// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "flutter/testing/testing.h"  // IWYU pragma: keep.
#include "fml/synchronization/waitable_event.h"
#include "impeller/renderer/backend/vulkan/descriptor_pool_vk.h"
#include "impeller/renderer/backend/vulkan/resource_manager_vk.h"
#include "impeller/renderer/backend/vulkan/test/mock_vulkan.h"

namespace impeller {
namespace testing {

TEST(DescriptorPoolRecyclerVKTest, GetDescriptorPoolRecyclerCreatesNewPools) {
  auto const context = MockVulkanContextBuilder().Build();

  auto const pool1 = context->GetDescriptorPoolRecycler()->Get();
  auto const pool2 = context->GetDescriptorPoolRecycler()->Get();

  // The two descriptor pools should be different.
  EXPECT_NE(pool1.get(), pool2.get());

  context->Shutdown();
}

namespace {

// Invokes the provided callback when the destructor is called.
//
// Can be moved, but not copied.
class DeathRattle final {
 public:
  explicit DeathRattle(std::function<void()> callback)
      : callback_(std::move(callback)) {}

  DeathRattle(DeathRattle&&) = default;
  DeathRattle& operator=(DeathRattle&&) = default;

  ~DeathRattle() { callback_(); }

 private:
  std::function<void()> callback_;
};

}  // namespace

TEST(DescriptorPoolRecyclerVKTest, ReclaimMakesDescriptorPoolAvailable) {
  auto const context = MockVulkanContextBuilder().Build();

  {
    // Fetch a pool (which will be created).
    auto pool = DescriptorPoolVK(context);
    pool.AllocateDescriptorSets({}, *context);
  }

  // There is a chance that the first death rattle item below is destroyed in
  // the same reclaim cycle as the pool allocation above. These items are placed
  // into a std::vector and free'd, which may free in reverse order. That would
  // imply that the death rattle and subsequent waitable event fires before the
  // pool is reset. To work around this, we can either manually remove items
  // from the vector or use two death rattles.
  for (auto i = 0u; i < 2; i++) {
    // Add something to the resource manager and have it notify us when it's
    // destroyed. That should give us a non-flaky signal that the pool has been
    // reclaimed as well.
    auto waiter = fml::AutoResetWaitableEvent();
    auto rattle = DeathRattle([&waiter]() { waiter.Signal(); });
    {
      UniqueResourceVKT<DeathRattle> resource(context->GetResourceManager(),
                                              std::move(rattle));
    }
    waiter.Wait();
  }

  auto const pool = context->GetDescriptorPoolRecycler()->Get();

  // Now check that we only ever created one pool.
  auto const called = GetMockVulkanFunctions(context->GetDevice());
  EXPECT_EQ(
      std::count(called->begin(), called->end(), "vkCreateDescriptorPool"), 1u);

  context->Shutdown();
}

TEST(DescriptorPoolRecyclerVKTest, ReclaimDropsDescriptorPoolIfSizeIsExceeded) {
  auto const context = MockVulkanContextBuilder().Build();

  // Create 33 pools
  {
    std::vector<std::unique_ptr<DescriptorPoolVK>> pools;
    for (auto i = 0u; i < 33; i++) {
      auto pool = std::make_unique<DescriptorPoolVK>(context);
      pool->AllocateDescriptorSets({}, *context);
      pools.push_back(std::move(pool));
    }
  }

  // See note above.
  for (auto i = 0u; i < 2; i++) {
    auto waiter = fml::AutoResetWaitableEvent();
    auto rattle = DeathRattle([&waiter]() { waiter.Signal(); });
    {
      UniqueResourceVKT<DeathRattle> resource(context->GetResourceManager(),
                                              std::move(rattle));
    }
    waiter.Wait();
  }

  auto const called = GetMockVulkanFunctions(context->GetDevice());
  EXPECT_EQ(
      std::count(called->begin(), called->end(), "vkCreateDescriptorPool"),
      33u);
  EXPECT_EQ(std::count(called->begin(), called->end(), "vkResetDescriptorPool"),
            33u);

  // Now create 33 more descriptor pools and observe that only one more is
  // allocated.
  {
    std::vector<std::unique_ptr<DescriptorPoolVK>> pools;
    for (auto i = 0u; i < 33; i++) {
      auto pool = std::make_unique<DescriptorPoolVK>(context);
      pool->AllocateDescriptorSets({}, *context);
      pools.push_back(std::move(pool));
    }
  }

  for (auto i = 0u; i < 2; i++) {
    auto waiter = fml::AutoResetWaitableEvent();
    auto rattle = DeathRattle([&waiter]() { waiter.Signal(); });
    {
      UniqueResourceVKT<DeathRattle> resource(context->GetResourceManager(),
                                              std::move(rattle));
    }
    waiter.Wait();
  }

  auto const called_twice = GetMockVulkanFunctions(context->GetDevice());
  // 32 of the descriptor pools were recycled, so only one more is created.
  EXPECT_EQ(
      std::count(called->begin(), called->end(), "vkCreateDescriptorPool"),
      34u);

  context->Shutdown();
}

}  // namespace testing
}  // namespace impeller