first commit

lib/xapi/classes/local/statement/item.php

@@ -0,0 +1,79 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement base object for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+use stdClass;
+use JsonSerializable;
+use core_xapi\iri;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Item class used for xAPI statement elements without validation.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class item implements JsonSerializable {
+
+    /** @var stdClass the item structure. */
+    protected $data;
+
+    /**
+     * Item constructor.
+     *
+     * @param stdClass $data from the specific xAPI element
+     */
+    protected function __construct(stdClass $data) {
+        $this->data = $data;
+    }
+
+    /**
+     * Function to create an item from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item the xAPI item generated
+     */
+    public static function create_from_data(stdClass $data): item {
+        return new self($data);
+    }
+
+    /**
+     * Return the data to serialize in case JSON statement is needed.
+     *
+     * @return stdClass the original data structure
+     */
+    public function jsonSerialize(): stdClass {
+        return $this->get_data();
+    }
+
+    /**
+     * Return the original data from this item.
+     *
+     * @return stdClass the original data structure
+     */
+    public function get_data(): stdClass {
+        return $this->data;
+    }
+}

lib/xapi/classes/local/statement/item_activity.php

@@ -0,0 +1,129 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement activity object for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use core_xapi\xapi_exception;
+use core_xapi\iri;
+use stdClass;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Class that implements a xAPI activity compatible with xAPI object.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class item_activity extends item_object {
+
+    /** @var string Activity ID. */
+    protected $id;
+
+    /** @var item_definition Definition object. */
+    protected $definition;
+
+    /**
+     * Item activity constructor.
+     *
+     * An xAPI activity is mainly an IRI ID and an optional definition.
+     *
+     * @param stdClass $data from the specific xAPI element
+     * @param item_definition $definition option definition item
+     */
+    protected function __construct(stdClass $data, item_definition $definition = null) {
+        parent::__construct($data);
+        $this->id = iri::extract($data->id, 'activity');
+        $this->definition = $definition;
+    }
+
+    /**
+     * Function to create an item from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item item_activity xAPI generated
+     */
+    public static function create_from_data(stdClass $data): item {
+        if (!isset($data->objectType)) {
+            throw new xapi_exception('Missing activity objectType');
+        }
+        if ($data->objectType != 'Activity') {
+            throw new xapi_exception('Activity objectType must be "Activity"');
+        }
+        if (empty($data->id)) {
+            throw new xapi_exception("Missing Activity id");
+        }
+        if (!iri::check($data->id)) {
+            throw new xapi_exception("Activity id $data->id is not a valid IRI");
+        }
+
+        $definition = null;
+        if (!empty($data->definition)) {
+            $definition = item_definition::create_from_data($data->definition);
+        }
+
+        return new self($data, $definition);
+    }
+
+    /**
+     * Generate a valid item_activity from a simple ID string and an optional definition.
+     *
+     * @param string $id any string that will converted into a valid IRI
+     * @param item_definition|null $definition optional item_definition
+     * @return item_activity
+     */
+    public static function create_from_id(string $id, item_definition $definition = null): item_activity {
+        $data = (object) [
+            'objectType' => 'Activity',
+            'id' => iri::generate($id, 'activity'),
+        ];
+
+        if (!empty($definition)) {
+            $data->definition = $definition->get_data();
+        }
+
+        return new self($data, $definition);
+    }
+
+    /**
+     * Return the activity ID.
+     *
+     * If the ID was generated by iri::generate this function will return
+     * the iri:extract value.
+     *
+     * @return string the activity ID
+     */
+    public function get_id(): string {
+        return $this->id;
+    }
+
+    /**
+     * Returns the item_definition of this item.
+     *
+     * @return item_definition|null the item definition if available
+     */
+    public function get_definition(): ?item_definition {
+        return $this->definition;
+    }
+}

