'''
Asynchronous data loader
========================

This is the Asynchronous Loader. You can use it to load an image
and use it, even if data are not yet available. You must specify a default
loading image when using the loader::

    from kivy.loader import Loader
    image = Loader.image('mysprite.png')

You can also load an image from a url::

    image = Loader.image('http://mysite.com/test.png')

If you want to change the default loading image, you can do::

    Loader.loading_image = Image('another_loading.png')

Tweaking the asynchronous loader
--------------------------------

.. versionadded:: 1.6.0

You can tweak the loader to provide a better user experience or more
performance, depending of the images you are going to load. Take a look at the
parameters:

- :attr:`Loader.num_workers` - define the number of threads to start for
  loading images.
- :attr:`Loader.max_upload_per_frame` - define the maximum image uploads in
  GPU to do per frame.

'''

__all__ = ('Loader', 'LoaderBase', 'ProxyImage')

from kivy import kivy_data_dir
from kivy.logger import Logger
from kivy.clock import Clock
from kivy.cache import Cache
from kivy.core.image import ImageLoader, Image
from kivy.compat import PY2

from collections import deque
from time import sleep
from os.path import join
from os import write, close, unlink, environ
import threading

# Register a cache for loader
Cache.register('kv.loader', limit=500, timeout=60)


class ProxyImage(Image):
    '''Image returned by the Loader.image() function.

    :Properties:
        `loaded`: bool, defaults to False
            This value may be True if the image is already cached.

    :Events:
        `on_load`
            Fired when the image is loaded or changed.
    '''

    __events__ = ('on_load', )

    def __init__(self, arg, **kwargs):
        kwargs.setdefault('loaded', False)
        super(ProxyImage, self).__init__(arg, **kwargs)
        self.loaded = kwargs.get('loaded')

    def on_load(self):
        pass


class LoaderBase(object):
    '''Common base for the Loader and specific implementations.
    By default, the Loader will be the best available loader implementation.

    The _update() function is called every 1 / 25.s or each frame if we have
    less than 25 FPS.
    '''

    def __init__(self):
        self._loading_image = None
        self._error_image = None
        self._num_workers = 2
        self._max_upload_per_frame = 2
        self._paused = False
        self._resume_cond = threading.Condition()

        self._q_load = deque()
        self._q_done = deque()
        self._client = []
        self._running = False
        self._start_wanted = False
        self._trigger_update = Clock.create_trigger(self._update)

    def __del__(self):
        try:
            Clock.unschedule(self._update)
        except Exception:
            pass

    def _set_num_workers(self, num):
        if num < 2:
            raise Exception('Must have at least 2 workers')
        self._num_workers = num

    def _get_num_workers(self):
        return self._num_workers

    num_workers = property(_get_num_workers, _set_num_workers)
    '''Number of workers to use while loading (used only if the loader
    implementation supports it). This setting impacts the loader only on
    initialization. Once the loader is started, the setting has no impact::

        from kivy.loader import Loader
        Loader.num_workers = 4

    The default value is 2 for giving a smooth user experience. You could
    increase the number of workers, then all the images will be loaded faster,
    but the user will not been able to use the application while loading.
    Prior to 1.6.0, the default number was 20, and loading many full-hd images
    was completly blocking the application.

    .. versionadded:: 1.6.0
    '''

    def _set_max_upload_per_frame(self, num):
        if num is not None and num < 1:
            raise Exception('Must have at least 1 image processing per image')
        self._max_upload_per_frame = num

    def _get_max_upload_per_frame(self):
        return self._max_upload_per_frame

    max_upload_per_frame = property(_get_max_upload_per_frame,
                                    _set_max_upload_per_frame)
    '''The number of images to upload per frame. By default, we'll
    upload only 2 images to the GPU per frame. If you are uploading many
    small images, you can easily increase this parameter to 10 or more.
    If you are loading multiple full HD images, the upload time may have
    consequences and block the application. If you want a
    smooth experience, use the default.

    As a matter of fact, a Full-HD RGB image will take ~6MB in memory,
    so it may take time. If you have activated mipmap=True too, then the
    GPU must calculate the mipmap of these big images too, in real time.
    Then it may be best to reduce the :attr:`max_upload_per_frame` to 1
    or 2. If you want to get rid of that (or reduce it a lot), take a
    look at the DDS format.

