<?php

namespace Zotlabs\Lib;

use Zotlabs\Zot6\HTTPSig;
use Zotlabs\Access\Permissions;
use Zotlabs\Access\PermissionLimits;
use Zotlabs\Daemon\Master;

require_once('include/crypto.php');

/**
 * @brief Lowlevel implementation of Zot6 protocol.
 *
 */
class Libzot {

	/**
	 * @brief Generates a unique string for use as a zot guid.
	 *
	 * Generates a unique string for use as a zot guid using our DNS-based url,
	 * the channel nickname and some entropy.
	 * The entropy ensures uniqueness against re-installs where the same URL and
	 * nickname are chosen.
	 *
	 * @note zot doesn't require this to be unique. Internally we use a whirlpool
	 * hash of this guid and the signature of this guid signed with the channel
	 * private key. This can be verified and should make the probability of
	 * collision of the verified result negligible within the constraints of our
	 * immediate universe.
	 *
	 * @param string $channel_nick a unique nickname of controlling entity
	 * @return string
	 */
	static function new_uid($channel_nick) {
		$rawstr = z_root() . '/' . $channel_nick . '.' . mt_rand();
		return(base64url_encode(hash('whirlpool', $rawstr, true), true));
	}


	/**
	 * @brief Generates a portable hash identifier for a channel.
	 *
	 * Generates a portable hash identifier for the channel identified by $guid and
	 * $pubkey.
	 *
	 * @note This ID is portable across the network but MUST be calculated locally
	 * by verifying the signature and can not be trusted as an identity.
	 *
	 * @param string $guid
	 * @param string $pubkey
	 * @return string
	 */
	static function make_xchan_hash($guid, $pubkey) {
		return base64url_encode(hash('whirlpool', $guid . $pubkey, true));
	}

	/**
	 * @brief Given a zot hash, return all distinct hubs.
	 *
	 * This function is used in building the zot discovery packet and therefore
	 * should only be used by channels which are defined on this hub.
	 *
	 * @param string $hash - xchan_hash
	 * @return array of hubloc (hub location structures)
	 */
	static function get_hublocs($hash) {

		/* Only search for active hublocs - e.g. those that haven't been marked deleted */

		$ret = q("select * from hubloc where hubloc_hash = '%s' and hubloc_deleted = 0 order by hubloc_url ",
			dbesc($hash)
		);

		return $ret;
	}

	/**
	 * @brief Builds a zot6 notification packet.
	 *
	 * Builds a zot6 notification packet that you can either store in the queue with
	 * a message array or call zot_zot to immediately zot it to the other side.
	 *
	 * @param array $channel
	 *   sender channel structure
	 * @param string $type
	 *   packet type: one of 'ping', 'pickup', 'purge', 'refresh', 'keychange', 'force_refresh', 'notify', 'auth_check'
	 * @param array $recipients
	 *   envelope recipients, array of portable_id's; empty for public posts
	 * @param string $msg
	 *   optional message
	 * @param string $encoding
	 *   optional encoding, default 'activitystreams'
	 * @param string $remote_key
	 *   optional public site key of target hub used to encrypt entire packet
	 *   NOTE: remote_key and encrypted packets are required for 'auth_check' packets, optional for all others
	 * @param string $methods
	 *   optional comma separated list of encryption methods @ref best_algorithm()
	 * @returns string json encoded zot packet
	 */
	static function build_packet($channel, $type = 'activity', $recipients = null, $msg = '', $encoding = 'activitystreams', $remote_key = null, $methods = '') {

		$sig_method = get_config('system','signature_algorithm','sha256');

		$data = [
			'type'     => $type,
			'encoding' => $encoding,
			'sender'   => $channel['channel_portable_id'],
			'site_id'  => self::make_xchan_hash(z_root(), get_config('system','pubkey')),
			'version'  => System::get_zot_revision(),
		];

		if ($recipients) {
			$data['recipients'] = $recipients;
		}

		if ($msg) {
			$actor = channel_url($channel);
			if ($encoding === 'activitystreams' && array_key_exists('actor',$msg) && is_string($msg['actor']) && $actor === $msg['actor']) {
				$msg = JSalmon::sign($msg,$actor,$channel['channel_prvkey']);
			}
			$data['data'] = $msg;
		}
		else {
			unset($data['encoding']);
		}

		logger('packet: ' . print_r($data,true), LOGGER_DATA, LOG_DEBUG);

		if ($remote_key) {
			$algorithm = self::best_algorithm($methods);
			if ($algorithm) {
				$data = crypto_encapsulate(json_encode($data),$remote_key, $algorithm);
			}
		}

		return json_encode($data);
	}


	/**
	 * @brief Choose best encryption function from those available on both sites.
	 *
	 * @param string $methods
	 *   Comma separated list of encryption methods
	 * @return string first match from our site method preferences crypto_methods() array
	 *   of a method which is common to both sites; or 'aes256cbc' if no matches are found.
	 */
	static function best_algorithm($methods) {

		$x = [
			'methods' => $methods,
			'result' => ''
		];

		/**
		 * @hooks zot_best_algorithm
		 *   Called when negotiating crypto algorithms with remote sites.
		 *   * \e string \b methods - comma separated list of encryption methods
		 *   * \e string \b result - the algorithm to return
		 */
		call_hooks('zot_best_algorithm', $x);

		if($x['result'])
			return $x['result'];

		if($methods) {
			$x = explode(',', $methods);
			if($x) {
				$y = crypto_methods();
				if($y) {
					foreach($y as $yv) {
						$yv = trim($yv);
						if(in_array($yv, $x)) {
							return($yv);
						}
					}
				}
			}
		}

		return '';
	}


	/**
	 * @brief Send a zot message.
	 *
	 * @see z_post_url()
	 *
	 * @param string $url
	 * @param array $data
	 * @param array $channel (required if using zot6 delivery)
	 * @param array $crypto (required if encrypted httpsig, requires hubloc_sitekey and site_crypto elements)
	 * @return array see z_post_url() for returned data format
	 */
	static function zot($url, $data, $channel = null,$crypto = null) {

		if($channel) {
			$headers = [
				'X-Zot-Token'      => random_string(),
				'Digest'           => HTTPSig::generate_digest_header($data),
				'Content-type'     => 'application/x-zot+json',
				'(request-target)' => 'post ' . get_request_string($url)
			];

			$h = HTTPSig::create_sig($headers,$channel['channel_prvkey'],channel_url($channel),false,'sha512',
				(($crypto) ? [ 'key' => $crypto['hubloc_sitekey'], 'algorithm' => self::best_algorithm($crypto['site_crypto']) ] : false));
		}
		else {
			$h = [];
		}

		$redirects = 0;

		return z_post_url($url,$data,$redirects,((empty($h)) ? [] : [ 'headers' => $h ]));
	}


	/**
	 * @brief Refreshes after permission changed or friending, etc.
	 *
	 * refresh is typically invoked when somebody has changed permissions of a channel and they are notified
	 * to fetch new permissions via a finger/discovery operation. This may result in a new connection
	 * (abook entry) being added to a local channel and it may result in auto-permissions being granted.
	 *
	 * Friending in zot is accomplished by sending a refresh packet to a specific channel which indicates a
	 * permission change has been made by the sender which affects the target channel. The hub controlling
	 * the target channel does targetted discovery (a zot-finger request requesting permissions for the local
	 * channel). These are decoded here, and if necessary and abook structure (addressbook) is created to store
	 * the permissions assigned to this channel.
	 *
	 * Initially these abook structures are created with a 'pending' flag, so that no reverse permissions are
	 * implied until this is approved by the owner channel. A channel can also auto-populate permissions in
	 * return and send back a refresh packet of its own. This is used by forum and group communication channels
	 * so that friending and membership in the channel's "club" is automatic.
	 *
	 * @param array $them => xchan structure of sender
	 * @param array $channel => local channel structure of target recipient, required for "friending" operations
	 * @param array $force (optional) default false
	 *
	 * @return boolean
	 *   * \b true if successful
	 *   * otherwise \b false
	 */
	static function refresh($them, $channel = null, $force = false) {

		logger('them: ' . print_r($them,true), LOGGER_DATA, LOG_DEBUG);
		if ($channel)
			logger('channel: ' . print_r($channel,true), LOGGER_DATA, LOG_DEBUG);

		$url = null;

		if ($them['hubloc_id_url']) {
			$url = $them['hubloc_id_url'];
		}
		else {
			$r = null;

			// if they re-installed the server we could end up with the wrong record - pointing to the old install.
			// We'll order by reverse id to try and pick off the newest one first and hopefully end up with the
			// correct hubloc. If this doesn't work we may have to re-write this section to try them all.

			if(array_key_exists('xchan_addr',$them) && $them['xchan_addr']) {
				$r = q("select hubloc_id_url, hubloc_primary from hubloc where hubloc_addr = '%s' and hubloc_network = 'zot6' order by hubloc_id desc",
					dbesc($them['xchan_addr'])
				);
			}
			if(! $r) {
				$r = q("select hubloc_id_url, hubloc_primary from hubloc where hubloc_hash = '%s' order by hubloc_id desc",
					dbesc($them['xchan_hash'])
				);
			}

			if ($r) {
				foreach ($r as $rr) {
					if (intval($rr['hubloc_primary'])) {
						$url = $rr['hubloc_id_url'];
						$record = $rr;
					}
				}
				if (! $url) {
					$url = $r[0]['hubloc_id_url'];
				}
			}
		}
		if (! $url) {
			logger('zot_refresh: no url');
			return false;
		}

		$s = q("select site_dead from site where site_url = '%s' limit 1",
			dbesc($url)
		);

		if($s && intval($s[0]['site_dead']) && (! $force)) {
			logger('zot_refresh: site ' . $url . ' is marked dead and force flag is not set. Cancelling operation.');
			return false;
		}

		$record = Zotfinger::exec($url,$channel);

		// Check the HTTP signature

		$hsig = $record['signature'];
		if($hsig && $hsig['signer'] === $url && $hsig['header_valid'] === true && $hsig['content_valid'] === true)
			$hsig_valid = true;

		if(! $hsig_valid) {
			logger('http signature not valid: ' . print_r($hsig,true));
			return false;
		}


		logger('zot-info: ' . print_r($record,true), LOGGER_DATA, LOG_DEBUG);

		$x = self::import_xchan($record['data'], (($force) ? UPDATE_FLAGS_FORCED : UPDATE_FLAGS_UPDATED));

		if(! $x['success'])
			return false;

		if($channel && $record['data']['permissions']) {
			$permissions = explode(',',$record['data']['permissions']);
			if($permissions && is_array($permissions)) {
				$old_read_stream_perm = get_abconfig($channel['channel_id'],$x['hash'],'their_perms','view_stream');

				foreach($permissions as $p) {
					set_abconfig($channel['channel_id'],$x['hash'],'their_perms',$p,'1');
				}
			}

			if(array_key_exists('profile',$record['data']) && array_key_exists('next_birthday',$record['data']['profile'])) {
				$next_birthday = datetime_convert('UTC','UTC',$record['data']['profile']['next_birthday']);
			}
			else {
				$next_birthday = NULL_DATE;
			}

			$profile_assign = get_pconfig($channel['channel_id'],'system','profile_assign','');

			// Keep original perms to check if we need to notify them
			$previous_perms = get_all_perms($channel['channel_id'],$x['hash']);

			$r = q("select * from abook where abook_xchan = '%s' and abook_channel = %d and abook_self = 0 limit 1",
				dbesc($x['hash']),
				intval($channel['channel_id'])
			);

			if($r) {

				// connection exists

				// if the dob is the same as what we have stored (disregarding the year), keep the one
				// we have as we may have updated the year after sending a notification; and resetting
				// to the one we just received would cause us to create duplicated events.

				if(substr($r[0]['abook_dob'],5) == substr($next_birthday,5))
					$next_birthday = $r[0]['abook_dob'];

				$y = q("update abook set abook_dob = '%s'
					where abook_xchan = '%s' and abook_channel = %d
					and abook_self = 0 ",
					dbescdate($next_birthday),
					dbesc($x['hash']),
					intval($channel['channel_id'])
				);

				if(! $y)
					logger('abook update failed');
				else {
					// if we were just granted read stream permission and didn't have it before, try to pull in some posts
					if((! $old_read_stream_perm) && (intval($permissions['view_stream'])))
						Master::Summon([ 'Onepoll', $r[0]['abook_id'] ]);
				}
			}
			else {

				$p = Permissions::connect_perms($channel['channel_id']);
				$my_perms = $p['perms'];

				$automatic = $p['automatic'];

				// new connection

				if($my_perms) {
					foreach($my_perms as $k => $v) {
						set_abconfig($channel['channel_id'],$x['hash'],'my_perms',$k,$v);
					}
				}

