streams/Code/Lib/ActivityStreams.php

<?php

namespace Code\Lib;

use Code\Web\HTTPSig;
    
/**
 * @brief ActivityStreams class.
 *
 * Parses an ActivityStream JSON string.
 */
class ActivityStreams
{

    public $raw = null;
    public $data = null;
    public $meta = null;
    public $hub = null;
    public $client = false;
    public $valid = false;
    public $deleted = false;
    public $id = '';
    public $parent_id = '';
    public $type = '';
    public $actor = null;
    public $obj = null;
    public $tgt = null;
    public $replyto = null;
    public $origin = null;
    public $owner = null;
    public $signer = null;
    public $ldsig = null;
    public $sigok = false;
    public $recips = null;
    public $raw_recips = null;
    public $implied_create = false;

    /**
     * @brief Constructor for ActivityStreams.
     *
     * Takes a JSON string or previously decode activity array as parameter,
     * decodes it and sets up this object/activity, fetching any required attributes
     * which were only referenced by @id/URI.
     *
     * @param string $string
     */
    public function __construct($string, $hub = null, $client = null)
    {

        $this->raw = $string;
        $this->hub = $hub;
        $this->client = $client;
    
        if (is_array($string)) {
            $this->data = $string;
            $this->raw = json_encode($string, JSON_UNESCAPED_SLASHES);
        } else {
            $this->data = json_decode($string, true);
        }

        if ($this->data) {
            // This indicates only that we have sucessfully decoded JSON.
            $this->valid = true;

            // Special handling for Mastodon "delete actor" activities which will often fail to verify
            // because the key cannot be fetched. We will catch this condition elsewhere.

            if (array_key_exists('type', $this->data) && array_key_exists('actor', $this->data) && array_key_exists('object', $this->data)) {
                if ($this->data['type'] === 'Delete' && $this->data['actor'] === $this->data['object']) {
                    $this->deleted = $this->data['actor'];
                    $this->valid = false;
                }
            }

            // verify and unpack JSalmon signature if present
            // This will only be the case for Zot6 packets

            if ($this->valid && is_array($this->data) && array_key_exists('signed', $this->data)) {
                $ret = JSalmon::verify($this->data);
                $tmp = JSalmon::unpack($this->data['data']);
                if ($ret && $ret['success'] && $tmp) {
                    if ($ret['signer']) {
                        logger('Unpacked: ' . json_encode($tmp, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT), LOGGER_DATA, LOG_DEBUG);
                        $saved = json_encode($this->data, JSON_UNESCAPED_SLASHES);
                        $this->data = $tmp;
                        $this->meta['signer'] = $ret['signer'];
                        $this->meta['signed_data'] = $saved;
                        if ($ret['hubloc']) {
                            $this->meta['hubloc'] = $ret['hubloc'];
                        }
                    }
                }
                else {
                    logger('JSalmon verification failure.');
                    $this->valid = false;
                }                
            }
        }

        // Attempt to assemble an Activity from what we were given.

        if ($this->is_valid()) {
            $this->id = $this->get_property_obj('id');
            $this->type = $this->get_primary_type();
            $this->actor = $this->get_actor('actor', '', '');
            $this->obj = $this->get_compound_property('object');
            $this->tgt = $this->get_compound_property('target');
            $this->origin = $this->get_compound_property('origin');
            $this->recips = $this->collect_recips();
            $this->replyto = $this->get_property_obj('replyTo');

            $this->ldsig = $this->get_compound_property('signature');
            if ($this->ldsig) {
                $this->signer = $this->get_compound_property('creator', $this->ldsig);
                if (
                    $this->signer && is_array($this->signer) && array_key_exists('publicKey', $this->signer)
                    && is_array($this->signer['publicKey']) && $this->signer['publicKey']['publicKeyPem']
                ) {
                    $this->sigok = LDSignatures::verify($this->data, $this->signer['publicKey']['publicKeyPem']);
                }
            }

            // Implied create activity required by C2S specification if no object is present

            if (!$this->obj) {
                if (!$client) {
                    $this->implied_create = true;
                }
                $this->obj = $this->data;
                $this->type = 'Create';
                if (!$this->actor) {
                    $this->actor = $this->get_actor('attributedTo', $this->obj);
                }
            }

            // fetch recursive or embedded activities

            if ($this->obj && is_array($this->obj) && array_key_exists('object', $this->obj)) {
                $this->obj['object'] = $this->get_compound_property($this->obj['object']);
            }

