import numpy
from typing import List, Tuple
Color = Tuple[int, int, int]
Pixels = List[List[Color]]


class Picture:
    def __init__(self, pixels: Pixels = None):
        self.pixels = numpy.array(pixels)

    def clear(self):
        self.pixels[:, :, :] = 0

    def get_height(self):
        return self.pixels.shape[0]

    def get_width(self):
        return self.pixels.shape[1]

    def compare(self, other: "Picture") -> float:
        return numpy.sum((self.pixels - other.pixels)**2)

    def write_ppm(self, path: str):
        with open(path, 'wb') as ppmfile:
            ppmfile.write(b"P6\n")
            ppmfile.write("{} {} 255\n".format(
                self.get_width(),
                self.get_height()
            ).encode('utf-8'))
            ppmfile.write((self.pixels * 255.0).astype(numpy.uint8).tobytes())

    def blend_rect(self,
                   x: int, y: int, w: int, h: int,
                   r: float, g: float, b: float, alpha: float):
        ph = self.get_height()
        pw = self.get_width()
        upper_y = min(ph, y + h)
        upper_x = min(pw, x + w)
        color = (r * alpha, g * alpha, b * alpha)
        # what does this line mean?
        new_colors = self.pixels[y: upper_y, x: upper_x] + color
        # why clip?
        self.pixels[y: upper_y, x: upper_x] = new_colors.clip(0, 1)