//------------------------------------------------------------------------------
/*
    This file is part of clio: https://github.com/XRPLF/clio
    Copyright (c) 2025, the clio developers.

    Permission to use, copy, modify, and distribute this software for any
    purpose with or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================

#include "util/ObservableValue.hpp"

#include <boost/signals2/connection.hpp>
#include <gmock/gmock.h>
#include <gtest/gtest.h>

#include <atomic>
#include <chrono>
#include <mutex>
#include <thread>
#include <vector>

using namespace testing;
using namespace util;

namespace {

}  // namespace

class ObservableValueAtomicTest : public ::testing::Test {};

TEST_F(ObservableValueAtomicTest, BasicConstruction)
{
    ObservableValue<std::atomic<int>> const obs{42};

    EXPECT_EQ(obs.get(), 42);
    EXPECT_EQ(static_cast<int>(obs), 42);
    EXPECT_FALSE(obs.hasObservers());
}

TEST_F(ObservableValueAtomicTest, DefaultConstruction)
{
    ObservableValue<std::atomic<int>> const obsInt;
    EXPECT_EQ(obsInt.get(), 0);

    ObservableValue<std::atomic<bool>> const obsBool;
    EXPECT_FALSE(obsBool.get());

    EXPECT_FALSE(obsInt.hasObservers());
    EXPECT_FALSE(obsBool.hasObservers());
}

TEST_F(ObservableValueAtomicTest, BasicObservation)
{
    ObservableValue<std::atomic<int>> obs{10};
    testing::StrictMock<testing::MockFunction<void(int const&)>> mockObserver;

    auto connection = obs.observe(mockObserver.AsStdFunction());

    EXPECT_CALL(mockObserver, Call(20));
    obs = 20;
    EXPECT_EQ(obs.get(), 20);
}

TEST_F(ObservableValueAtomicTest, SetMethod)
{
    ObservableValue<std::atomic<int>> obs{5};
    testing::StrictMock<testing::MockFunction<void(int const&)>> mockObserver;

    auto connection = obs.observe(mockObserver.AsStdFunction());

    EXPECT_CALL(mockObserver, Call(15));
    obs.set(15);
    EXPECT_EQ(obs.get(), 15);

    obs.set(15);  // Same value should not notify
    EXPECT_EQ(obs.get(), 15);
}

TEST_F(ObservableValueAtomicTest, AtomicBasicUsage)
{
    ObservableValue<std::atomic<int>> obs{10};
    testing::StrictMock<testing::MockFunction<void(int const&)>> mockObserver;

    auto connection = obs.observe(mockObserver.AsStdFunction());

    EXPECT_CALL(mockObserver, Call(25));
    obs.set(25);

    EXPECT_EQ(obs.get(), 25);
}

TEST_F(ObservableValueAtomicTest, AtomicMultipleChanges)
{
    ObservableValue<std::atomic<int>> obs{50};
    testing::StrictMock<testing::MockFunction<void(int const&)>> mockObserver;

    auto connection = obs.observe(mockObserver.AsStdFunction());

    EXPECT_CALL(mockObserver, Call(100));  // First change: 50→100
    EXPECT_CALL(mockObserver, Call(50));   // Second change: 100→50
    obs.set(100);                          // Should notify: 50→100
    obs.set(50);                           // Should notify: 100→50

    EXPECT_EQ(obs.get(), 50);
}

TEST_F(ObservableValueAtomicTest, AtomicNoChangeNoNotification)
{
    ObservableValue<std::atomic<int>> obs{42};
    testing::StrictMock<testing::MockFunction<void(int const&)>> mockObserver;

    auto connection = obs.observe(mockObserver.AsStdFunction());

    // No EXPECT_CALL since no notification should occur
    obs.set(42);  // Same value, should not notify
    obs.set(42);  // Same value again, should not notify

    EXPECT_EQ(obs.get(), 42);
}

TEST_F(ObservableValueAtomicTest, AtomicSequentialChanges)
{
    ObservableValue<std::atomic<int>> obs{1};
    testing::StrictMock<testing::MockFunction<void(int const&)>> mockObserver;

    auto connection = obs.observe(mockObserver.AsStdFunction());

    EXPECT_CALL(mockObserver, Call(2));
    obs.set(2);

    EXPECT_CALL(mockObserver, Call(3));
    obs.set(3);

    EXPECT_EQ(obs.get(), 3);
}

TEST_F(ObservableValueAtomicTest, MultipleObservers)
{
    ObservableValue<std::atomic<int>> obs{0};

    testing::StrictMock<testing::MockFunction<void(int const&)>> mockObserver1;
    testing::StrictMock<testing::MockFunction<void(int const&)>> mockObserver2;

    auto conn1 = obs.observe(mockObserver1.AsStdFunction());
    auto conn2 = obs.observe(mockObserver2.AsStdFunction());