            // Enumerate and store actors in referenced objects

            if ($this->obj && is_array($this->obj) && isset($this->obj['actor'])) {
                $this->obj['actor'] = $this->get_actor('actor', $this->obj);
            }
            if ($this->tgt && is_array($this->tgt) && isset($this->tgt['actor'])) {
                $this->tgt['actor'] = $this->get_actor('actor', $this->tgt);
            }

            // Determine if this is a followup or response activity

            $this->parent_id = $this->get_property_obj('inReplyTo');

            if ((!$this->parent_id) && is_array($this->obj)) {
                $this->parent_id = $this->obj['inReplyTo'];
            }
            if ((!$this->parent_id) && is_array($this->obj)) {
                $this->parent_id = $this->obj['id'];
            }
        }
    }

    /**
     * @brief Return if instantiated ActivityStream is valid.
     *
     * @return bool Return true if the JSON string could be decoded.
     */

    public function is_valid()
    {
        return $this->valid;
    }

    public function set_recips($arr)
    {
        $this->saved_recips = $arr;
    }

    /**
     * @brief Collects all recipients.
     *
     * @param string $base
     * @param string $namespace (optional) default empty
     * @return array
     */
    public function collect_recips($base = '', $namespace = '')
    {
        $x = [];

        $fields = ['to', 'cc', 'bto', 'bcc', 'audience'];
        foreach ($fields as $f) {
            // don't expand these yet
            $y = $this->get_property_obj($f, $base, $namespace);
            if ($y) {
                if (!is_array($this->raw_recips)) {
                    $this->raw_recips = [];
                }
                if (!is_array($y)) {
                    $y = [$y];
                }
                $this->raw_recips[$f] = $y;
                $x = array_merge($x, $y);
            }
        }

// not yet ready for prime time
//      $x = $this->expand($x,$base,$namespace);
        return $x;
    }

    public function expand($arr, $base = '', $namespace = '')
    {
        $ret = [];

        // right now use a hardwired recursion depth of 5

        for ($z = 0; $z < 5; $z++) {
            if (is_array($arr) && $arr) {
                foreach ($arr as $a) {
                    if (is_array($a)) {
                        $ret[] = $a;
                    } else {
                        $x = $this->get_compound_property($a, $base, $namespace);
                        if ($x) {
                            $ret = array_merge($ret, $x);
                        }
                    }
                }
            }
        }

        /// @fixme de-duplicate

        return $ret;
    }

    /**
     * @brief
     *
     * @param array $base
     * @param string $namespace if not set return empty string
     * @return string|NULL
     */

    public function get_namespace($base, $namespace)
    {

        if (!$namespace) {
            return EMPTY_STR;
        }

        $key = null;

        foreach ([$this->data, $base] as $b) {
            if (!$b) {
                continue;
            }

            if (array_key_exists('@context', $b)) {
                if (is_array($b['@context'])) {
                    foreach ($b['@context'] as $ns) {
                        if (is_array($ns)) {
                            foreach ($ns as $k => $v) {
                                if ($namespace === $v) {
                                    $key = $k;
                                }
                            }
                        } else {
                            if ($namespace === $ns) {
                                $key = '';
                            }
                        }
                    }
                } else {
                    if ($namespace === $b['@context']) {
                        $key = '';
                    }
                }
            }
        }

        return $key;
    }

    /**
     * @brief get single property from Activity object
     *
     * @param string $property
     * @param mixed return value if property or object not set
     *    or object is a string id which could not be fetched.
     * @return mixed
     */
    public function objprop($property, $default = false) {
        $x = $this->get_property_obj($property,$this->obj);
        return (isset($x)) ? $x : $default;
    }
    
    /**
     * @brief
     *
     * @param string $property
     * @param array $base (optional)
     * @param string $namespace (optional) default empty
     * @return NULL|mixed
     */

    public function get_property_obj($property, $base = '', $namespace = '')
    {
        $prefix = $this->get_namespace($base, $namespace);
        if ($prefix === null) {
            return null;
        }

        $base = (($base) ? $base : $this->data);
        $propname = (($prefix) ? $prefix . ':' : '') . $property;

        return ((is_array($base) && array_key_exists($propname, $base)) ? $base[$propname] : null);
    }


    /**
     * @brief Fetches a property from an URL.
     *
     * @param string $url
     * @param array $channel (signing channel, default system channel)
     * @return NULL|mixed
     */

    public function fetch_property($url, $channel = null, $hub = null)
    {
        $x = Activity::fetch($url, $channel, $hub);
        if ($x === null && strpos($url, '/channel/')) {
            // look for other nomadic channels which might be alive
            $zf = Zotfinger::exec($url, $channel);

