<?php
/**
 * Plugin Update Checker Library 1.3.2
 * http://w-shadow.com/
 *
 * Copyright 2013 Janis Elsts
 * Licensed under the GNU GPL license.
 * http://www.gnu.org/licenses/gpl.html
 */

if ( ! class_exists( 'TVE_PluginUpdateChecker_1_3_2', false ) ) {

	/**
	 * A custom plugin update checker.
	 *
	 * @author    Janis Elsts
	 * @copyright 2013
	 * @version   1.3.1
	 * @access    public
	 */
	class TVE_PluginUpdateChecker_1_3_2 {
		protected $secret_key = '@#$()%*%$^&*(#@$%@#$%93827456MASDFJIK3245';

		public $metadataUrl = ''; //The URL of the plugin's metadata file.
		public $pluginAbsolutePath = ''; //Full path of the main plugin file.
		public $pluginFile = '';  //Plugin filename relative to the plugins directory. Many WP APIs use this to identify plugins.
		public $slug = '';        //Plugin slug.
		public $checkPeriod = 12; //How often to check for updates (in hours).
		public $optionName = '';  //Where to store the update info.

		public $debugMode = false; //Set to TRUE to enable error reporting. Errors are raised using trigger_error()
		//and should be logged to the standard PHP error log.

		private $cronHook = null;
		private $debugBarPlugin = null;
		private $cachedInstalledVersion = null;
		private $php_version = 0;
		private $required_php_version = '5.3.0';

		protected $api_slug = '';

		/**
		 * Class constructor.
		 *
		 * @param string  $metadataUrl The URL of the plugin's metadata file.
		 * @param string  $pluginFile  Fully qualified path to the main plugin file.
		 * @param string  $slug        The plugin's 'slug'. If not specified, the filename part of $pluginFile sans '.php' will be used as the slug.
		 * @param integer $checkPeriod How often to check for updates (in hours). Defaults to checking every 12 hours. Set to 0 to disable automatic update checks.
		 * @param string  $optionName  Where to store book-keeping info about update checks. Defaults to 'external_updates-$slug'.
		 */
		public function __construct( $metadataUrl, $pluginFile, $slug = '', $checkPeriod = 12, $optionName = '', $api_slug = '' ) {
			$this->metadataUrl        = $metadataUrl;
			$this->pluginAbsolutePath = $pluginFile;
			$this->pluginFile         = plugin_basename( $this->pluginAbsolutePath );
			$this->checkPeriod        = $checkPeriod;
			$this->slug               = $slug;
			$this->optionName         = $optionName;
			$this->debugMode          = defined( 'WP_DEBUG' ) && WP_DEBUG;
			$this->api_slug           = $api_slug;
			$this->php_version        = PHP_VERSION;

			//If no slug is specified, use the name of the main plugin file as the slug.
			//For example, 'my-cool-plugin/cool-plugin.php' becomes 'cool-plugin'.
			if ( empty( $this->slug ) ) {
				$this->slug = basename( $this->pluginFile, '.php' );
			}

			if ( empty( $this->optionName ) ) {
				$this->optionName = 'external_updates-' . $this->slug;
			}

			if ( ! function_exists( 'get_plugin_data' ) ) {
				require_once( ABSPATH . '/wp-admin/includes/plugin.php' );
			}

			$this->installHooks();

			if ( version_compare( PHP_VERSION, $this->required_php_version ) === - 1 ) {
				add_action( 'admin_notices', array( $this, 'php_version_notice' ) );
			}


		}

		/**
		 * Install the hooks required to run periodic update checks and inject update info
		 * into WP data structures.
		 *
		 * @return void
		 */
		protected function installHooks() {
			//Override requests for plugin information
			add_filter( 'plugins_api', array( $this, 'injectInfo' ), 20, 3 );

			//Insert our update info into the update array maintained by WP
			add_filter( 'site_transient_update_plugins', array( $this, 'injectUpdate' ) ); //WP 3.0+
			add_filter( 'transient_update_plugins', array( $this, 'injectUpdate' ) ); //WP 2.8+

			add_filter( 'plugin_row_meta', array( $this, 'addCheckForUpdatesLink' ), 10, 2 );
			add_action( 'admin_init', array( $this, 'handleManualCheck' ) );
			add_action( 'all_admin_notices', array( $this, 'displayManualCheckResult' ) );

