lti-consumer.php

<?php
/**
 * Plugin Name: LTI-compatible consumer
 * Plugin URI:
 * Description: An LTI-compatible launching plugin for Wordpress.
 * Version: 0.4.1
 * Author: John Weaver <john.weaver@saltbox.com>
 * License: GPLv3
 */

namespace Saltbox;

require('OAuth.php');


/*
 * Create the lti_launch custom post type.
 */
add_action('init', 'Saltbox\sb_create_lti_post_type_func');
function sb_create_lti_post_type_func() {
    register_post_type(
        'lti_launch',
        array(
            'labels' => array(
                'name' => __('LTI content'),
                'singular_name' => __('LTI content'),
                'add_new_item' => __('Add new LTI content'),
                'edit_item' => __('Edit LTI content'),
                'new_item' => __('New LTI content'),
                'view_item' => __('View LTI content'),
                'search_items' => __('Search LTI content'),
                'not_found' => __('No LTI content found'),
                'not_found_in_trash' => __('No LTI content found in Trash'),
            ),
            'description' => __('An LTI-compatible tool for content launch'),
            'publicly_queryable' => true,
            'public' => true,
            'has_archive' => true,
            'supports' => array(
                'title',
                'editor',
            ),
        )
    );
}

add_filter('post_row_actions', 'Saltbox\sb_add_shortcode_generator_link', 10, 2);
add_filter('page_row_actions', 'Saltbox\sb_add_shortcode_generator_link', 10, 2);
function sb_add_shortcode_generator_link($actions, $post) {
    if ( $post->post_type == 'lti_launch' ) {
        unset($actions['view']);
        $actions['shortcode_generator'] = 'Shortcode: [lti-launch id=' . $post->post_name . ']';
    }

    return $actions;
}



add_action('add_meta_boxes', 'Saltbox\sb_lti_content_meta_box');
function sb_lti_content_meta_box() {
    add_meta_box(
        'lti_content_custom_section_id',
        __('LTI launch settings', 'lti-consumer'),
        'Saltbox\sb_lti_content_inner_custom_box',
        'lti_launch'
    );
}


add_filter('get_sample_permalink_html', 'Saltbox\sb_permalink_removal', 1000, 4);
function sb_permalink_removal($return, $id, $new_title, $new_slug) {
    global $post;
    if ( $post && $post->post_type == 'lti_launch' ) {
        return '';
    } else {
        return $return;
    }
}


function sb_lti_content_inner_custom_box($lti_content) {
    wp_nonce_field('lti_content_inner_custom_box', 'lti_content_inner_custom_nonce');

    $consumer_key = get_post_meta($lti_content->ID, '_lti_meta_consumer_key', true);
    $secret_key = get_post_meta($lti_content->ID, '_lti_meta_secret_key', true);
    $display = get_post_meta($lti_content->ID, '_lti_meta_display', true);
    $action = get_post_meta($lti_content->ID, '_lti_meta_action', true);
    $launch_url = get_post_meta($lti_content->ID, '_lti_meta_launch_url', true);
    $configuration_url = get_post_meta($lti_content->ID, '_lti_meta_configuration_url', true);
    $return_url = get_post_meta($lti_content->ID, '_lti_meta_return_url', true);
    $version = get_post_meta($lti_content->ID, '_lti_meta_version', true);

    if ( $display === '' ) {
        $display = 'iframe';
    }

    if ( $version !== 'LTI-1p1' && $version !== 'LTI-1p0' ) {
        $version = 'LTI-1p1';
    }

?>
    <p>All of the following fields are optional, and can be overridden by specifying the corresponding parameters to the lti-launch shortcode.</p>


<table class="form-table">
  <tbody>
    <tr>
      <th><label for="lti_content_field_"><?php echo _e( "OAuth Consumer Key", 'lti-consumer' ); ?></label></th>
      <td><input type="text" id="lti_content_field_consumer_key" name="lti_content_field_consumer_key" value="<?php echo esc_attr( $consumer_key ); ?>" size="25" /></td>
    </tr>

    <tr>
      <th><label for="lti_content_field_"><?php echo _e( "OAuth Secret Key", 'lti-consumer' ); ?></label></th>
      <td><input type="text" id="lti_content_field_secret_key" name="lti_content_field_secret_key" value="<?php echo esc_attr( $secret_key ); ?>" size="25" /></td>
    </tr>

