<?php

require_once 'OAuth.php';

  // Replace this with some real function that pulls from the LMS.
function getLMSDummyData()
{
    $parms = [
    "resource_link_id" => "120988f929-274612",
    "resource_link_title" => "Weekly Blog",
    "resource_link_description" => "Each student needs to reflect on the weekly reading.  These should be one paragraph long.",
    "user_id" => "292832126",
    "roles" => "Instructor",  // or Learner
    "lis_person_name_full" => 'Jane Q. Public',
    "lis_person_contact_email_primary" => "user@school.edu",
    "lis_person_sourcedid" => "school.edu:user",
    "context_id" => "456434513",
    "context_title" => "Design of Personal Environments",
    "context_label" => "SI182",
    ];

    return $parms;
}

function validateDescriptor($descriptor)
{
    $xml = new SimpleXMLElement($xmldata);
    if (! $xml) {
        echo("Error parsing Descriptor XML\n");
        return;
    }
    $launch_url = $xml->secure_launch_url[0];
    if (! $launch_url) {
        $launch_url = $xml->launch_url[0];
    }
    if ($launch_url) {
        $launch_url = (string) $launch_url;
    }
    return $launch_url;
}

  // Parse a descriptor
function launchInfo($xmldata)
{
    $xml = new SimpleXMLElement($xmldata);
    if (! $xml) {
        echo("Error parsing Descriptor XML\n");
        return;
    }
    $launch_url = $xml->secure_launch_url[0];
    if (! $launch_url) {
        $launch_url = $xml->launch_url[0];
    }
    if ($launch_url) {
        $launch_url = (string) $launch_url;
    }
    $custom = [];
    if ($xml->custom[0]->parameter) {
        foreach ($xml->custom[0]->parameter as $resource) {
            $key = (string) $resource['key'];
            $key = strtolower($key);
            $nk = "";
            for ($i = 0; $i < strlen($key); $i++) {
                $ch = substr($key, $i, 1);
                if ($ch >= "a" && $ch <= "z") {
                    $nk .= $ch;
                } elseif ($ch >= "0" && $ch <= "9") {
                    $nk .= $ch;
                } else {
                    $nk .= "_";
                }
            }
            $value = (string) $resource;
            $custom["custom_" . $nk] = $value;
        }
    }
    return ["launch_url" => $launch_url, "custom" => $custom ] ;
}

function split_custom_parameters($customstr)
{
    $lines = preg_split("/[\n;]/", $customstr);
    $retval = [];
    foreach ($lines as $line) {
        $pos = strpos($line, "=");
        if ($pos === false || $pos < 1) {
            continue;
        }
        $key = trim(substr($line, 0, $pos));
        $val = trim(substr($line, $pos + 1));
        $key = map_keyname($key);
        $retval['custom_' . $key] = $val;
    }
    return $retval;
}

function map_keyname($key)
{
    $newkey = "";
    $key = strtolower(trim($key));
    foreach (str_split($key) as $ch) {
        if (($ch >= 'a' && $ch <= 'z') || ($ch >= '0' && $ch <= '9')) {
            $newkey .= $ch;
        } else {
            $newkey .= '_';
        }
    }
    return $newkey;
}

function signParameters(
    $oldparms,
    $endpoint,
    $method,
    $oauth_consumer_key,
    $oauth_consumer_secret,
    $submit_text = false,
    $org_id = false,
    $org_desc = false
) {
    global $last_base_string;
    $parms = $oldparms;
    if (! isset($parms["lti_version"])) {
        $parms["lti_version"] = "LTI-1p0";
    }
    if (! isset($parms["lti_message_type"])) {
        $parms["lti_message_type"] = "basic-lti-launch-request";
    }
    if (! isset($parms["oauth_callback"])) {
        $parms["oauth_callback"] = "about:blank";
    }
    if ($org_id) {
        $parms["tool_consumer_instance_guid"] = $org_id;
    }
    if ($org_desc) {
        $parms["tool_consumer_instance_description"] = $org_desc;
    }
    if ($submit_text) {
        $parms["ext_submit"] = $submit_text;
    }

    $test_token = '';

    $hmac_method = new OAuthSignatureMethod_HMAC_SHA1();
    $test_consumer = new OAuthConsumer($oauth_consumer_key, $oauth_consumer_secret, null);

    $acc_req = OAuthRequest::from_consumer_and_token($test_consumer, $test_token, $method, $endpoint, $parms);
    $acc_req->sign_request($hmac_method, $test_consumer, $test_token);

    // Pass this back up "out of band" for debugging
    $last_base_string = $acc_req->get_signature_base_string();

    $newparms = $acc_req->get_parameters();

    return $newparms;
}

function signOnly($oldparms, $endpoint, $method, $oauth_consumer_key, $oauth_consumer_secret)
{
    global $last_base_string;
    $parms = $oldparms;

    $test_token = '';

    $hmac_method = new OAuthSignatureMethod_HMAC_SHA1();
    $test_consumer = new OAuthConsumer($oauth_consumer_key, $oauth_consumer_secret, null);