			//Clear the version number cache when something - anything - is upgraded or WP clears the update cache.
			add_filter( 'upgrader_post_install', array( $this, 'clearCachedVersion' ) );
			add_action( 'delete_site_transient_update_plugins', array( $this, 'clearCachedVersion' ) );

			//Set up the periodic update checks
			$this->cronHook = 'check_plugin_updates-' . $this->slug;
			if ( $this->checkPeriod > 0 ) {

				//Trigger the check via Cron.
				//Try to use one of the default schedules if possible as it's less likely to conflict
				//with other plugins and their custom schedules.
				$defaultSchedules = array(
					1  => 'hourly',
					12 => 'twicedaily',
					24 => 'daily',
				);
				if ( array_key_exists( $this->checkPeriod, $defaultSchedules ) ) {
					$scheduleName = $defaultSchedules[ $this->checkPeriod ];
				} else {
					//Use a custom cron schedule.
					$scheduleName = 'every' . $this->checkPeriod . 'hours';
					add_filter( 'cron_schedules', array( $this, '_addCustomSchedule' ) );
				}

				if ( ! wp_next_scheduled( $this->cronHook ) && ! defined( 'WP_INSTALLING' ) ) {
					wp_schedule_event( time(), $scheduleName, $this->cronHook );
				}
				add_action( $this->cronHook, array( $this, 'checkForUpdates' ) );

				register_deactivation_hook( $this->pluginFile, array( $this, '_removeUpdaterCron' ) );

				//In case Cron is disabled or unreliable, we also manually trigger
				//the periodic checks while the user is browsing the Dashboard.
				add_action( 'admin_init', array( $this, 'maybeCheckForUpdates' ) );

				//Like WordPress itself, we check more often on certain pages.
				add_action( 'load-update-core.php', array( $this, 'maybeCheckForUpdates' ) );

			} else {
				//Periodic checks are disabled.
				wp_clear_scheduled_hook( $this->cronHook );
			}

			if ( did_action( 'plugins_loaded' ) ) {
				$this->initDebugBarPanel();
			} else {
				add_action( 'plugins_loaded', array( $this, 'initDebugBarPanel' ) );
			}
		}

		/**
		 * Displays an error notice informing the users that the environment PHP Version is not compatible with Thrive Suite PHP Version
		 */
		public function php_version_notice() {
			$plugin_data = get_plugin_data( $this->pluginAbsolutePath, false, false );

			$message = __( $plugin_data['Name'] . ' requires PHP version ' . $this->required_php_version . '. Your current version is ' . $this->php_version . '. Please contact your hosting provider and ask them to update your PHP.', TVE_DASH_TRANSLATE_DOMAIN );

			echo sprintf( '<div class="error"><p>%s</p></div>', $message );
		}

		/**
		 * Add our custom schedule to the array of Cron schedules used by WP.
		 *
		 * @param array $schedules
		 *
		 * @return array
		 */
		public function _addCustomSchedule( $schedules ) {
			if ( $this->checkPeriod && ( $this->checkPeriod > 0 ) ) {
				$scheduleName               = 'every' . $this->checkPeriod . 'hours';
				$schedules[ $scheduleName ] = array(
					'interval' => $this->checkPeriod * 3600,
					'display'  => sprintf( 'Every %d hours', $this->checkPeriod ),
				);
			}

			return $schedules;
		}

		/**
		 * Remove the scheduled cron event that the library uses to check for updates.
		 *
		 * @return void
		 */
		public function _removeUpdaterCron() {
			wp_clear_scheduled_hook( $this->cronHook );
		}

		/**
		 * Get the name of the update checker's WP-cron hook. Mostly useful for debugging.
		 *
		 * @return string
		 */
		public function getCronHookName() {
			return $this->cronHook;
		}

		/**
		 * Retrieve plugin info from the configured API endpoint.
		 *
		 * @uses wp_remote_get()
		 *
		 * @param array $queryArgs Additional query arguments to append to the request. Optional.
		 *
		 * @return TVE_PluginInfo
		 */
		public function requestInfo( $queryArgs = array() ) {
			//Query args to append to the URL. Plugins can add their own by using a filter callback (see addQueryArgFilter()).
			$installedVersion               = $this->getInstalledVersion();
			$queryArgs['installed_version'] = ( $installedVersion !== null ) ? $installedVersion : '';
			$queryArgs                      = apply_filters( 'puc_request_info_query_args-' . $this->slug, $queryArgs );

