//SPDX-License-Identifier: LGPL-3.0-only
//SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

// The deletion queue takes handles from any thread. Every Vulkan handle
// owner's destructor queues its handles, and owners go where they're made: a
// loader thread drops the buffers of a model it built while the render loop
// reclaims the queue each frame. The queue was a plain deque, so those
// pushes and pops raced and corrupted it.
//
// Four threads make and drop buffers while this one steps frames and
// reclaims, as Window::Render does; then everything has to drain cleanly.
//
// Needs a Vulkan device and no window.

#include <cstdlib>
#include "vulkan/vulkan.h"

import Crafter.Graphics;
import std;

using namespace Crafter;

int main() {
    Device::Initialize();
    Device::framesInFlight = 2;
    Device::frameCounter = 0;

    // Each round, every thread makes its buffers, then all drop theirs at
    // once, so the queue's pushes overlap each other and the reclaims.
    constexpr int kThreads = 4;
    constexpr int kBuffers = 400;
    constexpr int kRounds = 5;
    for (int round = 0; round < kRounds; ++round) {
        std::latch made(kThreads + 1);
        std::atomic<int> dropping = kThreads;
        std::vector<std::thread> makers;
        for (int t = 0; t < kThreads; ++t) {
            makers.emplace_back([&] {
                std::vector<VulkanBuffer<std::uint32_t, false>> buffers(kBuffers);
                for (VulkanBuffer<std::uint32_t, false>& buffer : buffers) {
                    buffer.Create(VK_BUFFER_USAGE_TRANSFER_DST_BIT, VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT, 16);
                }
                made.arrive_and_wait();
                buffers.clear();
                --dropping;
            });
        }
        made.arrive_and_wait();
        while (dropping > 0) {
            ++Device::frameCounter;
            Device::ReclaimDeletions();
        }
        for (std::thread& maker : makers) maker.join();
    }
    Device::DrainDeletions();

    const bool empty = Device::deletionQueue.empty();
    std::println("{}  {} buffers dropped at once on {} threads while frames were reclaimed, {} times, and drained", empty ? "PASS" : "FAIL", kThreads * kBuffers, kThreads, kRounds);
    return empty ? EXIT_SUCCESS : EXIT_FAILURE;
}