// Copyright 2018 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "dawn/utils/ComboRenderPipelineDescriptor.h"

#include "dawn/utils/WGPUHelpers.h"

namespace utils {

    ComboVertexState::ComboVertexState() {
        vertexBufferCount = 0;

        // Fill the default values for vertexBuffers and vertexAttributes in buffers.
        wgpu::VertexAttribute vertexAttribute;
        vertexAttribute.shaderLocation = 0;
        vertexAttribute.offset = 0;
        vertexAttribute.format = wgpu::VertexFormat::Float32;
        for (uint32_t i = 0; i < kMaxVertexAttributes; ++i) {
            cAttributes[i] = vertexAttribute;
        }
        for (uint32_t i = 0; i < kMaxVertexBuffers; ++i) {
            cVertexBuffers[i].arrayStride = 0;
            cVertexBuffers[i].stepMode = wgpu::VertexStepMode::Vertex;
            cVertexBuffers[i].attributeCount = 0;
            cVertexBuffers[i].attributes = nullptr;
        }
        // cVertexBuffers[i].attributes points to somewhere in cAttributes.
        // cVertexBuffers[0].attributes points to &cAttributes[0] by default. Assuming
        // cVertexBuffers[0] has two attributes, then cVertexBuffers[1].attributes should point to
        // &cAttributes[2]. Likewise, if cVertexBuffers[1] has 3 attributes, then
        // cVertexBuffers[2].attributes should point to &cAttributes[5].
        cVertexBuffers[0].attributes = &cAttributes[0];
    }

    ComboRenderPipelineDescriptor::ComboRenderPipelineDescriptor() {
        wgpu::RenderPipelineDescriptor* descriptor = this;

        // Set defaults for the vertex state.
        {
            wgpu::VertexState* vertex = &descriptor->vertex;
            vertex->module = nullptr;
            vertex->entryPoint = "main";
            vertex->bufferCount = 0;

            // Fill the default values for vertexBuffers and vertexAttributes in buffers.
            for (uint32_t i = 0; i < kMaxVertexAttributes; ++i) {
                cAttributes[i].shaderLocation = 0;
                cAttributes[i].offset = 0;
                cAttributes[i].format = wgpu::VertexFormat::Float32;
            }
            for (uint32_t i = 0; i < kMaxVertexBuffers; ++i) {
                cBuffers[i].arrayStride = 0;
                cBuffers[i].stepMode = wgpu::VertexStepMode::Vertex;
                cBuffers[i].attributeCount = 0;
                cBuffers[i].attributes = nullptr;
            }
            // cBuffers[i].attributes points to somewhere in cAttributes.
            // cBuffers[0].attributes points to &cAttributes[0] by default. Assuming
            // cBuffers[0] has two attributes, then cBuffers[1].attributes should point to
            // &cAttributes[2]. Likewise, if cBuffers[1] has 3 attributes, then
            // cBuffers[2].attributes should point to &cAttributes[5].
            cBuffers[0].attributes = &cAttributes[0];
            vertex->buffers = &cBuffers[0];
        }

        // Set the defaults for the primitive state
        {
            wgpu::PrimitiveState* primitive = &descriptor->primitive;
            primitive->topology = wgpu::PrimitiveTopology::TriangleList;
            primitive->stripIndexFormat = wgpu::IndexFormat::Undefined;
            primitive->frontFace = wgpu::FrontFace::CCW;
            primitive->cullMode = wgpu::CullMode::None;
        }

        // Set the defaults for the depth-stencil state
        {
            wgpu::StencilFaceState stencilFace;
            stencilFace.compare = wgpu::CompareFunction::Always;
            stencilFace.failOp = wgpu::StencilOperation::Keep;
            stencilFace.depthFailOp = wgpu::StencilOperation::Keep;
            stencilFace.passOp = wgpu::StencilOperation::Keep;

            cDepthStencil.format = wgpu::TextureFormat::Depth24PlusStencil8;
            cDepthStencil.depthWriteEnabled = false;
            cDepthStencil.depthCompare = wgpu::CompareFunction::Always;
            cDepthStencil.stencilBack = stencilFace;
            cDepthStencil.stencilFront = stencilFace;
            cDepthStencil.stencilReadMask = 0xff;
            cDepthStencil.stencilWriteMask = 0xff;
            cDepthStencil.depthBias = 0;
            cDepthStencil.depthBiasSlopeScale = 0.0;
            cDepthStencil.depthBiasClamp = 0.0;
        }

        // Set the defaults for the multisample state
        {
            wgpu::MultisampleState* multisample = &descriptor->multisample;
            multisample->count = 1;
            multisample->mask = 0xFFFFFFFF;
            multisample->alphaToCoverageEnabled = false;
        }

        // Set the defaults for the fragment state
        {
            cFragment.module = nullptr;
            cFragment.entryPoint = "main";
            cFragment.targetCount = 1;
            cFragment.targets = &cTargets[0];
            descriptor->fragment = &cFragment;

            wgpu::BlendComponent blendComponent;
            blendComponent.srcFactor = wgpu::BlendFactor::One;
            blendComponent.dstFactor = wgpu::BlendFactor::Zero;
            blendComponent.operation = wgpu::BlendOperation::Add;

            for (uint32_t i = 0; i < kMaxColorAttachments; ++i) {
                cTargets[i].format = wgpu::TextureFormat::RGBA8Unorm;
                cTargets[i].blend = nullptr;
                cTargets[i].writeMask = wgpu::ColorWriteMask::All;

                cBlends[i].color = blendComponent;
                cBlends[i].alpha = blendComponent;
            }
        }
    }

    wgpu::DepthStencilState* ComboRenderPipelineDescriptor::EnableDepthStencil(
        wgpu::TextureFormat format) {
        this->depthStencil = &cDepthStencil;
        cDepthStencil.format = format;
        return &cDepthStencil;
    }

}  // namespace utils