				$closeness = get_pconfig($channel['channel_id'],'system','new_abook_closeness',80);

				$y = abook_store_lowlevel(
					[
						'abook_account'   => intval($channel['channel_account_id']),
						'abook_channel'   => intval($channel['channel_id']),
						'abook_closeness' => intval($closeness),
						'abook_xchan'     => $x['hash'],
						'abook_profile'   => $profile_assign,
						'abook_created'   => datetime_convert(),
						'abook_updated'   => datetime_convert(),
						'abook_dob'       => $next_birthday,
						'abook_pending'   => intval(($automatic) ? 0 : 1)
					]
				);

				if($y) {
					logger("New introduction received for {$channel['channel_name']}");
					$new_perms = get_all_perms($channel['channel_id'],$x['hash'],false);

					// Send a clone sync packet and a permissions update if permissions have changed

					$new_connection = q("select * from abook left join xchan on abook_xchan = xchan_hash where abook_xchan = '%s' and abook_channel = %d and abook_self = 0 order by abook_created desc limit 1",
						dbesc($x['hash']),
						intval($channel['channel_id'])
					);

					if($new_connection) {
						if(! Permissions::PermsCompare($new_perms,$previous_perms))
							Master::Summon([ 'Notifier', 'permissions_create', $new_connection[0]['abook_id'] ]);
						Enotify::submit(
							[
							'type'       => NOTIFY_INTRO,
							'from_xchan' => $x['hash'],
							'to_xchan'   => $channel['channel_portable_id'],
							'link'       => z_root() . '/connedit/' . $new_connection[0]['abook_id']
							]
						);

						if(intval($permissions['view_stream'])) {
							if(intval(get_pconfig($channel['channel_id'],'perm_limits','send_stream') & PERMS_PENDING)
								|| (! intval($new_connection[0]['abook_pending'])))
								Master::Summon([ 'Onepoll', $new_connection[0]['abook_id'] ]);
						}


						// If there is a default group for this channel, add this connection to it
						// for pending connections this will happens at acceptance time.

						if(! intval($new_connection[0]['abook_pending'])) {
							$default_group = $channel['channel_default_group'];
							if($default_group) {
								$g = Group::rec_byhash($channel['channel_id'],$default_group);
								if($g)
									Group::member_add($channel['channel_id'],'',$x['hash'],$g['id']);
							}
						}

						unset($new_connection[0]['abook_id']);
						unset($new_connection[0]['abook_account']);
						unset($new_connection[0]['abook_channel']);
						$abconfig = load_abconfig($channel['channel_id'],$new_connection['abook_xchan']);
						if($abconfig)
							$new_connection['abconfig'] = $abconfig;

						Libsync::build_sync_packet($channel['channel_id'], array('abook' => $new_connection));
					}
				}

			}
			return true;
		}
		return false;
	}

	/**
	 * @brief Look up if channel is known and previously verified.
	 *
	 * A guid and a url, both signed by the sender, distinguish a known sender at a
	 * known location.
	 * This function looks these up to see if the channel is known and therefore
	 * previously verified. If not, we will need to verify it.
	 *
	 * @param array $arr an associative array which must contain:
	 *  * \e string \b id => id of conversant
	 *  * \e string \b id_sig => id signed with conversant's private key
	 *  * \e string \b location => URL of the origination hub of this communication
	 *  * \e string \b location_sig => URL signed with conversant's private key
	 * @param boolean $multiple (optional) default false
	 *
	 * @return array|null
	 *   * null if site is blacklisted or not found
	 *   * otherwise an array with an hubloc record
	 */

	static function gethub($arr, $multiple = false) {

		if($arr['id'] && $arr['id_sig'] && $arr['location'] && $arr['location_sig']) {

			if(! check_siteallowed($arr['location'])) {
				logger('blacklisted site: ' . $arr['location']);
				return null;
			}

			$limit = (($multiple) ? '' : ' limit 1 ');

			$r = q("select hubloc.*, site.site_crypto from hubloc left join site on hubloc_url = site_url
					where hubloc_guid = '%s' and hubloc_guid_sig = '%s'
					and hubloc_url = '%s' and hubloc_url_sig = '%s'
					and hubloc_network = 'zot6'
					and hubloc_site_id = '%s' $limit",
				dbesc($arr['id']),
				dbesc($arr['id_sig']),
				dbesc($arr['location']),
				dbesc($arr['location_sig']),
				dbesc($arr['site_id'])
			);
			if($r) {
				logger('Found', LOGGER_DEBUG);
				return (($multiple) ? $r : $r[0]);
			}
		}
		logger('Not found: ' . print_r($arr,true), LOGGER_DEBUG);

		return false;
	}

	/**
	 * @brief
	 *
	 * @param string $sender
	 * @param string $site_id
	 * @return null|array
	 */
	static function valid_hub($sender, $site_id) {

		$r = q("select hubloc.*, site.site_crypto from hubloc left join site on hubloc_url = site_url where hubloc_hash = '%s' and hubloc_site_id = '%s' limit 1",
			dbesc($sender),
			dbesc($site_id)
		);
		if(! $r) {
			return null;
		}

		if(! check_siteallowed($r[0]['hubloc_url'])) {
			logger('blacklisted site: ' . $r[0]['hubloc_url']);
			return null;
		}

		if(! check_channelallowed($r[0]['hubloc_hash'])) {
			logger('blacklisted channel: ' . $r[0]['hubloc_hash']);
			return null;
		}

		return $r[0];
	}

	/**
	 * @brief Registers an unknown hub.
	 *
	 * A communication has been received which has an unknown (to us) sender.
	 * Perform discovery based on our calculated hash of the sender at the
	 * origination address. This will fetch the discovery packet of the sender,
	 * which contains the public key we need to verify our guid and url signatures.
	 *
	 * @param string $id
	 *
	 * @return array An associative array with
	 *  * \e boolean \b success
	 *  * \e string \b message (optional, unused) error string only if success is false
	 */
	static function register_hub($id) {

		$hsig_valid = false;

		$result  = [ 'success' => false ];

		if(! $id) {
			return $result;
		}

		$record = Zotfinger::exec($id);

		// Check the HTTP signature

		$hsig = $record['signature'];
		if($hsig['signer'] === $id && $hsig['header_valid'] === true && $hsig['content_valid'] === true) {
			$hsig_valid = true;
		}
		if(! $hsig_valid) {
			logger('http signature not valid: ' . print_r($hsig,true));
			return $result;
		}

		$c = self::import_xchan($record['data']);
		if($c['success']) {
			$result['success'] = true;
		}
		else {
			logger('Failure to verify zot packet');
		}

		return $result;
	}

	/**
	 * @brief Takes an associative array of a fetch discovery packet and updates
	 *   all internal data structures which need to be updated as a result.
	 *
	 * @param array $arr => json_decoded discovery packet
	 * @param int $ud_flags
	 *    Determines whether to create a directory update record if any changes occur, default is UPDATE_FLAGS_UPDATED
	 *    $ud_flags = UPDATE_FLAGS_FORCED indicates a forced refresh where we unconditionally create a directory update record
	 *      this typically occurs once a month for each channel as part of a scheduled ping to notify the directory
	 *      that the channel still exists
	 * @param array $ud_arr
	 *    If set [typically by update_directory_entry()] indicates a specific update table row and more particularly
	 *    contains a particular address (ud_addr) which needs to be updated in that table.
	 *
	 * @return array An associative array with:
	 *   * \e boolean \b success boolean true or false
	 *   * \e string \b message (optional) error string only if success is false
	 */

	static function import_xchan($arr, $ud_flags = UPDATE_FLAGS_UPDATED, $ud_arr = null) {

		/**
		 * @hooks import_xchan
		 *   Called when processing the result of zot_finger() to store the result
		 *   * \e array
		 */
		call_hooks('import_xchan', $arr);

		$ret = array('success' => false);
		$dirmode = intval(get_config('system','directory_mode'));

		$changed = false;
		$what = '';

		if(! ($arr['id'] && $arr['id_sig'])) {
			logger('No identity information provided. ' . print_r($arr,true));
			return $ret;
		}

		$xchan_hash = self::make_xchan_hash($arr['id'],$arr['public_key']);
		$arr['hash'] = $xchan_hash;

		$import_photos = false;

		$sig_methods = ((array_key_exists('signing',$arr) && is_array($arr['signing'])) ? $arr['signing'] : [ 'sha256' ]);
		$verified = false;

		if(! self::verify($arr['id'],$arr['id_sig'],$arr['public_key'])) {
			logger('Unable to verify channel signature for ' . $arr['address']);
			return $ret;
		}
		else {
			$verified = true;
		}

		if(! $verified) {
			$ret['message'] = t('Unable to verify channel signature');
			return $ret;
		}

		logger('import_xchan: ' . $xchan_hash, LOGGER_DEBUG);

		$r = q("select * from xchan where xchan_hash = '%s' limit 1",
			dbesc($xchan_hash)
		);

		if(! array_key_exists('connect_url', $arr))
			$arr['connect_url'] = '';

		if($r) {
			if($arr['photo'] && array_key_exists('updated',$arr['photo']) && $r[0]['xchan_photo_date'] != $arr['photo']['updated']) {
				$import_photos = true;
			}

			// if we import an entry from a site that's not ours and either or both of us is off the grid - hide the entry.
			/** @TODO: check if we're the same directory realm, which would mean we are allowed to see it */

			$dirmode = get_config('system','directory_mode');

			if((($arr['site']['directory_mode'] === 'standalone') || ($dirmode & DIRECTORY_MODE_STANDALONE)) && ($arr['site']['url'] != z_root()))
				$arr['searchable'] = false;

			$hidden = (1 - intval($arr['searchable']));

			$hidden_changed = $adult_changed = $deleted_changed = $pubforum_changed = 0;

			if(intval($r[0]['xchan_hidden']) != (1 - intval($arr['searchable'])))
				$hidden_changed = 1;
			if(intval($r[0]['xchan_selfcensored']) != intval($arr['adult_content']))
				$adult_changed = 1;
			if(intval($r[0]['xchan_deleted']) != intval($arr['deleted']))
				$deleted_changed = 1;

			// new style 6-MAR-2019

			if(array_key_exists('channel_type',$arr)) {
				if($arr['channel_type'] === 'collection') {
					// do nothing at this time.
				}
				elseif($arr['channel_type'] === 'group') {
					$arr['public_forum'] = 1;
				}
				else {
					$arr['public_forum'] = 0;
				}
			}

			// old style

			if(intval($r[0]['xchan_pubforum']) != intval($arr['public_forum']))
				$pubforum_changed = 1;


			if($arr['protocols']) {
				$protocols = implode(',',$arr['protocols']);
				if($protocols !== 'zot6') {
					set_xconfig($xchan_hash,'system','protocols',$protocols);
				}
				else {
					del_xconfig($xchan_hash,'system','protocols');
				}
			}

			if(($r[0]['xchan_name_date'] != $arr['name_updated'])
				|| ($r[0]['xchan_connurl'] != $arr['primary_location']['connections_url'])
				|| ($r[0]['xchan_addr'] != $arr['primary_location']['address'])
				|| ($r[0]['xchan_follow'] != $arr['primary_location']['follow_url'])
				|| ($r[0]['xchan_connpage'] != $arr['connect_url'])
				|| ($r[0]['xchan_url'] != $arr['primary_location']['url'])
				|| $hidden_changed || $adult_changed || $deleted_changed || $pubforum_changed ) {
				$rup = q("update xchan set xchan_name = '%s', xchan_name_date = '%s', xchan_connurl = '%s', xchan_follow = '%s',
					xchan_connpage = '%s', xchan_hidden = %d, xchan_selfcensored = %d, xchan_deleted = %d, xchan_pubforum = %d,
					xchan_addr = '%s', xchan_url = '%s' where xchan_hash = '%s'",
					dbesc(($arr['name']) ? escape_tags($arr['name']) : '-'),
					dbesc($arr['name_updated']),
					dbesc($arr['primary_location']['connections_url']),
					dbesc($arr['primary_location']['follow_url']),
					dbesc($arr['primary_location']['connect_url']),
					intval(1 - intval($arr['searchable'])),
					intval($arr['adult_content']),
					intval($arr['deleted']),
					intval($arr['public_forum']),
					dbesc(escape_tags($arr['primary_location']['address'])),
					dbesc(escape_tags($arr['primary_location']['url'])),
					dbesc($xchan_hash)
				);

				logger('Update: existing: ' . print_r($r[0],true), LOGGER_DATA, LOG_DEBUG);
				logger('Update: new: ' . print_r($arr,true), LOGGER_DATA, LOG_DEBUG);
				$what .= 'xchan ';
				$changed = true;
			}
		}
		else {
			$import_photos = true;

			if((($arr['site']['directory_mode'] === 'standalone')
					|| ($dirmode & DIRECTORY_MODE_STANDALONE))
					&& ($arr['site']['url'] != z_root()))
				$arr['searchable'] = false;

