Set uploaded image or image url as featured image

I am creating a custom submit form (yes, its heavily customized to suit my needs) but the only problem is, when I try to upload the image (via Dropzone.js) or image url, the image doesn’t upload and it is not set as featured image. The uploader can only upload images 1 at a time. Am I doing something wrong here? Unfortunately, I cannot link it to a website, as this is all done on localhost. Sorry if the code is messy, just making a basic functioning script before I secure it and clean it up.

Here’s the code.
HEADING

<script src="<?php echo esc_url( get_template_directory_uri() ); ?>/js/ta.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/dropzone/4.0.1/dropzone.js"></script>
 <link href="https://cdnjs.cloudflare.com/ajax/libs/dropzone/4.0.1/dropzone.css" rel="stylesheet" />
 <script type="text/javascript"> 

 Dropzone.autoDiscover = false;
 Dropzone.options.myAwesomeDropzone = {
  maxFiles: 1,
  accept: function(file, done) {
    console.log("uploaded");
    done();
  },
  init: function() {
    this.on("maxfilesexceeded", function(file){
        alert("No more files please!");
    });
  }
};
    $(document).ready(function() {
$( "#showurlupload" ).click(function() {
  $( "#dropupload" ).slideToggle( "slow", function() {
    // Animation complete.
      $( "#urlupload" ).slideToggle( "slow", function() {
    // Animation complete.
  });
  });
});
      $("div#myAwesomeDropzone").dropzone({
        url: "/file/post"
      });
    });</script>
</head>

PAGE

<?php
// Check if the form was submitted
if( 'POST' == $_SERVER['REQUEST_METHOD'] && !empty( $_POST['action'] )) {

        // Do some minor form validation to make sure there is content
        if (isset ($_POST['title'])) {
                $title =  $_POST['title'];
        } else {
                echo 'Please enter a title';
        }
 /*       if (isset ($_POST['description'])) {
                $description = htmlentities(trim(stripcslashes($_POST['description'])));
    } else {
        echo 'Please enter the content';
        }
        */

        $tags = $_POST['post_tags'];
        $source = $_POST['source'];
        $imgurl = $_POST['imgurl'];

        // Add the content of the form to $post as an array
        $type = trim($_POST['Type']);
        $post = array(
                'post_title'    => $title,
                'post_content'  => $description,
                'post_category' =>   array($_POST['cat']),  // Usable for custom taxonomies too
                'post_status'   => 'pending',                     // Choose: publish, preview, future, etc.
                'tags_input'    => array($tags),
                'comment_status' => 'open',
                'post_author' => '2',
                'source'    =>   $source
        );
        $post_id = wp_insert_post($post);
        wp_set_post_terms($post_id,$type,'Type',true);
        add_post_meta($post_id, 'source', $source, false);
        $upload_dir = wp_upload_dir();
        // if using image url
        if ($imgurl) {
            $image_data = file_get_contents($imgurl);
            $filename = basename($imgurl);
            if(wp_mkdir_p($upload_dir['path']))
                $file = $upload_dir['path'] . '/' . $filename;
            else
                $file = $upload_dir['basedir'] . '/' . $filename;
            file_put_contents($file, $image_data);

            $wp_filetype = wp_check_filetype($filename, null );
            $attachment = array(
                'post_mime_type' => $wp_filetype['type'],
                'post_title' => sanitize_file_name($filename),
                'post_content' => '',
                'post_status' => 'inherit'
            );
            $attach_id = wp_insert_attachment( $attachment, $file, $post_id );
            require_once(ABSPATH . 'wp-admin/includes/image.php');
            $attach_data = wp_generate_attachment_metadata( $attach_id, $file );
            wp_update_attachment_metadata( $attach_id, $attach_data );

            set_post_thumbnail( $post_id, $attach_id );
        } else if ($_FILES) {
                foreach ($_FILES as $file => $array) {
                $filename = $file;
                if(wp_mkdir_p($upload_dir['path']))
                    $file = $upload_dir['path'] . '/' . $filename;
                else
                    $file = $upload_dir['basedir'] . '/' . $filename;
                file_put_contents($file, $image_data);

                $wp_filetype = wp_check_filetype($filename, null );
                $attachment = array(
                    'post_mime_type' => $wp_filetype['type'],
                    'post_title' => sanitize_file_name($filename),
                    'post_content' => '',
                    'post_status' => 'inherit'
                );
                $attach_id = wp_insert_attachment( $attachment, $file, $post_id );
                require_once(ABSPATH . 'wp-admin/includes/image.php');
                $attach_data = wp_generate_attachment_metadata( $attach_id, $file );
                wp_update_attachment_metadata( $attach_id, $attach_data );

                set_post_thumbnail( $post_id, $attach_id );
                }
             }

        wp_redirect( home_url('/listing-submitted/') ); // redirect to home page after submit
        exit();
}
 // end IF
?>
<?php get_header() ?>
<div class="container">
                        <h1>Share something awesome!</h1>

<!--SUBMIT POST-->
                        <form id="new_post" name="new_post" class="form-horizontal" method="post" enctype="multipart/form-data">
<div id="dropupload"><div class="dropzone dropzone-previews" id="myAwesomeDropzone"></div></div>
                                <a href="#" class="lead" id="showurlupload">Upload via URL</a>
                                <div id="urlupload" style="display:none;">
                                <div class="form-group">
                                <label for="imgurl" class="col-sm-3 control-label">Image URL</label>
                                    <div class="col-sm-9">
                                        <input type="text" id="imgurl" class="form-control required" value="" tabindex="1" size="20" name="imgurl" />
                                    </div>
                                </div>
                                </div>
                                <div class="form-group">
                                <label for="title" class="col-sm-3 control-label">Title</label>
                                    <div class="col-sm-9">
                                        <input type="text" id="title" class="form-control required" value="" tabindex="1" size="20" name="title" />
                                    </div>
                                </div>
                                <div class="form-group">
                                        <label for="cat" class="col-sm-3 control-label">Content Type:</label>
                                        <div class="col-sm-9">
                                        <?php wp_dropdown_categories( 'tab_index=10&taxonomy=category&hide_empty=0' ); ?>
                                    </div>
</div>
<!-- Source -->
                                <div class="form-group">
                                        <label for="source" class="col-sm-3 control-label">Source</label>
                                        <div class="col-sm-9">
                                        <input type="text" value="" id="source" class="form-control" tabindex="20" name="source" />
                                    </div>
 </div>
<!-- Listing Services -->
                                <div class="form-group">
                                        <label for="post_tags" class="col-sm-3 control-label">Tags (7 max)</label>
                                        <div class="col-sm-9">
<div class="tagsinput-primary"><input type="text" value="" tabindex="35" name="post_tags" id="post_tags" class="tagsinput" data-role="tagsinput" />
</div>
</div>
 </div>
                                <input type="hidden" name="post_type" id="post_type" value="domande" />
                                <input type="hidden" name="action" value="post" />

                                <input type="submit" value="Submit" class="btn btn-primary btn-lg" tabindex="6" id="submit" name="submit" />

                                <?php wp_nonce_field( 'new-post' ); ?>
                        </form>