<?php
/**
 * Beacon endpoint for reader events.
 *
 * @package KarmaDocs
 */

namespace KarmaDocs\Analytics;

use KarmaDocs\PostTypes;
use KarmaDocs\Rest\Routes;
use KarmaDocs\Taxonomies;

defined( 'ABSPATH' ) || exit;

/**
 * POST /collect receives one batch per page (navigator.sendBeacon when the page is
 * hidden or left), so it works with page caching and adds no request while reading.
 *
 * Body: { "s": "<session id>", "e": [ { "t": "view", "a": 12, "k": 3, ... }, … ] }
 */
class Collector {

	/**
	 * Largest batch accepted.
	 */
	const MAX_EVENTS = 50;

	/**
	 * Hooks.
	 */
	public function register() {
		add_action( 'rest_api_init', array( $this, 'routes' ) );
		add_action( 'kdocs_feedback_submitted', array( $this, 'feedback' ), 20, 5 );
	}

	/**
	 * Routes.
	 */
	public function routes() {
		register_rest_route(
			Routes::NS,
			'/collect',
			array(
				'methods'             => 'POST',
				'callback'            => array( $this, 'collect' ),
				'permission_callback' => '__return_true',
			)
		);
	}

	/**
	 * Stores a batch of events.
	 *
	 * @param \WP_REST_Request $request Request.
	 * @return \WP_REST_Response
	 */
	public function collect( $request ) {
		$body = json_decode( (string) $request->get_body(), true );
		if ( ! is_array( $body ) || empty( $body['e'] ) || ! is_array( $body['e'] ) || ! Identity::countable() ) {
			return new \WP_REST_Response( null, 204 );
		}
		$session = self::token( $body['s'] ?? '' );
		$events  = array();
		foreach ( array_slice( $body['e'], 0, self::MAX_EVENTS ) as $raw ) {
			$event = is_array( $raw ) ? self::clean( $raw, $session ) : null;
			if ( $event ) {
				$events[] = $event;
			}
		}
		if ( $events && Identity::within_limit( count( $events ) ) ) {
			Store::insert( $events );
			foreach ( $events as $event ) {
				if ( 'view' === $event['type'] && $event['article_id'] ) {
					self::count_view( $event['article_id'] );
				}
			}
		}
		// Beacons ignore the response; 204 keeps it tiny.
		return new \WP_REST_Response( null, 204 );
	}

	/**
	 * Validates one event.
	 *
	 * @param array  $raw     Event from the browser.
	 * @param string $session Session id.
	 * @return array|null
	 */
	private static function clean( array $raw, $session ) {
		$type = sanitize_key( (string) ( $raw['t'] ?? '' ) );
		// Feedback is recorded server side by the feedback endpoint.
		if ( 'feedback' === $type || ! in_array( $type, Store::types(), true ) ) {
			return null;
		}
		$article = absint( $raw['a'] ?? 0 );
		if ( $article ) {
			$post = get_post( $article );
			if ( ! $post || PostTypes::ARTICLE !== $post->post_type || 'publish' !== $post->post_status ) {
				return null;
			}
			$kb = Taxonomies::article_kb( $post );
		} else {
			$kb_id = absint( $raw['k'] ?? 0 );
			$kb    = $kb_id ? get_term( $kb_id, Taxonomies::KB ) : null;
			$kb    = $kb && ! is_wp_error( $kb ) ? $kb : null;
		}

		$label = '';
		$n1    = 0;
		$n2    = 0;
		switch ( $type ) {
			case 'search':
			case 'widget_search':
				$label = self::term( $raw['q'] ?? '' );
				$n1    = min( 1000, absint( $raw['n'] ?? 0 ) );
				if ( '' === $label ) {
					return null;
				}
				break;
			case 'search_click':
				$label = self::term( $raw['q'] ?? '' );
				$n1    = min( 100, max( 1, absint( $raw['p'] ?? 1 ) ) );
				break;
			case 'read':
				$n1 = min( 100, absint( $raw['d'] ?? 0 ) );
				$n2 = min( 3600, absint( $raw['s'] ?? 0 ) );
				break;
			case 'link_out':
				$label = sanitize_text_field( (string) wp_parse_url( esc_url_raw( (string) ( $raw['u'] ?? '' ) ), PHP_URL_HOST ) );
				break;
			case '404':
			case 'widget_open':
				// A path on this site (where the widget was opened).
				$label = mb_substr( sanitize_text_field( (string) wp_parse_url( (string) ( $raw['u'] ?? '' ), PHP_URL_PATH ) ), 0, 191 );
				break;
			case 'ai_rating':
			case 'summary_rating':
				$label = in_array( $raw['l'] ?? '', array( 'yes', 'no' ), true ) ? $raw['l'] : '';
				if ( '' === $label ) {
					return null;
				}
				break;
		}

		$ref = sanitize_key( (string) ( $raw['r'] ?? '' ) );
		return array(
			'type'       => $type,
			'kb_id'      => $kb ? (int) $kb->term_id : 0,
			'article_id' => $article,
			'session'    => $session,
			'search_id'  => self::token( $raw['i'] ?? '' ),
			'label'      => $label,
			'n1'         => $n1,
			'n2'         => $n2,
			'ref'        => in_array( $ref, array( 'direct', 'search', 'internal', 'external', 'widget' ), true ) ? $ref : '',
		);
	}

	/**
	 * Random id from the browser (session or search id): 16 alphanumerics.
	 *
	 * @param mixed $value Value.
	 * @return string
	 */
	private static function token( $value ) {
		$value = preg_replace( '/[^A-Za-z0-9]/', '', (string) $value );
		return substr( $value, 0, 16 );
	}

	/**
	 * Normalized search term (lower case, single spaces, 100 characters).
	 *
	 * @param mixed $value Term.
	 * @return string
	 */
	public static function term( $value ) {
		$term = sanitize_text_field( (string) $value );
		$term = function_exists( 'mb_strtolower' ) ? mb_strtolower( $term ) : strtolower( $term );
		$term = trim( preg_replace( '/\s+/', ' ', $term ) );
		return mb_substr( $term, 0, 100 );
	}

	/**
	 * Keeps the cached total view count on the article (shown in lists and sorts).
	 *
	 * @param int $article_id Article.
	 */
	private static function count_view( $article_id ) {
		update_post_meta( $article_id, '_kdocs_views', (int) get_post_meta( $article_id, '_kdocs_views', true ) + 1 );

		/**
		 * Fires after a view was counted.
		 *
		 * @param int $article_id Article.
		 */
		do_action( 'kdocs_article_viewed', $article_id );
	}

	/**
	 * Records votes and reasons as events.
	 *
	 * @param int    $article_id Article.
	 * @param string $vote       yes|no.
	 * @param string $message    Message.
	 * @param string $email      Email.
	 * @param string $reason     Reason.
	 */
	public function feedback( $article_id, $vote, $message, $email, $reason = '' ) {
		$kb   = Taxonomies::article_kb( $article_id );
		$base = array(
			'kb_id'      => $kb ? (int) $kb->term_id : 0,
			'article_id' => (int) $article_id,
		);
		if ( '' === $message && '' === $reason ) {
			Store::log( 'feedback', $base + array( 'label' => $vote ) );
		} elseif ( $reason ) {
			Store::log( 'feedback_reason', $base + array( 'label' => $reason ) );
		}
	}
}