// Copyright 2018 yuzu Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <algorithm>
#include "common/assert.h"
#include "common/logging/log.h"
#include "video_core/renderer_vulkan/declarations.h"
#include "video_core/renderer_vulkan/vk_device.h"
#include "video_core/renderer_vulkan/vk_resource_manager.h"

namespace Vulkan {

// TODO(Rodrigo): Fine tune these numbers.
constexpr std::size_t FENCES_GROW_STEP = 0x40;

VKResource::VKResource() = default;

VKResource::~VKResource() = default;

VKFence::VKFence(const VKDevice& device, UniqueFence handle)
    : device{device}, handle{std::move(handle)} {}

VKFence::~VKFence() = default;

void VKFence::Wait() {
    const auto dev = device.GetLogical();
    const auto& dld = device.GetDispatchLoader();
    dev.waitForFences({*handle}, true, std::numeric_limits<u64>::max(), dld);
}

void VKFence::Release() {
    is_owned = false;
}

void VKFence::Commit() {
    is_owned = true;
    is_used = true;
}

bool VKFence::Tick(bool gpu_wait, bool owner_wait) {
    if (!is_used) {
        // If a fence is not used it's always free.
        return true;
    }
    if (is_owned && !owner_wait) {
        // The fence is still being owned (Release has not been called) and ownership wait has
        // not been asked.
        return false;
    }

    const auto dev = device.GetLogical();
    const auto& dld = device.GetDispatchLoader();
    if (gpu_wait) {
        // Wait for the fence if it has been requested.
        dev.waitForFences({*handle}, true, std::numeric_limits<u64>::max(), dld);
    } else {
        if (dev.getFenceStatus(*handle, dld) != vk::Result::eSuccess) {
            // Vulkan fence is not ready, not much it can do here
            return false;
        }
    }

    // Broadcast resources their free state.
    for (auto* resource : protected_resources) {
        resource->OnFenceRemoval(this);
    }
    protected_resources.clear();

    // Prepare fence for reusage.
    dev.resetFences({*handle}, dld);
    is_used = false;
    return true;
}

void VKFence::Protect(VKResource* resource) {
    protected_resources.push_back(resource);
}

void VKFence::Unprotect(const VKResource* resource) {
    const auto it = std::find(protected_resources.begin(), protected_resources.end(), resource);
    if (it != protected_resources.end()) {
        protected_resources.erase(it);
    }
}

VKFenceWatch::VKFenceWatch() = default;

VKFenceWatch::~VKFenceWatch() {
    if (fence) {
        fence->Unprotect(this);
    }
}

void VKFenceWatch::Wait() {
    if (!fence) {
        return;
    }
    fence->Wait();
    fence->Unprotect(this);
    fence = nullptr;
}

void VKFenceWatch::Watch(VKFence& new_fence) {
    Wait();
    fence = &new_fence;
    fence->Protect(this);
}

bool VKFenceWatch::TryWatch(VKFence& new_fence) {
    if (fence) {
        return false;
    }
    fence = &new_fence;
    fence->Protect(this);
    return true;
}

void VKFenceWatch::OnFenceRemoval(VKFence* signaling_fence) {
    ASSERT_MSG(signaling_fence == fence, "Removing the wrong fence");
    fence = nullptr;
}

VKResourceManager::VKResourceManager(const VKDevice& device) : device{device} {
    GrowFences(FENCES_GROW_STEP);
}

VKResourceManager::~VKResourceManager() = default;

VKFence& VKResourceManager::CommitFence() {
    const auto StepFences = [&](bool gpu_wait, bool owner_wait) -> VKFence* {
        const auto Tick = [=](auto& fence) { return fence->Tick(gpu_wait, owner_wait); };
        const auto hinted = fences.begin() + fences_iterator;

        auto it = std::find_if(hinted, fences.end(), Tick);
        if (it == fences.end()) {
            it = std::find_if(fences.begin(), hinted, Tick);
            if (it == hinted) {
                return nullptr;
            }
        }
        fences_iterator = std::distance(fences.begin(), it) + 1;
        if (fences_iterator >= fences.size())
            fences_iterator = 0;

        auto& fence = *it;
        fence->Commit();
        return fence.get();
    };

    VKFence* found_fence = StepFences(false, false);
    if (!found_fence) {
        // Try again, this time waiting.
        found_fence = StepFences(true, false);

        if (!found_fence) {
            // Allocate new fences and try again.
            LOG_INFO(Render_Vulkan, "Allocating new fences {} -> {}", fences.size(),
                     fences.size() + FENCES_GROW_STEP);

            GrowFences(FENCES_GROW_STEP);
            found_fence = StepFences(true, false);
            ASSERT(found_fence != nullptr);
        }
    }
    return *found_fence;
}

void VKResourceManager::GrowFences(std::size_t new_fences_count) {
    const auto dev = device.GetLogical();
    const auto& dld = device.GetDispatchLoader();
    const vk::FenceCreateInfo fence_ci;

    const std::size_t previous_size = fences.size();
    fences.resize(previous_size + new_fences_count);

    std::generate(fences.begin() + previous_size, fences.end(), [&]() {
        return std::make_unique<VKFence>(device, dev.createFenceUnique(fence_ci, nullptr, dld));
    });
}

} // namespace Vulkan