// Copyright 2017 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_native/opengl/PipelineGL.h"

#include "common/BitSetIterator.h"
#include "dawn_native/BindGroupLayout.h"
#include "dawn_native/Device.h"
#include "dawn_native/Pipeline.h"
#include "dawn_native/opengl/Forward.h"
#include "dawn_native/opengl/OpenGLFunctions.h"
#include "dawn_native/opengl/PipelineLayoutGL.h"
#include "dawn_native/opengl/SamplerGL.h"
#include "dawn_native/opengl/ShaderModuleGL.h"

#include <set>
#include <sstream>

namespace dawn_native::opengl {

    namespace {

        GLenum GLShaderType(SingleShaderStage stage) {
            switch (stage) {
                case SingleShaderStage::Vertex:
                    return GL_VERTEX_SHADER;
                case SingleShaderStage::Fragment:
                    return GL_FRAGMENT_SHADER;
                case SingleShaderStage::Compute:
                    return GL_COMPUTE_SHADER;
            }
            UNREACHABLE();
        }

    }  // namespace

    PipelineGL::PipelineGL() : mProgram(0) {
    }

    PipelineGL::~PipelineGL() = default;

    MaybeError PipelineGL::InitializeBase(const OpenGLFunctions& gl,
                                          const PipelineLayout* layout,
                                          const PerStage<ProgrammableStage>& stages) {
        auto CreateShader = [](const OpenGLFunctions& gl, GLenum type,
                               const char* source) -> ResultOrError<GLuint> {
            GLuint shader = gl.CreateShader(type);
            gl.ShaderSource(shader, 1, &source, nullptr);
            gl.CompileShader(shader);

            GLint compileStatus = GL_FALSE;
            gl.GetShaderiv(shader, GL_COMPILE_STATUS, &compileStatus);
            if (compileStatus == GL_FALSE) {
                GLint infoLogLength = 0;
                gl.GetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLogLength);

                if (infoLogLength > 1) {
                    std::vector<char> buffer(infoLogLength);
                    gl.GetShaderInfoLog(shader, infoLogLength, nullptr, &buffer[0]);
                    return DAWN_FORMAT_VALIDATION_ERROR("%s\nProgram compilation failed:\n%s",
                                                        source, buffer.data());
                }
            }
            return shader;
        };

        mProgram = gl.CreateProgram();

        // Compute the set of active stages.
        wgpu::ShaderStage activeStages = wgpu::ShaderStage::None;
        for (SingleShaderStage stage : IterateStages(kAllStages)) {
            if (stages[stage].module != nullptr) {
                activeStages |= StageBit(stage);
            }
        }

        // Create an OpenGL shader for each stage and gather the list of combined samplers.
        PerStage<CombinedSamplerInfo> combinedSamplers;
        bool needsDummySampler = false;
        std::vector<GLuint> glShaders;
        for (SingleShaderStage stage : IterateStages(activeStages)) {
            const ShaderModule* module = ToBackend(stages[stage].module.Get());
            std::string glsl;
            DAWN_TRY_ASSIGN(glsl, module->TranslateToGLSL(stages[stage].entryPoint.c_str(), stage,
                                                          &combinedSamplers[stage], layout,
                                                          &needsDummySampler));
            GLuint shader;
            DAWN_TRY_ASSIGN(shader, CreateShader(gl, GLShaderType(stage), glsl.c_str()));
            gl.AttachShader(mProgram, shader);
            glShaders.push_back(shader);
        }

        if (needsDummySampler) {
            SamplerDescriptor desc = {};
            ASSERT(desc.minFilter == wgpu::FilterMode::Nearest);
            ASSERT(desc.magFilter == wgpu::FilterMode::Nearest);
            ASSERT(desc.mipmapFilter == wgpu::FilterMode::Nearest);
            mDummySampler =
                ToBackend(layout->GetDevice()->GetOrCreateSampler(&desc).AcquireSuccess());
        }

        // Link all the shaders together.
        gl.LinkProgram(mProgram);

