<?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/>.

/**
 * This file is serving optimised JS for RequireJS.
 *
 * @package    core
 * @copyright  2015 Damyon Wiese
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

// Disable moodle specific debug messages and any errors in output,
// comment out when debugging or better look into error log!
define('NO_DEBUG_DISPLAY', true);

// We need just the values from config.php and minlib.php.
define('ABORT_AFTER_CONFIG', true);
require('../config.php'); // This stops immediately at the beginning of lib/setup.php.
require_once("$CFG->dirroot/lib/jslib.php");
require_once("$CFG->dirroot/lib/classes/requirejs.php");

$slashargument = min_get_slash_argument();
if (!$slashargument) {
    // The above call to min_get_slash_argument should always work.
    die('Invalid request');
}

$slashargument = ltrim($slashargument, '/');
if (substr_count($slashargument, '/') < 1) {
    header('HTTP/1.0 404 not found');
    die('Slash argument must contain both a revision and a file path');
}
// Split into revision and module name.
list($rev, $file) = explode('/', $slashargument, 2);
$rev  = min_clean_param($rev, 'INT');
$file = '/' . min_clean_param($file, 'SAFEPATH');

// Only load js files from the js modules folder from the components.
$jsfiles = array();
list($unused, $component, $module) = explode('/', $file, 3);

// No subdirs allowed - only flat module structure please.
if (strpos('/', $module) !== false) {
    die('Invalid module');
}

// Some (huge) modules are better loaded lazily (when they are used). If we are requesting
// one of these modules, only return the one module, not the combo.
$lazysuffix = "-lazy.js";
$lazyload = (strpos($module, $lazysuffix) !== false);

if ($lazyload) {
    // We are lazy loading a single file - so include the component/filename pair in the etag.
    $etag = sha1($rev . '/' . $component . '/' . $module);
} else {
    // We loading all (non-lazy) files - so only the rev makes this request unique.
    $etag = sha1($rev);
}


// Use the caching only for meaningful revision numbers which prevents future cache poisoning.
if ($rev > 0 and $rev < (time() + 60 * 60)) {
    $candidate = $CFG->localcachedir . '/requirejs/' . $etag;

    if (file_exists($candidate)) {
        if (!empty($_SERVER['HTTP_IF_NONE_MATCH']) || !empty($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
            // We do not actually need to verify the etag value because our files
            // never change in cache because we increment the rev parameter.
            js_send_unmodified(filemtime($candidate), $etag);
        }
        js_send_cached($candidate, $etag, 'requirejs.php');
        exit(0);

    } else {
        $jsfiles = array();
        if ($lazyload) {
            $jsfiles = core_requirejs::find_one_amd_module($component, $module);
        } else {
            // Here we respond to the request by returning ALL amd modules. This saves
            // round trips in production.

            $jsfiles = core_requirejs::find_all_amd_modules();
        }

        $content = '';
        foreach ($jsfiles as $modulename => $jsfile) {
            $js = file_get_contents($jsfile);
            if ($js === false) {
                error_log('Failed to load JavaScript file ' . $jsfile);
                $js = "/* Failed to load JavaScript file {$jsfile}. */\n";
                $content = $js . $content;
                continue;
            }
            $js .= "\n";
            // Inject the module name into the define.
            $replace = 'define(\'' . $modulename . '\', ';
            $search = 'define(';
            // Replace only the first occurrence.
            $js = implode($replace, explode($search, $js, 2));
            $content .= $js;
        }

        js_write_cache_file_content($candidate, $content);
        // Verify nothing failed in cache file creation.
        clearstatcache();
        if (file_exists($candidate)) {
            js_send_cached($candidate, $etag, 'requirejs.php');
            exit(0);
        }
    }
}

if ($lazyload) {
    $jsfiles = core_requirejs::find_one_amd_module($component, $module, true);
} else {
    $jsfiles = core_requirejs::find_all_amd_modules(true);
}

$content = '';
foreach ($jsfiles as $modulename => $jsfile) {
    $shortfilename = str_replace($CFG->dirroot, '', $jsfile);
    $js = "// ---- $shortfilename ----\n";
    $js .= file_get_contents($jsfile) . "\n";
    // Inject the module name into the define.
    $replace = 'define(\'' . $modulename . '\', ';
    $search = 'define(';

    if (strpos($js, $search) === false) {
        // We can't call debugging because we only have minimal config loaded.
        header('HTTP/1.0 500 error');
        die('JS file: ' . $shortfilename . ' cannot be loaded, or does not contain a javascript module in AMD format. "define()" not found.');
    }

    // Replace only the first occurrence.
    $js = implode($replace, explode($search, $js, 2));
    $content .= $js;
}
js_send_uncached($content, 'requirejs.php');