			$x = xchan_store_lowlevel(
				[
					'xchan_hash'           => $xchan_hash,
					'xchan_guid'           => $arr['id'],
					'xchan_guid_sig'       => $arr['id_sig'],
					'xchan_pubkey'         => $arr['public_key'],
					'xchan_photo_mimetype' => $arr['photo_mimetype'],
					'xchan_photo_l'        => $arr['photo'],
					'xchan_addr'           => escape_tags($arr['primary_location']['address']),
					'xchan_url'            => escape_tags($arr['primary_location']['url']),
					'xchan_connurl'        => $arr['primary_location']['connections_url'],
					'xchan_follow'         => $arr['primary_location']['follow_url'],
					'xchan_connpage'       => $arr['connect_url'],
					'xchan_name'           => (($arr['name']) ? escape_tags($arr['name']) : '-'),
					'xchan_network'        => 'zot6',
					'xchan_photo_date'     => $arr['photo_updated'],
					'xchan_name_date'      => $arr['name_updated'],
					'xchan_hidden'         => intval(1 - intval($arr['searchable'])),
					'xchan_selfcensored'   => $arr['adult_content'],
					'xchan_deleted'        => $arr['deleted'],
					'xchan_pubforum'       => $arr['public_forum']
				]
			);

			$what .= 'new_xchan';
			$changed = true;
		}

		if($import_photos) {

			require_once('include/photo/photo_driver.php');

			// see if this is a channel clone that's hosted locally - which we treat different from other xchans/connections

			$local = q("select channel_account_id, channel_id from channel where channel_portable_id = '%s' limit 1",
				dbesc($xchan_hash)
			);
			if($local) {
				$ph = z_fetch_url($arr['photo']['url'], true);
				if($ph['success']) {

					$hash = import_channel_photo($ph['body'], $arr['photo']['type'], $local[0]['channel_account_id'], $local[0]['channel_id']);

					if($hash) {
						// unless proven otherwise
						$is_default_profile = 1;

						$profile = q("select is_default from profile where aid = %d and uid = %d limit 1",
							intval($local[0]['channel_account_id']),
							intval($local[0]['channel_id'])
						);
						if($profile) {
							if(! intval($profile[0]['is_default']))
								$is_default_profile = 0;
						}

						// If setting for the default profile, unset the profile photo flag from any other photos I own
						if($is_default_profile) {
							q("UPDATE photo SET photo_usage = %d WHERE photo_usage = %d AND resource_id != '%s' AND aid = %d AND uid = %d",
								intval(PHOTO_NORMAL),
								intval(PHOTO_PROFILE),
								dbesc($hash),
								intval($local[0]['channel_account_id']),
								intval($local[0]['channel_id'])
							);
						}
					}

					// reset the names in case they got messed up when we had a bug in this function
					$photos = array(
						z_root() . '/photo/profile/l/' . $local[0]['channel_id'],
						z_root() . '/photo/profile/m/' . $local[0]['channel_id'],
						z_root() . '/photo/profile/s/' . $local[0]['channel_id'],
						$arr['photo_mimetype'],
						false
					);
				}
			}
			else {
				$photos = import_xchan_photo($arr['photo']['url'], $xchan_hash);
			}
			if($photos) {
				if($photos[4]) {
					// importing the photo failed somehow. Leave the photo_date alone so we can try again at a later date.
					// This often happens when somebody joins the matrix with a bad cert.
					$r = q("update xchan set xchan_photo_l = '%s', xchan_photo_m = '%s', xchan_photo_s = '%s', xchan_photo_mimetype = '%s'
						where xchan_hash = '%s'",
						dbesc($photos[0]),
						dbesc($photos[1]),
						dbesc($photos[2]),
						dbesc($photos[3]),
						dbesc($xchan_hash)
					);
				}
				else {
					$r = q("update xchan set xchan_photo_date = '%s', xchan_photo_l = '%s', xchan_photo_m = '%s', xchan_photo_s = '%s', xchan_photo_mimetype = '%s'
						where xchan_hash = '%s'",
						dbescdate(datetime_convert('UTC','UTC',$arr['photo_updated'])),
						dbesc($photos[0]),
						dbesc($photos[1]),
						dbesc($photos[2]),
						dbesc($photos[3]),
						dbesc($xchan_hash)
					);
				}
				$what .= 'photo ';
				$changed = true;
			}
		}

		// what we are missing for true hub independence is for any changes in the primary hub to
		// get reflected not only in the hublocs, but also to update the URLs and addr in the appropriate xchan

		$s = Libsync::sync_locations($arr, $arr);

		if($s) {
			if($s['change_message'])
				$what .= $s['change_message'];
			if($s['changed'])
				$changed = $s['changed'];
			if($s['message'])
				$ret['message'] .= $s['message'];
		}

		// Which entries in the update table are we interested in updating?

		$address = (($ud_arr && $ud_arr['ud_addr']) ? $ud_arr['ud_addr'] : $arr['address']);


		// Are we a directory server of some kind?

		$other_realm = false;
		$realm = get_directory_realm();
		if(array_key_exists('site',$arr)
			&& array_key_exists('realm',$arr['site'])
			&& (strpos($arr['site']['realm'],$realm) === false))
			$other_realm = true;


		if($dirmode != DIRECTORY_MODE_NORMAL) {

			// We're some kind of directory server. However we can only add directory information
			// if the entry is in the same realm (or is a sub-realm). Sub-realms are denoted by
			// including the parent realm in the name. e.g. 'RED_GLOBAL:foo' would allow an entry to
			// be in directories for the local realm (foo) and also the RED_GLOBAL realm.

			if(array_key_exists('profile',$arr) && is_array($arr['profile']) && (! $other_realm)) {
				$profile_changed = Libzotdir::import_directory_profile($xchan_hash,$arr['profile'],$address,$ud_flags, 1);
				if($profile_changed) {
					$what .= 'profile ';
					$changed = true;
				}
			}
			else {
				logger('Profile not available - hiding');
				// they may have made it private
				$r = q("delete from xprof where xprof_hash = '%s'",
					dbesc($xchan_hash)
				);
				$r = q("delete from xtag where xtag_hash = '%s' and xtag_flags = 0",
					dbesc($xchan_hash)
				);
			}
		}

		if(array_key_exists('site',$arr) && is_array($arr['site'])) {
			$profile_changed = self::import_site($arr['site']);
			if($profile_changed) {
				$what .= 'site ';
				$changed = true;
			}
		}

		if(($changed) || ($ud_flags == UPDATE_FLAGS_FORCED)) {
			$guid = random_string() . '@' . \App::get_hostname();
			Libzotdir::update_modtime($xchan_hash,$guid,$address,$ud_flags);
			logger('Changed: ' . $what,LOGGER_DEBUG);
		}
		elseif(! $ud_flags) {
			// nothing changed but we still need to update the updates record
			q("update updates set ud_flags = ( ud_flags | %d ) where ud_addr = '%s' and not (ud_flags & %d) > 0 ",
				intval(UPDATE_FLAGS_UPDATED),
				dbesc($address),
				intval(UPDATE_FLAGS_UPDATED)
			);
		}

		if(! x($ret,'message')) {
			$ret['success'] = true;
			$ret['hash'] = $xchan_hash;
		}

		logger('Result: ' . print_r($ret,true), LOGGER_DATA, LOG_DEBUG);
		return $ret;
	}

	/**
	 * @brief Called immediately after sending a zot message which is using queue processing.
	 *
	 * Updates the queue item according to the response result and logs any information
	 * returned to aid communications troubleshooting.
	 *
	 * @param string $hub - url of site we just contacted
	 * @param array $arr - output of z_post_url()
	 * @param array $outq - The queue structure attached to this request
	 * @return void
	 */
	static function process_response($hub, $arr, $outq) {

		logger('remote: ' . print_r($arr,true),LOGGER_DATA);

		if(! $arr['success']) {
			logger('Failed: ' . $hub);
			return;
		}

		$x = json_decode($arr['body'], true);

		if(! $x) {
			logger('No json from ' . $hub);
			logger('Headers: ' . print_r($arr['header'], true), LOGGER_DATA, LOG_DEBUG);
		}

		$x = crypto_unencapsulate($x, get_config('system','prvkey'));

		if(! is_array($x)) {
			$x = json_decode($x,true);
		}

		if(! is_array($x)) {
			btlogger('failed communication - no response');
		}

		if($x) {
			if(! $x['success']) {

				// handle remote validation issues

				$b = q("update dreport set dreport_result = '%s', dreport_time = '%s' where dreport_queue = '%s'",
					dbesc(($x['message']) ? $x['message'] : 'unknown delivery error'),
					dbesc(datetime_convert()),
					dbesc($outq['outq_hash'])
				);
			}

			if(is_array($x) && array_key_exists('delivery_report',$x) && is_array($x['delivery_report'])) {

				foreach($x['delivery_report'] as $xx) {
					call_hooks('dreport_process',$xx);
					if(is_array($xx) && array_key_exists('message_id',$xx) && DReport::is_storable($xx)) {

						// legacy recipients add a space and their name to the xchan. split those if true.
						$legacy_recipient = strpos($xx['recipient'], ' ');
						if($legacy_recipient !== false) {
							$legacy_recipient_parts = explode(' ', $xx['recipient'], 2);
							$xx['recipient'] = $legacy_recipient_parts[0];
							$xx['name'] = $legacy_recipient_parts[1];
						}

						q("insert into dreport ( dreport_mid, dreport_site, dreport_recip, dreport_name, dreport_result, dreport_time, dreport_xchan ) values ( '%s', '%s', '%s','%s','%s','%s','%s' ) ",
							dbesc($xx['message_id']),
							dbesc($xx['location']),
							dbesc($xx['recipient']),
							dbesc($xx['name']),
							dbesc($xx['status']),
							dbesc(datetime_convert('UTC','UTC',$xx['date'])),
							dbesc($xx['sender'])
						);
					}
				}

				// we have a more descriptive delivery report, so discard the per hub 'queue' report.

				q("delete from dreport where dreport_queue = '%s' ",
					dbesc($outq['outq_hash'])
				);
			}
		}
		// update the timestamp for this site

		q("update site set site_dead = 0, site_update = '%s' where site_url = '%s'",
			dbesc(datetime_convert()),
			dbesc(dirname($hub))
		);

		// synchronous message types are handled immediately
		// async messages remain in the queue until processed.

		if(intval($outq['outq_async']))
			Queue::remove($outq['outq_hash'],$outq['outq_channel']);

		logger('zot_process_response: ' . print_r($x,true), LOGGER_DEBUG);
	}

	/**
	 * @brief
	 *
	 * We received a notification packet (in mod_post) that a message is waiting for us, and we've verified the sender.
	 * Check if the site is using zot6 delivery and includes a verified HTTP Signature, signed content, and a 'msg' field,
	 * and also that the signer and the sender match.
	 * If that happens, we do not need to fetch/pickup the message - we have it already and it is verified.
	 * Translate it into the form we need for zot_import() and import it.
	 *
	 * Otherwise send back a pickup message, using our message tracking ID ($arr['secret']), which we will sign with our site
	 * private key.
	 * The entire pickup message is encrypted with the remote site's public key.
	 * If everything checks out on the remote end, we will receive back a packet containing one or more messages,
	 * which will be processed and delivered before this function ultimately returns.
	 *
	 * @see zot_import()
	 *
	 * @param array $arr
	 *     decrypted and json decoded notify packet from remote site
	 * @return array from zot_import()
	 */

	static function fetch($arr) {

		logger('zot_fetch: ' . print_r($arr,true), LOGGER_DATA, LOG_DEBUG);

		return self::import($arr);

	}

	/**
	 * @brief Process incoming array of messages.
	 *
	 * Process an incoming array of messages which were obtained via pickup, and
	 * import, update, delete as directed.
	 *
	 * The message types handled here are 'activity' (e.g. posts), and 'sync'.
	 *
	 * @param array $arr
	 *  'pickup' structure returned from remote site
	 *
	 * @returns array
	 *   Suitable for logging remotely, enumerating the processing results of each message/recipient combination
	 *   * [0] => \e string $channel_hash
	 *   * [1] => \e string $delivery_status
	 *   * [2] => \e string $address
	 */
	static function import($arr) {

		$env = $arr;
		$private = false;
		$return = [];

		$result = null;

		logger('Notify: ' . print_r($env,true), LOGGER_DATA, LOG_DEBUG);

		if(! is_array($env)) {
			logger('decode error');
			return;
		}

		$message_request = false;