            $url = $zf['signature']['signer'];
            $x = Activity::fetch($url, $channel);
        }

        return $x;
    }

    /**
     * @brief given a type, determine if this object represents an actor
	 *
	 * If $type is an array, recurse through each element and return true if any
	 * of the elements are a known actor type
	 *
	 * @param string|array $type
	 * @return boolean
	 */

    public static function is_an_actor($type)
    {
        if (!$type) {
            return false;
        }
		if (is_array($type)) {
			foreach ($type as $x) {
				if (self::is_an_actor($x)) {
					return true;
				}
			}
			return false;
		}
        return (in_array($type, ['Application', 'Group', 'Organization', 'Person', 'Service']));
    }

    public static function is_response_activity($s)
    {
        if (!$s) {
            return false;
        }
        return (in_array($s, ['Like', 'Dislike', 'Flag', 'Block', 'Announce', 'Accept', 'Reject', 'TentativeAccept', 'TentativeReject', 'emojiReaction', 'EmojiReaction', 'EmojiReact']));
    }


    /**
     * @brief
     *
     * @param string $property
     * @param array $base
     * @param string $namespace (optional) default empty
     * @return NULL|mixed
     */

    public function get_actor($property, $base = '', $namespace = '')
    {
        $x = $this->get_property_obj($property, $base, $namespace);
        if (self::is_url($x)) {
            $y = Activity::get_cached_actor($x);
            if ($y) {
                return $y;
            }
        }

        $actor = $this->get_compound_property($property, $base, $namespace, true);
        if (is_array($actor) && self::is_an_actor($actor['type'])) {
            if (array_key_exists('id', $actor) && (!array_key_exists('inbox', $actor))) {
                $actor = $this->fetch_property($actor['id']);
            }
            return $actor;
        }
        return null;
    }


    /**
     * @brief
     *
     * @param string $property
     * @param array $base
     * @param string $namespace (optional) default empty
     * @param bool $first (optional) default false, if true and result is a sequential array return only the first element
     * @return NULL|mixed
     */

    public function get_compound_property($property, $base = '', $namespace = '', $first = false)
    {
        $x = $this->get_property_obj($property, $base, $namespace);
        if (self::is_url($x)) {
            $y = $this->fetch_property($x);
            if (is_array($y)) {
                $x = $y;
            }
        }

        // verify and unpack JSalmon signature if present
        // This may be present in Zot6 packets

        if (is_array($x) && array_key_exists('signed', $x)) {
            $ret = JSalmon::verify($x);
            $tmp = JSalmon::unpack($x['data']);
            if ($ret && $ret['success']) {
                if ($ret['signer']) {
                    logger('Unpacked: ' . json_encode($tmp, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT), LOGGER_DATA, LOG_DEBUG);
                    $saved = json_encode($x, JSON_UNESCAPED_SLASHES);
                    $x = $tmp;
                    $x['meta']['signer'] = $ret['signer'];
                    $x['meta']['signed_data'] = $saved;
                    if ($ret['hubloc']) {
                        $x['meta']['hubloc'] = $ret['hubloc'];
                    }
                }
            }
        }
        if ($first && is_array($x) && array_key_exists(0, $x)) {
            return $x[0];
        }

        return $x;
    }

    /**
     * @brief Check if string starts with http.
     *
     * @param string $url
     * @return bool
     */

    public static function is_url($url)
    {
        if (($url) && (!is_array($url)) && ((strpos($url, 'http') === 0) || (strpos($url, 'x-zot') === 0) || (strpos($url, 'bear') === 0))) {
            return true;
        }

        return false;
    }

    /**
     * @brief Gets the type property.
     *
     * @param array $base
     * @param string $namespace (optional) default empty
     * @return NULL|mixed
     */

    public function get_primary_type($base = '', $namespace = '')
    {
        if (!$base) {
            $base = $this->data;
        }
        $x = $this->get_property_obj('type', $base, $namespace);
        if (is_array($x)) {
            foreach ($x as $y) {
                if (strpos($y, ':') === false) {
                    return $y;
                }
            }
        }

        return $x;
    }

    public function debug()
    {
        $x = var_export($this, true);
        return $x;
    }


    public static function is_as_request()
    {

        $x = getBestSupportedMimeType([
            'application/ld+json;profile="https://www.w3.org/ns/activitystreams"',
            'application/activity+json',
            'application/ld+json;profile="http://www.w3.org/ns/activitystreams"',
            'application/ld+json', 
            'application/x-zot-activity+json'
        ]);

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