lib/xapi/classes/local/statement/item_actor.php

@@ -0,0 +1,79 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement actor (user or group) object for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use core_xapi\xapi_exception;
+use stdClass;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Abstract xAPI actor class.
+ *
+ * This class extends from item_object instead of basic item
+ * because both actors (agent and group) could be used as
+ * statement actor or object.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+abstract class item_actor extends item_object {
+
+    /**
+     * Function to create an actor from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item item_agent|item_grou|item_activity xAPI generated
+     */
+    public static function create_from_data(stdClass $data): item {
+        if (!isset($data->objectType)) {
+            $data->objectType = 'Agent';
+        }
+        switch ($data->objectType) {
+            case 'Agent':
+                return item_agent::create_from_data($data);
+                break;
+            case 'Group':
+                return item_group::create_from_data($data);
+                break;
+            default:
+                throw new xapi_exception("Unknown Actor type '{$data->objectType}'");
+        }
+    }
+
+    /**
+     * Returns the moodle user represented by this item.
+     *
+     * @return stdClass user record
+     */
+    abstract public function get_user(): stdClass;
+
+    /**
+     * Return all moodle users represented by this item.
+     *
+     * @return array user records
+     */
+    abstract public function get_all_users(): array;
+}

lib/xapi/classes/local/statement/item_agent.php

@@ -0,0 +1,142 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement agent (user) object for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use core_xapi\xapi_exception;
+use core_user;
+use stdClass;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Agent xAPI statement element representing a Moodle user.
+ *
+ * Agents can be used either as actor or object in a statement.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class item_agent extends item_actor {
+
+    /** @var stdClass The user record of this actor. */
+    protected $user;
+
+    /**
+     * Function to create an agent (user) from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @param stdClass $user user record
+     */
+    protected function __construct(stdClass $data, stdClass $user) {
+        parent::__construct($data);
+        $this->user = $user;
+    }
+
+    /**
+     * Function to create an item from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item item_agentxAPI generated
+     */
+    public static function create_from_data(stdClass $data): item {
+        global $CFG;
+        if (!isset($data->objectType)) {
+            throw new xapi_exception('Missing agent objectType');
+        }
+        if ($data->objectType != 'Agent') {
+            throw new xapi_exception("Agent objectType must be 'Agent'");
+        }
+        if (isset($data->account) && isset($data->mbox)) {
+            throw new xapi_exception("Agent cannot have more than one identifier");
+        }
+        $user = null;
+        if (!empty($data->account)) {
+            if ($data->account->homePage != $CFG->wwwroot) {
+                throw new xapi_exception("Invalid agent homePage '{$data->account->homePage}'");
+            }
+            if (!is_numeric($data->account->name)) {
+                throw new xapi_exception("Agent account name must be integer '{$data->account->name}' found");
+            }
+            $user = core_user::get_user($data->account->name);
+            if (empty($user)) {
+                throw new xapi_exception("Inexistent agent '{$data->account->name}'");
+            }
+        }
+        if (!empty($data->mbox)) {
+            $mbox = str_replace('mailto:', '', $data->mbox);
+            $user = core_user::get_user_by_email($mbox);
+            if (empty($user)) {
+                throw new xapi_exception("Inexistent agent '{$data->mbox}'");
+            }
+        }
+        if (empty($user)) {
+            throw new xapi_exception("Unsupported agent definition");
+        }
+        return new self($data, $user);
+    }
+
+    /**
+     * Create a item_agent from a existing user.
+     *
+     * @param stdClass $user A user record.
+     * @return item_agent
+     */
+    public static function create_from_user(stdClass $user): item_agent {
+        global $CFG;
+
+        if (!isset($user->id)) {
+            throw new xapi_exception("Missing user id");
+        }
+        $data = (object) [
+            'objectType' => 'Agent',
+            'account' => (object) [
+                'homePage' => $CFG->wwwroot,
+                'name' => $user->id,
+            ],
+        ];
+        return new self($data, $user);
+    }
+
+    /**
+     * Returns the moodle user represented by this item.
+     *
+     * @return stdClass user record
+     */
+    public function get_user(): stdClass {
+        return $this->user;
+    }
+
+    /**
+     * Return all users represented by this item.
+     *
+     * In this case the item is an agent so a single element array
+     * will be returned always.
+     *
+     * @return array list of users
+     */
+    public function get_all_users(): array {
+        return [$this->user->id => $this->user];
+    }
+}