		$has_data = array_key_exists('data',$env) && $env['data'];
		$data = (($has_data) ? $env['data'] : false);

		$AS = null;

		if($env['encoding'] === 'activitystreams') {

				$AS = new ActivityStreams($data);
				if(! $AS->is_valid()) {
					logger('Activity rejected: ' . print_r($data,true));
					return;
				}
				if (is_array($AS->obj)) {
					$arr = Activity::decode_note($AS);
				}
				else {
					$arr = [];
				}

				logger($AS->debug(),LOGGER_DATA);
		}


		$deliveries = null;

		if(array_key_exists('recipients',$env) && count($env['recipients'])) {
			logger('specific recipients');
			logger('recipients: ' . print_r($env['recipients'],true),LOGGER_DEBUG);

			$recip_arr = [];
			foreach($env['recipients'] as $recip) {
				$recip_arr[] =  $recip;
			}

			$r = false;
			if($recip_arr) {
				stringify_array_elms($recip_arr,true);
				$recips = implode(',',$recip_arr);
				$r = q("select channel_portable_id as hash from channel where channel_portable_id in ( " . $recips . " ) and channel_removed = 0 ");
			}

			if(! $r) {
				logger('recips: no recipients on this site');
				return;
			}

			// Response messages will inherit the privacy of the parent

			if($env['type'] !== 'response')
				$private = true;

			$deliveries = ids_to_array($r,'hash');

			// We found somebody on this site that's in the recipient list.
		}
		else {

			logger('public post');


			// Public post. look for any site members who are or may be accepting posts from this sender
			// and who are allowed to see them based on the sender's permissions
			// @fixme;

			$deliveries = self::public_recips($env,$AS);

		}

		$deliveries = array_unique($deliveries);

		if(! $deliveries) {
			logger('No deliveries on this site');
			return;
		}


		if($has_data) {

			if(in_array($env['type'],['activity','response'])) {

				$arr = Activity::decode_note($AS);

				//logger($AS->debug());

				$r = q("select hubloc_hash from hubloc where hubloc_id_url = '%s' and hubloc_network = 'zot6' limit 1",
					dbesc($AS->actor['id'])
				);

				if($r) {
					$arr['author_xchan'] = $r[0]['hubloc_hash'];
				}


				$s = q("select hubloc_hash from hubloc where hubloc_id_url = '%s' and hubloc_network = 'zot6' limit 1",
					dbesc($env['sender'])
				);

				// in individual delivery, change owner if needed
				if($s) {
					$arr['owner_xchan'] = $s[0]['hubloc_hash'];
				}
				else {
					$arr['owner_xchan'] = $env['sender'];
				}

				if($private) {
					$arr['item_private'] = true;
				}
				/// @FIXME - spoofable
				if($AS->data['hubloc']) {
					$arr['item_verified'] = true;
				}
				if($AS->data['signed_data']) {
					IConfig::Set($arr,'activitystreams','signed_data',$AS->data['signed_data'],false);
				}


				logger('Activity received: ' . print_r($arr,true), LOGGER_DATA, LOG_DEBUG);
				logger('Activity recipients: ' . print_r($deliveries,true), LOGGER_DATA, LOG_DEBUG);

				$relay = (($env['type'] === 'response') ? true : false );

				$result = self::process_delivery($env['sender'],$AS,$arr,$deliveries,$relay,false,$message_request);
			}
			elseif($env['type'] === 'sync') {
				// $arr = get_channelsync_elements($data);

				$arr = json_decode($data,true);

				logger('Channel sync received: ' . print_r($arr,true), LOGGER_DATA, LOG_DEBUG);
				logger('Channel sync recipients: ' . print_r($deliveries,true), LOGGER_DATA, LOG_DEBUG);

				$result = Libsync::process_channel_sync_delivery($env['sender'],$arr,$deliveries);
			}
		}
		if ($result) {
			$return = array_merge($return, $result);
		}
		return $return;
	}


	/**
	 * @brief
	 *
	 * @param array $env
	 * @param object $act
	 * @return boolean
	 */
	static function is_top_level($env, $act) {
		if($env['encoding'] === 'zot' && array_key_exists('flags',$env) && in_array('thread_parent', $env['flags'])) {
			return true;
		}
		if($act) {
			if(in_array($act->type, ['Like','Dislike'])) {
				return false;
			}
			$x = self::find_parent($env,$act);
			if($x === $act->id || $x === $act->obj['id']) {
				return true;
			}
		}
		return false;
	}


	static function find_parent($env,$act) {
		if($act) {
			if(in_array($act->type, ['Like','Dislike'])) {
				return $act->obj['id'];
			}
			if($act->parent_id) {
				return $act->parent_id;
			}
		}
		return false;
	}


	/**
	 * @brief
	 *
	 * A public message with no listed recipients can be delivered to anybody who
	 * has PERMS_NETWORK for that type of post, PERMS_AUTHED (in-network senders are
	 * by definition authenticated) or PERMS_SITE and is one the same site,
	 * or PERMS_SPECIFIC and the sender is a contact who is granted permissions via
	 * their connection permissions in the address book.
	 * Here we take a given message and construct a list of hashes of everybody
	 * on the site that we should try and deliver to.
	 * Some of these will be rejected, but this gives us a place to start.
	 *
	 * @param array $msg
	 * @param object $act
	 * @return array
	 */
	static function public_recips($msg, $act) {

		require_once('include/channel.php');

		$check_mentions = false;
		$include_sys = false;

		if($msg['type'] === 'activity') {
			$disable_discover_tab = get_config('system','disable_discover_tab') || get_config('system','disable_discover_tab') === false;
			if(! $disable_discover_tab)
				$include_sys = true;

			$perm = 'send_stream';

			if(self::is_top_level($msg,$act)) {
				$check_mentions = true;
			}
		}
		elseif($msg['type'] === 'mail')
			$perm = 'post_mail';

		$r = [];

		$c = q("select channel_id, channel_portable_id from channel where channel_removed = 0");

		if($c) {
			foreach($c as $cc) {
				if(perm_is_allowed($cc['channel_id'],$msg['sender'],$perm)) {
					$r[] = $cc['channel_portable_id'];
				}
			}
		}

		if($include_sys) {
			$sys = get_sys_channel();
			if($sys)
				$r[] = $sys['channel_portable_id'];
		}


		// look for any public mentions on this site
		// They will get filtered by tgroup_check() so we don't need to check permissions now

		if($check_mentions) {
			// It's a top level post. Look at the tags. See if any of them are mentions and are on this hub.
			if($act && $act->obj) {
				if(is_array($act->obj['tag']) && $act->obj['tag']) {
					foreach($act->obj['tag'] as $tag) {
						if($tag['type'] === 'Mention' && (strpos($tag['href'],z_root()) !== false)) {
							$address = basename($tag['href']);
							if($address) {
								$z = q("select channel_portable_id as hash from channel where channel_address = '%s'
									and channel_removed = 0 limit 1",
									dbesc($address)
								);
								if($z) {
									$r[] = $z[0]['hash'];
								}
							}
						}
					}
				}
			}
		}
		else {
			// This is a comment. We need to find any parent with ITEM_UPLINK set. But in fact, let's just return
			// everybody that stored a copy of the parent. This way we know we're covered. We'll check the
			// comment permissions when we deliver them.

			$thread_parent = self::find_parent($msg,$act);

			if($thread_parent) {
				$z = q("select channel_portable_id as hash from channel left join item on channel.channel_id = item.uid where ( item.thr_parent = '%s' OR item.parent_mid = '%s' ) ",
					dbesc($thread_parent),
					dbesc($thread_parent)
				);
				if($z) {
					foreach($z as $zv) {
						$r[] = $zv['hash'];
					}
				}
			}
		}

		// There are probably a lot of duplicates in $r at this point. We need to filter those out.
		// It's a bit of work since it's a multi-dimensional array

		if($r) {
			$r = array_values(array_unique($r));
		}

		logger('public_recips: ' . print_r($r,true), LOGGER_DATA, LOG_DEBUG);
		return $r;
	}


	/**
	 * @brief
	 *
	 * @param string $sender
	 * @param array $arr
	 * @param array $deliveries
	 * @param boolean $relay
	 * @param boolean $public (optional) default false
	 * @param boolean $request (optional) default false
	 * @return array
	 */

	static function process_delivery($sender, $act, $arr, $deliveries, $relay, $public = false, $request = false) {

		$result = [];

		// We've validated the sender. Now make sure that the sender is the owner or author

		if(! $public) {
			if($sender != $arr['owner_xchan'] && $sender != $arr['author_xchan']) {
				logger("Sender $sender is not owner {$arr['owner_xchan']} or author {$arr['author_xchan']} - mid {$arr['mid']}");
				return;
			}
		}

		foreach($deliveries as $d) {

			$local_public = $public;

			$DR = new DReport(z_root(),$sender,$d,$arr['mid']);

			$channel = channelx_by_portid($d);

			if (! $channel) {
				$DR->update('recipient not found');
				$result[] = $DR->get();
				continue;
			}

			$DR->set_name($channel['channel_name'] . ' <' . channel_reddress($channel) . '>');

			if(($act) && ($act->obj) && (! is_array($act->obj))) {
				// The initial object fetch failed using the sys channel credentials. 
				// Try again using the delivery channel credentials.
				// We will also need to re-parse the $item array, 
				// but preserve any values that were set during anonymous parsing.
							   
				$o = Activity::fetch($act->obj,$channel);
				if($o) {
					$act->obj = $o;
					$arr = array_merge(Activity::decode_note($act),$arr);
				}
				else {
					$DR->update('Incomplete or corrupt activity');
					$result[] = $DR->get();
					continue;
				}
			}       

			/**
			 * We need to block normal top-level message delivery from our clones, as the delivered
			 * message doesn't have ACL information in it as the cloned copy does. That copy
			 * will normally arrive first via sync delivery, but this isn't guaranteed.
			 * There's a chance the current delivery could take place before the cloned copy arrives
			 * hence the item could have the wrong ACL and *could* be used in subsequent deliveries or
			 * access checks.
			 */

			if($sender === $channel['channel_portable_id'] && $arr['author_xchan'] === $channel['channel_portable_id'] && $arr['mid'] === $arr['parent_mid']) {
				$DR->update('self delivery ignored');
				$result[] = $DR->get();
				continue;
			}

			// allow public postings to the sys channel regardless of permissions, but not
			// for comments travelling upstream. Wait and catch them on the way down.
			// They may have been blocked by the owner.

			if(intval($channel['channel_system']) && (! $arr['item_private']) && (! $relay)) {
				$local_public = true;

				$r = q("select xchan_selfcensored from xchan where xchan_hash = '%s' limit 1",
					dbesc($sender)
				);
				// don't import sys channel posts from selfcensored authors
				if($r && (intval($r[0]['xchan_selfcensored']))) {
					$local_public = false;
					continue;
				}
				if(! MessageFilter::evaluate($arr,get_config('system','pubstream_incl'),get_config('system','pubstream_excl'))) {
					$local_public = false;
					continue;
				}
			}

			$tag_delivery = tgroup_check($channel['channel_id'],$arr);

			$perm = 'send_stream';
			if(($arr['mid'] !== $arr['parent_mid']) && ($relay))
				$perm = 'post_comments';

			// This is our own post, possibly coming from a channel clone

			if($arr['owner_xchan'] == $d) {
				$arr['item_wall'] = 1;
			}
			else {
				$arr['item_wall'] = 0;
			}

			$friendofriend = false;

			if ((! $tag_delivery) && (! $local_public)) {
				$allowed = (perm_is_allowed($channel['channel_id'],$sender,$perm));
				if((! $allowed) && $perm === 'post_comments') {
					$parent = q("select * from item where mid = '%s' and uid = %d limit 1",
						dbesc($arr['parent_mid']),
						intval($channel['channel_id'])
					);
					if ($parent) {
						$allowed = can_comment_on_post($sender,$parent[0]);
					}
				}

				if ($request) {

					// Conversation fetches (e.g. $request == true) take place for
					//   a) new comments on expired posts
					//   b) hyperdrive (friend-of-friend) conversations
					//   c) Repeats of posts by others


					// over-ride normal connection permissions for hyperdrive (friend-of-friend) conversations
					// (if hyperdrive is enabled) and repeated posts by a friend.
					// If $allowed is already true, this is probably the conversation of a direct friend or a
					// conversation fetch for a new comment on an expired post
					// Comments of all these activities are allowed and will only be rejected (later) if the parent
					// doesn't exist.

					if ($perm === 'send_stream') {
						if (get_pconfig($channel['channel_id'],'system','hyperdrive',false) || $arr['verb'] === ACTIVITY_SHARE) {
							$allowed = true;
						}
					}
					else {
						$allowed = true;
					}

					$friendofriend = true;
				}

				if (! $allowed) {
					logger("permission denied for delivery to channel {$channel['channel_id']} {$channel['channel_address']}");
					$DR->update('permission denied');
					$result[] = $DR->get();
					continue;
				}
			}

			//	logger('item: ' . print_r($arr,true), LOGGER_DATA);

			if($arr['mid'] !== $arr['parent_mid']) {

				logger('checking source: "' . $arr['mid'] . '" != "' . $arr['parent_mid'] . '"');

				// check source route.
				// We are only going to accept comments from this sender if the comment has the same route as the top-level-post,
				// this is so that permissions mismatches between senders apply to the entire conversation
				// As a side effect we will also do a preliminary check that we have the top-level-post, otherwise
				// processing it is pointless.

