# Copyright (c) 2018 Ultimaker B.V.
# Cura is released under the terms of the LGPLv3 or higher.
from UM.Application import Application
from UM.Math.Color import Color
from UM.Resources import Resources

from UM.View.RenderPass import RenderPass
from UM.View.GL.OpenGL import OpenGL
from UM.View.RenderBatch import RenderBatch

from UM.Scene.Iterator.DepthFirstIterator import DepthFirstIterator


##  A RenderPass subclass that renders a depthmap of selectable objects to a texture.
#   It uses the active camera by default, but it can be overridden to use a different camera.
#
#   Note that in order to increase precision, the 24 bit depth value is encoded into all three of the R,G & B channels
class DepthPass(RenderPass):
    def __init__(self, width: int, height: int):
        super().__init__("preview", width, height, 0)

        self._renderer = Application.getInstance().getRenderer()

        self._shader = None
        self._scene = Application.getInstance().getController().getScene()


    def render(self) -> None:
        if not self._shader:
            self._shader = OpenGL.getInstance().createShaderProgram(Resources.getPath(Resources.Shaders, "camera_distance.shader"))

        self._gl.glClearColor(0.0, 0.0, 0.0, 0.0)
        self._gl.glClear(self._gl.GL_COLOR_BUFFER_BIT | self._gl.GL_DEPTH_BUFFER_BIT)

        # Create a new batch to be rendered
        batch = RenderBatch(self._shader)

        # Fill up the batch with objects that can be sliced. `
        for node in DepthFirstIterator(self._scene.getRoot()):
            if node.callDecoration("isSliceable") and node.getMeshData() and node.isVisible():
                batch.addItem(node.getWorldTransformation(), node.getMeshData())

        self.bind()
        batch.render(self._scene.getActiveCamera())
        self.release()

    ##  Get the distance in mm from the camera to at a certain pixel coordinate.
    def getDepthAtPosition(self, x, y):
        output = self.getOutput()

        window_size = self._renderer.getWindowSize()

        px = (0.5 + x / 2.0) * window_size[0]
        py = (0.5 + y / 2.0) * window_size[1]

        if px < 0 or px > (output.width() - 1) or py < 0 or py > (output.height() - 1):
            return None

        distance = output.pixel(px, py) # distance in micron, from in r, g & b channels
        return distance / 1000.