FileStore for ATK (version 2.0) draft - You will need https://github.com/blueimp/jQuery-File-Upload and tpyo/amazon-s3-php-class

Model_File.php

<?php

class Model_File extends LF_Model {

    public $table = 'file';
    public $storage = null;

    public $local_copy = null;

    function init(){
        parent::init();

        $this->addField('location');     // e.g. s3://bucket/file or http://host/file, or file://path/to/file
        $this->addField('url');          // public access URL if file is available
        $this->addField('storage');      // storage controller used

        $this->addField('status')->enum(['draft','uploaded','verified']);

        $this->containsOne(['file_metadata', 'json'=>true], [$this, 'initFileMetadata']);

        $this->addHook('beforeDelete,afterUnload,afterLoad', $this);
    }

    function initFileMetadata($m){
        $m->addField('extension');
        $m->addField('size');
        $m->addField('md5');
        $m->addField('original_filename');

        $m->addField('is_image')->type('boolean');
        $m->addField('mime');
        $m->addField('width');
        $m->addField('height');
    }

    /**
     * Call to associate with a file storage service (such as Amazon S3)
     */
    function setStorage($controller){
        $controller = $this->api->normalizeClassName($controller, 'Storage');
        $this->storage = $this->setController($controller);
        return $this;
    }

    function import($source, $original_filename=null){
        if(!$this->storage)throw $this->exception('Set Storage Controller first');

        $this->unload();
        $this['status']='draft';
        $this->save();

        $m = $this->ref('file_metadata');
        $m['original_filename'] = basename($original_filename?:$source);
        $m['size'] = filesize($source);
        $m['extension'] = pathinfo($original_filename?:$source, PATHINFO_EXTENSION);

        // TODO: that's only for images
        $is = getimagesize($source);
        if($m['is_image'] = (boolean)$is){
            $m['mime'] = $is['mime'];
            $m['width'] = $is[0];
            $m['height'] = $is[1];
            $m['md5'] = md5_file($source);
            //$m['extension'] = $is['mime'];
        }

        $m->save();

        $this->storage->put($this, $source);
        $this['status']='uploaded';
        //$this->local_copy = $source;
        $this->save();
    }

    /**
     * Verify that the file is uploaded correctly
     * @param  [type] $source [description]
     * @return [type]         [description]
     */
    function verify($source = null){
        // make sure, that public URL is accessible
        if(md5_file($this['url']) == $this->ref('file_metadata')['md5']){
            $this['status'] = 'verified';
            $this->save();
            return true;
        }
        return false;
    }

    /**
     * Retrieve file and store in local file
     */
    function getFile(){
        if($this->local_copy)return $this->local_copy;
        return $this->local_copy = $this->storage->get($this);
    }

    function beforeDelete(){
        try {
            if($this->loaded() and $this->storage){
                $this->storage->delete($this);
            }
        }catch(Exception $e){
            // ignore
        }
    }

    function __destruct(){
        if($this->local_copy)@unlink($this->local_copy);
    }

    function afterLoad(){
        if($this['storage'] == 's3' && !$this->storage)$this->setStorage('S3');
    }

    function afterUnload(){
        if($this->local_copy)@unlink($this->local_copy);
        $this->local_copy=null;
    }
}

Model_Image.php

<?php
/**
 * Represents an uploaded file which is still being processed
 */
class Model_Image extends SQL_Model
{
    public $table="image";
    public $default_storage='S3';
    public $title_field='thumb_url';
    public $thumb_width = 600;
    public $thumb_height = 400;

    function init()
    {
        parent::init();

        $this->addField('status')
            ->enum(['draft','uploaded','thumbok','normalok','ready','linked']);

        $this->hasOne('File','original_file_id');
        $this->addField('original_url');

        $this->hasOne('File','thumb_file_id');
        $this->addField('thumb_url');

        $this->hasOne('File','normal_file_id');
        $this->addField('url');

        $this->addField('type')->enum(['testing','loan','gallery']);

        $this->addHook('beforeDelete', $this);
    }

    function setStorage($st){
        $this->default_storage = $st;
        return $this;
    }

    function autoRotateImage($i){
        $orientation = $i->getImageOrientation();

        switch($orientation) {
            case imagick::ORIENTATION_BOTTOMRIGHT:
                $i->rotateimage("#000", 180); // rotate 180 degrees
                break;

            case imagick::ORIENTATION_RIGHTTOP:
                $i->rotateimage("#000", 90); // rotate 90 degrees CW
                break;

            case imagick::ORIENTATION_LEFTBOTTOM:
                $i->rotateimage("#000", -90); // rotate 90 degrees CCW
                break;
        }