			//Various options for the wp_remote_get() call. Plugins can filter these, too.
			$options = array(
				'timeout' => 10, //seconds
				'headers' => array(
					'Accept' => 'application/json',
				),
			);
			$options = apply_filters( 'puc_request_info_options-' . $this->slug, $options );

			//The plugin info should be at 'http://your-api.com/url/here/$slug/info.json'
			$url = $this->metadataUrl;

			/**
			 * prepare the POST parameters
			 */
			$options['body']                       = $queryArgs;
			$options['body']['api_slug']           = $this->api_slug;
			$options['body']['client_php_version'] = $this->php_version;
			$url                                   = add_query_arg( array( 'p' => $this->calc_hash( $options['body'] ) ), $url );

			$result = wp_remote_post(
				$url,
				$options
			);

			//Try to parse the response
			$pluginInfo = null;
			if ( ! is_wp_error( $result ) && isset( $result['response']['code'] ) && ( $result['response']['code'] == 200 ) && ! empty( $result['body'] ) ) {
				$pluginInfo = TVE_PluginInfo_1_3::fromJson( $result['body'], $this->debugMode );
			} else if ( $this->debugMode ) {
				$message = sprintf( "The URL %s does not point to a valid plugin metadata file. ", $url );
				if ( is_wp_error( $result ) ) {
					$message .= "WP HTTP error: " . $result->get_error_message();
				} else if ( isset( $result['response']['code'] ) ) {
					$message .= "HTTP response code is " . $result['response']['code'] . " (expected: 200)";
				} else {
					$message .= "wp_remote_get() returned an unexpected result.";
				}
				trigger_error( $message, E_USER_WARNING );
			}

			$pluginInfo = apply_filters( 'puc_request_info_result-' . $this->slug, $pluginInfo, $result );

			return $pluginInfo;
		}

		public function calc_hash( $data ) {
			return md5( $this->secret_key . serialize( $data ) . $this->secret_key );
		}

		/**
		 * Retrieve the latest update (if any) from the configured API endpoint.
		 *
		 * @uses PluginUpdateChecker::requestInfo()
		 *
		 * @return TVE_PluginUpdate An instance of PluginUpdate, or NULL when no updates are available.
		 */
		public function requestUpdate() {
			//For the sake of simplicity, this function just calls requestInfo()
			//and transforms the result accordingly.
			$pluginInfo = $this->requestInfo( array( 'checking_for_updates' => '1' ) );
			if ( $pluginInfo == null ) {
				return null;
			}

			return TVE_PluginUpdate_1_3::fromPluginInfo( $pluginInfo );
		}

		/**
		 * Get the currently installed version of the plugin.
		 *
		 * @return string Version number.
		 */
		public function getInstalledVersion() {
			if ( isset( $this->cachedInstalledVersion ) ) {
				return $this->cachedInstalledVersion;
			}

			if ( ! is_file( $this->pluginAbsolutePath ) ) {
				//This can happen if the plugin filename is wrong.
				if ( $this->debugMode ) {
					trigger_error(
						sprintf(
							"Can't to read the Version header for %s. The file does not exist.",
							$this->pluginFile
						),
						E_USER_WARNING
					);
				}

				return null;
			}

			$pluginHeader = get_plugin_data( $this->pluginAbsolutePath, false, false );
			if ( isset( $pluginHeader['Version'] ) ) {
				$this->cachedInstalledVersion = $pluginHeader['Version'];

				return $pluginHeader['Version'];
			} else {
				//This can happen if the filename points to something that is not a plugin.
				if ( $this->debugMode ) {
					trigger_error(
						sprintf(
							"Can't to read the Version header for %s. The filename is incorrect or is not a plugin.",
							$this->pluginFile
						),
						E_USER_WARNING
					);
				}

				return null;
			}
		}

		/**
		 * Check for plugin updates.
		 * The results are stored in the DB option specified in $optionName.
		 *
		 * @return TVE_PluginUpdate|null
		 */
		public function checkForUpdates() {
			$installedVersion = $this->getInstalledVersion();
			//Fail silently if we can't find the plugin or read its header.
			if ( $installedVersion === null ) {
				if ( $this->debugMode ) {
					trigger_error(
						sprintf( 'Skipping update check for %s - installed version unknown.', $this->pluginFile ),
						E_USER_WARNING
					);
				}

				return null;
			}

			$state = $this->getUpdateState();
			if ( empty( $state ) ) {
				$state                 = new StdClass;
				$state->lastCheck      = 0;
				$state->checkedVersion = '';
				$state->update         = null;
			}