    </tr>

    <tr>
      <th><label for="lti_content_field_display_newwindow"><?php echo _e( "Display Style", 'lti-consumer' ); ?></label></th>
      <td>
        <label>Open in a new browser window <input type="radio" <?php checked($display, 'newwindow'); ?> id="lti_content_field_display_newwindow" name="lti_content_field_display" value="newwindow" /></label><br>
        <label>Inline in an iframe <input type="radio" <?php checked($display, 'iframe'); ?> id="lti_content_field_display_iframe" name="lti_content_field_display" value="iframe" /></label><br>
        <label>Open in the current browser window <input type="radio" <?php checked($display, 'self'); ?> id="lti_content_field_display_self" name="lti_content_field_display" value="self" /></label>
      </td>
    </tr>

    <tr>
      <th><label for="lti_content_field_action_button"><?php _e( "Launch trigger control", 'lti-consumer' ); ?></label></th>
      <td>
        <label>Button <input type="radio" <?php checked($action, 'button'); ?> id="lti_content_field_action_button" name="lti_content_field_action" value="button" /></label><br>
        <label>Link <input type="radio" <?php checked($action, 'link'); ?> id="lti_content_field_action_link" name="lti_content_field_action" value="link"  /></label>
      </td>
    </tr>

    <tr>
      <th><label for="lti_content_field_launch_url"><?php echo _e( "Launch URL", 'lti-consumer' ); ?></label></th>
      <td><input type="url" id="lti_content_field_launch_url" name="lti_content_field_launch_url" value="<?php echo esc_attr( $launch_url ); ?>" size="35" /></td>
    </tr>

    <tr>
      <th><label for="lti_content_field_configuration_url"><?php echo _e( "Configuration XML URL", 'lti-consumer' ); ?></label></th>
      <td><input type="url" id="lti_content_field_configuration_url" name="lti_content_field_configuration_url" value="<?php echo esc_attr( $configuration_url ) ?>" size="35" /></td>
    </tr>

    <tr>
      <th><label for="lti_content_field_return_url"><?php echo _e( "Return URL after completion", 'lti-consumer' ); ?></label></th>
      <td><input type="url" id="lti_content_field_return_url" name="lti_content_field_return_url" value="<?php echo esc_attr( $return_url ); ?>" size="35" /></td>
    </tr>

    <tr>
      <th><label for="lti_content_field_version_1_1"><?php _e( "LTI version", 'lti-consumer' ); ?></label></th>
      <td>
        <label>1.1 <input type="radio" <?php checked($version, 'LTI-1p1'); ?> id="lti_content_field_version_1_1" name="lti_content_field_version" value="LTI-1p1" /></label><br>
        <label>1.0 <input type="radio" <?php checked($version, 'LTI-1p0'); ?> id="lti_content_field_version_1_0" name="lti_content_field_version" value="LTI-1p0"  /></label>
      </td>
    </tr>
  </tbody>
</table>

<?php
}


add_filter('the_content', 'Saltbox\sb_lti_content_include_launcher');
function sb_lti_content_include_launcher($content) {
    global $post;

    if ( $post->post_type == 'lti_launch' ) {
        $content .= '<p>[lti-launch id=' . $post->post_name . ' resource_link_id=' . $post->ID . ']</p>';
    }

    return $content;
}


add_action('save_post', 'Saltbox\sb_lti_content_save_post');
function sb_lti_content_save_post($post_id) {
    // From http://codex.wordpress.org/Function_Reference/add_meta_box
    // Check if our nonce is set.
    if ( ! isset( $_POST['lti_content_inner_custom_nonce'] ) ) {
        return $post_id;
    }

    $nonce = $_POST['lti_content_inner_custom_nonce'];

    // Verify that the nonce is valid.
    if ( !wp_verify_nonce( $nonce, 'lti_content_inner_custom_box' ) ) {
          return $post_id;
    }

    // If this is an autosave, our form has not been submitted, so we don't want to do anything.
    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
        return $post_id;
    }

    if ( !current_user_can( 'edit_post', $post_id ) ) {
        return $post_id;
    }

