Courses and course formats

Dear Gareth,

Sorry, but I've been out. I red the 3 documents you said and I can't find my mistake yet. I'm using ajax to retrieve the form to this .php:

 $courseid = required_param('courseid', PARAM_INT);
    
    $context = get_context_instance(CONTEXT_COURSE, $courseid);
    
    //$context = context_system::instance();
    
    $fs = get_file_storage();
    $draftid = file_get_submitted_draft_itemid('attachments');//Generate unique id
    
    $PAGE->set_context( $context );    
    //$itemid = 0;
    
    $itemid = file_get_submitted_draft_itemid('attachments');
    
    $filemanageropts = array('subdirs' => 0, 'maxbytes' => '0', 'maxfiles' => 10, 'accepted_types' => array('document','.jpg'),'context' => $context);    
    
    // Copy all the files from the 'real' area, into the draft area
    file_prepare_draft_area($draftid, $context->id, 'format_socialmedia', 'attachment', $itemid, $filemanageropts);
    
    file_save_draft_area_files($draftid, $context->id, 'format_socialmedia', 'attachment', $itemid, $filemanageropts);
    
    //Get area files
    $files = $fs->get_area_files($context->id, 'format_socialmedia', 'attachment', $itemid);
        
    foreach($files as $file)
    {
        $out = $file->get_filename();
        if ($file->is_directory()) {
                $out = $file->get_filepath();
            }
        else {
            $fileurl = moodle_url::make_pluginfile_url($file->get_contextid(), $file->get_component(), $file->get_filearea(),
                                                       $file->get_itemid(), $file->get_filepath(), $file->get_filename());
            $out = html_writer::link($fileurl, $out);
        }
                  
        
        echo $out;
    }

So I'm trying to obtain the url to get the document. I think that I have to put the course_socialmedia_pluginfile in lib.php so:

function format_socialmedia_pluginfile($course,$cm, $context, $filearea, $args, $forcedownload, array $options=array()) {
    global $CFG, $DB;

            $fs = get_file_storage();
            global $DB;
            
            list($itemid, $filename) = $args;
            
            $params = array(
                'component' => 'format_socialmedia',
                'filearea' => $filearea,
                'itemid' => $itemid,
                'filename' => $filename
            );
            
             $instanceid = $DB->get_field('files', 'id', $params);

        if (empty($instanceid)) {
            send_file_not_found();
        } else {
            $file = $fs->get_file_by_id($instanceid);
            send_stored_file($file);
        }
            
                    
    }

When I get the url I put as browser's address and gave the error file not found. Hope you can help me. Thanks in advance!!

Cheers,

Tony