    EXPECT_CALL(mockObserver1, Call(42));
    EXPECT_CALL(mockObserver2, Call(42));
    obs = 42;

    conn1.disconnect();
    EXPECT_CALL(mockObserver2, Call(100));
    obs = 100;
}

TEST_F(ObservableValueAtomicTest, ThreadSafetyBasic)
{
    ObservableValue<std::atomic<int>> obs{0};
    std::atomic<int> notificationCount{0};
    std::vector<int> values;
    std::mutex valuesMutex;

    auto connection = obs.observe([&](int const& value) {
        notificationCount.fetch_add(1);
        std::lock_guard<std::mutex> const lock(valuesMutex);
        values.push_back(value);
    });

    static constexpr auto kNUM_THREADS = 4;
    static constexpr auto kINCREMENTS_PER_THREAD = 100;

    std::vector<std::thread> threads;
    threads.reserve(kNUM_THREADS);

    for (int i = 0; i < kNUM_THREADS; ++i) {
        threads.emplace_back([&obs]() {
            for (int j = 0; j < kINCREMENTS_PER_THREAD; ++j) {
                int const expected = obs.get();
                int const newValue = expected + 1;
                obs.set(newValue);
                std::this_thread::sleep_for(std::chrono::microseconds(1));
            }
        });
    }

    for (auto& thread : threads)
        thread.join();

    // Final value may be less than kNumThreads * kIncrementsPerThread due to race conditions
    EXPECT_GT(obs.get(), 0);
    EXPECT_GT(notificationCount.load(), 0);

    std::lock_guard<std::mutex> const lock(valuesMutex);
    for (auto const& value : values) {
        EXPECT_GT(value, 0);
    }
}

TEST_F(ObservableValueAtomicTest, ThreadSafetyWithDirectAccess)
{
    ObservableValue<std::atomic<int>> obs{0};
    std::atomic<int> notificationCount{0};

    auto connection = obs.observe([&](int const&) { notificationCount.fetch_add(1); });

    static constexpr auto kNUM_THREADS = 4;
    static constexpr auto kOPERATIONS_PER_THREAD = 50;

    std::vector<std::thread> threads;
    threads.reserve(kNUM_THREADS);

    for (int i = 0; i < kNUM_THREADS; ++i) {
        threads.emplace_back([&obs]() {
            for (int j = 0; j < kOPERATIONS_PER_THREAD; ++j) {
                int const current = obs.get();
                obs.set(current + 1);
                std::this_thread::sleep_for(std::chrono::microseconds(1));
            }
        });
    }

    for (auto& thread : threads)
        thread.join();

    EXPECT_GT(obs.get(), 0);
    EXPECT_GT(notificationCount.load(), 0);
}

TEST_F(ObservableValueAtomicTest, AtomicBoolSpecialization)
{
    ObservableValue<std::atomic<bool>> obs{false};
    testing::StrictMock<testing::MockFunction<void(bool const&)>> mockObserver;

    auto connection = obs.observe(mockObserver.AsStdFunction());

    EXPECT_CALL(mockObserver, Call(true));
    obs = true;
    EXPECT_TRUE(obs.get());

    obs = true;  // Same value should not notify

    EXPECT_CALL(mockObserver, Call(false));
    obs.set(false);
    EXPECT_FALSE(obs.get());
}

TEST_F(ObservableValueAtomicTest, CompareAndSwapBehavior)
{
    ObservableValue<std::atomic<int>> obs{10};
    testing::StrictMock<testing::MockFunction<void(int const&)>> mockObserver;

    auto connection = obs.observe(mockObserver.AsStdFunction());

    // Test that compare-and-swap works correctly in set()
    obs.set(10);  // Same value, should not notify

    EXPECT_CALL(mockObserver, Call(20));
    obs.set(20);  // Different value, should notify
}

TEST_F(ObservableValueAtomicTest, RaceConditionNotificationIntegrity)
{
    ObservableValue<std::atomic<int>> obs{0};
    std::atomic<int> notificationCount{0};
    std::vector<int> values;
    std::mutex valuesMutex;

    auto connection = obs.observe([&](int const& value) {
        notificationCount.fetch_add(1);
        std::lock_guard<std::mutex> const lock(valuesMutex);
        values.push_back(value);
    });

    static constexpr auto kNUM_THREADS = 10;
    static constexpr auto kOPERATIONS_PER_THREAD = 20;

    std::vector<std::thread> threads;
    threads.reserve(kNUM_THREADS);

    for (int i = 0; i < kNUM_THREADS; ++i) {
        threads.emplace_back([&obs]() {
            for (int j = 0; j < kOPERATIONS_PER_THREAD; ++j) {
                obs.set(j % 3);
                std::this_thread::sleep_for(std::chrono::microseconds(1));
            }
        });
    }

    for (auto& thread : threads)
        thread.join();