    /* OK, its safe for us to save the data now. */

    // Sanitize user input.
    $consumer_key = sanitize_text_field($_POST['lti_content_field_consumer_key']);
    $secret_key = sanitize_text_field($_POST['lti_content_field_secret_key']);
    $display = sanitize_text_field($_POST['lti_content_field_display']);
    $action = sanitize_text_field($_POST['lti_content_field_action']);
    $launch_url = esc_url_raw($_POST['lti_content_field_launch_url']);
    $configuration_url = esc_url_raw($_POST['lti_content_field_configuration_url']);
    $return_url = esc_url_raw($_POST['lti_content_field_return_url']);
    $version = sanitize_text_field($_POST['lti_content_field_version']);

    // Update the meta field in the database.
    update_post_meta($post_id, '_lti_meta_consumer_key', $consumer_key);
    update_post_meta($post_id, '_lti_meta_secret_key', $secret_key);
    update_post_meta($post_id, '_lti_meta_display', $display);
    update_post_meta($post_id, '_lti_meta_action', $action);
    update_post_meta($post_id, '_lti_meta_launch_url', $launch_url);
    update_post_meta($post_id, '_lti_meta_configuration_url', $configuration_url);
    update_post_meta($post_id, '_lti_meta_return_url', $return_url);
    update_post_meta($post_id, '_lti_meta_version', $version);
}



/*
 * Add the lti-launch shortcode.
 */
add_shortcode('lti-launch', 'Saltbox\sb_lti_launch_func');
function sb_lti_launch_func($attrs) {
    $data = sb_lti_launch_process($attrs);

    if ( array_key_exists('error', $data) ) {
        $html = '<div class="error"><p><strong>' . $data['error'] . '</strong></p></div>';
    } else {
        $html = '';
        $id = uniqid();
        $iframeId = uniqid();

        if ( $data['display'] == 'newwindow' ) {
            $target = '_blank';
        } else if ( $data['display'] == 'iframe' ) {
            $target = 'frame-' . $iframeId;
        } else {
            $target = '_self';
        }

        if ( $data['action'] == 'auto' || $data['display'] == 'iframe' ) {
            $autolaunch = 'yes';
        } else {
            $autolaunch = 'no';
        }

        $html .= "<form method=\"post\" action=\"" . esc_url($data['url']) . "\" target=\"$target\" id=\"launch-$id\" data-id=\"$id\" data-post=\"$data[id]\" data-auto-launch=\"$autolaunch\">";
        foreach ( $data['parameters'] as $key => $value ) {
            $html .= "<input type=\"hidden\" name=\"$key\" value=\"$value\">";
        }

        if ( $data['display'] == 'iframe' ) {
            $html .= '<iframe style="width: 100%; height: 55em;" class="launch-frame" name="frame-' . $iframeId . '"></iframe>';
            // Immediately send the lti_launch action when showing the iframe.
            if ( $data['id'] ) {
                do_action('lti_launch', $data['id']);
            }
        } else if ( $data['action'] == 'link' ) {
            $html .= '<a href="#" onclick="lti_consumer_launch(\'' . $id . '\')">Launch ' . $data['text'] . '</a>';
        } else {
            $html .= '<button onclick="lti_consumer_launch(\'' . $id . '\')">Launch ' . $data['text'] . '</button>';
        }

        $html .= '</form>';
    }

    return $html;
}


add_action('wp_head', 'Saltbox\sb_lti_launch_ajaxurl');
function sb_lti_launch_ajaxurl() {
?>
        <script type="text/javascript">
        var ajaxurl = '<?php echo admin_url('admin-ajax.php'); ?>';
</script>
<?php
}


/*
 * Emit an 'lti_launch' action when the Javascript informs us about a
 * launch.
 */
add_action('wp_ajax_lti_launch', 'Saltbox\sb_hook_lti_launch_action_func');
add_action('wp_ajax_nopriv_lti_launch', 'Saltbox\sb_hook_lti_launch_action_func');
function sb_hook_lti_launch_action_func() {
    $lti_launch = get_post($_POST['post']);
    // make sure that at least the post id is valid
    if ( $lti_launch && $lti_launch->post_type == 'lti_launch' ) {
        do_action('lti_launch', $_POST['post']);
    }
}


/*
 * Find lti-launch shortcodes in posts and add a resource_link_id to any found
 * if they don't already have one set.
 */
add_action('save_post', 'Saltbox\sb_ensure_resource_link_id_func', 5, 1);
function sb_ensure_resource_link_id_func($post_id) {
    // get post content
    $content = get_post($post_id)->post_content;

