box',
				__( 'Page views', 'acs-seo-plus' ),
				array( $this, 'render_meta_box' ),
				$post_type,
				'side',
				'default'
			);
		}
	}

	/**
	 * Print the statistics meta box.
	 *
	 * @param WP_Post $post Current post.
	 * @return void
	 */
	public function render_meta_box( $post ) {
		$summary = self::summary( $post->ID );
		$rows    = array(
			__( 'Today', 'acs-seo-plus' )      => $summary['today'],
			__( 'Yesterday', 'acs-seo-plus' )  => $summary['yesterday'],
			__( 'This month', 'acs-seo-plus' ) => $summary['month'],
			__( 'All time', 'acs-seo-plus' )   => $summary['total'],
		);
		?>
		<table class="acsseo-stats-table">
			<tbody>
			<?php foreach ( $rows as $label => $value ) : ?>
				<tr>
					<th scope="row"><?php echo esc_html( $label ); ?></th>
					<td><?php echo esc_html( number_format_i18n( (int) $value ) ); ?></td>
				</tr>
			<?php endforeach; ?>
			</tbody>
		</table>
		<p class="acsseo-help"><?php esc_html_e( 'Counted on this site only. Views by logged in editors and obvious crawlers are skipped.', 'acs-seo-plus' ); ?></p>
		<?php
	}

	/**
	 * Drop per day counters older than roughly thirteen months.
	 *
	 * The lifetime total is kept, so trimming the daily rows does not lose the
	 * overall figure.
	 *
	 * @return void
	 */
	public function prune_old_days() {
		global $wpdb;

		$cutoff = gmdate( 'Y-m-d', time() - ( 400 * DAY_IN_SECONDS ) );

		$stale = $wpdb->get_results( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- housekeeping task that runs once a day and has no core API equivalent.
			$wpdb->prepare(
				"SELECT post_id, meta_key FROM {$wpdb->postmeta} WHERE meta_key LIKE %s AND meta_key < %s LIMIT 5000",
				$wpdb->esc_like( self::DAY_PREFIX ) . '%',
				self::DAY_PREFIX . $cutoff
			)
		);

		foreach ( $stale as $row ) {
			delete_post_meta( (int) $row->post_id, $row->meta_key );
		}
	}
}