<?php
/**
 * The TrackWP API: WordPress.org figures for a username or for slugs.
 *
 * @package TrackPluse
 */

defined( 'ABSPATH' ) || exit;

/**
 * Fetches figures from TrackWP's public API and keeps them for a few hours,
 * so a dashboard or a page never asks more than once in that time. When a
 * fetch fails, the last figures that worked are used for up to a week.
 */
class TrackPluse_Api {

	/**
	 * Hours fetched figures are kept.
	 */
	const CACHE_HOURS = 6;

	/**
	 * Minutes to wait after a failed fetch before trying again.
	 */
	const RETRY_MINUTES = 30;

	/**
	 * Option listing the transients this plugin made, so they can be removed.
	 */
	const KEYS_OPTION = 'trackpluse_cache_keys';

	/**
	 * The service's address. The trackpluse_api_base filter points it elsewhere,
	 * for development.
	 *
	 * @return string
	 */
	public static function base() {
		return untrailingslashit( (string) apply_filters( 'trackpluse_api_base', 'https://trackwp.com' ) );
	}

	/**
	 * Figures for a WordPress.org username's plugins and themes, and for slugs.
	 *
	 * @param string   $author  WordPress.org username, or ''.
	 * @param string[] $plugins Plugin slugs.
	 * @param string[] $themes  Theme slugs.
	 * @param int      $timeout Seconds to wait for TrackWP.
	 * @return array|WP_Error The figures, one array per listing under 'data', and the current WordPress branch.
	 */
	public static function stats( $author, $plugins = array(), $themes = array(), $timeout = 10 ) {
		$query = array_filter(
			array(
				'author'  => (string) $author,
				'plugins' => array_values( $plugins ),
				'themes'  => array_values( $themes ),
			)
		);

		if ( empty( $query ) ) {
			return array(
				'data'      => array(),
				'wordpress' => '',
			);
		}

		$key    = 'trackpluse_stats_' . md5( (string) wp_json_encode( $query ) );
		$cached = get_transient( $key );

		if ( is_array( $cached ) ) {
			return $cached;
		}

		$last = get_transient( $key . '_last' );

		// A recent failure: don't make every page wait on it again.
		if ( get_transient( $key . '_failed' ) ) {
			return is_array( $last ) ? $last : new WP_Error( 'trackpluse_unavailable', __( 'TrackWP couldn’t be reached. The figures will try again shortly.', 'trackpluse' ) );
		}

		$response = wp_remote_get(
			self::base() . '/api/public/v1/stats?' . http_build_query( $query, '', '&' ),
			array(
				'timeout'    => $timeout,
				// WordPress's default user agent carries the site's address; this one doesn't.
				'user-agent' => 'TrackPluse/' . TRACKPLUSE_VERSION,
				'headers'    => array( 'Accept' => 'application/json' ),
			)
		);

		$body = is_wp_error( $response ) ? null : json_decode( wp_remote_retrieve_body( $response ), true );

		if ( ! is_array( $body ) || 200 !== wp_remote_retrieve_response_code( $response ) || ! isset( $body['data'] ) || ! is_array( $body['data'] ) ) {
			set_transient( $key . '_failed', 1, self::RETRY_MINUTES * MINUTE_IN_SECONDS );
			self::remember( $key . '_failed' );

			return is_array( $last ) ? $last : new WP_Error( 'trackpluse_unavailable', __( 'TrackWP couldn’t be reached. The figures will try again shortly.', 'trackpluse' ) );
		}

		$result = array(
			'data'      => array_values( array_filter( $body['data'], 'is_array' ) ),
			'wordpress' => isset( $body['wordpress'] ) ? (string) $body['wordpress'] : '',
		);

		set_transient( $key, $result, self::CACHE_HOURS * HOUR_IN_SECONDS );
		set_transient( $key . '_last', $result, WEEK_IN_SECONDS );
		self::remember( $key );
		self::remember( $key . '_last' );

		return $result;
	}

	/**
	 * Forget every kept figure, so the next view fetches fresh ones.
	 */
	public static function flush() {
		foreach ( (array) get_option( self::KEYS_OPTION, array() ) as $key ) {
			delete_transient( (string) $key );
		}

		delete_option( self::KEYS_OPTION );
	}

	/**
	 * Note a transient's name for flush().
	 *
	 * @param string $key Transient name.
	 */
	private static function remember( $key ) {
		$keys = (array) get_option( self::KEYS_OPTION, array() );

		if ( ! in_array( $key, $keys, true ) ) {
			// The newest 200 are plenty: older ones expire on their own.
			$keys = array_slice( array_merge( $keys, array( $key ) ), -200 );
			update_option( self::KEYS_OPTION, $keys, false );
		}
	}
}