			$state->lastCheck      = time();
			$state->checkedVersion = $installedVersion;
			$this->setUpdateState( $state ); //Save before checking in case something goes wrong

			$state->update = $this->requestUpdate();
			$this->setUpdateState( $state );

			return $this->getUpdate();
		}

		/**
		 * Check for updates if the configured check interval has already elapsed.
		 * Will use a shorter check interval on certain admin pages like "Dashboard -> Updates".
		 *
		 * @return void
		 */
		public function maybeCheckForUpdates() {
			if ( empty( $this->checkPeriod ) ) {
				return;
			}
			$state = $this->getUpdateState();

			//Check more often when the user visits Dashboard -> Updates.
			if ( current_filter() == 'load-update-core.php' ) {
				$timeout = 60;
			} else {
				$timeout = $this->checkPeriod * 3600;
			}

			$shouldCheck
				= empty( $state )
				  ||
				  ! isset( $state->lastCheck )
				  || ( ( time() - $state->lastCheck ) >= $timeout );

			if ( $shouldCheck ) {
				$this->checkForUpdates();
			}
		}

		/**
		 * Load the update checker state from the DB.
		 *
		 * @return StdClass|null
		 */
		public function getUpdateState() {
			$state = get_site_option( $this->optionName, null );
			if ( empty( $state ) || ! is_object( $state ) ) {
				$state = null;
			}

			if ( ! empty( $state ) && isset( $state->update ) && is_object( $state->update ) ) {
				$state->update = TVE_PluginUpdate_1_3::fromObject( $state->update );
			}

			return $state;
		}


		/**
		 * Persist the update checker state to the DB.
		 *
		 * @param StdClass $state
		 *
		 * @return void
		 */
		private function setUpdateState( $state ) {
			if ( isset( $state->update ) && is_object( $state->update ) && method_exists( $state->update, 'toStdClass' ) ) {
				$update = $state->update;
				/** @var TVE_PluginUpdate $update */
				$state->update = $update->toStdClass();
			}
			update_site_option( $this->optionName, $state );
		}

		/**
		 * Reset update checker state - i.e. last check time, cached update data and so on.
		 *
		 * Call this when your plugin is being uninstalled, or if you want to
		 * clear the update cache.
		 */
		public function resetUpdateState() {
			delete_site_option( $this->optionName );
		}

		/**
		 * Intercept plugins_api() calls that request information about our plugin and
		 * use the configured API endpoint to satisfy them.
		 *
		 * @see plugins_api()
		 *
		 * @param mixed        $result
		 * @param string       $action
		 * @param array|object $args
		 *
		 * @return mixed
		 */
		public function injectInfo( $result, $action = null, $args = null ) {
			$relevant = ( $action == 'plugin_information' ) && isset( $args->slug ) && ( $args->slug == $this->slug );
			if ( ! $relevant ) {
				return $result;
			}

			$pluginInfo = $this->requestInfo();
			$pluginInfo = apply_filters( 'puc_pre_inject_info-' . $this->slug, $pluginInfo );
			if ( $pluginInfo ) {
				return $pluginInfo->toWpFormat();
			}

			return $result;
		}

		/**
		 * Insert the latest update (if any) into the update list maintained by WP.
		 *
		 * @param StdClass $updates Update list.
		 *
		 * @return StdClass Modified update list.
		 */
		public function injectUpdate( $updates ) {
			//Is there an update to insert?
			$update = $this->getUpdate();
			if ( ! empty( $update ) ) {
				//Let plugins filter the update info before it's passed on to WordPress.
				$update = apply_filters( 'puc_pre_inject_update-' . $this->slug, $update );
				if ( ! is_object( $updates ) ) {
					$updates           = new StdClass();
					$updates->response = array();
				}
				$updates->response[ $this->pluginFile ] = $update->toWpFormat();
				// WP 4.2 added a check using the 'plugin' field of the update response without checking if it exists
				$updates->response[ $this->pluginFile ]->plugin = $this->pluginFile;
			} else if ( isset( $updates, $updates->response ) ) {
				unset( $updates->response[ $this->pluginFile ] );
			}

			return $updates;
		}

		/**
		 * Get the details of the currently available update, if any.
		 *
		 * If no updates are available, or if the last known update version is below or equal
		 * to the currently installed version, this method will return NULL.
		 *
		 * Uses cached update data. To retrieve update information straight from
		 * the metadata URL, call requestUpdate() instead.
		 *
		 * @return TVE_PluginUpdate|null
		 */
		public function getUpdate() {
			$state = $this->getUpdateState();
			/** @var StdClass $state */

