import numpy as np
import scipy.ndimage as ndi

from moviepy.video.VideoClip import ImageClip


def findObjects(clip, rem_thr=500, preview=False):
    """
    Returns a list of ImageClips representing each a separate object on
    the screen.

    rem_thr : all objects found with size < rem_Thr will be
         considered false positives and will be removed

    """

    image = clip.get_frame(0)
    if not clip.mask:
        clip = clip.add_mask()

    mask = clip.mask.get_frame(0)
    labelled, num_features = ndi.measurements.label(image[:, :, 0])

    # find the objects
    slices = []
    for e in ndi.find_objects(labelled):
        if mask[e[0], e[1]].mean() <= 0.2:
            # remove letter holes (in o,e,a, etc.)
            continue
        if image[e[0], e[1]].size <= rem_thr:
            # remove very small slices
            continue
        slices.append(e)
    islices = sorted(enumerate(slices), key=lambda s: s[1][1].start)

    letters = []
    for i, (ind, (sy, sx)) in enumerate(islices):
        """ crop each letter separately """
        sy = slice(sy.start - 1, sy.stop + 1)
        sx = slice(sx.start - 1, sx.stop + 1)
        letter = image[sy, sx]
        labletter = labelled[sy, sx]
        maskletter = (labletter == (ind + 1)) * mask[sy, sx]
        letter = ImageClip(image[sy, sx])
        letter.mask = ImageClip(maskletter, ismask=True)
        letter.screenpos = np.array((sx.start, sy.start))
        letters.append(letter)

    if preview:
        import matplotlib.pyplot as plt

        print("found %d objects" % (num_features))
        fig, ax = plt.subplots(2)
        ax[0].axis("off")
        ax[0].imshow(labelled)
        ax[1].imshow([range(num_features)], interpolation="nearest")
        ax[1].set_yticks([])
        plt.show()

    return letters
