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

// Issue #101: fence-keyed deferred resource-deletion queue. Since #40 dropped
// the per-frame vkQueueWaitIdle, a buffer the CPU is done with may still be
// read by the GPU for up to framesInFlight-1 more frames — so destroying it
// immediately (VulkanBuffer::Clear / the old Resize path) is a use-after-free.
// VulkanBuffer::DeferredClear() / Resize() now hand the handles to Device's
// deletion queue, tagged with the current frameCounter; ReclaimDeletions frees
// an entry only once framesInFlight frames have elapsed, and DrainDeletions
// (called after a wait-idle) frees everything unconditionally.
//
// The retire-timing is the load-bearing logic: free too early and it's the
// very UAF the queue exists to prevent; free too late and resources leak. This
// test drives it on a real headless Vulkan device (real VkBuffer/VkDeviceMemory
// so the frees actually execute and the validation layer can object), manually
// stepping Device::frameCounter to pin down the exact frame an entry is
// reclaimed on. It needs no swapchain/window — the queue itself is window-free.

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

import Crafter.Graphics;
import std;

using namespace Crafter;

namespace {

int failures = 0;

void Check(bool ok, std::string_view what) {
    std::println("{}  {}", ok ? "PASS" : "FAIL", what);
    if (!ok) ++failures;
}

constexpr VkBufferUsageFlags2 USAGE =
    VK_BUFFER_USAGE_2_TRANSFER_SRC_BIT | VK_BUFFER_USAGE_2_SHADER_DEVICE_ADDRESS_BIT;
constexpr auto DEVICE_LOCAL = VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT;

} // namespace

int main() {
    Device::Initialize();

    // No Window here, so set the in-flight depth ourselves (Window::Render
    // normally does this at init). Use the real window depth so the timing
    // matches production.
    Device::framesInFlight = Window::numFrames;
    Device::frameCounter = 0;
    Device::deletionQueue.clear();

    // ── DeferredClear enqueues, nulls the handle, and retires after exactly
    //    framesInFlight frames ──────────────────────────────────────────────
    {
        VulkanBuffer<float, false> buf;
        buf.Create(USAGE, DEVICE_LOCAL, 16);
        Check(buf.buffer != VK_NULL_HANDLE, "Create produced a real buffer handle");

        buf.DeferredClear();
        Check(buf.buffer == VK_NULL_HANDLE,
              "DeferredClear nulls the handle so the buffer no longer owns it");
        Check(Device::deletionQueue.size() == 1,
              "DeferredClear enqueues exactly one pending deletion");

        // Walk right up to the retire frame: still queued at every frame before
        // frameCounter reaches retireAfter + framesInFlight.
        for (std::uint64_t f = 0; f < Window::numFrames; ++f) {
            Device::frameCounter = f;
            Device::ReclaimDeletions();
            Check(Device::deletionQueue.size() == 1,
                  std::format("entry survives ReclaimDeletions at frame {} "
                              "(< retire frame {})", f, Window::numFrames));
        }

        // At retireAfter(0) + framesInFlight it is finally freed.
        Device::frameCounter = Window::numFrames;
        Device::ReclaimDeletions();
        Check(Device::deletionQueue.empty(),
              std::format("entry is reclaimed once frameCounter reaches {}",
                          Window::numFrames));
    }

    // ── Resize's reallocate path defers the OLD allocation, not the new one ──
    {
        Device::frameCounter = 100;
        Device::deletionQueue.clear();

        VulkanBuffer<float, false> buf;
        buf.Create(USAGE, DEVICE_LOCAL, 4);
        VkBuffer original = buf.buffer;

        // Grow past capacity → forces destroy+recreate, which must DEFER the old
        // buffer (the #63 UAF this whole queue exists to close).
        buf.Resize(USAGE, DEVICE_LOCAL, 64);
        Check(buf.buffer != VK_NULL_HANDLE && buf.buffer != original,
              "Resize past capacity allocates a fresh buffer");
        Check(Device::deletionQueue.size() == 1
                  && Device::deletionQueue.front().buffer == original,
              "Resize defers the OLD allocation to the deletion queue");
        Check(Device::deletionQueue.front().retireAfter == 100,
              "deferred entry is tagged with the frameCounter at enqueue time");

        // Not yet due (tagged at 100, retires at 100 + framesInFlight).
        Device::frameCounter = 100 + Window::numFrames - 1;
        Device::ReclaimDeletions();
        Check(Device::deletionQueue.size() == 1,
              "old allocation is not freed before its retire frame");

        Device::frameCounter = 100 + Window::numFrames;
        Device::ReclaimDeletions();
        Check(Device::deletionQueue.empty(),
              "old allocation is freed on its retire frame");

        buf.Clear(); // immediate cleanup of the live buffer (no GPU work pending)
    }

    // ── DrainDeletions frees everything regardless of retire frame ───────────
    {
        Device::frameCounter = 0;
        Device::deletionQueue.clear();

        VulkanBuffer<float, false> a;
        VulkanBuffer<float, false> b;
        a.Create(USAGE, DEVICE_LOCAL, 8);
        b.Create(USAGE, DEVICE_LOCAL, 8);
        a.DeferredClear();
        b.DeferredClear();
        Check(Device::deletionQueue.size() == 2, "two entries queued");

        // Far from any retire frame — ReclaimDeletions would free nothing here.
        Device::DrainDeletions();
        Check(Device::deletionQueue.empty(),
              "DrainDeletions frees every queued entry unconditionally");
    }

    // ── EnqueueDeletion ignores a null handle (nothing to free) ──────────────
    {
        Device::deletionQueue.clear();
        Device::EnqueueDeletion(VK_NULL_HANDLE, VK_NULL_HANDLE);
        Check(Device::deletionQueue.empty(),
              "EnqueueDeletion drops a VK_NULL_HANDLE buffer");
    }

    Check(Device::validationErrorCount == 0,
          std::format("no Vulkan validation errors across the run ({} seen)",
                      Device::validationErrorCount));

    if (failures != 0) {
        std::println("{} check(s) failed", failures);
        return EXIT_FAILURE;
    }
    std::println("all checks passed");
    return EXIT_SUCCESS;
}