			//Is there an update available insert?
			if ( ! empty( $state ) && isset( $state->update ) && ! empty( $state->update ) ) {
				$update = $state->update;
				//Check if the update is actually newer than the currently installed version.
				$installedVersion = $this->getInstalledVersion();
				if ( ( $installedVersion !== null ) && version_compare( $update->version, $installedVersion, '>' ) ) {
					return $update;
				}
			}

			return null;
		}

		/**
		 * Add a "Check for updates" link to the plugin row in the "Plugins" page. By default,
		 * the new link will appear after the "Visit plugin site" link.
		 *
		 * You can change the link text by using the "puc_manual_check_link-$slug" filter.
		 * Returning an empty string from the filter will disable the link.
		 *
		 * @param array  $pluginMeta Array of meta links.
		 * @param string $pluginFile
		 *
		 * @return array
		 */
		public function addCheckForUpdatesLink( $pluginMeta, $pluginFile ) {
			if ( $pluginFile == $this->pluginFile && current_user_can( 'update_plugins' ) ) {
				$linkUrl = wp_nonce_url(
					add_query_arg(
						array(
							'puc_check_for_updates' => 1,
							'puc_slug'              => $this->slug,
						),
						is_network_admin() ? network_admin_url( 'plugins.php' ) : admin_url( 'plugins.php' )
					),
					'puc_check_for_updates'
				);

				$linkText = apply_filters( 'puc_manual_check_link-' . $this->slug, 'Check for updates' );
				if ( ! empty( $linkText ) ) {
					$pluginMeta[] = sprintf( '<a href="%s">%s</a>', esc_attr( $linkUrl ), $linkText );
				}
			}

			return $pluginMeta;
		}

		/**
		 * Check for updates when the user clicks the "Check for updates" link.
		 *
		 * @see self::addCheckForUpdatesLink()
		 *
		 * @return void
		 */
		public function handleManualCheck() {
			$shouldCheck
				= isset( $_GET['puc_check_for_updates'], $_GET['puc_slug'] )
				  && $_GET['puc_slug'] == $this->slug
				  && current_user_can( 'update_plugins' )
				  && check_admin_referer( 'puc_check_for_updates' );

			if ( $shouldCheck ) {
				$update = $this->checkForUpdates();
				$status = ( $update === null ) ? 'no_update' : 'update_available';
				wp_redirect( add_query_arg(
					array(
						'puc_update_check_result' => $status,
						'puc_slug'                => $this->slug,
					),
					is_network_admin() ? network_admin_url( 'plugins.php' ) : admin_url( 'plugins.php' )
				) );
			}
		}

		/**
		 * Display the results of a manual update check.
		 *
		 * @see self::handleManualCheck()
		 *
		 * You can change the result message by using the "puc_manual_check_message-$slug" filter.
		 */
		public function displayManualCheckResult() {
			if ( isset( $_GET['puc_update_check_result'], $_GET['puc_slug'] ) && ( $_GET['puc_slug'] == $this->slug ) ) {
				$status = strval( $_GET['puc_update_check_result'] );
				if ( $status == 'no_update' ) {
					$message = 'This plugin is up to date.';
				} else if ( $status == 'update_available' ) {
					$message = 'A new version of this plugin is available.';
				} else {
					$message = sprintf( 'Unknown update checker status "%s"', htmlentities( $status ) );
				}
				printf(
					'<div class="updated"><p>%s</p></div>',
					apply_filters( 'puc_manual_check_message-' . $this->slug, $message, $status )
				);
			}
		}

		/**
		 * Clear the cached plugin version. This method can be set up as a filter (hook) and will
		 * return the filter argument unmodified.
		 *
		 * @param mixed $filterArgument
		 *
		 * @return mixed
		 */
		public function clearCachedVersion( $filterArgument = null ) {
			$this->cachedInstalledVersion = null;

			return $filterArgument;
		}

		/**
		 * Register a callback for filtering query arguments.
		 *
		 * The callback function should take one argument - an associative array of query arguments.
		 * It should return a modified array of query arguments.
		 *
		 * @uses add_filter() This method is a convenience wrapper for add_filter().
		 *
		 * @param callable $callback
		 *
		 * @return void
		 */
		public function addQueryArgFilter( $callback ) {
			add_filter( 'puc_request_info_query_args-' . $this->slug, $callback );
		}

