# Refer https://github.com/intel-isl/MiDaS
"""Utils for monoDepth.
"""
import sys
import numpy as np
import cv2


def write_pfm(path, image, scale=1):
    """Write pfm file.

    Args:
        path (str): pathto file
        image (array): data
        scale (int, optional): Scale. Defaults to 1.
    """

    with open(path, "wb") as file:
        color = None

        if image.dtype.name != "float32":
            raise Exception("Image dtype must be float32.")

        image = np.flipud(image)

        if len(image.shape) == 3 and image.shape[2] == 3:  # color image
            color = True
        elif (len(image.shape) == 2
              or len(image.shape) == 3 and image.shape[2] == 1):  # greyscale
            color = False
        else:
            raise Exception(
                "Image must have H x W x 3, H x W x 1 or H x W dimensions.")

        file.write("PF\n" if color else "Pf\n".encode())
        file.write("%d %d\n".encode() % (image.shape[1], image.shape[0]))

        endian = image.dtype.byteorder

        if endian == "<" or endian == "=" and sys.byteorder == "little":
            scale = -scale

        file.write("%f\n".encode() % scale)

        image.tofile(file)


def read_image(path):
    """Read image and output RGB image (0-1).

    Args:
        path (str): path to file

    Returns:
        array: RGB image (0-1)
    """
    img = cv2.imread(path)
    if img.ndim == 2:
        img = cv2.cvtColor(img, cv2.COLOR_GRAY2BGR)
    img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB) / 255.0
    return img


def write_depth(path, depth, bits=1):
    """Write depth map to pfm and png file.

    Args:
        path (str): filepath without extension
        depth (array): depth
    """
    write_pfm(path + ".pfm", depth.astype(np.float32))

    depth_min = depth.min()
    depth_max = depth.max()

    max_val = (2**(8 * bits)) - 1

    if depth_max - depth_min > np.finfo("float").eps:
        out = max_val * (depth - depth_min) / (depth_max - depth_min)
    else:
        out = np.zeros(depth.shape, dtype=depth.type)

    if bits == 1:
        cv2.imwrite(path + ".png", out.astype("uint8"))
    elif bits == 2:
        cv2.imwrite(path + ".png", out.astype("uint16"))
    return path + '.pfm', path + ".png"