				$r = q("select route, id, owner_xchan, item_private from item where mid = '%s' and uid = %d limit 1",
					dbesc($arr['parent_mid']),
					intval($channel['channel_id'])
				);
				if(! $r) {
					$DR->update('comment parent not found');
					$result[] = $DR->get();

					// We don't seem to have a copy of this conversation or at least the parent
					// - so request a copy of the entire conversation to date.
					// Don't do this if it's a relay post as we're the ones who are supposed to
					// have the copy and we don't want the request to loop.
					// Also don't do this if this comment came from a conversation request packet.
					// It's possible that comments are allowed but posting isn't and that could
					// cause a conversation fetch loop. 
					// We'll also check the send_stream permission - because if it isn't allowed,
					// the top level post is unlikely to be imported and
					// this is just an exercise in futility.

					if((! $relay) && (! $request) && (! $local_public)
						&& perm_is_allowed($channel['channel_id'],$sender,'send_stream')) {
						self::fetch_conversation($channel,$arr['parent_mid']);
					}
					continue;
				}

				if($relay || $friendofriend || (intval($r[0]['item_private']) === 0 && intval($arr['item_private']) === 0)) {
					// reset the route in case it travelled a great distance upstream
					// use our parent's route so when we go back downstream we'll match
					// with whatever route our parent has.
					// Also friend-of-friend conversations may have been imported without a route,
					// but we are now getting comments via listener delivery
					// and if there is no privacy on this or the parent, we don't care about the route,
					// so just set the owner and route accordingly.
					$arr['route'] = $r[0]['route'];
					$arr['owner_xchan'] = $r[0]['owner_xchan'];
				}
				else {

					// going downstream check that we have the same upstream provider that
					// sent it to us originally. Ignore it if it came from another source
					// (with potentially different permissions).
					// only compare the last hop since it could have arrived at the last location any number of ways.
					// Always accept empty routes and firehose items (route contains 'undefined') .

					$existing_route = explode(',', $r[0]['route']);
					$routes = count($existing_route);
					if($routes) {
						$last_hop = array_pop($existing_route);
						$last_prior_route = implode(',',$existing_route);
					}
					else {
						$last_hop = '';
						$last_prior_route = '';
					}

					if(in_array('undefined',$existing_route) || $last_hop == 'undefined' || $sender == 'undefined')
						$last_hop = '';

					$current_route = (($arr['route']) ? $arr['route'] . ',' : '') . $sender;

					if($last_hop && $last_hop != $sender) {
						logger('comment route mismatch: parent route = ' . $r[0]['route'] . ' expected = ' . $current_route, LOGGER_DEBUG);
						logger('comment route mismatch: parent msg = ' . $r[0]['id'],LOGGER_DEBUG);
						$DR->update('comment route mismatch');
						$result[] = $DR->get();
						continue;
					}

					// we'll add sender onto this when we deliver it. $last_prior_route now has the previously stored route
					// *except* for the sender which would've been the last hop before it got to us.

					$arr['route'] = $last_prior_route;
				}
			}

			$ab = q("select * from abook where abook_channel = %d and abook_xchan = '%s'",
				intval($channel['channel_id']),
				dbesc($arr['owner_xchan'])
			);
			$abook = (($ab) ? $ab[0] : null);

			if(intval($arr['item_deleted'])) {

				// remove_community_tag is a no-op if this isn't a community tag activity
				self::remove_community_tag($sender,$arr,$channel['channel_id']);

				// set these just in case we need to store a fresh copy of the deleted post.
				// This could happen if the delete got here before the original post did.

				$arr['aid'] = $channel['channel_account_id'];
				$arr['uid'] = $channel['channel_id'];

				$item_id = self::delete_imported_item($sender,$arr,$channel['channel_id'],$relay);
				$DR->update(($item_id) ? 'deleted' : 'delete_failed');
				$result[] = $DR->get();

				if($relay && $item_id) {
					logger('process_delivery: invoking relay');
					Master::Summon([ 'Notifier', 'relay', intval($item_id) ]);
					$DR->update('relayed');
					$result[] = $DR->get();
				}

				continue;
			}


			$r = q("select * from item where mid = '%s' and uid = %d limit 1",
				dbesc($arr['mid']),
				intval($channel['channel_id'])
			);
			if($r) {
				// We already have this post.
				$item_id = $r[0]['id'];

				if(intval($r[0]['item_deleted'])) {
					// It was deleted locally.
					$DR->update('update ignored');
					$result[] = $DR->get();

					continue;
				}
				// Maybe it has been edited?
				elseif($arr['edited'] > $r[0]['edited']) {
					$arr['id'] = $r[0]['id'];
					$arr['uid'] = $channel['channel_id'];
					if(($arr['mid'] == $arr['parent_mid']) && (! post_is_importable($arr,$abook))) {
						$DR->update('update ignored');
						$result[] = $DR->get();
					}
					else {
						$item_result = self::update_imported_item($sender,$arr,$r[0],$channel['channel_id'],$tag_delivery);
						$DR->update('updated');
						$result[] = $DR->get();
						if(! $relay)
							add_source_route($item_id,$sender);
					}
				}
				else {
					$DR->update('update ignored');
					$result[] = $DR->get();

					// We need this line to ensure wall-to-wall comments are relayed (by falling through to the relay bit),
					// and at the same time not relay any other relayable posts more than once, because to do so is very wasteful.
					if(! intval($r[0]['item_origin']))
						continue;
				}
			}
			else {
				$arr['aid'] = $channel['channel_account_id'];
				$arr['uid'] = $channel['channel_id'];

				// if it's a sourced post, call the post_local hooks as if it were
				// posted locally so that crosspost connectors will be triggered.

				if(check_item_source($arr['uid'], $arr)) {
					/**
					 * @hooks post_local
					 *   Called when an item has been posted on this machine via mod/item.php (also via API).
					 *   * \e array with an item
					 */
					call_hooks('post_local', $arr);
				}

				$item_id = 0;

				if(($arr['mid'] == $arr['parent_mid']) && (! post_is_importable($arr,$abook))) {
					$DR->update('post ignored');
					$result[] = $DR->get();
				}
				else {
					$item_result = item_store($arr);
					if($item_result['success']) {
						$item_id = $item_result['item_id'];
						$parr = [
								'item_id' => $item_id,
								'item' => $arr,
								'sender' => $sender,
								'channel' => $channel
						];
						/**
						 * @hooks activity_received
						 *   Called when an activity (post, comment, like, etc.) has been received from a zot source.
						 *   * \e int \b item_id
						 *   * \e array \b item
						 *   * \e array \b sender
						 *   * \e array \b channel
						 */
						call_hooks('activity_received', $parr);
						// don't add a source route if it's a relay or later recipients will get a route mismatch
						if(! $relay)
							add_source_route($item_id,$sender);
					}
					$DR->update(($item_id) ? 'posted' : 'storage failed: ' . $item_result['message']);
					$result[] = $DR->get();
				}
			}

			// preserve conversations with which you are involved from expiration

			$stored = (($item_result && $item_result['item']) ? $item_result['item'] : false);
			if((is_array($stored)) && ($stored['id'] != $stored['parent'])
				&& ($stored['author_xchan'] === $channel['channel_hash'] || $stored['author_xchan'] === $channel['channel_portable_id'])) {
				retain_item($stored['item']['parent']);
			}

			if($relay && $item_id) {
				logger('Invoking relay');
				Master::Summon([ 'Notifier', 'relay', intval($item_id) ]);
				$DR->addto_update('relayed');
				$result[] = $DR->get();
			}
		}

		if(! $deliveries)
			$result[] = array('', 'no recipients', '', $arr['mid']);

		logger('Local results: ' . print_r($result, true), LOGGER_DEBUG);

		return $result;
	}

	static public function fetch_conversation($channel,$mid) {

		// Use Zotfinger to create a signed request

		$a = Zotfinger::exec($mid,$channel);

		logger('received conversation: ' . print_r($a,true), LOGGER_DATA);

		if($a['data']['type'] !== 'OrderedCollection') {
			return;
		}

		if(! intval($a['data']['totalItems'])) {
			return;
		}

		$ret = [];

		foreach($a['data']['orderedItems'] as $activity) {

			$AS = new ActivityStreams($activity);
			if(! $AS->is_valid()) {
				logger('FOF Activity rejected: ' . print_r($activity,true));
				continue;
			}
			$arr = Activity::decode_note($AS);

			logger($AS->debug());


			$r = q("select hubloc_hash from hubloc where hubloc_id_url = '%s' and hubloc_network = 'zot6' limit 1",
				dbesc($AS->actor['id'])
			);

			if(! $r) {
				$y = import_author_xchan([ 'url' => $AS->actor['id'] ]);
				if($y) {
					$r = q("select hubloc_hash from hubloc where hubloc_id_url = '%s' and hubloc_network = 'zot6' limit 1",
						dbesc($AS->actor['id'])
					);
				}
				if(! $r) {
					logger('FOF Activity: no actor');
					continue;
				}
			}

			if($AS->obj['actor'] && $AS->obj['actor']['id'] && $AS->obj['actor']['id'] !== $AS->actor['id']) {
				$y = import_author_xchan([ 'url' => $AS->obj['actor']['id'] ]);
				if(! $y) {
					logger('FOF Activity: no object actor');
					continue;
				}
			}


			if($r) {
				$arr['author_xchan'] = $r[0]['hubloc_hash'];
			}

			$s = q("select hubloc_hash from hubloc where hubloc_id_url = '%s' and hubloc_network = 'zot6' limit 1",
				dbesc($a['signature']['signer'])
			);

			if($s) {
				$arr['owner_xchan'] = $s[0]['hubloc_hash'];
			}
			else {
				$arr['owner_xchan'] = $a['signature']['signer'];
			}


			/// @FIXME - spoofable
			if($AS->data['hubloc']) {
				$arr['item_verified'] = true;
			}
			if($AS->data['signed_data']) {
				IConfig::Set($arr,'activitystreams','signed_data',$AS->data['signed_data'],false);
			}

			logger('FOF Activity received: ' . print_r($arr,true), LOGGER_DATA, LOG_DEBUG);
			logger('FOF Activity recipient: ' . $channel['channel_portable_id'], LOGGER_DATA, LOG_DEBUG);

			$result = self::process_delivery($arr['owner_xchan'],$AS, $arr, [ $channel['channel_portable_id'] ],false,false,true);
			if ($result) {
				$ret = array_merge($ret, $result);
			}
		}

		return $ret;
	}


	/**
	 * @brief Remove community tag.
	 *
	 * @param string $sender
	 * @param array $arr an associative array
	 *   * \e int \b verb
	 *   * \e int \b obj_type
	 *   * \e int \b mid
	 * @param int $uid
	 * @return void
	 */
	static function remove_community_tag($sender, $arr, $uid) {

		if(! (activity_match($arr['verb'], ACTIVITY_TAG) && ($arr['obj_type'] == ACTIVITY_OBJ_TAGTERM)))
			return;

		logger('remove_community_tag: invoked');

		if(! get_pconfig($uid,'system','blocktags')) {
			logger('Permission denied.');
			return;
		}

		$r = q("select * from item where mid = '%s' and uid = %d limit 1",
			dbesc($arr['mid']),
			intval($uid)
		);
		if(! $r) {
			logger('No item');
			return;
		}

		if(($sender != $r[0]['owner_xchan']) && ($sender != $r[0]['author_xchan'])) {
			logger('Sender not authorised.');
			return;
		}

		$i = $r[0];

		if($i['target'])
			$i['target'] = json_decode($i['target'],true);
		if($i['object'])
			$i['object'] = json_decode($i['object'],true);

		if(! ($i['target'] && $i['object'])) {
			logger('No target/object');
			return;
		}

		$message_id = $i['target']['id'];

