// Copyright 2021 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//
// AsyncTaskTests:
//     Simple tests for native::AsyncTask and native::AsnycTaskManager.

#include <memory>
#include <mutex>
#include <set>
#include <utility>
#include <vector>

#include "dawn/platform/DawnPlatform.h"
#include "gtest/gtest.h"
#include "src/dawn/native/AsyncTask.h"
#include "src/utils/non_copyable.h"

namespace dawn::native {
namespace {

struct SimpleTaskResult {
    uint32_t id;
};

// A thread-safe queue that stores the task results.
class ConcurrentTaskResultQueue : public NonCopyable {
  public:
    void AddResult(std::unique_ptr<SimpleTaskResult> result) {
        std::lock_guard<std::mutex> lock(mMutex);
        mTaskResults.push_back(std::move(result));
    }

    std::vector<std::unique_ptr<SimpleTaskResult>> GetAllResults() {
        std::vector<std::unique_ptr<SimpleTaskResult>> outputResults;
        {
            std::lock_guard<std::mutex> lock(mMutex);
            outputResults.swap(mTaskResults);
        }
        return outputResults;
    }

  private:
    std::mutex mMutex;
    std::vector<std::unique_ptr<SimpleTaskResult>> mTaskResults;
};

void DoTask(ConcurrentTaskResultQueue* resultQueue, uint32_t id) {
    std::unique_ptr<SimpleTaskResult> result = std::make_unique<SimpleTaskResult>();
    result->id = id;
    resultQueue->AddResult(std::move(result));
}

class AsyncTaskTest : public testing::Test {};

// TODO(crbug.com/454672586): Causing flaky fatal errors on multiple platforms.
// Emulate the basic usage of worker thread pool in Create*PipelineAsync().
TEST_F(AsyncTaskTest, DISABLED_Basic) {
    platform::Platform platform;
    std::unique_ptr<platform::WorkerTaskPool> pool = platform.CreateWorkerTaskPool();

    AsyncTaskManager taskManager(pool.get());
    ConcurrentTaskResultQueue taskResultQueue;

    constexpr size_t kTaskCount = 4u;
    std::set<uint32_t> idset;
    for (uint32_t i = 0; i < kTaskCount; ++i) {
        taskManager.PostTask<AsyncTask>([&taskResultQueue, i] { DoTask(&taskResultQueue, i); });
        idset.insert(i);
    }

    taskManager.WaitAllPendingTasks();

    std::vector<std::unique_ptr<SimpleTaskResult>> results = taskResultQueue.GetAllResults();
    ASSERT_EQ(kTaskCount, results.size());
    for (std::unique_ptr<SimpleTaskResult>& result : results) {
        idset.erase(result->id);
    }
    ASSERT_TRUE(idset.empty());
}

// Test that the task status is updated based on the task's running state
TEST_F(AsyncTaskTest, Status) {
    platform::Platform platform;
    std::unique_ptr<platform::WorkerTaskPool> pool = platform.CreateWorkerTaskPool();

    AsyncTaskManager taskManager(pool.get());
    ConcurrentTaskResultQueue taskResultQueue;

    // Use a mutex to force the task to wait on the main thread before completing
    std::mutex mutex;
    std::unique_lock lock(mutex);

    auto task = taskManager.PostTask<AsyncTask>(
        [&mutex]() { std::scoped_lock<std::mutex> taskLock(mutex); });

    ASSERT_FALSE(task->IsCompleted());

    // Allow the task to complete
    lock.unlock();
    task->Wait();
    ASSERT_TRUE(task->IsCompleted());
}

// Test coverage of the completion callbacks for tasks
TEST_F(AsyncTaskTest, Callbacks) {
    platform::Platform platform;
    std::unique_ptr<platform::WorkerTaskPool> pool = platform.CreateWorkerTaskPool();

    AsyncTaskManager taskManager(pool.get());
    ConcurrentTaskResultQueue taskResultQueue;

    // Use a mutex to force the task to wait on the main thread before completing
    std::mutex mutex;
    std::unique_lock lock(mutex);

    // Use a completion callback that simply counts how many times it's been called
    std::atomic<uint64_t> completionCallbackCounter = 0;
    AsyncTaskCompletionCallback completionCallback = [&completionCallbackCounter]() {
        completionCallbackCounter++;
    };

    // Spawn a task that waits for the mutex. Add a completion callback and confirm that it's not
    // called before the task completes
    auto task = taskManager.PostTask<AsyncTask>(
        [&mutex]() { std::scoped_lock<std::mutex> taskLock(mutex); });
    task->AddCompletionCallback(completionCallback);
    EXPECT_EQ(completionCallbackCounter, 0u);

    // Allow the task to complete and expect that the completion callback has been called
    lock.unlock();
    task->Wait();
    EXPECT_EQ(completionCallbackCounter, 1u);

    // Add another completion callback to the already-completed task and check that it is called
    // immediately
    task->AddCompletionCallback(completionCallback);
    EXPECT_EQ(completionCallbackCounter, 2u);
}
}  // anonymous namespace
}  // namespace dawn::native