<?php
/**
 * Privacy-first reader identity.
 *
 * @package KarmaDocs
 */

namespace KarmaDocs\Analytics;

use KarmaDocs\Settings;

defined( 'ABSPATH' ) || exit;

/**
 * No cookies and no stored IP addresses:
 *
 * - visitor: a hash of IP + user agent + a salt that changes every day, so the same
 *   reader can't be recognised across days and the IP can't be recovered.
 * - session: a random id the browser keeps in sessionStorage for 30 idle minutes.
 *
 * Readers who send Do Not Track are not counted, nor are logged-in editors unless
 * the site owner turns that on (Settings → Analytics).
 */
class Identity {

	/**
	 * Today's visitor hash (16 hex characters).
	 *
	 * @return string
	 */
	public static function visitor() {
		$ip = isset( $_SERVER['REMOTE_ADDR'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REMOTE_ADDR'] ) ) : '';
		$ua = isset( $_SERVER['HTTP_USER_AGENT'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) ) : '';
		// The salt is derived from the site's secret keys and today's date: never stored.
		$salt = wp_hash( 'kdocs-visitor|' . current_time( 'Y-m-d' ) );
		return substr( hash( 'sha256', $ip . '|' . $ua . '|' . $salt ), 0, 16 );
	}

	/**
	 * Device class from the user agent.
	 *
	 * @return string mobile|tablet|desktop
	 */
	public static function device() {
		$ua = isset( $_SERVER['HTTP_USER_AGENT'] ) ? strtolower( sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) ) ) : '';
		if ( preg_match( '/ipad|tablet|kindle|silk/', $ua ) || ( false !== strpos( $ua, 'android' ) && false === strpos( $ua, 'mobile' ) ) ) {
			return 'tablet';
		}
		return preg_match( '/mobi|iphone|android/', $ua ) ? 'mobile' : 'desktop';
	}

	/**
	 * Visitor country from a CDN header (Cloudflare, CloudFront, Fastly, most
	 * hosts with GeoIP), when present. The IP address is never looked up.
	 *
	 * @return string Two letters, or ''.
	 */
	public static function country() {
		foreach ( array( 'HTTP_CF_IPCOUNTRY', 'HTTP_CLOUDFRONT_VIEWER_COUNTRY', 'HTTP_X_COUNTRY_CODE', 'HTTP_FASTLY_GEO_COUNTRY_CODE', 'GEOIP_COUNTRY_CODE' ) as $header ) {
			$value = isset( $_SERVER[ $header ] ) ? strtoupper( sanitize_text_field( wp_unslash( $_SERVER[ $header ] ) ) ) : '';
			if ( preg_match( '/^[A-Z]{2}$/', $value ) && ! in_array( $value, array( 'XX', 'T1' ), true ) ) {
				return $value;
			}
		}
		return '';
	}

	/**
	 * Role of a logged-in reader ('' for guests).
	 *
	 * @return string
	 */
	public static function member() {
		if ( ! is_user_logged_in() ) {
			return '';
		}
		$roles = (array) wp_get_current_user()->roles;
		return mb_substr( $roles ? (string) reset( $roles ) : 'member', 0, 20 );
	}

	/**
	 * Whether the user agent looks like a bot.
	 *
	 * @return bool
	 */
	public static function is_bot() {
		$ua = isset( $_SERVER['HTTP_USER_AGENT'] ) ? strtolower( sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) ) ) : '';
		return '' === $ua || (bool) preg_match( '/bot|crawl|spider|slurp|preview|headless|lighthouse|monitor|curl|wget|python-requests/', $ua );
	}

	/**
	 * Whether the current request should be counted.
	 *
	 * @return bool
	 */
	public static function countable() {
		if ( self::is_bot() ) {
			return false;
		}
		if ( isset( $_SERVER['HTTP_DNT'] ) && '1' === $_SERVER['HTTP_DNT'] ) {
			return false;
		}
		if ( current_user_can( 'edit_posts' ) && ! self::count_editors() ) {
			return false;
		}
		return true;
	}

	/**
	 * Whether logged-in editors' visits are counted.
	 *
	 * @return bool
	 */
	public static function count_editors() {
		/**
		 * Whether to count visits from logged-in editors (default: the analytics setting).
		 *
		 * @param bool $count Count.
		 */
		return (bool) apply_filters( 'kdocs_count_editor_views', (bool) Settings::get( 'analytics_count_editors', false ) );
	}

	/**
	 * Simple per-visitor rate limit for the collector.
	 *
	 * @param int $events Events in this request.
	 * @return bool Allowed.
	 */
	public static function within_limit( $events ) {
		$key   = 'kdocs_rl_' . self::visitor();
		$count = (int) get_transient( $key );
		if ( $count + $events > 300 ) {
			return false;
		}
		set_transient( $key, $count + $events, MINUTE_IN_SECONDS );
		return true;
	}
}