		$r = q("select id from item where mid = '%s' and uid = %d limit 1",
			dbesc($message_id),
			intval($uid)
		);
		if(! $r) {
			logger('No parent message');
			return;
		}

		q("delete from term where uid = %d and oid = %d and otype = %d and ttype in  ( %d, %d ) and term = '%s' and url = '%s'",
			intval($uid),
			intval($r[0]['id']),
			intval(TERM_OBJ_POST),
			intval(TERM_HASHTAG),
			intval(TERM_COMMUNITYTAG),
			dbesc($i['object']['title']),
			dbesc(get_rel_link($i['object']['link'],'alternate'))
		);
	}

	/**
	 * @brief Updates an imported item.
	 *
	 * @see item_store_update()
	 *
	 * @param string $sender
	 * @param array $item
	 * @param array $orig
	 * @param int $uid
	 * @param boolean $tag_delivery
	 * @return void|array
	 */
	static function update_imported_item($sender, $item, $orig, $uid, $tag_delivery) {

		// If this is a comment being updated, remove any privacy information
		// so that item_store_update will set it from the original.

		if($item['mid'] !== $item['parent_mid']) {
			unset($item['allow_cid']);
			unset($item['allow_gid']);
			unset($item['deny_cid']);
			unset($item['deny_gid']);
			unset($item['item_private']);
		}

		// we need the tag_delivery check for downstream flowing posts as the stored post
		// may have a different owner than the one being transmitted.

		if(($sender != $orig['owner_xchan'] && $sender != $orig['author_xchan']) && (! $tag_delivery)) {
			logger('sender is not owner or author');
			return;
		}


		$x = item_store_update($item);

		// If we're updating an event that we've saved locally, we store the item info first
		// because event_addtocal will parse the body to get the 'new' event details

		if($orig['resource_type'] === 'event') {
			$res = event_addtocal($orig['id'], $uid);
			if(! $res)
				logger('update event: failed');
		}

		if(! $x['item_id'])
			logger('update_imported_item: failed: ' . $x['message']);
		else
			logger('update_imported_item');

		return $x;
	}

	/**
	 * @brief Deletes an imported item.
	 *
	 * @param string $sender
	 *   * \e string \b hash a xchan_hash
	 * @param array $item
	 * @param int $uid
	 * @param boolean $relay
	 * @return boolean|int post_id
	 */

	static function delete_imported_item($sender, $item, $uid, $relay) {

		logger('invoked', LOGGER_DEBUG);

		$ownership_valid = false;
		$item_found = false;
		$post_id = 0;

		$r = q("select id, author_xchan, owner_xchan, source_xchan, item_deleted from item where ( author_xchan = '%s' or owner_xchan = '%s' or source_xchan = '%s' )
			and mid = '%s' and uid = %d limit 1",
			dbesc($sender),
			dbesc($sender),
			dbesc($sender),
			dbesc($item['mid']),
			intval($uid)
		);

		if($r) {
			if($r[0]['author_xchan'] === $sender || $r[0]['owner_xchan'] === $sender || $r[0]['source_xchan'] === $sender)
				$ownership_valid = true;

			$post_id = $r[0]['id'];
			$item_found = true;
		}
		else {

			// perhaps the item is still in transit and the delete notification got here before the actual item did. Store it with the deleted flag set.
			// item_store() won't try to deliver any notifications or start delivery chains if this flag is set.
			// This means we won't end up with potentially even more delivery threads trying to push this delete notification.
			// But this will ensure that if the (undeleted) original post comes in at a later date, we'll reject it because it will have an older timestamp.

			logger('delete received for non-existent item - storing item data.');

			if($item['author_xchan'] === $sender || $item['owner_xchan'] === $sender || $item['source_xchan'] === $sender) {
				$ownership_valid = true;
				$item_result = item_store($item);
				$post_id = $item_result['item_id'];
			}
		}

		if($ownership_valid === false) {
			logger('delete_imported_item: failed: ownership issue');
			return false;
		}

		if($item_found) {
			if(intval($r[0]['item_deleted'])) {
				logger('delete_imported_item: item was already deleted');
				if(! $relay)
					return false;

				// This is a bit hackish, but may have to suffice until the notification/delivery loop is optimised
				// a bit further. We're going to strip the ITEM_ORIGIN on this item if it's a comment, because
				// it was already deleted, and we're already relaying, and this ensures that no other process or
				// code path downstream can relay it again (causing a loop). Since it's already gone it's not coming
				// back, and we aren't going to (or shouldn't at any rate) delete it again in the future - so losing
				// this information from the metadata should have no other discernible impact.

				if (($r[0]['id'] != $r[0]['parent']) && intval($r[0]['item_origin'])) {
					q("update item set item_origin = 0 where id = %d and uid = %d",
						intval($r[0]['id']),
						intval($r[0]['uid'])
					);
				}
			}


			// Use phased deletion to set the deleted flag, call both tag_deliver and the notifier to notify downstream channels
			// and then clean up after ourselves with a cron job after several days to do the delete_item_lowlevel() (DROPITEM_PHASE2).

			drop_item($post_id, false, DROPITEM_PHASE1);
			tag_deliver($uid, $post_id);
		}

		return $post_id;
	}

	static function process_mail_delivery($sender, $arr, $deliveries) {

		$result = array();

		if($sender != $arr['from_xchan']) {
			logger('process_mail_delivery: sender is not mail author');
			return;
		}

		foreach($deliveries as $d) {

			$DR = new DReport(z_root(),$sender,$d,$arr['mid']);

			$r = q("select * from channel where channel_portable_id = '%s' limit 1",
				dbesc($d['hash'])
			);

			if(! $r) {
				$DR->update('recipient not found');
				$result[] = $DR->get();
				continue;
			}

			$channel = $r[0];
			$DR->set_name($channel['channel_name'] . ' <' . channel_reddress($channel) . '>');


			if(! perm_is_allowed($channel['channel_id'],$sender,'post_mail')) {

				/*
				 * Always allow somebody to reply if you initiated the conversation. It's anti-social
				 * and a bit rude to send a private message to somebody and block their ability to respond.
				 * If you are being harrassed and want to put an end to it, delete the conversation.
				 */

				$return = false;
				if($arr['parent_mid']) {
					$return = q("select * from mail where mid = '%s' and channel_id = %d limit 1",
						dbesc($arr['parent_mid']),
						intval($channel['channel_id'])
					);
				}
				if(! $return) {
					logger("permission denied for mail delivery {$channel['channel_id']}");
					$DR->update('permission denied');
					$result[] = $DR->get();
					continue;
				}
			}


			$r = q("select id from mail where mid = '%s' and channel_id = %d limit 1",
				dbesc($arr['mid']),
				intval($channel['channel_id'])
			);
			if($r) {
				if(intval($arr['mail_recalled'])) {
					$x = q("delete from mail where id = %d and channel_id = %d",
						intval($r[0]['id']),
						intval($channel['channel_id'])
					);
					$DR->update('mail recalled');
					$result[] = $DR->get();
					logger('mail_recalled');
				}
				else {
					$DR->update('duplicate mail received');
					$result[] = $DR->get();
					logger('duplicate mail received');
				}
				continue;
			}
			else {
				$arr['account_id'] = $channel['channel_account_id'];
				$arr['channel_id'] = $channel['channel_id'];
				$item_id = mail_store($arr);
				$DR->update('mail delivered');
				$result[] = $DR->get();
			}
		}

		return $result;
	}


	/**
	 * @brief Processes delivery of profile.
	 *
	 * @see import_directory_profile()
	 *
	 * @param string $sender 
	 * @param array $arr
	 * @param array $deliveries (unused)
	 * @return void
	 */
	static function process_profile_delivery($sender, $arr, $deliveries) {

		logger('process_profile_delivery', LOGGER_DEBUG);

		$r = q("select xchan_addr from xchan where xchan_hash = '%s' limit 1",
			dbesc($sender)
		);
		if($r) {
			Libzotdir::import_directory_profile($sender, $arr, $r[0]['xchan_addr'], UPDATE_FLAGS_UPDATED, 0);
		}
	}


	/**
	 * @brief
	 *
	 * @param string $sender 
	 * @param array $arr
	 * @param array $deliveries (unused) deliveries is irrelevant
	 * @return void
	 */
	static function process_location_delivery($sender, $arr, $deliveries) {

		// deliveries is irrelevant
		logger('process_location_delivery', LOGGER_DEBUG);

		$r = q("select * from xchan where xchan_hash = '%s' limit 1",
			dbesc($sender)
		);
		if($r) {
			$xchan = [ 'id' => $r[0]['xchan_guid'], 'id_sig' => $r[0]['xchan_guid_sig'],
				'hash' => $r[0]['xchan_hash'], 'public_key' => $r[0]['xchan_pubkey'] ];
		}
		if(array_key_exists('locations',$arr) && $arr['locations']) {
			$x = Libsync::sync_locations($xchan,$arr,true);
			logger('results: ' . print_r($x,true), LOGGER_DEBUG);
			if($x['changed']) {
				//$guid = random_string() . '@' . App::get_hostname();
				Libzotdir::update_modtime($sender,$r[0]['xchan_guid'],$arr['locations'][0]['address'],UPDATE_FLAGS_UPDATED);
			}
		}
	}

	/**
	 * @brief Checks for a moved channel and sets the channel_moved flag.
	 *
	 * Currently the effect of this flag is to turn the channel into 'read-only' mode.
	 * New content will not be processed (there was still an issue with blocking the
	 * ability to post comments as of 10-Mar-2016).
	 * We do not physically remove the channel at this time. The hub admin may choose
	 * to do so, but is encouraged to allow a grace period of several days in case there
	 * are any issues migrating content. This packet will generally be received by the
	 * original site when the basic channel import has been processed.
	 *
	 * This will only be executed on the old location
	 * if a new location is reported and there is only one location record.
	 * The rest of the hubloc syncronisation will be handled within
	 * sync_locations
	 *
	 * @param string $sender_hash A channel hash
	 * @param array $locations
	 * @return void
	 */
	static function check_location_move($sender_hash, $locations) {

		if(! $locations)
			return;

		if(count($locations) != 1)
			return;

		$loc = $locations[0];

		$r = q("select * from channel where channel_portable_id = '%s' limit 1",
			dbesc($sender_hash)
		);

		if(! $r)
			return;

		if($loc['url'] !== z_root()) {
			$x = q("update channel set channel_moved = '%s' where channel_portable_id = '%s' limit 1",
				dbesc($loc['url']),
				dbesc($sender_hash)
			);

			// federation plugins may wish to notify connections
			// of the move on singleton networks

			$arr = [
				'channel' => $r[0],
				'locations' => $locations
			];
			/**
			 * @hooks location_move
			 *   Called when a new location has been provided to a UNO channel (indicating a move rather than a clone).
			 *   * \e array \b channel
			 *   * \e array \b locations
			 */
			call_hooks('location_move', $arr);
		}
	}


	/**
	 * @brief Returns an array with all known distinct hubs for this channel.
	 *
	 * @see self::get_hublocs()
	 * @param array $channel an associative array which must contain
	 *  * \e string \b channel_hash the hash of the channel
	 * @return array an array with associative arrays
	 */
	static function encode_locations($channel) {
		$ret = [];

		$x = self::get_hublocs($channel['channel_portable_id']);

		if($x && count($x)) {
			foreach($x as $hub) {

				// if this is a local channel that has been deleted, the hubloc is no good - make sure it is marked deleted
				// so that nobody tries to use it.

				if(intval($channel['channel_removed']) && $hub['hubloc_url'] === z_root())
					$hub['hubloc_deleted'] = 1;


				$z = [
					'host'     => $hub['hubloc_host'],
					'address'  => $hub['hubloc_addr'],
					'id_url'   => $hub['hubloc_id_url'],
					'primary'  => (intval($hub['hubloc_primary']) ? true : false),
					'url'      => $hub['hubloc_url'],
					'url_sig'  => $hub['hubloc_url_sig'],
					'site_id'  => $hub['hubloc_site_id'],
					'callback' => $hub['hubloc_url'] . '/zot',
					'sitekey'  => $hub['hubloc_sitekey'],
					'deleted'  => (intval($hub['hubloc_deleted']) ? true : false)
				];

				// version compatibility tweaks

				if(! strpos($z['url_sig'],'.')) {
					$z['url_sig'] = 'sha256.' . $z['url_sig'];
				}

				if(! $z['id_url']) {
					$z['id_url'] = $z['url'] . '/channel/' . substr($z['address'],0,strpos($z['address'],'@'));
				}
				if(! $z['site_id']) {
					$z['site_id'] = Libzot::make_xchan_hash($z['url'],$z['sitekey']);
				}

				$ret[] = $z;
			}
		}

		return $ret;
	}


	/**
	 * @brief
	 *
	 * @param array $arr
	 * @return boolean true if updated or inserted
	 */
	static function import_site($arr) {

		if( (! is_array($arr)) || (! $arr['url']) || (! $arr['site_sig']))
			return false;

		if(! self::verify($arr['url'], $arr['site_sig'], $arr['sitekey'])) {
			logger('Bad url_sig');
			return false;
		}