lib/xapi/classes/local/statement/item_attachment.php

@@ -0,0 +1,73 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement attachment for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use core_xapi\xapi_exception;
+use core_xapi\iri;
+use stdClass;
+
+/**
+ * Abstract xAPI attachment class.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class item_attachment extends item {
+
+    /**
+     * Function to create an item from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item item_attachment xAPI generated
+     */
+    public static function create_from_data(stdClass $data): item {
+
+        if (empty($data->usageType)) {
+            throw new xapi_exception("missing attachment usageType");
+        }
+        if (!iri::check($data->usageType)) {
+            throw new xapi_exception("attachment usageType $data->usageType is not a valid IRI");
+        }
+        if (empty($data->display)) {
+            throw new xapi_exception("missing attachment display");
+        }
+        if (empty($data->contentType)) {
+            throw new xapi_exception("missing attachment contentType");
+        }
+        if (empty($data->length)) {
+            throw new xapi_exception("missing attachment length");
+        }
+        if (!is_numeric($data->length)) {
+            throw new xapi_exception("invalid attachment length format");
+        }
+        if (empty($data->sha2)) {
+            throw new xapi_exception("missing attachment sha2");
+        }
+
+        // More required property checks will appear here in the future.
+
+        return new self($data);
+    }
+}

lib/xapi/classes/local/statement/item_context.php

@@ -0,0 +1,49 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement context for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use stdClass;
+
+/**
+ * Abstract xAPI context class.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class item_context extends item {
+
+    /**
+     * Function to create an item from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item item_context xAPI generated
+     */
+    public static function create_from_data(stdClass $data): item {
+
+        // Required property checks will appear here in the future.
+
+        return new self($data);
+    }
+}

lib/xapi/classes/local/statement/item_definition.php

@@ -0,0 +1,93 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement definition object for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use core_xapi\xapi_exception;
+use core_xapi\iri;
+use stdClass;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Validation and usage of xAPI definition.
+ *
+ * Definition contains extra information about user interaction with
+ * questions and other activities inside a xAPI statement. For now
+ * it performs a basic validation on the provided data.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class item_definition extends item {
+
+    /** @var string The statement. */
+    protected $interactiontype;
+
+    /**
+     * Function to create a definition from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element.
+     */
+    protected function __construct(stdClass $data) {
+        parent::__construct($data);
+        $this->interactiontype = $data->interactionType ?? null;
+    }
+
+    /**
+     * Function to create an item from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item item_definition xAPI generated
+     */
+    public static function create_from_data(stdClass $data): item {
+        // Interaction Type is a optopnal param.
+        if (!empty($data->interactionType)) {
+            $posiblevalues = [
+                'choice' => true,
+                'fill-in' => true,
+                'long-fill-in' => true,
+                'true-false' => true,
+                'matching' => true,
+                'performance' => true,
+                'sequencing' => true,
+                'likert' => true,
+                'numeric' => true,
+                'other' => true,
+                'compound' => true,
+            ];
+            if (!isset($posiblevalues[$data->interactionType])) {
+                throw new xapi_exception("Invalid definition \"{$data->interactionType}\"");
+            }
+        }
+        return new self($data);
+    }
+
+    /**
+     * Return the definition interaction type.
+     */
+    public function get_interactiontype(): ?string {
+        return $this->interactiontype;
+    }
+}

