# Copyright (C) 2023 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from __future__ import annotations

import numpy
import sys

from PySide6.QtCore import (QEvent, QFile, QIODevice, QPointF, QRectF, QSize,
                            qFatal, qWarning, Qt)
from PySide6.QtGui import (QColor, QFont, QGradient, QImage, QMatrix4x4,
                           QPainter, QPlatformSurfaceEvent, QSurface, QWindow)
from PySide6.QtGui import (QRhi, QRhiBuffer,
                           QRhiDepthStencilClearValue,
                           QRhiGraphicsPipeline, QRhiNullInitParams,
                           QRhiGles2InitParams, QRhiRenderBuffer,
                           QRhiSampler, QRhiShaderResourceBinding,
                           QRhiShaderStage, QRhiTexture,
                           QRhiVertexInputAttribute, QRhiVertexInputBinding,
                           QRhiVertexInputLayout, QRhiViewport,
                           QShader)
from PySide6.support import VoidPtr

if sys.platform == "win32":
    from PySide6.QtGui import QRhiD3D11InitParams, QRhiD3D12InitParams
elif sys.platform == "darwin":
    from PySide6.QtGui import QRhiMetalInitParams


# Y up (note clipSpaceCorrMatrix in m_viewProjection), CCW
VERTEX_DATA = numpy.array([
    0.0, 0.5, 1.0, 0.0, 0.0,
    -0.5, -0.5, 0.0, 1.0, 0.0,
    0.5, -0.5, 0.0, 0.0, 1.0], dtype=numpy.float32)


UBUF_SIZE = 68


def getShader(name):
    f = QFile(name)
    if f.open(QIODevice.OpenModeFlag.ReadOnly):
        result = QShader.fromSerialized(f.readAll())
        f.close()
        return result
    return QShader()


class RhiWindow(QWindow):

    def __init__(self, graphicsApi):
        super().__init__()
        self.m_graphicsApi = QRhi.Implementation.Null
        self.m_initialized = False
        self.m_notExposed = False
        self.m_newlyExposed = False

        self.m_fallbackSurface = None
        self.m_rhi = None
        self.m_sc = None
        self.m_ds = None
        self.m_rp = None
        self.m_hasSwapChain = False
        self.m_viewProjection = QMatrix4x4()

        self.m_graphicsApi = graphicsApi
        match graphicsApi:
            case QRhi.Implementation.OpenGLES2:
                self.setSurfaceType(QSurface.SurfaceType.OpenGLSurface)
            case QRhi.Implementation.Vulkan:
                self.setSurfaceType(QSurface.SurfaceType.VulkanSurface)
            case QRhi.Implementation.D3D11 | QRhi.Implementation.D3D12:
                self.setSurfaceType(QSurface.SurfaceType.Direct3DSurface)
            case QRhi.Implementation.Metal:
                self.setSurfaceType(QSurface.SurfaceType.MetalSurface)

    def __del__(self):
        # destruction order matters to a certain degree: the fallbackSurface
        # must outlive the rhi, the rhi must outlive all other resources.
        # The resources need no special order when destroying.
        del self.m_rp
        self.m_rp = None
        del self.m_ds
        self.m_ds = None
        del self.m_sc
        self.m_sc = None
        del self.m_rhi
        self.m_rhi = None
        if self.m_fallbackSurface:
            del self.m_fallbackSurface
            self.m_fallbackSurface = None

    def graphicsApiName(self):
        if self.m_graphicsApi == QRhi.Implementation.Null:
            return "Null (no output)"
        if self.m_graphicsApi == QRhi.Implementation.OpenGLES2:
            return "OpenGL"
        if self.m_graphicsApi == QRhi.Implementation.Vulkan:
            return "Vulkan"
        if self.m_graphicsApi == QRhi.Implementation.D3D11:
            return "Direct3D 11"
        if self.m_graphicsApi == QRhi.Implementation.D3D12:
            return "Direct3D 12"
        if self.m_graphicsApi == QRhi.Implementation.Metal:
            return "Metal"
        return ""

    def customInit(self):
        pass

    def customRender(self):
        pass

    def exposeEvent(self, e):
        # initialize and start rendering when the window becomes usable
        # for graphics purposes
        is_exposed = self.isExposed()
        if is_exposed and not self.m_initialized:
            self.init()
            self.resizeSwapChain()
            self.m_initialized = True

        surfaceSize = self.m_sc.surfacePixelSize() if self.m_hasSwapChain else QSize()

        # stop pushing frames when not exposed (or size is 0)
        if ((not is_exposed or (self.m_hasSwapChain and surfaceSize.isEmpty()))
                and self.m_initialized and not self.m_notExposed):
            self.m_notExposed = True