		/**
		 * Register a callback for filtering arguments passed to wp_remote_get().
		 *
		 * The callback function should take one argument - an associative array of arguments -
		 * and return a modified array or arguments. See the WP documentation on wp_remote_get()
		 * for details on what arguments are available and how they work.
		 *
		 * @uses add_filter() This method is a convenience wrapper for add_filter().
		 *
		 * @param callable $callback
		 *
		 * @return void
		 */
		public function addHttpRequestArgFilter( $callback ) {
			add_filter( 'puc_request_info_options-' . $this->slug, $callback );
		}

		/**
		 * Register a callback for filtering the plugin info retrieved from the external API.
		 *
		 * The callback function should take two arguments. If the plugin info was retrieved
		 * successfully, the first argument passed will be an instance of  PluginInfo. Otherwise,
		 * it will be NULL. The second argument will be the corresponding return value of
		 * wp_remote_get (see WP docs for details).
		 *
		 * The callback function should return a new or modified instance of PluginInfo or NULL.
		 *
		 * @uses add_filter() This method is a convenience wrapper for add_filter().
		 *
		 * @param callable $callback
		 *
		 * @return void
		 */
		public function addResultFilter( $callback ) {
			add_filter( 'puc_request_info_result-' . $this->slug, $callback, 10, 2 );
		}

		/**
		 * Register a callback for one of the update checker filters.
		 *
		 * Identical to add_filter(), except it automatically adds the "puc_" prefix
		 * and the "-$plugin_slug" suffix to the filter name. For example, "request_info_result"
		 * becomes "puc_request_info_result-your_plugin_slug".
		 *
		 * @param string   $tag
		 * @param callable $callback
		 * @param int      $priority
		 * @param int      $acceptedArgs
		 */
		public function addFilter( $tag, $callback, $priority = 10, $acceptedArgs = 1 ) {
			add_filter( 'puc_' . $tag . '-' . $this->slug, $callback, $priority, $acceptedArgs );
		}

		/**
		 * Initialize the update checker Debug Bar plugin/add-on thingy.
		 */
		public function initDebugBarPanel() {
			if ( class_exists( 'Debug_Bar' ) ) {
				require_once dirname( __FILE__ ) . '/debug-bar-plugin.php';
				$this->debugBarPlugin = new PucDebugBarPlugin( $this );
			}
		}
	}

}

if ( ! class_exists( 'TVE_PluginInfo_1_3', false ) ) {

	/**
	 * A container class for holding and transforming various plugin metadata.
	 *
	 * @author    Janis Elsts
	 * @copyright 2012
	 * @version   1.3
	 * @access    public
	 */
	class TVE_PluginInfo_1_3 {
		//Most fields map directly to the contents of the plugin's info.json file.
		//See the relevant docs for a description of their meaning.
		public $name;
		public $slug;
		public $version;
		public $homepage;
		public $sections;
		public $download_url;

		public $author;
		public $author_homepage;

		public $requires;
		public $tested;
		public $upgrade_notice;

		public $rating;
		public $num_ratings;
		public $downloaded;
		public $last_updated;

		public $id = 0; //The native WP.org API returns numeric plugin IDs, but they're not used for anything.

		/**
		 * Create a new instance of PluginInfo from JSON-encoded plugin info
		 * returned by an external update API.
		 *
		 * @param string $json Valid JSON string representing plugin info.
		 * @param bool   $triggerErrors
		 *
		 * @return TVE_PluginInfo|null New instance of PluginInfo, or NULL on error.
		 */
		public static function fromJson( $json, $triggerErrors = false ) {
			/** @var StdClass $apiResponse */
			$apiResponse = json_decode( $json );
			if ( empty( $apiResponse ) || ! is_object( $apiResponse ) ) {
				if ( $triggerErrors ) {
					trigger_error(
						"Failed to parse plugin metadata. Try validating your .json file with http://jsonlint.com/",
						E_USER_NOTICE
					);
				}

				return null;
			}

			//Very, very basic validation.
			$valid = isset( $apiResponse->name ) && ! empty( $apiResponse->name ) && isset( $apiResponse->version ) && ! empty( $apiResponse->version );
			if ( ! $valid ) {
				if ( $triggerErrors ) {
					trigger_error(
						"The plugin metadata file does not contain the required 'name' and/or 'version' keys.",
						E_USER_NOTICE
					);
				}

				return null;
			}

			$info = new self();
			foreach ( get_object_vars( $apiResponse ) as $key => $value ) {
				$info->$key = $value;
			}

			return $info;
		}

		/**
		 * Transform plugin info into the format used by the native WordPress.org API
		 *
		 * @return object
		 */
		public function toWpFormat() {
			$info = new StdClass;