        // Now that it's auto-rotated, make sure the EXIF data is correct in case the EXIF gets saved with the image!
        $i->setImageOrientation(imagick::ORIENTATION_TOPLEFT);
    }

    function import($original,$original_filename = null) {
        $this->unload();

        $f = $this->ref('original_file_id','model');
        $f->setStorage(
            $this->default_storage,
            $this->app->getConfig('amazon/s3/image-bucket').'/original'
        );
        if($this->debug)$f->debug();
        $f->import($original,$original_filename);
        $f->verify();
        $this['original_file_id'] = $f->id;
        $this['original_url'] = $f['url'];

        $orig = $f->getFile();
        $i = new \Imagick($orig);
        $this->autoRotateImage($i);
        $i->cropThumbnailImage($this->thumb_width, $this->thumb_height);
        $thumb = tempnam('/tmp',$f->ref('file_metadata')['original_filename'].'.thumb.');
        $i->writeImage($thumb);
        unset($i);







        $f = $this->ref('thumb_file_id','model');
        if($this->debug)$f->debug();
        $f->setStorage(
            $this->default_storage,
            $this->app->getConfig('amazon/s3/image-bucket').'/thumb'
        );
        $f->import($thumb, $original_filename);
        $f->verify();
        $this['thumb_file_id'] = $f->id;
        $this['thumb_url'] = $f['url'];





        $i = new \Imagick($orig);
        $this->autoRotateImage($i);
        $i->cropThumbnailImage($this->thumb_width*2, $this->thumb_height*2);


        $norm = tempnam('/tmp',$f->ref('file_metadata')['original_filename'].'.norm.');
        $i->writeImage($norm);

        $f = $this->ref('normal_file_id','model');
        if($this->debug)$f->debug();
        $f->setStorage(
            $this->default_storage,
            $this->app->getConfig('amazon/s3/image-bucket').'/normal'
        );
        $f->import($norm, $original_filename);
        $f->verify();
        $this['normal_file_id'] = $f->id;
        $this['url'] = $f['url'];
        $this->save();
    }

    function ref($x,$t = null){
        $m = parent::ref($x,$t);
        if($m instanceof Model_File){
            $m->setStorage('S3');
        }
        return $m;
    }

    function beforeDelete(){
        try {
            if($this['original_file_id'])$this->ref('original_file_id')->delete();
            if($this['thumb_file_id'])$this->ref('thumb_file_id')->delete();
            if($this['normal_file_id'])$this->ref('normal_file_id')->delete();
        }catch(Exception $e){
            //
        }
    }
}

Storage.php

<?php
abstract class Controller_Storage extends AbstractController {
    public $default_exception = 'Exception_Storage';

    /**
     * Some file storage systems support public URLs to the
     * file (CDN)
     */
    public $supportPublicURL = false;

    function init(){
        parent::init();
        if(!$this->owner instanceof Model_File)throw $this->exception('Add only into File model');
    }

    /**
     * Places currently loaded file into the store. Second argument
     * must contain the file which is being imported and it must be
     * readable. Model will be modified with some additional information
     * which can then further be used to retrieve the file.
     */
    abstract function put($model, $source_file);

    /**
     * Retrieve file from the store, store in a local file and
     * return name of that file. Can also return URL to public
     * file.
     */
    abstract function get($model);

    /**
     * Deletes associtaed file from the store.
     */
    abstract function delete($model);

}

Storage_S3.php

<?php
class Controller_Storage_S3 extends Controller_Storage {

    public $useSSL = true;
    public $endpoint = 's3-eu-west-1.amazonaws.com';

    function connect(){
        return new S3(
            $this->app->getConfig('amazon/s3/Access_Key_ID'),
            $this->app->getConfig('amazon/s3/Secret_Access_Key'),
            $this->useSSL,
            $this->endpoint
        );
    }

    function put($model, $source_file){
        // genetare unique filename
        $uniq = uniqid().'.'.$model->ref('file_metadata')['extension'];

        $s3 = $this->connect();

