"""Display helpers shared by the pipeline examples.

These exist so an example can show a result without hand-rolling OpenCV arithmetic. Everything
here is presentation only: the SDK never draws, and nothing in ``orisys`` imports this module.

The examples import it through a sibling import, which works when the examples are run from the
examples directory or with ``examples/`` on ``sys.path``.
"""

from __future__ import annotations

import cv2
import numpy as np


def draw_flow_arrows(image, flow, *, threshold=0.4, grid_spacing=10, arrow_scale=1.0,
                     valid_mask=None):
    """Return the deformation field drawn over ``image``."""
    import orisys

    return orisys.util.draw_arrows(
        image,
        flow,
        threshold=threshold,
        grid_spacing=grid_spacing,
        arrow_scale=arrow_scale,
        valid_mask=valid_mask,
    )


def depth_to_color(depth_map):
    """Normalise a depth/divergence map to 8-bit and apply a colormap for the ``depth`` window.

    Returns ``None`` for an empty map, which is what ``read_info`` gives when the field was never
    generated, so a caller can skip the window instead of showing saturated noise.
    """
    if depth_map is None or not isinstance(depth_map, np.ndarray) or depth_map.size == 0:
        return None
    lo = float(depth_map.min())
    hi = float(depth_map.max())
    if hi <= lo:
        scaled = np.zeros_like(depth_map, dtype=np.uint8)
    else:
        scaled = ((depth_map - lo) / (hi - lo) * 255.0).astype(np.uint8)
    return cv2.applyColorMap(scaled, cv2.COLORMAP_JET)


def draw_contact(image, contour, centroid):
    """Return ``image`` with the contact region and centroid drawn on it."""
    import orisys

    return orisys.util.draw_contact(image, contour, centroid)