        GLint linkStatus = GL_FALSE;
        gl.GetProgramiv(mProgram, GL_LINK_STATUS, &linkStatus);
        if (linkStatus == GL_FALSE) {
            GLint infoLogLength = 0;
            gl.GetProgramiv(mProgram, GL_INFO_LOG_LENGTH, &infoLogLength);

            if (infoLogLength > 1) {
                std::vector<char> buffer(infoLogLength);
                gl.GetProgramInfoLog(mProgram, infoLogLength, nullptr, &buffer[0]);
                return DAWN_FORMAT_VALIDATION_ERROR("Program link failed:\n%s", buffer.data());
            }
        }

        // Compute links between stages for combined samplers, then bind them to texture units
        gl.UseProgram(mProgram);
        const auto& indices = layout->GetBindingIndexInfo();

        std::set<CombinedSampler> combinedSamplersSet;
        for (SingleShaderStage stage : IterateStages(activeStages)) {
            for (const CombinedSampler& combined : combinedSamplers[stage]) {
                combinedSamplersSet.insert(combined);
            }
        }

        mUnitsForSamplers.resize(layout->GetNumSamplers());
        mUnitsForTextures.resize(layout->GetNumSampledTextures());

        GLuint textureUnit = layout->GetTextureUnitsUsed();
        for (const auto& combined : combinedSamplersSet) {
            const std::string& name = combined.GetName();
            GLint location = gl.GetUniformLocation(mProgram, name.c_str());

            if (location == -1) {
                continue;
            }

            gl.Uniform1i(location, textureUnit);

            bool shouldUseFiltering;
            {
                const BindGroupLayoutBase* bgl =
                    layout->GetBindGroupLayout(combined.textureLocation.group);
                BindingIndex bindingIndex = bgl->GetBindingIndex(combined.textureLocation.binding);

                GLuint textureIndex = indices[combined.textureLocation.group][bindingIndex];
                mUnitsForTextures[textureIndex].push_back(textureUnit);

                shouldUseFiltering = bgl->GetBindingInfo(bindingIndex).texture.sampleType ==
                                     wgpu::TextureSampleType::Float;
            }
            {
                if (combined.useDummySampler) {
                    mDummySamplerUnits.push_back(textureUnit);
                } else {
                    const BindGroupLayoutBase* bgl =
                        layout->GetBindGroupLayout(combined.samplerLocation.group);
                    BindingIndex bindingIndex =
                        bgl->GetBindingIndex(combined.samplerLocation.binding);

                    GLuint samplerIndex = indices[combined.samplerLocation.group][bindingIndex];
                    mUnitsForSamplers[samplerIndex].push_back({textureUnit, shouldUseFiltering});
                }
            }

            textureUnit++;
        }

        for (GLuint glShader : glShaders) {
            gl.DetachShader(mProgram, glShader);
            gl.DeleteShader(glShader);
        }

        return {};
    }

    void PipelineGL::DeleteProgram(const OpenGLFunctions& gl) {
        gl.DeleteProgram(mProgram);
    }

    const std::vector<PipelineGL::SamplerUnit>& PipelineGL::GetTextureUnitsForSampler(
        GLuint index) const {
        ASSERT(index < mUnitsForSamplers.size());
        return mUnitsForSamplers[index];
    }

    const std::vector<GLuint>& PipelineGL::GetTextureUnitsForTextureView(GLuint index) const {
        ASSERT(index < mUnitsForTextures.size());
        return mUnitsForTextures[index];
    }

    GLuint PipelineGL::GetProgramHandle() const {
        return mProgram;
    }

    void PipelineGL::ApplyNow(const OpenGLFunctions& gl) {
        gl.UseProgram(mProgram);
        for (GLuint unit : mDummySamplerUnits) {
            ASSERT(mDummySampler.Get() != nullptr);
            gl.BindSampler(unit, mDummySampler->GetNonFilteringHandle());
        }
    }

}  // namespace dawn_native::opengl