# coding: utf-8
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# Copyright (c) 2017-2018 European Synchrotron Radiation Facility
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"""This module provides convenient functions to use with Qt objects.

It provides:
- conversion between numpy and QImage:
  :func:`convertArrayToQImage`, :func:`convertQImageToArray`
- Execution of function in Qt main thread: :func:`submitToQtMainThread`
"""

from __future__ import division


__authors__ = ["T. Vincent"]
__license__ = "MIT"
__date__ = "16/01/2017"


import sys
import numpy

from silx.third_party.concurrent_futures import Future

from . import qt


def convertArrayToQImage(image):
    """Convert an array-like RGB888 image to a QImage.

    The created QImage is using a copy of the array data.

    Limitation: Only supports RGB888 format.

    :param image: Array-like image data
    :type image: numpy.ndarray of uint8 of dimension HxWx3
    :return: Corresponding Qt image
    :rtype: QImage
    """
    # Possible extension: add a format argument to support more formats

    image = numpy.array(image, copy=False, order='C', dtype=numpy.uint8)

    height, width, depth = image.shape
    assert depth == 3

    qimage = qt.QImage(
        image.data,
        width,
        height,
        image.strides[0],  # bytesPerLine
        qt.QImage.Format_RGB888)

    return qimage.copy()  # Making a copy of the image and its data


def convertQImageToArray(image):
    """Convert a RGB888 QImage to a numpy array.

    Limitation: Only supports RGB888 format.
    If QImage is not RGB888 it gets converted to this format.

    :param QImage: The QImage to convert.
    :return: The image array
    :rtype: numpy.ndarray of uint8 of shape HxWx3
    """
    # Possible extension: avoid conversion to support more formats

    if image.format() != qt.QImage.Format_RGB888:
        # Convert to RGB888 if needed
        image = image.convertToFormat(qt.QImage.Format_RGB888)

    ptr = image.bits()
    if qt.BINDING not in ('PySide', 'PySide2'):
        ptr.setsize(image.byteCount())
        if qt.BINDING == 'PyQt4' and sys.version_info[0] == 2:
            ptr = ptr.asstring()
    elif sys.version_info[0] == 3:  # PySide with Python3
        ptr = ptr.tobytes()

    array = numpy.fromstring(ptr, dtype=numpy.uint8)

    # Lines are 32 bits aligned: remove padding bytes
    array = array.reshape(image.height(), -1)[:, :image.width() * 3]
    array.shape = image.height(), image.width(), 3
    return array


class _QtExecutor(qt.QObject):
    """Executor of tasks in Qt main thread"""

    __sigSubmit = qt.Signal(Future, object, tuple, dict)
    """Signal used to run tasks."""

    def __init__(self):
        super(_QtExecutor, self).__init__(parent=None)

        # Makes sure the executor lives in the main thread
        app = qt.QApplication.instance()
        assert app is not None
        mainThread = app.thread()
        if self.thread() != mainThread:
            self.moveToThread(mainThread)

        self.__sigSubmit.connect(self.__run)

    def submit(self, fn, *args, **kwargs):
        """Submit fn(*args, **kwargs) to Qt main thread

        :param callable fn: Function to call in main thread
        :return: Future object to retrieve result
        :rtype: concurrent.future.Future
        """
        future = Future()
        self.__sigSubmit.emit(future, fn, args, kwargs)
        return future

    def __run(self, future, fn, args, kwargs):
        """Run task in Qt main thread

        :param concurrent.future.Future future:
        :param callable fn: Function to run
        :param tuple args: Arguments
        :param dict kwargs: Keyword arguments
        """
        if not future.set_running_or_notify_cancel():
            return

        try:
            result = fn(*args, **kwargs)
        except BaseException as e:
            future.set_exception(e)
        else:
            future.set_result(result)


_executor = None
"""QObject running the tasks in main thread"""


def submitToQtMainThread(fn, *args, **kwargs):
    """Run fn(*args, **kwargs) in Qt's main thread.

    If not called from the main thread, this is run asynchronously.

    :param callable fn: Function to call in main thread.
    :return: A future object to retrieve the result
    :rtype: concurrent.future.Future
    """
    global _executor
    if _executor is None:  # Lazy-loading
        _executor = _QtExecutor()

    return _executor.submit(fn, *args, **kwargs)