        $res = $s3 -> putObject(
            S3::inputFile($source_file, false),
            $bucket = $this->app->getConfig('amazon/s3/image-bucket').'/original',
            $uniq,
            S3::ACL_PUBLIC_READ,
            [],
            ['Content-Type' => $model->ref('file_metadata')['mime']]
        );

        $model['storage']='s3';
        $model['location']='s3://'.$this->endpoint.'/'.$bucket.'/'.$uniq;

        list($b1, $b2) = explode('/', $bucket, 2);


        $model['url']='https://'.$b1.'.s3.amazonaws.com/'.$b2.'/'.$uniq;

        return $res;

    }

    /**
     * Break location such as s3://s3-eu-west-1.amazonaws.com/lf-image/original/55dc62824072f.png
     * into bucket and filename.
     *
     * @return array(bucket, uri);
     */
    function splitLocation($location){

        // s3://s3-eu-west-1.amazonaws.com/lf-image/original/55dc62824072f.png
        list(,$location) = explode('//', $location, 2);

        // s3-eu-west-1.amazonaws.com/lf-image/original/55dc62824072f.png

        list(,$location) = explode('/', $location, 2);

        // lf-image/original/55dc62824072f.png

        return [dirname($location), basename($location)];

        // lf-image/original   |   55dc62824072f.png

    }

    /**
     * Retrieve file from the store, store in a local file and
     * return name of that file. Can also return URL to public
     * file.
     */
    function get($model){
        $s3 = $this->connect();
        list($bucket,$file) = $this->splitLocation($model['location']);

        $s = tempnam('/tmp','atk-file-');
        $s3->getObject($bucket, $file, $s);
        return $s;
    }

    /**
     * Deletes associtaed file from the store.
     */
    function delete($model){
        $s3 = $this->connect();
        list($bucket,$file) = $this->splitLocation($model['location']);

        $s = tempnam('/tmp','atk-file-');
        return $s3->deleteObject($bucket, $file, $s);
    }

}

Upload2.php

<?php
class Form_Field_Upload2 extends Form_Field {

    public $vp;

    function init(){
        parent::init();
        $this->app->jquery->addStaticInclude('jquery.iframe-transport');
        $this->app->jquery->addStaticInclude('jquery.fileupload');

    }

    function setModel($m){
        parent::setModel($m);


        $this->vp = $this->app->page_object->add('VirtualPage');
        $this->vp->set(function($f){

            try {

                error_reporting(E_ALL | E_STRICT);
                if(!$_FILES[$this->short_name]['tmp_name']){

                    throw $this->exception('File data empty. Possibly it is too large')
                        ->addMoreInfo('content-length',$_SERVER['CONTENT_LENGTH'])
                        ->addMoreInfo('post_max_size',ini_get('post_max_size'))
                        ;
                }

                $this->model->import($_FILES[$this->short_name]['tmp_name'], $_FILES[$this->short_name]['name']);
                $res = $this->model->get();
                echo json_encode($res);
                exit;

            }catch(Exception $e){

                $res = ['exception' => $e->getHTML()];
                echo json_encode($res);
                exit;
            }
        });
        return $this->model;
    }

    function getInput(){

        if($_GET['val']){
            if(!$this->value)$this->js(true)->trigger('uploaded'); // we just changed our value.
            $this->value=$_GET['val'];
        }

        if($_GET['del']){
            $f = $this->model->tryLoad($_GET['del']);

            $this->js(true)->trigger('removed'); // we just changed our value.

            if($f->loaded())$f->delete() ;
            $this->value=null;
        }

        if($this->value){
            $f = $this->model->tryLoad($this->value);
            if($f->loaded()){
                if($f instanceof Model_Image)$f=$f->ref('thumb_file_id');

                $this->on('click', '.do-link')->univ()->dialogOK('Image','<img src="'.$f['url'].'"/>',null,['width'=>'1000']);
                $this->on('click', '.do-remove-but', $this->form->js()->atk4_form('reloadField',$this->short_name,null,null,null,['del'=>$this->value]));

                        return '<div class="atk-form-field" data-shortname="'.$this->short_name.'" id="'.$this->getJSID().'">'.
                        parent::getInput(array('type'=>'hidden')).
                    '<div class="atk-cells atk-cells-gutter-small"><div class="atk-cell"><button class=" atk-button do-remove-but"><span class=" icon-trash" style=""></span>&nbsp;Remove</button></div><div class="atk-cell atk-expand"><div class="atk-effect-info atk-box-small atk-shape-rounded atk-text-nowrap">'.
                    'File: <a href="javascript: void(0)" class="do-link"><span class=" icon-file-image"
                style=""></span>&nbsp;'.$f->ref('file_metadata')['original_filename'].'</a></div>
                    </div></div></div>';
            }

