<?php

require_once 'OAuth.php';
require_once 'TrivialOAuthDataStore.php';

// Returns true if this is a Basic LTI message
// with minimum values to meet the protocol
function is_basic_lti_request()
{
    $good_message_type = $_REQUEST["lti_message_type"] == "basic-lti-launch-request";
    $good_lti_version = $_REQUEST["lti_version"] == "LTI-1p0";
    $resource_link_id = $_REQUEST["resource_link_id"];
    if ($good_message_type and $good_lti_version and isset($resource_link_id)) {
        return(true);
    }
    return false;
}

// Basic LTI Class that does the setup and provides utility
// functions
class BLTI
{

    public $valid = false;
    public $complete = false;
    public $message = false;
    public $basestring = false;
    public $info = false;
    public $row = false;
    public $context_id = false;  // Override context_id

    function __construct($parm = false, $usesession = true, $doredirect = true)
    {

        // If this request is not an LTI Launch, either
        // give up or try to retrieve the context from session
        if (! is_basic_lti_request()) {
            if ($usesession === false) {
                return;
            }
            if (strlen(session_id()) > 0) {
                $row = $_SESSION['_basiclti_lti_row'];
                if (isset($row)) {
                    $this->row = $row;
                }
                $context_id = $_SESSION['_basiclti_lti_context_id'];
                if (isset($context_id)) {
                    $this->context_id = $context_id;
                }
                $info = $_SESSION['_basic_lti_context'];
                if (isset($info)) {
                    $this->info = $info;
                    $this->valid = true;
                    return;
                }
                $this->message = "Could not find context in session";
                return;
            }
            $this->message = "Session not available";
            return;
        }

        // Insure we have a valid launch
        if (empty($_REQUEST["oauth_consumer_key"])) {
            $this->message = "Missing oauth_consumer_key in request";
            return;
        }
        $oauth_consumer_key = $_REQUEST["oauth_consumer_key"];

        // Find the secret - either form the parameter as a string or
        // look it up in a database from parameters we are given
        $secret = false;
        $row = false;
        if (is_string($parm)) {
            $secret = $parm;
        } elseif (! is_array($parm)) {
            $this->message = "Constructor requires a secret or database information.";
            return;
        } else {
            $sql = 'SELECT * FROM ' . $parm['table'] . ' WHERE ' .
                ($parm['key_column'] ? $parm['key_column'] : 'oauth_consumer_key') .
                '=' .
                "'" . mysql_real_escape_string($oauth_consumer_key) . "'";
            $result = mysql_query($sql);
            $num_rows = mysql_num_rows($result);
            if ($num_rows != 1) {
                $this->message = "Your consumer is not authorized oauth_consumer_key=" . $oauth_consumer_key;
                return;
            } else {
                while ($row = mysql_fetch_assoc($result)) {
                    $secret = $row[$parms['secret_column'] ? $parms['secret_column'] : 'secret'];
                    $context_id = $row[$parms['context_column'] ? $parms['context_column'] : 'context_id'];
                    if ($context_id) {
                        $this->context_id = $context_id;
                    }
                    $this->row = $row;
                    break;
                }
                if (! is_string($secret)) {
                    $this->message = "Could not retrieve secret oauth_consumer_key=" . $oauth_consumer_key;
                    return;
                }
            }
        }

        // Verify the message signature
        $store = new TrivialOAuthDataStore();
        $store->add_consumer($oauth_consumer_key, $secret);

        $server = new OAuthServer($store);

        $method = new OAuthSignatureMethod_HMAC_SHA1();
        $server->add_signature_method($method);
        $request = OAuthRequest::from_request();
        
        $this->basestring = $request->get_signature_base_string();

        try {
            $server->verify_request($request);
            $this->valid = true;
        } catch (Exception $e) {
            $this->message = $e->getMessage();
            return;
        }

        // Store the launch information in the session for later
        $newinfo = [];
        foreach ($_POST as $key => $value) {
            if ($key == "basiclti_submit") {
                continue;
            }
            if (strpos($key, "oauth_") === false) {
                $newinfo[$key] = $value;
                continue;
            }
            if ($key == "oauth_consumer_key") {
                $newinfo[$key] = $value;
                continue;
            }
        }

        $this->info = $newinfo;
        if ($usesession == true and strlen(session_id()) > 0) {
             $_SESSION['_basic_lti_context'] = $this->info;
             unset($_SESSION['_basiclti_lti_row']);
             unset($_SESSION['_basiclti_lti_context_id']);
            if ($this->row) {
                $_SESSION['_basiclti_lti_row'] = $this->row;
            }
            if ($this->context_id) {
                $_SESSION['_basiclti_lti_context_id'] = $this->context_id;
            }
        }

        if ($this->valid && $doredirect) {
            $this->redirect();
            $this->complete = true;
        }
    }

    function addSession($location)
    {
        if (ini_get('session.use_cookies') == 0) {
            if (strpos($location, '?') > 0) {
                $location = $location . '&';
            } else {
                $location = $location . '?';
            }
            $location = $location . session_name() . '=' . session_id();
        }
        return $location;
    }