        # Continue when exposed again and the surface has a valid size. Note
        # that surfaceSize can be (0, 0) even though size() reports a valid
        # one, hence trusting surfacePixelSize() and not QWindow.
        if is_exposed and self.m_initialized and self.m_notExposed and not surfaceSize.isEmpty():
            self.m_notExposed = False
            self.m_newlyExposed = True

        # always render a frame on exposeEvent() (when exposed) in order to
        # update immediately on window resize.
        if is_exposed and not surfaceSize.isEmpty():
            self.render()

    def event(self, e):
        if e.type() == QEvent.Type.UpdateRequest:
            self.render()
        elif e.type() == QEvent.Type.PlatformSurface:
            # this is the proper time to tear down the swapchain (while
            # the native window and surface are still around)
            if e.surfaceEventType() == QPlatformSurfaceEvent.SurfaceEventType.SurfaceAboutToBeDestroyed:  # noqa: E501
                self.releaseSwapChain()

        return super().event(e)

    def init(self):
        match self.m_graphicsApi:
            case QRhi.Implementation.Null:
                params = QRhiNullInitParams()
                self.m_rhi = QRhi.create(QRhi.Implementation.Null, params)

            case QRhi.Implementation.OpenGLES2:
                self.m_fallbackSurface = QRhiGles2InitParams.newFallbackSurface()
                params = QRhiGles2InitParams()
                params.fallbackSurface = self.m_fallbackSurface
                params.window = self
                self.m_rhi = QRhi.create(QRhi.Implementation.OpenGLES2, params)
            case QRhi.Implementation.D3D11:
                params = QRhiD3D11InitParams()
                # Enable the debug layer, if available. This is optional
                # and should be avoided in production builds.
                params.enableDebugLayer = True
                self.m_rhi = QRhi.create(QRhi.Implementation.D3D11, params)
            case QRhi.Implementation.D3D12:
                params = QRhiD3D12InitParams()
                # Enable the debug layer, if available. This is optional
                # and should be avoided in production builds.
                params.enableDebugLayer = True
                self.m_rhi = QRhi.create(QRhi.Implementation.D3D12, params)
            case QRhi.Implementation.Metal:
                params = QRhiMetalInitParams()
                self.m_rhi = QRhi.create(QRhi.Implementation.Metal, params)

        if not self.m_rhi:
            qFatal("Failed to create RHI backend")

        self.m_sc = self.m_rhi.newSwapChain()
        # no need to set the size here, due to UsedWithSwapChainOnly
        self.m_ds = self.m_rhi.newRenderBuffer(QRhiRenderBuffer.Type.DepthStencil,
                                               QSize(), 1,
                                               QRhiRenderBuffer.Flag.UsedWithSwapChainOnly)
        self.m_sc.setWindow(self)
        self.m_sc.setDepthStencil(self.m_ds)
        self.m_rp = self.m_sc.newCompatibleRenderPassDescriptor()
        self.m_sc.setRenderPassDescriptor(self.m_rp)
        self.customInit()

    def resizeSwapChain(self):
        self.m_hasSwapChain = self.m_sc.createOrResize()  # also handles self.m_ds
        outputSize = self.m_sc.currentPixelSize()
        self.m_viewProjection = self.m_rhi.clipSpaceCorrMatrix()
        r = float(outputSize.width()) / float(outputSize.height())
        self.m_viewProjection.perspective(45.0, r, 0.01, 1000.0)
        self.m_viewProjection.translate(0, 0, -4)

    def releaseSwapChain(self):
        if self.m_hasSwapChain:
            self.m_hasSwapChain = False
            self.m_sc.destroy()

    def render(self):
        if not self.m_hasSwapChain or self.m_notExposed:
            return

        # If the window got resized or newly exposed, resize the swapchain.
        # (the newly-exposed case is not actually required by some platforms,
        # but is here for robustness and portability)
        #
        # This (exposeEvent + the logic here) is the only safe way to perform
        # resize handling. Note the usage of the RHI's surfacePixelSize(), and
        # never QWindow::size(). (the two may or may not be the same under the
        # hood, # depending on the backend and platform)
        if self.m_sc.currentPixelSize() != self.m_sc.surfacePixelSize() or self.m_newlyExposed:
            self.resizeSwapChain()
            if not self.m_hasSwapChain:
                return
            self.m_newlyExposed = False

        result = self.m_rhi.beginFrame(self.m_sc)
        if result == QRhi.FrameOpResult.FrameOpSwapChainOutOfDate:
            self.resizeSwapChain()
            if not self.m_hasSwapChain:
                return
            result = self.m_rhi.beginFrame(self.m_sc)

        if result != QRhi.FrameOpResult.FrameOpSuccess:
            qWarning(f"beginFrame failed with {result}, will retry")
            self.requestUpdate()
            return

        self.customRender()

        self.m_rhi.endFrame(self.m_sc)