    EXPECT_GT(notificationCount.load(), 0);

    std::lock_guard<std::mutex> const lock(valuesMutex);
    for (auto const& value : values) {
        EXPECT_GE(value, 0);
        EXPECT_LE(value, 2);
    }

    int const finalValue = obs.get();
    EXPECT_GE(finalValue, 0);
    EXPECT_LE(finalValue, 2);
}

TEST_F(ObservableValueAtomicTest, DeterministicNotificationTest)
{
    ObservableValue<std::atomic<int>> obs{0};
    std::atomic<int> notificationCount{0};
    std::vector<int> values;
    std::mutex valuesMutex;

    auto connection = obs.observe([&](int const& value) {
        notificationCount.fetch_add(1);
        std::lock_guard<std::mutex> const lock(valuesMutex);
        values.push_back(value);
    });

    static constexpr auto kNUM_THREADS = 5;

    std::vector<std::thread> threads;
    threads.reserve(kNUM_THREADS);

    for (int i = 0; i < kNUM_THREADS; ++i) {
        threads.emplace_back([&obs, i]() { obs.set(i + 1); });
    }

    for (auto& thread : threads)
        thread.join();

    // Each thread sets a unique value, so expect exactly kNumThreads notifications
    EXPECT_EQ(notificationCount.load(), kNUM_THREADS);

    std::lock_guard<std::mutex> const lock(valuesMutex);
    EXPECT_EQ(values.size(), kNUM_THREADS);

    for (auto const& value : values) {
        EXPECT_GE(value, 1);
        EXPECT_LE(value, kNUM_THREADS);
    }

    int const finalValue = obs.get();
    EXPECT_GE(finalValue, 1);
    EXPECT_LE(finalValue, kNUM_THREADS);
}

TEST_F(ObservableValueAtomicTest, NoNotificationForSameValue)
{
    ObservableValue<std::atomic<int>> obs{42};
    std::atomic<int> notificationCount{0};

    auto connection = obs.observe([&](int const&) { notificationCount.fetch_add(1); });

    static constexpr auto kNUM_THREADS = 10;

    std::vector<std::thread> threads;
    threads.reserve(kNUM_THREADS);

    for (int i = 0; i < kNUM_THREADS; ++i) {
        threads.emplace_back([&obs]() { obs.set(42); });
    }

    for (auto& thread : threads)
        thread.join();

    EXPECT_EQ(notificationCount.load(), 0);  // No notifications since value never changed
    EXPECT_EQ(obs.get(), 42);
}

TEST_F(ObservableValueAtomicTest, AtomicRaceConditionCorrectness)
{
    ObservableValue<std::atomic<int>> obs{0};
    std::atomic<int> notificationCount{0};
    std::vector<int> values;
    std::mutex valuesMutex;

    auto connection = obs.observe([&](int const& value) {
        notificationCount.fetch_add(1);
        std::lock_guard<std::mutex> const lock(valuesMutex);
        values.push_back(value);
    });

    static constexpr auto kNUM_THREADS = 3;

    std::vector<std::thread> threads;
    threads.reserve(kNUM_THREADS);

    // Test that direct access properly notifies for all value changes
    // Each thread will make unique changes to avoid race condition conflicts
    for (int i = 0; i < kNUM_THREADS; ++i) {
        threads.emplace_back([&obs, i]() {
            int const baseValue = (i + 1) * 10;  // 10, 20, 30
            obs.set(baseValue);                  // Store unique values
            obs.set(baseValue + 1);              // Then increment
        });
    }

    for (auto& thread : threads)
        thread.join();

    // We should get some notifications (exact count depends on race conditions)
    // but at least one per thread since they use unique base values
    EXPECT_GE(notificationCount.load(), kNUM_THREADS);

    std::lock_guard<std::mutex> const lock(valuesMutex);
    EXPECT_GE(values.size(), kNUM_THREADS);

    for (auto const& value : values)
        EXPECT_GT(value, 0);
}

TEST_F(ObservableValueAtomicTest, ForceNotify)
{
    ObservableValue<std::atomic<int>> obs{42};
    testing::StrictMock<testing::MockFunction<void(int const&)>> mockObserver;

    obs.forceNotify();

    auto connection = obs.observe(mockObserver.AsStdFunction());

    EXPECT_CALL(mockObserver, Call(42));
    obs.forceNotify();

    EXPECT_CALL(mockObserver, Call(42));
    obs.forceNotify();

    EXPECT_CALL(mockObserver, Call(100));
    obs.set(100);
    EXPECT_CALL(mockObserver, Call(100));
    obs.forceNotify();

    EXPECT_CALL(mockObserver, Call(100)).Times(3);
    obs.forceNotify();
    obs.forceNotify();
    obs.forceNotify();
}