    // does it contains our shortcode
    $pattern = get_shortcode_regex();
    preg_match_all("/$pattern/s", $content, $matches);

    foreach ( $matches[0] as $match ) {
        if ( strpos($match, '[lti-launch') === 0 ) {
            // Replace the original shortcode with the rewritten one
            $content = substr_replace(
                $content,
                sb_add_resource_link_id_if_not_present($match),
                strpos($content, $match),
                strlen($match));
        }
    }

    // transform content

    // unhook this function so it doesn't loop infinitely
    remove_action('save_post', 'Saltbox\sb_ensure_resource_link_id_func', 5, 1);

    // update the post, which calls save_post again
    wp_update_post(array('ID' => $post_id, 'post_content' => $content));

    // re-hook this function
    add_action('save_post', 'Saltbox\sb_ensure_resource_link_id_func', 5, 1);

    return $post_id;
}


/*
 * Insert our LTI launch script into the page.
 */
add_action('wp_enqueue_scripts', 'Saltbox\sb_add_launch_script_func');
add_action('admin_enqueue_scripts', 'Saltbox\sb_add_launch_script_func');
function sb_add_launch_script_func() {
    wp_enqueue_script('lti_launch', plugins_url('scripts/launch.js', __FILE__), array('jquery'));
}


function sb_add_resource_link_id_if_not_present($shortcode) {
    // split args out of shortcode, excluding the [] as well
    $pieces = explode(' ', substr($shortcode, 1, -1));

    // check if resource_link_id is present
    $found = false;
    foreach ( $pieces as $piece ) {
        if ( strpos(trim($piece), 'resource_link_id=') === 0 ) {
            $found = true;
            break;
        }
    }

    // add resource_link_id if not present
    if ( !$found ) {
        array_push($pieces, 'resource_link_id=' . uniqid());
    }

    // recombine args
    return '[' . implode(' ', $pieces) . ']';
}

/*
 * Utilities
 */
function sb_extract_user_id() {
    // Find some relevant information about the current user
    $current_user = wp_get_current_user();

    return array(
        'user_id' => $current_user->ID,
        'lis_person_contact_email_primary' => $current_user->user_email,
        'lis_person_name_given' => $current_user->user_firstname,
        'lis_person_name_family' => $current_user->user_lastname,
    );
}

function sb_extract_site_id() {
    // Find some relevant information about the site
    return array(
        'context_id' => basename(get_permalink()),
        'tool_consumer_instance_url' => get_site_url(),
    );
}


function sb_determine_launch_url($configuration_url) {
    $launch_url = wp_cache_get($configuration_url, 'lti-consumer', false, $found);
    if ( $found ) {
        return $launch_url;
    }

    $parts = parse_url($configuration_url);

    if ( $parts == false || !array_key_exists('scheme', $parts) || ($parts['scheme'] != 'http' && $parts['scheme'] != 'https') ) {
        // Don't trust weird URLs (could be file path or something).
        $launch_url = false;
    } else {
        try {
            $opts = array(
                'http' => array(
                    'header' => "Accept: application/xml\r\n"
                )
            );

            $context = stream_context_create($opts);
            $config_string = file_get_contents($configuration_url, false, $context);

            $config = simplexml_load_string($config_string);
            $launch_url = (string) $config->children('blti', true)->launch_url;
        } catch ( Exception $e ) {
            $launch_url = false;
        }
    }

    // Keep it for 30 minutes
    wp_cache_set($configuration_url, $launch_url, 'lti-consumer', 30 * 60);
    return $launch_url;
}


function sb_lti_launch_process($attrs) {
    // Reject launch for non-logged in users
    if ( !is_user_logged_in() ) {
        return array('error' => 'You must be logged in to launch this content.');
    } else {
        $parameters = array();
        // grab user information
        $parameters = array_merge($parameters, sb_extract_user_id());
        // grab site information
        $parameters = array_merge($parameters, sb_extract_site_id());