        # Always request the next frame via requestUpdate(). On some platforms
        # this is backed by a platform-specific solution, e.g. CVDisplayLink
        # on macOS, which is potentially more efficient than a timer,
        # queued metacalls, etc.
        self.requestUpdate()


class HelloWindow(RhiWindow):

    def __init__(self, graphicsApi):
        super().__init__(graphicsApi)
        self.m_vbuf = None
        self.m_ubuf = None
        self.m_texture = None
        self.m_sampler = None
        self.m_colorTriSrb = None
        self.m_colorPipeline = None
        self.m_fullscreenQuadSrb = None
        self.m_fullscreenQuadPipeline = None
        self.m_initialUpdates = None

        self.m_rotation = 0
        self.m_opacity = 1
        self.m_opacityDir = -1

    def ensureFullscreenTexture(self, pixelSize, u):
        if self.m_texture and self.m_texture.pixelSize() == pixelSize:
            return

        if not self.m_texture:
            self.m_texture = self.m_rhi.newTexture(QRhiTexture.Format.RGBA8, pixelSize)
        else:
            self.m_texture.setPixelSize(pixelSize)
        self.m_texture.create()
        image = QImage(pixelSize, QImage.Format.Format_RGBA8888_Premultiplied)
        with QPainter(image) as painter:
            painter.fillRect(QRectF(QPointF(0, 0), pixelSize),
                             QColor.fromRgbF(0.4, 0.7, 0.0, 1.0))
            painter.setPen(Qt.GlobalColor.transparent)
            painter.setBrush(QGradient(QGradient.Preset.DeepBlue))
            painter.drawRoundedRect(QRectF(QPointF(20, 20), pixelSize - QSize(40, 40)),
                                    16, 16)
            painter.setPen(Qt.GlobalColor.black)
            font = QFont()
            font.setPixelSize(0.05 * min(pixelSize.width(), pixelSize.height()))
            painter.setFont(font)
            name = self.graphicsApiName()
            t = (f"Rendering with QRhi to a resizable QWindow.\nThe 3D API is {name}."
                 "\nUse the command-line options to choose a different API.")
            painter.drawText(QRectF(QPointF(60, 60), pixelSize - QSize(120, 120)), 0, t)

        if self.m_rhi.isYUpInNDC():
            image = image.mirrored()

        u.uploadTexture(self.m_texture, image)

    def customInit(self):
        self.m_initialUpdates = self.m_rhi.nextResourceUpdateBatch()

        vertex_size = 4 * VERTEX_DATA.size
        self.m_vbuf = self.m_rhi.newBuffer(QRhiBuffer.Type.Immutable,
                                           QRhiBuffer.UsageFlag.VertexBuffer,
                                           vertex_size)
        self.m_vbuf.create()
        self.m_initialUpdates.uploadStaticBuffer(self.m_vbuf,
                                                 VoidPtr(VERTEX_DATA.tobytes(), vertex_size))

        self.m_ubuf = self.m_rhi.newBuffer(QRhiBuffer.Type.Dynamic,
                                           QRhiBuffer.UsageFlag.UniformBuffer, UBUF_SIZE)
        self.m_ubuf.create()

        self.ensureFullscreenTexture(self.m_sc.surfacePixelSize(), self.m_initialUpdates)

        self.m_sampler = self.m_rhi.newSampler(QRhiSampler.Filter.Linear,
                                               QRhiSampler.Filter.Linear,
                                               QRhiSampler.Filter.None_,
                                               QRhiSampler.AddressMode.ClampToEdge,
                                               QRhiSampler.AddressMode.ClampToEdge)
        self.m_sampler.create()

        self.m_colorTriSrb = self.m_rhi.newShaderResourceBindings()
        visibility = (QRhiShaderResourceBinding.StageFlag.VertexStage
                      | QRhiShaderResourceBinding.StageFlag.FragmentStage)
        bindings = [
            QRhiShaderResourceBinding.uniformBuffer(0, visibility, self.m_ubuf)
        ]
        self.m_colorTriSrb.setBindings(bindings)
        self.m_colorTriSrb.create()