			//The custom update API is built so that many fields have the same name and format
			//as those returned by the native WordPress.org API. These can be assigned directly.
			$sameFormat = array(
				'name',
				'slug',
				'version',
				'requires',
				'tested',
				'rating',
				'upgrade_notice',
				'num_ratings',
				'downloaded',
				'homepage',
				'last_updated',
			);
			foreach ( $sameFormat as $field ) {
				if ( isset( $this->$field ) ) {
					$info->$field = $this->$field;
				} else {
					$info->$field = null;
				}
			}

			//Other fields need to be renamed and/or transformed.
			$info->download_link = $this->download_url;

			if ( ! empty( $this->author_homepage ) ) {
				$info->author = sprintf( '<a href="%s">%s</a>', $this->author_homepage, $this->author );
			} else {
				$info->author = $this->author;
			}

			if ( is_object( $this->sections ) ) {
				$info->sections = get_object_vars( $this->sections );
			} elseif ( is_array( $this->sections ) ) {
				$info->sections = $this->sections;
			} else {
				$info->sections = array( 'description' => '' );
			}

			return $info;
		}
	}
}

if ( ! class_exists( 'TVE_PluginUpdate_1_3', false ) ) {

	/**
	 * A simple container class for holding information about an available update.
	 *
	 * @author    Janis Elsts
	 * @copyright 2012
	 * @version   1.2
	 * @access    public
	 */
	class TVE_PluginUpdate_1_3 {
		public $id = 0;
		public $slug;
		public $version;
		public $homepage;
		public $download_url;
		public $upgrade_notice;
		private static $fields = array( 'id', 'slug', 'version', 'homepage', 'download_url', 'upgrade_notice' );

		/**
		 * Create a new instance of PluginUpdate from its JSON-encoded representation.
		 *
		 * @param string $json
		 * @param bool   $triggerErrors
		 *
		 * @return TVE_PluginUpdate|null
		 */
		public static function fromJson( $json, $triggerErrors = false ) {
			//Since update-related information is simply a subset of the full plugin info,
			//we can parse the update JSON as if it was a plugin info string, then copy over
			//the parts that we care about.
			$pluginInfo = TVE_PluginInfo_1_3::fromJson( $json, $triggerErrors );
			if ( $pluginInfo != null ) {
				return self::fromPluginInfo( $pluginInfo );
			} else {
				return null;
			}
		}

		/**
		 * Create a new instance of PluginUpdate based on an instance of PluginInfo.
		 * Basically, this just copies a subset of fields from one object to another.
		 *
		 * @param TVE_PluginInfo $info
		 *
		 * @return TVE_PluginUpdate
		 */
		public static function fromPluginInfo( $info ) {
			return self::fromObject( $info );
		}

		/**
		 * Create a new instance of PluginUpdate by copying the necessary fields from
		 * another object.
		 *
		 * @param StdClass|TVE_PluginInfo|TVE_PluginUpdate $object The source object.
		 *
		 * @return TVE_PluginUpdate The new copy.
		 */
		public static function fromObject( $object ) {
			$update = new self();
			foreach ( self::$fields as $field ) {
				$update->$field = $object->$field;
			}

			return $update;
		}

		/**
		 * Create an instance of StdClass that can later be converted back to
		 * a PluginUpdate. Useful for serialization and caching, as it avoids
		 * the "incomplete object" problem if the cached value is loaded before
		 * this class.
		 *
		 * @return StdClass
		 */
		public function toStdClass() {
			$object = new StdClass();
			foreach ( self::$fields as $field ) {
				$object->$field = $this->$field;
			}

			return $object;
		}


		/**
		 * Transform the update into the format used by WordPress native plugin API.
		 *
		 * @return object
		 */
		public function toWpFormat() {
			$update = new StdClass;