        }


        $this->js(true)
            ->_load('jquery.iframe-transport')
            ->_load('jquery.fileupload')
            ->_selector('#'.$this->getJSID().' .do-upload')->fileupload([
                'url'=>$this->vp->getURL(),
                'dataType'=>'json',
                'progressall'=>$this->js(null,'function (e, data) {
                        var progress = parseInt(data.loaded / data.total * 100, 10);
                        if(progress!=100){
                            $("#'.$this->getJSID().'").find(".do-pill").css("width",progress+"%").find("span:first").text(progress+"%");
                        }else{
                            $("#'.$this->getJSID().'").find(".do-pill").css("width","100%").find("span:first").text("Processing file..");
                            $("#'.$this->getJSID().'").find(".do-spinner").show();
                        }
                }'),
                'start'=>$this->js(null,'function (e, data) {
                    $("#'.$this->getJSID().' .do-upload-but").attr("disabled",true).hide();
                    $("#'.$this->getJSID().'").find(".do-info").remove();
                    $("#'.$this->getJSID().'").find(".do-pill").removeClass("atk-effect-danger").addClass("atk-effect-info").show().css("width","0%");
                }'),
                'done'=>$this->js(null,'function (e, data) { if(data.result.exception){

                    var but = $(document.createElement("button")).insertAfter("#'.$this->getJSID().' .do-upload-but").addClass("atk-button").text("OK");

                    but.click(function(e){ e.preventDefault(); but.closest(".atk4_form_widget").atk4_form("reloadField","'.$this->short_name.'"); });

                    $("#'.$this->getJSID().'").find(".do-pill").text("Upload file problem").removeClass("atk-effect-info").addClass("atk-effect-danger");

                    $.univ().dialogOK("Upload Problem",data.result.exception,null,{width:1200});
                    return;
                }; console.log(data);
                $("#'.$this->getJSID().'").find(".do-pill").closest(".atk4_form_widget").atk4_form("reloadField","'.$this->short_name.'",null,null,null,{val:data.result.id});
            }'),
                ]);
            ;

        //$this->js('click', $this->js()->_selector('#upload')->click())->_selector('#upload-but');
        $this->on('click','.do-upload-but',$this->js()->find('.do-upload')->click());
        //$this->js('click', $this->js()->_selector('#pill')->show()->css('width','100%'))->_selector('#info')->remove();
        //->css('width','100%');

//        $this->js('click')->_selector('#upload-but')->univ()->alert(1);

        return
            '<div class="atk-form-field" data-shortname="'.$this->short_name.'" id="'.$this->getJSID().'"><input class=" atk-button do-upload" type="file" name="'.$this->short_name.'" multiple style="display: none">'.
            '<div class="atk-cells atk-cells-gutter-small"><div class="atk-cell"><button class=" atk-button do-upload-but"><span  class=" icon-upload"
            style=""></span>&nbsp;Upload</button></div><div class="atk-cell atk-expand"><div
            style="display: none; -webkit-transition: width 0.3s; width: 0%; left: 0; padding-left: 10px; position: relative; overflow: none"
            class="atk-effect-info atk-box-small atk-shape-rounded atk-text-nowrap do-pill" style="overflow: hidden">Progress: <span>0%</span><span class="do-spinner animate-spin atk-move-right icon-spin4"
            style="display: none"></span></div><div class="do-info">Select file then wait until upload finishes before submitting form.</div>
            </div></div></div>';
    }


}

class MyUploadHandler extends UploadHandler {
    protected function handle_file_upload($uploaded_file, $name, $size, $type, $error,
            $index = null, $content_range = null) {

        $file = new \stdClass();
        $file->name = $this->get_file_name($uploaded_file, $name, $size, $type, $error,
            $index, $content_range);
        $file->size = $this->fix_integer_overflow((int)$size);
        $file->type = $type;
        if ($this->validate($uploaded_file, $file, $error, $index)) {
            $this->handle_form_data($file, $index);
            $file_path = $this->get_upload_path($file->name);

            var_dump($file_path, $uploaded_file, $name, $size, $type, $error, $index, $content_range);
        }


    }
}