from collections import deque

import cv2

class ImageManager():

    def __init__(self, update_fn):
        super().__init__()
        self.update_fn = update_fn
        self.close()

    def undo(self):
        if len(self._undo_deque) == 0:
            return
        prev = self._undo_deque.pop()
        self._redo_deque.append(self._curr_image)
        self._curr_image = prev
        self.update_fn(self._curr_image)

    def redo(self):
        if len(self._redo_deque) == 0:
            return
        latter = self._redo_deque.pop()
        self._undo_deque.append(self._curr_image)
        self._curr_image = latter
        self.update_fn(self._curr_image)

    def update(self, new_image):
        self._undo_deque.append(self._curr_image)
        self._redo_deque = deque()
        self._curr_image = new_image.copy()
        self.update_fn(self._curr_image)

    def open(self, file_name):
        self.close()
        self._curr_image = cv2.imread(file_name)
        self._curr_image = cv2.cvtColor(self._curr_image, cv2.COLOR_BGR2RGB)
        self.update_fn(self._curr_image)


    def close(self):
        self._undo_deque = deque()
        self._redo_deque = deque()
        self._curr_image = None

    def save(self, file_name):
        if self._curr_image is not None:
            cv2.imwrite(file_name, cv2.cvtColor(self._curr_image, cv2.COLOR_RGB2BGR))

    def refresh(self):
        self.update_fn(self._curr_image)

    def image(self):
        return self._curr_image

    def can_redo(self):
        return len(self._redo_deque) > 0

    def can_undo(self):
        return len(self._undo_deque) > 0