    function isInstructor()
    {
        $roles = $this->info['roles'];
        $roles = strtolower($roles);
        if (! ( strpos($roles, "instructor") === false )) {
            return true;
        }
        if (! ( strpos($roles, "administrator") === false )) {
            return true;
        }
        return false;
    }

    function getUserEmail()
    {
        $email = $this->info['lis_person_contact_email_primary'];
        if (strlen($email) > 0) {
            return $email;
        }
        # Sakai Hack
        $email = $this->info['lis_person_contact_emailprimary'];
        if (strlen($email) > 0) {
            return $email;
        }
        return false;
    }

    function getUserShortName()
    {
        $email = $this->getUserEmail();
        $givenname = $this->info['lis_person_name_given'];
        $familyname = $this->info['lis_person_name_family'];
        $fullname = $this->info['lis_person_name_full'];
        if (strlen($email) > 0) {
            return $email;
        }
        if (strlen($givenname) > 0) {
            return $givenname;
        }
        if (strlen($familyname) > 0) {
            return $familyname;
        }
        return $this->getUserName();
    }
  
    function getUserName()
    {
        $givenname = $this->info['lis_person_name_given'];
        $familyname = $this->info['lis_person_name_family'];
        $fullname = $this->info['lis_person_name_full'];
        if (strlen($fullname) > 0) {
            return $fullname;
        }
        if (strlen($familyname) > 0 and strlen($givenname) > 0) {
            return $givenname + $familyname;
        }
        if (strlen($givenname) > 0) {
            return $givenname;
        }
        if (strlen($familyname) > 0) {
            return $familyname;
        }
        return $this->getUserEmail();
    }

    function getUserKey()
    {
        $oauth = $this->info['oauth_consumer_key'];
        $id = $this->info['user_id'];
        if (strlen($id) > 0 and strlen($oauth) > 0) {
            return $oauth . ':' . $id;
        }
        return false;
    }

    function getUserImage()
    {
        $image = $this->info['user_image'];
        if (strlen($image) > 0) {
            return $image;
        }
        $email = $this->getUserEmail();
        if ($email === false) {
            return false;
        }
        $size = 40;
        $grav_url = $_SERVER['HTTPS'] ? 'https://' : 'http://';
        $grav_url = $grav_url . "www.gravatar.com/avatar.php?gravatar_id=" . md5(strtolower($email)) . "&size=" . $size;
        return $grav_url;
    }

    function getResourceKey()
    {
        $oauth = $this->info['oauth_consumer_key'];
        $id = $this->info['resource_link_id'];
        if (strlen($id) > 0 and strlen($oauth) > 0) {
            return $oauth . ':' . $id;
        }
        return false;
    }

    function getResourceTitle()
    {
        $title = $this->info['resource_link_title'];
        if (strlen($title) > 0) {
            return $title;
        }
        return false;
    }

    function getConsumerKey()
    {
        $oauth = $this->info['oauth_consumer_key'];
        return $oauth;
    }

    function getCourseKey()
    {
        if ($this->context_id) {
            return $this->context_id;
        }
        $oauth = $this->info['oauth_consumer_key'];
        $id = $this->info['context_id'];
        if (strlen($id) > 0 and strlen($oauth) > 0) {
            return $oauth . ':' . $id;
        }
        return false;
    }

    function getCourseName()
    {
        $label = $this->info['context_label'];
        $title = $this->info['context_title'];
        $id = $this->info['context_id'];
        if (strlen($label) > 0) {
            return $label;
        }
        if (strlen($title) > 0) {
            return $title;
        }
        if (strlen($id) > 0) {
            return $id;
        }
        return false;
    }

    // TODO: Add javasript version if headers are already sent
    function redirect()
    {
            $host = $_SERVER['HTTP_HOST'];
            $uri = $_SERVER['PHP_SELF'];
            $location = $_SERVER['HTTPS'] ? 'https://' : 'http://';
            $location = $location . $host . $uri;
            $location = $this->addSession($location);
            header("Location: $location");
    }

    function dump()
    {
        if (! $this->valid or $this->info == false) {
            return "Context not valid\n";
        }
        $ret = "";
        if ($this->isInstructor()) {
            $ret .= "isInstructor() = true\n";
        } else {
            $ret .= "isInstructor() = false\n";
        }
        $ret .= "getUserKey() = " . $this->getUserKey() . "\n";
        $ret .= "getUserEmail() = " . $this->getUserEmail() . "\n";
        $ret .= "getUserShortName() = " . $this->getUserShortName() . "\n";
        $ret .= "getUserName() = " . $this->getUserName() . "\n";
        $ret .= "getUserImage() = " . $this->getUserImage() . "\n";
        $ret .= "getResourceKey() = " . $this->getResourceKey() . "\n";
        $ret .= "getResourceTitle() = " . $this->getResourceTitle() . "\n";
        $ret .= "getCourseName() = " . $this->getCourseName() . "\n";
        $ret .= "getCourseKey() = " . $this->getCourseKey() . "\n";
        $ret .= "getConsumerKey() = " . $this->getConsumerKey() . "\n";
        return $ret;
    }
}