        self.m_colorPipeline = self.m_rhi.newGraphicsPipeline()
        # Enable depth testing; not quite needed for a simple triangle, but we
        # have a depth-stencil buffer so why not.
        self.m_colorPipeline.setDepthTest(True)
        self.m_colorPipeline.setDepthWrite(True)
        # Blend factors default to One, OneOneMinusSrcAlpha, which is convenient.
        premulAlphaBlend = QRhiGraphicsPipeline.TargetBlend()
        premulAlphaBlend.enable = True
        self.m_colorPipeline.setTargetBlends([premulAlphaBlend])
        stages = [
            QRhiShaderStage(QRhiShaderStage.Type.Vertex, getShader(":/color.vert.qsb")),
            QRhiShaderStage(QRhiShaderStage.Type.Fragment, getShader(":/color.frag.qsb"))
        ]
        self.m_colorPipeline.setShaderStages(stages)
        inputLayout = QRhiVertexInputLayout()
        input_bindings = [QRhiVertexInputBinding(5 * 4)]  # sizeof(float)
        inputLayout.setBindings(input_bindings)
        attributes = [
            QRhiVertexInputAttribute(0, 0, QRhiVertexInputAttribute.Format.Float2, 0),
            # sizeof(float)
            QRhiVertexInputAttribute(0, 1, QRhiVertexInputAttribute.Format.Float3, 2 * 4)]
        inputLayout.setAttributes(attributes)
        self.m_colorPipeline.setVertexInputLayout(inputLayout)
        self.m_colorPipeline.setShaderResourceBindings(self.m_colorTriSrb)
        self.m_colorPipeline.setRenderPassDescriptor(self.m_rp)
        self.m_colorPipeline.create()

        self.m_fullscreenQuadSrb = self.m_rhi.newShaderResourceBindings()
        bindings = [
            QRhiShaderResourceBinding.sampledTexture(0, QRhiShaderResourceBinding.StageFlag.FragmentStage,  # noqa: E501
                                                     self.m_texture, self.m_sampler)
        ]
        self.m_fullscreenQuadSrb.setBindings(bindings)
        self.m_fullscreenQuadSrb.create()

        self.m_fullscreenQuadPipeline = self.m_rhi.newGraphicsPipeline()
        stages = [
            QRhiShaderStage(QRhiShaderStage.Type.Vertex, getShader(":/quad.vert.qsb")),
            QRhiShaderStage(QRhiShaderStage.Type.Fragment, getShader(":/quad.frag.qsb"))
        ]
        self.m_fullscreenQuadPipeline.setShaderStages(stages)
        layout = QRhiVertexInputLayout()
        self.m_fullscreenQuadPipeline.setVertexInputLayout(layout)
        self.m_fullscreenQuadPipeline.setShaderResourceBindings(self.m_fullscreenQuadSrb)
        self.m_fullscreenQuadPipeline.setRenderPassDescriptor(self.m_rp)
        self.m_fullscreenQuadPipeline.create()

    def customRender(self):
        resourceUpdates = self.m_rhi.nextResourceUpdateBatch()

        if self.m_initialUpdates:
            resourceUpdates.merge(self.m_initialUpdates)
            self.m_initialUpdates = None

        self.m_rotation += 1.0
        modelViewProjection = self.m_viewProjection
        modelViewProjection.rotate(self.m_rotation, 0, 1, 0)
        projection = numpy.array(modelViewProjection.data(),
                                 dtype=numpy.float32)
        resourceUpdates.updateDynamicBuffer(self.m_ubuf, 0, 64,
                                            projection.tobytes())

        self.m_opacity += self.m_opacityDir * 0.005
        if self.m_opacity < 0.0 or self.m_opacity > 1.0:
            self.m_opacityDir *= -1
            self.m_opacity = max(0.0, min(1.0, self.m_opacity))

        opacity = numpy.array([self.m_opacity], dtype=numpy.float32)
        resourceUpdates.updateDynamicBuffer(self.m_ubuf, 64, 4,
                                            opacity.tobytes())

        cb = self.m_sc.currentFrameCommandBuffer()
        outputSizeInPixels = self.m_sc.currentPixelSize()

        # (re)create the texture with a size matching the output surface size,
        # when necessary.
        self.ensureFullscreenTexture(outputSizeInPixels, resourceUpdates)

        cv = QRhiDepthStencilClearValue(1.0, 0)
        cb.beginPass(self.m_sc.currentFrameRenderTarget(), Qt.GlobalColor.black,
                     cv, resourceUpdates)

        cb.setGraphicsPipeline(self.m_fullscreenQuadPipeline)
        viewport = QRhiViewport(0, 0, outputSizeInPixels.width(),
                                outputSizeInPixels.height())
        cb.setViewport(viewport)
        cb.setShaderResources()
        cb.draw(3)

        cb.setGraphicsPipeline(self.m_colorPipeline)
        cb.setShaderResources()
        vbufBinding = (self.m_vbuf, 0)
        cb.setVertexInput(0, [vbufBinding])
        cb.draw(3)
        cb.endPass()
