# Copyright (c) 2015 Ultimaker B.V.
# Uranium is released under the terms of the AGPLv3 or higher.

import sys
import ctypes

from UM.Application import Application
from UM.Logger import Logger
from UM.Platform import Platform

from UM.View.GL.OpenGL import OpenGL

##  Base class for a rendering pass.
#
#   The RenderPass class encapsulates a render pass, that is a single
#   step in the rendering process.
#
#   \note While the render pass could technically support render to
#   texture without using Framebuffer Objects, the PyQt bindings object
#   lacks support for any function like glReadPixels. Therefore, the
#   Qt OpenGL initialization code checks for FBO support and aborts the
#   program if no support is found.
class RenderPass:
    ##  The maximum priority of a render pass. Priority should always be
    #   less than this.
    MaximumPriority = 999

    def __init__(self, name, width, height, priority = 0):
        self._name = name
        self._width = width
        self._height = height
        self._priority = priority

        self._gl = OpenGL.getInstance().getBindingsObject()

        self._fbo = None

        self._updateRenderStorage()

    ##  Get the name of this RenderPass.
    #
    #   \return \type{string} The name of the render pass.
    def getName(self):
        return self._name

    ##  Get the priority of this RenderPass.
    #
    #   The priority is used for ordering the render passes. Lower priority render passes
    #   are rendered earlier and are available for later render passes to use as texture
    #   sources.
    #
    #   \return \type{int} The priority of this render pass.
    def getPriority(self):
        return self._priority

    ##  Set the size of this render pass.
    #
    #   \param width \type{int} The new width of the render pass.
    #   \param height \type{int} The new height of the render pass.
    #
    #   \note This will recreate the storage object used by the render
    #   pass. Due to that, the contents will be invalid after resizing
    #   until the render pass is rendered again.
    def setSize(self, width, height):
        if self._width != width or self._height != height:
            self._width = width
            self._height = height
            self._updateRenderStorage()

    ##  Bind the render pass so it can be rendered to.
    #
    #   This will make sure everything is set up so the contents of
    #   this render pass will be updated correctly. It should be called
    #   as part of your render() implementation.
    #
    #   \note It is very important to call release() after a call to
    #   bind(), once done with rendering.
    def bind(self):
        if self._fbo:
            self._fbo.bind()
            self._gl.glClear(self._gl.GL_COLOR_BUFFER_BIT | self._gl.GL_DEPTH_BUFFER_BIT)

    ##  Release the render pass.
    #
    #   This makes sure the contents of this render pass are properly
    #   updated at the end of rendering.
    def release(self):
        self._fbo.release()

        # Workaround for a driver bug with recent Intel chips on OSX.
        # Releasing the current FBO does not properly clear the depth buffer, so we have to do that manually.
        #if Platform.isOSX() and OpenGL.getInstance().getGPUVendor() == OpenGL.Vendor.Intel:
            #self._gl.glClear(self._gl.GL_COLOR_BUFFER_BIT | self._gl.GL_DEPTH_BUFFER_BIT)

    ##  Render the contents of this render pass.
    #
    #   This method should be reimplemented by subclasses to perform the
    #   actual rendering of the render pass.
    def render(self):
        raise NotImplementedError("Should be implemented by subclasses")

    ##  Get the texture ID of this render pass so it can be reused by other passes.
    #
    #   \return \type{int} The OpenGL texture ID used by this pass.
    def getTextureId(self):
        return self._fbo.getTextureId()

    ##  Get the pixel data produced by this render pass.
    #
    #   This returns an object that contains the pixel data for this render pass.
    #
    #   \note The current object type returned is currently dependant on the specific
    #   implementation of the UM.View.GL.FrameBufferObject class.
    def getOutput(self):
        return self._fbo.getContents()

    ## private:

    def _updateRenderStorage(self):
        if self._width <= 0 or self._height <= 0:
            Logger.log("w", "Tried to create render pass with size <= 0")
            return

        self._fbo = OpenGL.getInstance().createFrameBufferObject(self._width, self._height)