lib/xapi/classes/local/statement/item_group.php

@@ -0,0 +1,147 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement group object for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use core_xapi\xapi_exception;
+use stdClass;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Group item inside a xAPI statement.
+ *
+ * Only named groups are accepted (all groups must be real groups in the
+ * platform) so anonymous groups will be rejected on creation. Groups can
+ * be used as actor or as object inside a xAPI statement.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class item_group extends item_actor {
+
+    /** @var array */
+    protected $users;
+
+    /** @var stdClass */
+    protected $group;
+
+    /**
+     * Function to create an group from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @param stdClass $group group record
+     */
+    protected function __construct(stdClass $data, stdClass $group) {
+        parent::__construct($data);
+        $this->group = $group;
+        $this->users = groups_get_members($group->id);
+        if (!$this->users) {
+            $this->users = [];
+        }
+    }
+
+    /**
+     * Function to create an item from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item item_group xAPI item generated
+     */
+    public static function create_from_data(stdClass $data): item {
+        global $CFG;
+        if (!isset($data->objectType)) {
+            throw new xapi_exception('Missing group objectType');
+        }
+        if ($data->objectType != 'Group') {
+            throw new xapi_exception("Group objectType must be 'Group'");
+        }
+        if (!isset($data->account)) {
+            throw new xapi_exception("Missing Group account");
+        }
+        if ($data->account->homePage != $CFG->wwwroot) {
+            throw new xapi_exception("Invalid group homePage '{$data->account->homePage}'");
+        }
+        if (!is_numeric($data->account->name)) {
+            throw new xapi_exception("Agent account name must be integer '{$data->account->name}' found");
+        }
+        $group = groups_get_group($data->account->name);
+        if (empty($group)) {
+            throw new xapi_exception("Inexistent group '{$data->account->name}'");
+        }
+        return new self($data, $group);
+    }
+
+    /**
+     * Create a item_group from a existing group.
+     *
+     * @param stdClass $group A group record.
+     * @return item_group
+     */
+    public static function create_from_group(stdClass $group): item_group {
+        global $CFG;
+
+        if (!isset($group->id)) {
+            throw new xapi_exception("Missing group id");
+        }
+        $data = (object) [
+            'objectType' => 'Group',
+            'account' => (object) [
+                'homePage' => $CFG->wwwroot,
+                'name' => $group->id,
+            ],
+        ];
+        return new self($data, $group);
+    }
+
+    /**
+     * Returns the moodle user represented by this item.
+     *
+     * This is a group item. To avoid security problems this method
+     * thorws an exception when is called from a item_group class.
+     *
+     * @throws xapi_exception get_user must not be called from an item_group
+     * @return stdClass user record
+     */
+    public function get_user(): stdClass {
+        throw new xapi_exception("Group statements cannot be used as a individual user");
+    }
+
+    /**
+     * Return all users from the group represented by this item.
+     *
+     * @return array group users
+     */
+    public function get_all_users(): array {
+        return $this->users;
+    }
+
+    /**
+     * Return the moodle group represented by this item.
+     *
+     * @return stdClass a group record
+     */
+    public function get_group(): stdClass {
+        return $this->group;
+    }
+}

lib/xapi/classes/local/statement/item_object.php

@@ -0,0 +1,69 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement object (activity, user or group) for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use core_xapi\xapi_exception;
+use core_xapi\iri;
+use stdClass;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Abstract object item used in xAPI statements.
+ *
+ * Object represents the object in which a xAPI verb is applied. There
+ * are 3 types of objects supported: agent (user), group (of users) and
+ * activity (defined by every plugin).
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+abstract class item_object extends item {
+
+    /**
+     * Create a xAPI object compatible from data (Agent, Group or Activity).
+     *
+     * @param stdClass $data data structure from statement object
+     * @return item item_group|item_agent|item_activity resulting object
+     */
+    public static function create_from_data(stdClass $data): item {
+        if (!isset($data->objectType)) {
+            $data->objectType = 'Activity';
+        }
+        switch ($data->objectType) {
+            case 'Agent':
+                return item_agent::create_from_data($data);
+                break;
+            case 'Group':
+                return item_group::create_from_data($data);
+                break;
+            case 'Activity':
+                return item_activity::create_from_data($data);
+                break;
+            default:
+                throw new xapi_exception("Unknown Object type '{$data->objectType}'");
+        }
+    }
+}