			$update->id          = $this->id;
			$update->slug        = $this->slug;
			$update->new_version = $this->version;
			$update->url         = $this->homepage;
			$update->package     = $this->download_url;
			if ( ! empty( $this->upgrade_notice ) ) {
				$update->upgrade_notice = $this->upgrade_notice;
			}

			return $update;
		}
	}
}

if ( ! class_exists( 'TVE_PucFactory', false ) ) {

	/**
	 * A factory that builds instances of other classes from this library.
	 *
	 * When multiple versions of the same class have been loaded (e.g. PluginUpdateChecker 1.2
	 * and 1.3), this factory will always use the latest available version. Register class
	 * versions by calling {@link PucFactory::addVersion()}.
	 *
	 * At the moment it can only build instances of the PluginUpdateChecker class. Other classes
	 * are intended mainly for internal use and refer directly to specific implementations. If you
	 * want to instantiate one of them anyway, you can use {@link PucFactory::getLatestClassVersion()}
	 * to get the class name and then create it with <code>new $class(...)</code>.
	 */
	class TVE_PucFactory {
		protected static $classVersions = array();
		protected static $sorted = false;

		/**
		 * Create a new instance of PluginUpdateChecker.
		 *
		 * @see PluginUpdateChecker::__construct()
		 *
		 * @param        $metadataUrl
		 * @param        $pluginFile
		 * @param string $slug
		 * @param int    $checkPeriod
		 * @param string $optionName
		 *
		 * @return TVE_PluginUpdateChecker
		 */
		public static function buildUpdateChecker( $metadataUrl, $pluginFile, $slug = '', $checkPeriod = 12, $optionName = '' ) {
			$class = self::getLatestClassVersion( 'PluginUpdateChecker' );

			return new $class( $metadataUrl, $pluginFile, $slug, $checkPeriod, $optionName );
		}

		/**
		 * Get the specific class name for the latest available version of a class.
		 *
		 * @param string $class
		 *
		 * @return string|null
		 */
		public static function getLatestClassVersion( $class ) {
			if ( ! self::$sorted ) {
				self::sortVersions();
			}

			if ( isset( self::$classVersions[ $class ] ) ) {
				return reset( self::$classVersions[ $class ] );
			} else {
				return null;
			}
		}

		/**
		 * Sort available class versions in descending order (i.e. newest first).
		 */
		protected static function sortVersions() {
			foreach ( self::$classVersions as $class => $versions ) {
				uksort( $versions, array( __CLASS__, 'compareVersions' ) );
				self::$classVersions[ $class ] = $versions;
			}
			self::$sorted = true;
		}

		protected static function compareVersions( $a, $b ) {
			return - version_compare( $a, $b );
		}

		/**
		 * Register a version of a class.
		 *
		 * @access private This method is only for internal use by the library.
		 *
		 * @param string $generalClass   Class name without version numbers, e.g. 'PluginUpdateChecker'.
		 * @param string $versionedClass Actual class name, e.g. 'PluginUpdateChecker_1_2'.
		 * @param string $version        Version number, e.g. '1.2'.
		 */
		public static function addVersion( $generalClass, $versionedClass, $version ) {
			if ( ! isset( self::$classVersions[ $generalClass ] ) ) {
				self::$classVersions[ $generalClass ] = array();
			}
			self::$classVersions[ $generalClass ][ $version ] = $versionedClass;
			self::$sorted                                     = false;
		}
	}
}

//Register classes defined in this file with the factory.
TVE_PucFactory::addVersion( 'PluginUpdateChecker', 'TVE_PluginUpdateChecker_1_3_2', '1.3.2' );
TVE_PucFactory::addVersion( 'PluginUpdate', 'TVE_PluginUpdate_1_3', '1.3' );
TVE_PucFactory::addVersion( 'PluginInfo', 'TVE_PluginInfo_1_3', '1.3' );

/**
 * Create non-versioned variants of the update checker classes. This allows for backwards
 * compatibility with versions that did not use a factory, and it simplifies doc-comments.
 */
if ( ! class_exists( 'TVE_PluginUpdateChecker', false ) ) {
	class TVE_PluginUpdateChecker extends TVE_PluginUpdateChecker_1_3_2 {
	}
}

if ( ! class_exists( 'TVE_PluginUpdate', false ) ) {
	class TVE_PluginUpdate extends TVE_PluginUpdate_1_3 {
	}
}

if ( ! class_exists( 'TVE_PluginInfo', false ) ) {
	class TVE_PluginInfo extends TVE_PluginInfo_1_3 {
	}
}