		$update = false;
		$exists = false;

		$r = q("select * from site where site_url = '%s' limit 1",
			dbesc($arr['url'])
		);
		if($r) {
			$exists = true;
			$siterecord = $r[0];
		}

		$site_directory = 0;
		if($arr['directory_mode'] == 'normal')
			$site_directory = DIRECTORY_MODE_NORMAL;
		if($arr['directory_mode'] == 'primary')
			$site_directory = DIRECTORY_MODE_PRIMARY;
		if($arr['directory_mode'] == 'secondary')
			$site_directory = DIRECTORY_MODE_SECONDARY;
		if($arr['directory_mode'] == 'standalone')
			$site_directory = DIRECTORY_MODE_STANDALONE;

		$register_policy = 0;
		if($arr['register_policy'] == 'closed')
			$register_policy = REGISTER_CLOSED;
		if($arr['register_policy'] == 'open')
			$register_policy = REGISTER_OPEN;
		if($arr['register_policy'] == 'approve')
			$register_policy = REGISTER_APPROVE;

		$access_policy = 0;
		if(array_key_exists('access_policy',$arr)) {
			if($arr['access_policy'] === 'private')
				$access_policy = ACCESS_PRIVATE;
			if($arr['access_policy'] === 'paid')
				$access_policy = ACCESS_PAID;
			if($arr['access_policy'] === 'free')
				$access_policy = ACCESS_FREE;
			if($arr['access_policy'] === 'tiered')
				$access_policy = ACCESS_TIERED;
		}

		// don't let insecure sites register as public hubs

		if(strpos($arr['url'],'https://') === false)
			$access_policy = ACCESS_PRIVATE;

		if($access_policy != ACCESS_PRIVATE) {
			$x = z_fetch_url($arr['url'] . '/siteinfo.json');
			if(! $x['success'])
				$access_policy = ACCESS_PRIVATE;
		}

		$directory_url = htmlspecialchars($arr['directory_url'],ENT_COMPAT,'UTF-8',false);
		$url = htmlspecialchars(strtolower($arr['url']),ENT_COMPAT,'UTF-8',false);
		$sellpage = htmlspecialchars($arr['sellpage'],ENT_COMPAT,'UTF-8',false);
		$site_location = htmlspecialchars($arr['location'],ENT_COMPAT,'UTF-8',false);
		$site_realm = htmlspecialchars($arr['realm'],ENT_COMPAT,'UTF-8',false);
		$site_project = htmlspecialchars($arr['project'],ENT_COMPAT,'UTF-8',false);
		$site_crypto = ((array_key_exists('encryption',$arr) && is_array($arr['encryption'])) ? htmlspecialchars(implode(',',$arr['encryption']),ENT_COMPAT,'UTF-8',false) : '');
		$site_version = ((array_key_exists('version',$arr)) ? htmlspecialchars($arr['version'],ENT_COMPAT,'UTF-8',false) : '');

		// You can have one and only one primary directory per realm.
		// Downgrade any others claiming to be primary. As they have
		// flubbed up this badly already, don't let them be directory servers at all.

		if(($site_directory === DIRECTORY_MODE_PRIMARY)
			&& ($site_realm === get_directory_realm())
			&& ($arr['url'] != get_directory_primary())) {
			$site_directory = DIRECTORY_MODE_NORMAL;
		}

		$site_flags = $site_directory;

		if(array_key_exists('zot',$arr)) {
			set_sconfig($arr['url'],'system','zot_version',$arr['zot']);
		}

		if($exists) {
			if(($siterecord['site_flags'] != $site_flags)
				|| ($siterecord['site_access'] != $access_policy)
				|| ($siterecord['site_directory'] != $directory_url)
				|| ($siterecord['site_sellpage'] != $sellpage)
				|| ($siterecord['site_location'] != $site_location)
				|| ($siterecord['site_register'] != $register_policy)
				|| ($siterecord['site_project'] != $site_project)
				|| ($siterecord['site_realm'] != $site_realm)
				|| ($siterecord['site_crypto'] != $site_crypto)
				|| ($siterecord['site_version'] != $site_version)   ) {

				$update = true;

	//			logger('import_site: input: ' . print_r($arr,true));
	//			logger('import_site: stored: ' . print_r($siterecord,true));

				$r = q("update site set site_dead = 0, site_location = '%s', site_flags = %d, site_access = %d, site_directory = '%s', site_register = %d, site_update = '%s', site_sellpage = '%s', site_realm = '%s', site_type = %d, site_project = '%s', site_version = '%s', site_crypto = '%s'
					where site_url = '%s'",
					dbesc($site_location),
					intval($site_flags),
					intval($access_policy),
					dbesc($directory_url),
					intval($register_policy),
					dbesc(datetime_convert()),
					dbesc($sellpage),
					dbesc($site_realm),
					intval(SITE_TYPE_ZOT),
					dbesc($site_project),
					dbesc($site_version),
					dbesc($site_crypto),
					dbesc($url)
				);
				if(! $r) {
					logger('Update failed. ' . print_r($arr,true));
				}
			}
			else {
				// update the timestamp to indicate we communicated with this site
				q("update site set site_dead = 0, site_update = '%s' where site_url = '%s'",
					dbesc(datetime_convert()),
					dbesc($url)
				);
			}
		}
		else {
			$update = true;

			$r = site_store_lowlevel(
				[
					'site_location'  => $site_location,
					'site_url'       => $url,
					'site_access'    => intval($access_policy),
					'site_flags'     => intval($site_flags),
					'site_update'    => datetime_convert(),
					'site_directory' => $directory_url,
					'site_register'  => intval($register_policy),
					'site_sellpage'  => $sellpage,
					'site_realm'     => $site_realm,
					'site_type'      => intval(SITE_TYPE_ZOT),
					'site_project'   => $site_project,
					'site_version'   => $site_version,
					'site_crypto'    => $site_crypto
				]
			);

			if(! $r) {
				logger('Record create failed. ' . print_r($arr,true));
			}
		}

		return $update;
	}

	/**
	 * @brief Returns path to /rpost
	 *
	 * @todo We probably should make rpost discoverable.
	 *
	 * @param array $observer
	 *   * \e string \b xchan_url
	 * @return string
	 */
	static function get_rpost_path($observer) {
		if(! $observer)
			return '';

		$parsed = parse_url($observer['xchan_url']);

		return $parsed['scheme'] . '://' . $parsed['host'] . (($parsed['port']) ? ':' . $parsed['port'] : '') . '/rpost?f=';
	}

	/**
	 * @brief
	 *
	 * @param array $x
	 * @return boolean|string return false or a hash
	 */

	static function import_author_zot($x) {

		// Check that we have both a hubloc and xchan record - as occasionally storage calls will fail and
		// we may only end up with one; which results in posts with no author name or photo and are a bit
		// of a hassle to repair. If either or both are missing, do a full discovery probe.

		if(! array_key_exists('id',$x)) {
			return import_author_activitypub($x);
		}

		$hash = self::make_xchan_hash($x['id'],$x['key']);

		$desturl = $x['url'];

		$r1 = q("select hubloc_url, hubloc_updated, site_dead from hubloc left join site on
			hubloc_url = site_url where hubloc_guid = '%s' and hubloc_guid_sig = '%s' and hubloc_primary = 1 limit 1",
			dbesc($x['id']),
			dbesc($x['id_sig'])
		);

		$r2 = q("select xchan_hash from xchan where xchan_guid = '%s' and xchan_guid_sig = '%s' limit 1",
			dbesc($x['id']),
			dbesc($x['id_sig'])
		);

		$site_dead = false;

		if($r1 && intval($r1[0]['site_dead'])) {
			$site_dead = true;
		}

		// We have valid and somewhat fresh information. Always true if it is our own site.

		if($r1 && $r2 && ( $r1[0]['hubloc_updated'] > datetime_convert('UTC','UTC','now - 1 week') || $r1[0]['hubloc_url'] === z_root() ) ) {
			logger('in cache', LOGGER_DEBUG);
			return $hash;
		}

		logger('not in cache or cache stale - probing: ' . print_r($x,true), LOGGER_DEBUG,LOG_INFO);

		// The primary hub may be dead. Try to find another one associated with this identity that is
		// still alive. If we find one, use that url for the discovery/refresh probe. Otherwise, the dead site
		// is all we have and there is no point probing it. Just return the hash indicating we have a
		// cached entry and the identity is valid. It's just unreachable until they bring back their
		// server from the grave or create another clone elsewhere.

		if($site_dead) {
			logger('dead site - ignoring', LOGGER_DEBUG,LOG_INFO);

			$r = q("select hubloc_id_url from hubloc left join site on hubloc_url = site_url
				where hubloc_hash = '%s' and site_dead = 0",
				dbesc($hash)
			);
			if($r) {
				logger('found another site that is not dead: ' . $r[0]['hubloc_url'], LOGGER_DEBUG,LOG_INFO);
				$desturl = $r[0]['hubloc_url'];
			}
			else {
				return $hash;
			}
		}

		$them = [ 'hubloc_id_url' => $desturl ];
		if(self::refresh($them))
			return $hash;

		return false;
	}

	static function zotinfo($arr) {

		logger('arr: ' . print_r($arr,true));


		$ret = [];

		$zhash     = ((x($arr,'guid_hash'))  ? $arr['guid_hash']   : '');
		$zguid     = ((x($arr,'guid'))       ? $arr['guid']        : '');
		$zguid_sig = ((x($arr,'guid_sig'))   ? $arr['guid_sig']    : '');
		$zaddr     = ((x($arr,'address'))    ? $arr['address']     : '');
		$ztarget   = ((x($arr,'target_url')) ? $arr['target_url']  : '');
		$zsig      = ((x($arr,'target_sig')) ? $arr['target_sig']  : '');
		$zkey      = ((x($arr,'key'))        ? $arr['key']         : '');
		$mindate   = ((x($arr,'mindate'))    ? $arr['mindate']     : '');
		$token     = ((x($arr,'token'))      ? $arr['token']   : '');
		$feed      = ((x($arr,'feed'))       ? intval($arr['feed']) : 0);

		if($ztarget) {
			$t = q("select * from hubloc where hubloc_id_url = '%s' and hubloc_network = 'zot6' limit 1",
				dbesc($ztarget)
			);
			if($t) {

				$ztarget_hash = $t[0]['hubloc_hash'];

			}
			else {

				// should probably perform discovery of the requestor (target) but if they actually had
				// permissions we would know about them and we only want to know who they are to
				// enumerate their specific permissions

				$ztarget_hash = EMPTY_STR;
			}
		}


		$r = null;

		if(strlen($zhash)) {
			$r = q("select channel.*, xchan.* from channel left join xchan on channel_portable_id = xchan_hash
				where channel_portable_id = '%s' limit 1",
				dbesc($zhash)
			);
		}
		elseif(strlen($zguid) && strlen($zguid_sig)) {
			$r = q("select channel.*, xchan.* from channel left join xchan on channel_portable_id = xchan_hash
				where channel_guid = '%s' and channel_guid_sig = '%s' limit 1",
				dbesc($zguid),
				dbesc($zguid_sig)
			);
		}
		elseif(strlen($zaddr)) {
			if(strpos($zaddr,'[system]') === false) {       /* normal address lookup */
				$r = q("select channel.*, xchan.* from channel left join xchan on channel_portable_id = xchan_hash
					where ( channel_address = '%s' or xchan_addr = '%s' ) limit 1",
					dbesc($zaddr),
					dbesc($zaddr)
				);
			}

			else {

				/**
				 * The special address '[system]' will return a system channel if one has been defined,
				 * Or the first valid channel we find if there are no system channels.
				 *
				 * This is used by magic-auth if we have no prior communications with this site - and
				 * returns an identity on this site which we can use to create a valid hub record so that
				 * we can exchange signed messages. The precise identity is irrelevant. It's the hub
				 * information that we really need at the other end - and this will return it.
				 *
				 */

				$r = q("select channel.*, xchan.* from channel left join xchan on channel_portable_id = xchan_hash
					where channel_system = 1 order by channel_id limit 1");
				if(! $r) {
					$r = q("select channel.*, xchan.* from channel left join xchan on channel_portable_id = xchan_hash
						where channel_removed = 0 order by channel_id limit 1");
				}
			}
		}
		else {
			$ret['message'] = 'Invalid request';
			return($ret);
		}

		if(! $r) {
			$ret['message'] = 'Item not found.';
			return($ret);
		}

		$e = $r[0];

		$id = $e['channel_id'];

