/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * 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.
 */

#ifndef TNT_FILAMENT_BACKEND_PRIVATE_PROGRAM_H
#define TNT_FILAMENT_BACKEND_PRIVATE_PROGRAM_H

#include <utils/CString.h>
#include <utils/FixedCapacityVector.h>
#include <utils/Invocable.h>
#include <utils/ostream.h>

#include <backend/DriverEnums.h>

#include <array>
#include <unordered_map>
#include <tuple>
#include <utility>
#include <variant>

#include <stddef.h>
#include <stdint.h>

namespace filament::backend {

class Program {
public:

    static constexpr size_t SHADER_TYPE_COUNT = 3;
    static constexpr size_t UNIFORM_BINDING_COUNT = CONFIG_UNIFORM_BINDING_COUNT;
    static constexpr size_t SAMPLER_BINDING_COUNT = CONFIG_SAMPLER_BINDING_COUNT;

    struct Descriptor {
        utils::CString name;
        backend::DescriptorType type;
        backend::descriptor_binding_t binding;
    };

    struct SpecializationConstant {
        using Type = std::variant<int32_t, float, bool>;
        uint32_t id;    // id set in glsl
        Type value;     // value and type
    };

    struct Uniform { // For ES2 support
        utils::CString name;    // full qualified name of the uniform field
        uint16_t offset;        // offset in 'uint32_t' into the uniform buffer
        uint8_t size;           // >1 for arrays
        UniformType type;       // uniform type
    };

    using DescriptorBindingsInfo = utils::FixedCapacityVector<Descriptor>;
    using DescriptorSetInfo = std::array<DescriptorBindingsInfo, MAX_DESCRIPTOR_SET_COUNT>;
    using SpecializationConstantsInfo = utils::FixedCapacityVector<SpecializationConstant>;
    using ShaderBlob = utils::FixedCapacityVector<uint8_t>;
    using ShaderSource = std::array<ShaderBlob, SHADER_TYPE_COUNT>;

    using AttributesInfo = utils::FixedCapacityVector<std::pair<utils::CString, uint8_t>>;
    using UniformInfo = utils::FixedCapacityVector<Uniform>;
    using BindingUniformsInfo = utils::FixedCapacityVector<
            std::tuple<uint8_t, utils::CString, Program::UniformInfo>>;

    Program() noexcept;

    Program(const Program& rhs) = delete;
    Program& operator=(const Program& rhs) = delete;

    Program(Program&& rhs) noexcept;
    Program& operator=(Program&& rhs) noexcept = delete;

    ~Program() noexcept;

    Program& priorityQueue(CompilerPriorityQueue priorityQueue) noexcept;

    // sets the material name and variant for diagnostic purposes only
    Program& diagnostics(utils::CString const& name,
            utils::Invocable<utils::io::ostream&(utils::io::ostream& out)>&& logger);

    // Sets one of the program's shader (e.g. vertex, fragment)
    // string-based shaders are null terminated, consequently the size parameter must include the
    // null terminating character.
    Program& shader(ShaderStage shader, void const* data, size_t size);

    // Sets the language of the shader sources provided with shader() (defaults to ESSL3)
    Program& shaderLanguage(ShaderLanguage shaderLanguage);

    // Descriptor binding (set, binding, type -> shader name) info
    Program& descriptorBindings(backend::descriptor_set_t set,
            DescriptorBindingsInfo descriptorBindings) noexcept;

    Program& specializationConstants(SpecializationConstantsInfo specConstants) noexcept;

    struct PushConstant {
        utils::CString name;
        ConstantType type;
    };

    Program& pushConstants(ShaderStage stage,
            utils::FixedCapacityVector<PushConstant> constants) noexcept;

    Program& cacheId(uint64_t cacheId) noexcept;

    Program& multiview(bool multiview) noexcept;

    // For ES2 support only...
    Program& uniforms(uint32_t index, utils::CString name, UniformInfo uniforms) noexcept;
    Program& attributes(AttributesInfo attributes) noexcept;

    //
    // Getters for program construction...
    //

    ShaderSource const& getShadersSource() const noexcept { return mShadersSource; }
    ShaderSource& getShadersSource() noexcept { return mShadersSource; }

    utils::CString const& getName() const noexcept { return mName; }
    utils::CString& getName() noexcept { return mName; }

    auto const& getShaderLanguage() const { return mShaderLanguage; }

    uint64_t getCacheId() const noexcept { return mCacheId; }

    bool isMultiview() const noexcept { return mMultiview; }

    CompilerPriorityQueue getPriorityQueue() const noexcept { return mPriorityQueue; }

    SpecializationConstantsInfo const& getSpecializationConstants() const noexcept {
        return mSpecializationConstants;
    }

    SpecializationConstantsInfo& getSpecializationConstants() noexcept {
        return mSpecializationConstants;
    }

    DescriptorSetInfo& getDescriptorBindings() noexcept {
        return mDescriptorBindings;
    }

    utils::FixedCapacityVector<PushConstant> const& getPushConstants(
            ShaderStage stage) const noexcept {
        return mPushConstants[static_cast<uint8_t>(stage)];
    }

    utils::FixedCapacityVector<PushConstant>& getPushConstants(ShaderStage stage) noexcept {
        return mPushConstants[static_cast<uint8_t>(stage)];
    }

    auto const& getBindingUniformInfo() const { return mBindingUniformsInfo; }
    auto& getBindingUniformInfo() { return mBindingUniformsInfo; }

    auto const& getAttributes() const { return mAttributes; }
    auto& getAttributes() { return mAttributes; }

private:
    friend utils::io::ostream& operator<<(utils::io::ostream& out, const Program& builder);

    ShaderSource mShadersSource;
    ShaderLanguage mShaderLanguage = ShaderLanguage::ESSL3;
    utils::CString mName;
    uint64_t mCacheId{};
    CompilerPriorityQueue mPriorityQueue = CompilerPriorityQueue::HIGH;
    utils::Invocable<utils::io::ostream&(utils::io::ostream& out)> mLogger;
    SpecializationConstantsInfo mSpecializationConstants;
    std::array<utils::FixedCapacityVector<PushConstant>, SHADER_TYPE_COUNT> mPushConstants;
    DescriptorSetInfo mDescriptorBindings;

    // For ES2 support only
    AttributesInfo mAttributes;
    BindingUniformsInfo mBindingUniformsInfo;

    // Indicates the current engine was initialized with multiview stereo, and the variant for this
    // program contains STE flag. This will be referred later for the OpenGL shader compiler to
    // determine whether shader code replacement for the num_views should be performed.
    // This variable could be promoted as a more generic variable later if other similar needs occur.
    bool mMultiview = false;
};

} // namespace filament::backend

#endif // TNT_FILAMENT_BACKEND_PRIVATE_PROGRAM_H