    .. versionadded:: 1.6.0
    '''

    def _get_loading_image(self):
        if not self._loading_image:
            loading_png_fn = join(kivy_data_dir, 'images', 'image-loading.gif')
            self._loading_image = ImageLoader.load(filename=loading_png_fn)
        return self._loading_image

    def _set_loading_image(self, image):
        if isinstance(image, basestring):
            self._loading_image = ImageLoader.load(filename=image)
        else:
            self._loading_image = image

    loading_image = property(_get_loading_image, _set_loading_image)
    '''Image used for loading.
    You can change it by doing::

        Loader.loading_image = 'loading.png'

    .. versionchanged:: 1.6.0
        Not readonly anymore.
    '''

    def _get_error_image(self):
        if not self._error_image:
            error_png_fn = join(
                'atlas://data/images/defaulttheme/image-missing')
            self._error_image = ImageLoader.load(filename=error_png_fn)
        return self._error_image

    def _set_error_image(self, image):
        if isinstance(image, basestring):
            self._error_image = ImageLoader.load(filename=image)
        else:
            self._error_image = image

    error_image = property(_get_error_image, _set_error_image)
    '''Image used for error.
    You can change it by doing::

        Loader.error_image = 'error.png'

    .. versionchanged:: 1.6.0
        Not readonly anymore.
    '''

    def start(self):
        '''Start the loader thread/process.'''
        self._running = True

    def run(self, *largs):
        '''Main loop for the loader.'''
        pass

    def stop(self):
        '''Stop the loader thread/process.'''
        self._running = False

    def pause(self):
        '''Pause the loader, can be useful during interactions.

        .. versionadded:: 1.6.0
        '''
        self._paused = True

    def resume(self):
        '''Resume the loader, after a :meth:`pause`.

        .. versionadded:: 1.6.0
        '''
        self._paused = False
        self._resume_cond.acquire()
        self._resume_cond.notify_all()
        self._resume_cond.release()

    def _wait_for_resume(self):
        while self._running and self._paused:
            self._resume_cond.acquire()
            self._resume_cond.wait(0.25)
            self._resume_cond.release()

    def _load(self, kwargs):
        '''(internal) Loading function, called by the thread.
        Will call _load_local() if the file is local,
        or _load_urllib() if the file is on Internet.
        '''

        while len(self._q_done) >= (
                self.max_upload_per_frame * self._num_workers):
            sleep(0.1)

        self._wait_for_resume()

        filename = kwargs['filename']
        load_callback = kwargs['load_callback']
        post_callback = kwargs['post_callback']
        try:
            proto = filename.split(':', 1)[0]
        except:
            #if blank filename then return
            return
        if load_callback is not None:
            data = load_callback(filename)
        elif proto in ('http', 'https', 'ftp', 'smb'):
            data = self._load_urllib(filename, kwargs['kwargs'])
        else:
            data = self._load_local(filename, kwargs['kwargs'])

        if post_callback:
            data = post_callback(data)

        self._q_done.appendleft((filename, data))
        self._trigger_update()

    def _load_local(self, filename, kwargs):
        '''(internal) Loading a local file'''
        # With recent changes to CoreImage, we must keep data otherwise,
        # we might be unable to recreate the texture afterwise.
        return ImageLoader.load(filename, keep_data=True, **kwargs)

    def _load_urllib(self, filename, kwargs):
        '''(internal) Loading a network file. First download it, save it to a
        temporary file, and pass it to _load_local().'''
        if PY2:
            import urllib2 as urllib_request
        else:
            import urllib.request as urllib_request
        proto = filename.split(':', 1)[0]
        if proto == 'smb':
            try:
                # note: it's important to load SMBHandler every time
                # otherwise the data is occasionaly not loaded
                from smb.SMBHandler import SMBHandler
            except ImportError:
                Logger.warning(
                    'Loader: can not load PySMB: make sure it is installed')
                return
        import tempfile
        data = fd = _out_osfd = None
        try:
            _out_filename = ''
            suffix = '.%s' % (filename.split('.')[-1])
            _out_osfd, _out_filename = tempfile.mkstemp(
                prefix='kivyloader', suffix=suffix)

            if proto == 'smb':
                # read from samba shares
                fd = urllib_request.build_opener(SMBHandler).open(filename)
            else:
                # read from internet
                fd = urllib_request.urlopen(filename)
            idata = fd.read()
            fd.close()
            fd = None