lib/xapi/classes/local/statement/item_result.php

@@ -0,0 +1,107 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement result for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use core_xapi\xapi_exception;
+use DateInterval;
+use Exception;
+use stdClass;
+
+/**
+ * Abstract xAPI result class.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class item_result extends item {
+
+    /** @var int The second of duration if present. */
+    protected $duration;
+
+    /** @var item_score the result score if present. */
+    protected $score;
+
+    /**
+     * Function to create a result from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @param int $duration duration in seconds
+     * @param item_score $score the provided score
+     */
+    protected function __construct(stdClass $data, int $duration = null, item_score $score = null) {
+        parent::__construct($data);
+        $this->duration = $duration;
+        $this->score = $score;
+    }
+
+    /**
+     * Function to create an item from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item item_result xAPI generated
+     */
+    public static function create_from_data(stdClass $data): item {
+
+        $duration = null;
+        if (!empty($data->duration)) {
+            try {
+                // Duration uses ISO 8601 format which is ALMOST compatible with PHP DateInterval.
+                // Because we are mesuring human time we get rid of milliseconds, which are not
+                // compatible with DateInterval (More info: https://bugs.php.net/bug.php?id=53831),
+                // all other fractions like "P1.5Y" will throw an exception.
+                $value = preg_replace('/[.,][0-9]*S/', 'S', $data->duration);
+                $interval = new DateInterval($value);
+                $duration = date_create('@0')->add($interval)->getTimestamp();
+            } catch (Exception $e) {
+                throw new xapi_exception('Invalid duration format.');
+            }
+        }
+
+        $score = null;
+        if (!empty($data->score)) {
+            $score = item_score::create_from_data($data->score);
+        }
+
+        return new self($data, $duration, $score);
+    }
+
+    /**
+     * Returns the duration in seconds (if present).
+     *
+     * @return int|null duration in seconds
+     */
+    public function get_duration(): ?int {
+        return $this->duration;
+    }
+
+    /**
+     * Returns the score.
+     *
+     * @return item_score|null the score item
+     */
+    public function get_score(): ?item_score {
+        return $this->score;
+    }
+}

lib/xapi/classes/local/statement/item_score.php

@@ -0,0 +1,49 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement score for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use stdClass;
+
+/**
+ * Abstract xAPI score class.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class item_score extends item {
+
+    /**
+     * Function to create an item from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item item_score xAPI generated
+     */
+    public static function create_from_data(stdClass $data): item {
+
+        // Required property checks will appear here in the future.
+
+        return new self($data);
+    }
+}

lib/xapi/classes/local/statement/item_verb.php

@@ -0,0 +1,103 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Statement verb object for xAPI structure checking and usage.
+ *
+ * @package    core_xapi
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_xapi\local\statement;
+
+use core_xapi\xapi_exception;
+use core_xapi\iri;
+use stdClass;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Verb xAPI statement item.
+ *
+ * Verbs represent the interaction a user/group made inside a xAPI
+ * compatible plugin. Internally a xAPI verb must be representad as
+ * in a valid IRI format (which is a less restrictive version of a
+ * regular URL so a moodle_url out is completelly fine). To make it
+ * easy for plugins to generate valid IRI, a simple string van be
+ * provided and the class will convert into a valid IRI internally.
+ *
+ * @copyright  2020 Ferran Recio
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class item_verb extends item {
+
+    /** @var string The statement. */
+    protected $id;
+
+    /**
+     * An xAPI verb constructor based on xAPI data structure.
+     *
+     * @param stdClass $data from the specific xAPI element
+     */
+    protected function __construct(stdClass $data) {
+        parent::__construct($data);
+        $this->id = iri::extract($data->id, 'verb');
+    }
+
+    /**
+     * Function to create an item from part of the xAPI statement.
+     *
+     * @param stdClass $data the original xAPI element
+     * @return item item_verb xAPI generated
+     */
+    public static function create_from_data(stdClass $data): item {
+        if (empty($data->id)) {
+            throw new xapi_exception("missing verb id");
+        }
+        if (!iri::check($data->id)) {
+            throw new xapi_exception("verb id $data->id is not a valid IRI");
+        }
+        return new self($data);
+    }
+
+    /**
+     * Create a valid item_verb from a simple verb string.
+     *
+     * @param string $id string to convert to a valid IRI (or a valid IRI)
+     * @return item_verb the resulting item_verb
+     */
+    public static function create_from_id(string $id): item_verb {
+
+        $data = new stdClass();
+        $data->id = iri::generate($id, 'verb');
+
+        return new self($data);
+    }
+
+    /**
+     * Return the id used in this item.
+     *
+     * Id will be extracted from the provided IRI. If it's a valid IRI
+     * it will return all IRI value but if it is generate by the iri helper
+     * from this library it will extract the original value.
+     *
+     * @return string the ID (extracted from IRI value)
+     */
+    public function get_id(): string {
+        return $this->id;
+    }
+}