		$sys_channel     = (intval($e['channel_system'])   ? true : false);
		$special_channel = (($e['channel_pageflags'] & PAGE_PREMIUM)  ? true : false);
		$adult_channel   = (($e['channel_pageflags'] & PAGE_ADULT)    ? true : false);
		$censored        = (($e['channel_pageflags'] & PAGE_CENSORED) ? true : false);
		$searchable      = (($e['channel_pageflags'] & PAGE_HIDDEN)   ? false : true);
		$deleted         = (intval($e['xchan_deleted']) ? true : false);

		if($deleted || $censored || $sys_channel)
			$searchable = false;

		$public_forum = false;

		$role = get_pconfig($e['channel_id'],'system','permissions_role');
		if($role === 'forum' || $role === 'repository') {
			$public_forum = true;
		}
		else {
			// check if it has characteristics of a public forum based on custom permissions.
			$m = Permissions::FilledAutoperms($e['channel_id']);
			if($m) {
				foreach($m as $k => $v) {
					if($k == 'tag_deliver' && intval($v) == 1)
						$ch ++;
					if($k == 'send_stream' && intval($v) == 0)
						$ch ++;
				}
				if($ch == 2)
					$public_forum = true;
			}
		}


		//  This is for birthdays and keywords, but must check access permissions
		$p = q("select * from profile where uid = %d and is_default = 1",
			intval($e['channel_id'])
		);

		$profile = array();

		if($p) {

			if(! intval($p[0]['publish']))
				$searchable = false;

			$profile['description']   = $p[0]['pdesc'];
			$profile['birthday']      = $p[0]['dob'];
			if(($profile['birthday'] != '0000-00-00') && (($bd = z_birthday($p[0]['dob'],$e['channel_timezone'])) !== ''))
				$profile['next_birthday'] = $bd;

			if($age = age($p[0]['dob'],$e['channel_timezone'],''))
				$profile['age'] = $age;
			$profile['gender']        = $p[0]['gender'];
			$profile['marital']       = $p[0]['marital'];
			$profile['sexual']        = $p[0]['sexual'];
			$profile['locale']        = $p[0]['locality'];
			$profile['region']        = $p[0]['region'];
			$profile['postcode']      = $p[0]['postal_code'];
			$profile['country']       = $p[0]['country_name'];
			$profile['about']         = $p[0]['about'];
			$profile['homepage']      = $p[0]['homepage'];
			$profile['hometown']      = $p[0]['hometown'];

			if($p[0]['keywords']) {
				$tags = array();
				$k = explode(' ',$p[0]['keywords']);
				if($k) {
					foreach($k as $kk) {
						if(trim($kk," \t\n\r\0\x0B,")) {
							$tags[] = trim($kk," \t\n\r\0\x0B,");
						}
					}
				}
				if($tags)
					$profile['keywords'] = $tags;
			}
		}

		// Communication details

		$ret['id']             = $e['xchan_guid'];
		$ret['id_sig']         = self::sign($e['xchan_guid'], $e['channel_prvkey']);

		$ret['primary_location'] = [
			'address'            =>  $e['xchan_addr'],
			'url'                =>  $e['xchan_url'],
			'connections_url'    =>  $e['xchan_connurl'],
			'follow_url'         =>  $e['xchan_follow'],
		];

		$ret['public_key']     = $e['xchan_pubkey'];
		$ret['username']       = $e['channel_address'];
		$ret['name']           = $e['xchan_name'];
		$ret['name_updated']   = $e['xchan_name_date'];
		$ret['photo'] = [
			'url'     => $e['xchan_photo_l'],
			'type'    => $e['xchan_photo_mimetype'],
			'updated' => $e['xchan_photo_date']
		];

		$ret['channel_role'] = get_pconfig($e['channel_id'],'system','permissions_role','custom');
		$ret['protocols']    = [ 'zot', 'zot6' ];
		$ret['searchable']     = $searchable;
		$ret['adult_content']  = $adult_channel;
		$ret['public_forum']   = $public_forum;

		$ret['comments']       = map_scope(PermissionLimits::Get($e['channel_id'],'post_comments'));
		$ret['mail']           = map_scope(PermissionLimits::Get($e['channel_id'],'post_mail'));

		if($deleted)
			$ret['deleted']        = $deleted;

		if(intval($e['channel_removed']))
			$ret['deleted_locally'] = true;

		// premium or other channel desiring some contact with potential followers before connecting.
		// This is a template - %s will be replaced with the follow_url we discover for the return channel.

		if($special_channel) {
			$ret['connect_url'] = (($e['xchan_connpage']) ? $e['xchan_connpage'] : z_root() . '/connect/' . $e['channel_address']);
		}

		// This is a template for our follow url, %s will be replaced with a webbie
		if(! $ret['follow_url'])
			$ret['follow_url'] = z_root() . '/follow?f=&url=%s';

		$permissions = get_all_perms($e['channel_id'],$ztarget_hash,false,false);

		if($ztarget_hash) {
			$permissions['connected'] = false;
			$b = q("select * from abook where abook_xchan = '%s' and abook_channel = %d limit 1",
				dbesc($ztarget_hash),
				intval($e['channel_id'])
			);
			if($b)
				$permissions['connected'] = true;
		}

		if($permissions['view_profile'])
			$ret['profile']  = $profile;


		$concise_perms = [];
		if($permissions) {
			foreach($permissions as $k => $v) {
				if($v) {
					$concise_perms[] = $k;
				}
			}
			$permissions = implode(',',$concise_perms);
		}

		$ret['permissions'] = $permissions;
		$ret['permissions_for']         = $ztarget;


		// array of (verified) hubs this channel uses

		$x = self::encode_locations($e);
		if($x)
			$ret['locations'] = $x;

		$ret['site'] = self::site_info();
		/**
		 * @hooks zotinfo
		 *   Hook to manipulate the zotinfo array before it is returned.
		 */
		call_hooks('zotinfo', $ret);

		return $ret;
	}

	/**
	 * @brief Get siteinfo.
	 *
	 * @return array
	 */
	static function site_info() {

		$signing_key = get_config('system','prvkey');
		$sig_method  = get_config('system','signature_algorithm','sha256');

		$ret = [];
		$ret['site'] = [];
		$ret['site']['url'] = z_root();
		$ret['site']['site_sig'] = self::sign(z_root(), $signing_key);
		$ret['site']['post'] = z_root() . '/zot';
		$ret['site']['openWebAuth']  = z_root() . '/owa';
		$ret['site']['authRedirect'] = z_root() . '/magic';
		$ret['site']['sitekey'] = get_config('system','pubkey');

		$dirmode = get_config('system','directory_mode');
		if(($dirmode === false) || ($dirmode == DIRECTORY_MODE_NORMAL))
			$ret['site']['directory_mode'] = 'normal';

		if($dirmode == DIRECTORY_MODE_PRIMARY)
			$ret['site']['directory_mode'] = 'primary';
		elseif($dirmode == DIRECTORY_MODE_SECONDARY)
			$ret['site']['directory_mode'] = 'secondary';
		elseif($dirmode == DIRECTORY_MODE_STANDALONE)
			$ret['site']['directory_mode'] = 'standalone';
		if($dirmode != DIRECTORY_MODE_NORMAL)
			$ret['site']['directory_url'] = z_root() . '/dirsearch';


		$ret['site']['encryption'] = crypto_methods();
		$ret['site']['zot'] = System::get_zot_revision();

		// hide detailed site information if you're off the grid

		if($dirmode != DIRECTORY_MODE_STANDALONE) {

			$register_policy = intval(get_config('system','register_policy'));

			if($register_policy == REGISTER_CLOSED)
				$ret['site']['register_policy'] = 'closed';
			if($register_policy == REGISTER_APPROVE)
				$ret['site']['register_policy'] = 'approve';
			if($register_policy == REGISTER_OPEN)
				$ret['site']['register_policy'] = 'open';


			$access_policy = intval(get_config('system','access_policy'));

			if($access_policy == ACCESS_PRIVATE)
				$ret['site']['access_policy'] = 'private';
			if($access_policy == ACCESS_PAID)
				$ret['site']['access_policy'] = 'paid';
			if($access_policy == ACCESS_FREE)
				$ret['site']['access_policy'] = 'free';
			if($access_policy == ACCESS_TIERED)
				$ret['site']['access_policy'] = 'tiered';

			$ret['site']['accounts'] = account_total();

			require_once('include/channel.php');
			$ret['site']['channels'] = channel_total();

			$ret['site']['admin'] = get_config('system','admin_email');

			$visible_plugins = array();
			if(is_array(\App::$plugins) && count(\App::$plugins)) {
				$r = q("select * from addon where hidden = 0");
				if($r)
					foreach($r as $rr)
						$visible_plugins[] = $rr['aname'];
			}

			$ret['site']['plugins']    = $visible_plugins;
			$ret['site']['sitehash']   = get_config('system','location_hash');
			$ret['site']['sitename']   = get_config('system','sitename');
			$ret['site']['sellpage']   = get_config('system','sellpage');
			$ret['site']['location']   = get_config('system','site_location');
			$ret['site']['realm']      = get_directory_realm();
			$ret['site']['project']    = System::get_platform_name();
			$ret['site']['version']    = System::get_project_version();

		}

		return $ret['site'];
	}

	/**
	 * @brief
	 *
	 * @param array $hub
	 * @param string $site_id (optional, default empty)
	 *
	 * @return string hubloc_url
	 */
	static function update_hub_connected($hub, $site_id = '') {

		if ($site_id) {

			/*
			 * This hub has now been proven to be valid.
			 * Any hub with the same URL and a different sitekey cannot be valid.
			 * Get rid of them (mark them deleted). There's a good chance they were re-installs.
			 */

			q("update hubloc set hubloc_deleted = 1, hubloc_error = 1 where hubloc_hash = '%s' and hubloc_url = '%s' and hubloc_site_id != '%s' ",
				dbesc($hub['hubloc_hash']),
				dbesc($hub['hubloc_url']),
				dbesc($site_id)
			);

		}
		else {
			$site_id = $hub['hubloc_site_id'];
		}

		// $sender['sitekey'] is a new addition to the protocol to distinguish
		// hublocs coming from re-installed sites. Older sites will not provide
		// this field and we have to still mark them valid, since we can't tell
		// if this hubloc has the same sitekey as the packet we received.
		// Update our DB to show when we last communicated successfully with this hub
		// This will allow us to prune dead hubs from using up resources

		$t = datetime_convert('UTC', 'UTC', 'now - 15 minutes');

		$r = q("update hubloc set hubloc_connected = '%s' where hubloc_id = %d and hubloc_site_id = '%s' and hubloc_connected < '%s' ",
			dbesc(datetime_convert()),
			intval($hub['hubloc_id']),
			dbesc($site_id),
			dbesc($t)
		);

		// a dead hub came back to life - reset any tombstones we might have

		if (intval($hub['hubloc_error'])) {
			q("update hubloc set hubloc_error = 0 where hubloc_id = %d and hubloc_site_id = '%s' ",
				intval($hub['hubloc_id']),
				dbesc($site_id)
			);
			if (intval($hub['hubloc_orphancheck'])) {
				q("update hubloc set hubloc_orphancheck = 0 where hubloc_id = %d and hubloc_site_id = '%s' ",
					intval($hub['hubloc_id']),
					dbesc($site_id)
				);
			}
			q("update xchan set xchan_orphan = 0 where xchan_orphan = 1 and xchan_hash = '%s'",
				dbesc($hub['hubloc_hash'])
			);
		}

		return $hub['hubloc_url'];
	}

	/**
	 * @brief
	 *
	 * @param string $data
	 * @param string $key
	 * @param string $alg (optional) default 'sha256'
	 * @return string
	 */
	static function sign($data,$key,$alg = 'sha256') {
		if(! $key)
			return 'no key';

		$sig = '';
		openssl_sign($data,$sig,$key,$alg);

		return $alg . '.' . base64url_encode($sig);
	}

	static function verify($data,$sig,$key) {

		$verify = 0;

		$x = explode('.',$sig,2);

		if ($key && count($x) === 2) {
			$alg = $x[0];
			$signature = base64url_decode($x[1]);

			$verify = @openssl_verify($data,$signature,$key,$alg);

			if ($verify === (-1)) {
				while ($msg = openssl_error_string()) {
					logger('openssl_verify: ' . $msg,LOGGER_NORMAL,LOG_ERR);
				}
				btlogger('openssl_verify: key: ' . $key, LOGGER_DEBUG, LOG_ERR);
			}
		}
		return(($verify > 0) ? true : false);
	}

	/**
	 * @brief
	 *
	 * @return boolean
	 */
	static function is_zot_request() {
		$x = getBestSupportedMimeType([ 'application/x-zot+json' ]);

		return(($x) ? true : false);
	}

}