    $acc_req = OAuthRequest::from_consumer_and_token($test_consumer, $test_token, $method, $endpoint, $parms);
    $acc_req->sign_request($hmac_method, $test_consumer, $test_token);

    // Pass this back up "out of band" for debugging
    $last_base_string = $acc_req->get_signature_base_string();

    $newparms = $acc_req->get_parameters();

    return $newparms;
}

function postLaunchHTML($newparms, $endpoint, $debug = false, $iframeattr = false)
{
    global $last_base_string;
    $r = "<div id=\"ltiLaunchFormSubmitArea\">\n";
    if ($iframeattr) {
        $r = "<form action=\"" . $endpoint . "\" name=\"ltiLaunchForm\" id=\"ltiLaunchForm\" method=\"post\" target=\"basicltiLaunchFrame\" encType=\"application/x-www-form-urlencoded\">\n" ;
    } else {
        $r = "<form action=\"" . $endpoint . "\" name=\"ltiLaunchForm\" id=\"ltiLaunchForm\" method=\"post\" encType=\"application/x-www-form-urlencoded\">\n" ;
    }
    $submit_text = $newparms['ext_submit'];
    foreach ($newparms as $key => $value) {
        $key = htmlspecialchars($key);
        $value = htmlspecialchars($value);
        if ($key == "ext_submit") {
            $r .= "<input type=\"submit\" name=\"";
        } else {
            $r .= "<input type=\"hidden\" name=\"";
        }
        $r .= $key;
        $r .= "\" value=\"";
        $r .= $value;
        $r .= "\"/>\n";
    }
    if ($debug) {
        $r .= "<script language=\"javascript\"> \n";
        $r .= "  //<![CDATA[ \n" ;
        $r .= "function basicltiDebugToggle() {\n";
        $r .= "    var ele = document.getElementById(\"basicltiDebug\");\n";
        $r .= "    if(ele.style.display == \"block\") {\n";
        $r .= "        ele.style.display = \"none\";\n";
        $r .= "    }\n";
        $r .= "    else {\n";
        $r .= "        ele.style.display = \"block\";\n";
        $r .= "    }\n";
        $r .= "} \n";
        $r .= "  //]]> \n" ;
        $r .= "</script>\n";
        $r .= "<a id=\"displayText\" href=\"javascript:basicltiDebugToggle();\">";
        $r .= get_string("toggle_debug_data", "basiclti") . "</a>\n";
        $r .= "<div id=\"basicltiDebug\" style=\"display:none\">\n";
        $r .=  "<b>" . get_string("basiclti_endpoint", "basiclti") . "</b><br/>\n";
        $r .= $endpoint . "<br/>\n&nbsp;<br/>\n";
        $r .=  "<b>" . get_string("basiclti_parameters", "basiclti") . "</b><br/>\n";
        foreach ($newparms as $key => $value) {
            $key = htmlspecialchars($key);
            $value = htmlspecialchars($value);
            $r .= "$key = $value<br/>\n";
        }
        $r .= "&nbsp;<br/>\n";
        $r .= "<p><b>" . get_string("basiclti_base_string", "basiclti") . "</b><br/>\n" . $last_base_string . "</p>\n";
        $r .= "</div>\n";
    }
    $r .= "</form>\n";
    if ($iframeattr) {
        $r .= "<iframe name=\"basicltiLaunchFrame\"  id=\"basicltiLaunchFrame\" src=\"\"\n";
        $r .= $iframeattr . ">\n<p>" . get_string("frames_required", "basiclti") . "</p>\n</iframe>\n";
    }
    if (! $debug) {
        $ext_submit = "ext_submit";
        $ext_submit_text = $submit_text;
        $r .= " <script type=\"text/javascript\"> \n" .
            "  //<![CDATA[ \n" .
            "    document.getElementById(\"ltiLaunchForm\").style.display = \"none\";\n" .
            "    nei = document.createElement('input');\n" .
            "    nei.setAttribute('type', 'hidden');\n" .
            "    nei.setAttribute('name', '" . $ext_submit . "');\n" .
            "    nei.setAttribute('value', '" . $ext_submit_text . "');\n" .
            "    document.getElementById(\"ltiLaunchForm\").appendChild(nei);\n" .
            "    document.ltiLaunchForm.submit(); \n" .
            "  //]]> \n" .
            " </script> \n";
    }
    $r .= "</div>\n";
    return $r;
}

/* This is a bit of homage to Moodle's pattern of internationalisation */
function get_string($key, $bundle)
{
    return $key;
}

function do_post_request($url, $data, $optional_headers = null)
{
    $params = ['http' => [
              'method' => 'POST',
              'content' => $data
            ]];
    
    if ($optional_headers !== null) {
        $header = $optional_headers . "\r\n";
    }
    // $header = $header . "Content-type: application/x-www-form-urlencoded\r\n";
    $params['http']['header'] = $header;
    $ctx = stream_context_create($params);
    $fp = @fopen($url, 'rb', false, $ctx);
    if (!$fp) {
        throw new Exception("Problem with $url, $php_errormsg");
    }
    $response = @stream_get_contents($fp);
    if ($response === false) {
        throw new Exception("Problem reading data from $url, $php_errormsg");
    }
    return $response;
}