            # write to local filename
            write(_out_osfd, idata)
            close(_out_osfd)
            _out_osfd = None

            # load data
            data = self._load_local(_out_filename, kwargs)

            # FIXME create a clean API for that
            for imdata in data._data:
                imdata.source = filename
        except Exception:
            Logger.exception('Failed to load image <%s>' % filename)
            # close file when remote file not found or download error
            try:
                close(_out_osfd)
            except OSError:
                pass
            return self.error_image
        finally:
            if fd:
                fd.close()
            if _out_osfd:
                close(_out_osfd)
            if _out_filename != '':
                unlink(_out_filename)

        return data

    def _update(self, *largs):
        '''(internal) Check if a data is loaded, and pass to the client.'''
        # want to start it ?
        if self._start_wanted:
            if not self._running:
                self.start()
            self._start_wanted = False

        # in pause mode, don't unqueue anything.
        if self._paused:
            self._trigger_update()
            return

        for x in range(self.max_upload_per_frame):
            try:
                filename, data = self._q_done.pop()
            except IndexError:
                return

            # create the image
            image = data  # ProxyImage(data)
            if not image.nocache:
                Cache.append('kv.loader', filename, image)

            # update client
            for c_filename, client in self._client[:]:
                if filename != c_filename:
                    continue
                # got one client to update
                client.image = image
                client.loaded = True
                client.dispatch('on_load')
                self._client.remove((c_filename, client))

        self._trigger_update()

    def image(self, filename, load_callback=None, post_callback=None,
              **kwargs):
        '''Load a image using the Loader. A ProxyImage is returned with a
        loading image. You can use it as follows::

            from kivy.app import App
            from kivy.uix.image import Image
            from kivy.loader import Loader

            class TestApp(App):
                def _image_loaded(self, proxyImage):
                    if proxyImage.image.texture:
                        self.image.texture = proxyImage.image.texture

                def build(self):
                    proxyImage = Loader.image("myPic.jpg")
                    proxyImage.bind(on_load=self._image_loaded)
                    self.image = Image()
                    return self.image

            TestApp().run()

        In order to cancel all background loading, call *Loader.stop()*.
        '''
        data = Cache.get('kv.loader', filename)
        if data not in (None, False):
            # found image, if data is not here, need to reload.
            return ProxyImage(data,
                              loading_image=self.loading_image,
                              loaded=True, **kwargs)

        client = ProxyImage(self.loading_image,
                            loading_image=self.loading_image, **kwargs)
        self._client.append((filename, client))

        if data is None:
            # if data is None, this is really the first time
            self._q_load.appendleft({
                'filename': filename,
                'load_callback': load_callback,
                'post_callback': post_callback,
                'kwargs': kwargs})
            if not kwargs.get('nocache', False):
                Cache.append('kv.loader', filename, False)
            self._start_wanted = True
            self._trigger_update()
        else:
            # already queued for loading
            pass

        return client

#
# Loader implementation
#

if 'KIVY_DOC' in environ:

    Loader = None

else:

    #
    # Try to use pygame as our first choice for loader
    #

    from kivy.compat import queue
    from threading import Thread

    class _Worker(Thread):
        '''Thread executing tasks from a given tasks queue
        '''
        def __init__(self, pool, tasks):
            Thread.__init__(self)
            self.tasks = tasks
            self.daemon = True
            self.pool = pool
            self.start()

        def run(self):
            while self.pool.running:
                func, args, kargs = self.tasks.get()
                try:
                    func(*args, **kargs)
                except Exception as e:
                    print(e)
                self.tasks.task_done()

    class _ThreadPool(object):
        '''Pool of threads consuming tasks from a queue
        '''
        def __init__(self, num_threads):
            super(_ThreadPool, self).__init__()
            self.running = True
            self.tasks = queue.Queue()
            for _ in range(num_threads):
                _Worker(self, self.tasks)

        def add_task(self, func, *args, **kargs):
            '''Add a task to the queue
            '''
            self.tasks.put((func, args, kargs))

        def stop(self):
            self.running = False
            self.tasks.join()

    class LoaderThreadPool(LoaderBase):
        def __init__(self):
            super(LoaderThreadPool, self).__init__()
            self.pool = None

        def start(self):
            super(LoaderThreadPool, self).start()
            self.pool = _ThreadPool(self._num_workers)
            Clock.schedule_interval(self.run, 0)

        def stop(self):
            super(LoaderThreadPool, self).stop()
            Clock.unschedule(self.run)
            self.pool.stop()

        def run(self, *largs):
            while self._running:
                try:
                    parameters = self._q_load.pop()
                except:
                    return
                self.pool.add_task(self._load, parameters)

    Loader = LoaderThreadPool()
    Logger.info('Loader: using a thread pool of {} workers'.format(
        Loader.num_workers))