        $post_id = '';
        $text = '';

        if ( array_key_exists('id', $attrs) ) {
            $posts = get_posts(array(
                'name' => $attrs['id'],
                'post_type' => 'lti_launch',
                'post_status' => 'publish',
                'posts_per_page' => 1,
            ));

            if ( $posts ) {
                $lti_content = $posts[0];
                $post_id = $lti_content->ID;
                $consumer_key = get_post_meta($lti_content->ID, '_lti_meta_consumer_key', true);
                $consumer_secret = get_post_meta($lti_content->ID, '_lti_meta_secret_key', true);
                $display = get_post_meta($lti_content->ID, '_lti_meta_display', true);
                $action = get_post_meta($lti_content->ID, '_lti_meta_action', true);
                $launch_url = get_post_meta($lti_content->ID, '_lti_meta_launch_url', true);
                $configuration_url = get_post_meta($lti_content->ID, '_lti_meta_configuration_url', true);
                if ( $configuration_url === "" ) {
                        unset($configuration_url);
                }
                $return_url = get_post_meta($lti_content->ID, '_lti_meta_return_url', true);
                $text = $lti_content->post_title;
                $version = get_post_meta($lti_content->ID, '_lti_meta_version', true) or 'LTI-1p1';
            }
        }

        // incorporate information from $attrs
        if ( array_key_exists('resource_link_id', $attrs) ) {
            $parameters['resource_link_id'] = $attrs['resource_link_id'];
        } else {
            return array('error' => 'You must specify the resource_link_id.');
        }

        if ( array_key_exists('return_url', $attrs) ) {
            $parameters['launch_presentation_return_url'] = $attrs['return_url'];
        } else if ( isset($return_url) && $return_url ) {
            $parameters['launch_presentation_return_url'] = $return_url;
        }

        if ( array_key_exists('version', $attrs) ) {
            $version = $attrs['version'];
        } else if ( !isset($version) ) {
            $version = 'LTI-1p1';
        }

        if ( array_key_exists('configuration_url', $attrs) ) {
            $launch_url = sb_determine_launch_url($attrs['configuration_url']);

            if ( $launch_url == false ) {
                return array('error' => 'Could not determine launch URL.');
            }
        } else if ( array_key_exists('launch_url', $attrs) ) {
            $launch_url = $attrs['launch_url'];
        } else if ( isset($configuration_url) && $configuration_url ) {
            $launch_url = sb_determine_launch_url($configuration_url);

            if ( $launch_url == false ) {
                return array('error' => 'Could not determine launch URL.');
            }
        } else if ( !isset($launch_url) || $launch_url === "" ) {
            return array('error' => 'Missing launch URL and URL to configuration XML. One of these is required.');
        }

        if ( array_key_exists('consumer_key', $attrs) ) {
            $consumer_key = $attrs['consumer_key'];
        } else if ( !isset($consumer_key) ) {
            return array('error' => 'Missing OAuth consumer key.');
        }

        if ( array_key_exists('secret_key', $attrs) ) {
            $consumer_secret = $attrs['secret_key'];
        } else if ( !isset($consumer_secret) ) {
            return array('error' => 'Missing OAuth consumer secret.');
        }

        if ( !isset($display) ) {
            $display = 'newwindow';
        }

        if ( array_key_exists('display', $attrs) ) {
            $display = $attrs['display'];
        }

        if ( array_key_exists('action', $attrs) ) {
            $action = $attrs['action'];
        } else if ( !isset($action) )  {
            $action = 'button';
        }

        $parameters = sb_package_launch(
                $version,
                $consumer_key, $consumer_secret,
                $launch_url,
                $parameters);

        // Strip out GET parameters from the parameters we pass
        // into the POST body.
        parse_str(parse_url($launch_url, PHP_URL_QUERY), $qs_params);
        foreach ( $qs_params as $k => $v ) {
                unset($parameters[$k]);
        }

        return array(
            'parameters' => $parameters,
            'id' => $post_id,
            'display' => $display,
            'action' => $action,
            'url' => $launch_url,
            'text' => $text,
        );
    }
}


function sb_package_launch($version, $key, $secret, $launch_url, $parameters) {
    $parameters['lti_version'] = $version;
    $parameters['lti_message_type'] = 'basic-lti-launch-request';

    $consumer = new OAuthConsumer($key, $secret);
    $oauth_request = OAuthRequest::from_consumer_and_token(
        $consumer, null, 'POST',
        $launch_url, $parameters);
    $oauth_request->sign_request(
        new OAuthSignatureMethod_HMAC_SHA1(), $consumer, null);
    return $oauth_request->get_parameters();
};