#include "util/AsioContextTestFixture.hpp"
#include "util/BlockingCache.hpp"
#include "util/NameGenerator.hpp"
#include "util/Spawn.hpp"

#include <gmock/gmock.h>
#include <gtest/gtest.h>

#include <memory>

using testing::MockFunction;
using testing::Return;
using testing::StrictMock;

#include <boost/asio/spawn.hpp>

#include <expected>
#include <string>

struct BlockingCacheTest : SyncAsioContextTest {
    using ErrorType = std::string;
    using ValueType = int;
    using Cache = util::BlockingCache<ValueType, ErrorType>;
    using MockUpdater =
        StrictMock<MockFunction<std::expected<ValueType, ErrorType>(boost::asio::yield_context)>>;
    using MockVerifier = StrictMock<MockFunction<bool(ValueType const&)>>;

    std::unique_ptr<Cache> cache = std::make_unique<Cache>();
    MockUpdater mockUpdater;
    MockVerifier mockVerifier;
    int const value = 42;
    std::string error = "some error";
};

TEST_F(BlockingCacheTest, asyncGet_NoValueCacheUpdateSuccess)
{
    EXPECT_CALL(mockUpdater, Call).WillOnce(Return(value));
    EXPECT_CALL(mockVerifier, Call(value)).WillOnce(Return(true));

    runSpawn([&](boost::asio::yield_context yield) {
        auto result =
            cache->asyncGet(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());

        ASSERT_TRUE(result.has_value());
        EXPECT_EQ(result.value(), 42);
    });
}

TEST_F(BlockingCacheTest, asyncGet_NoValueCacheUpdateFailure)
{
    EXPECT_CALL(mockUpdater, Call).WillOnce(Return(std::unexpected{error}));

    runSpawn([&](boost::asio::yield_context yield) {
        auto result =
            cache->asyncGet(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());

        ASSERT_FALSE(result.has_value());
        EXPECT_EQ(result.error(), error);
    });
}

TEST_F(BlockingCacheTest, asyncGet_NoValueCacheUpdateSuccessButVerifierRejects)
{
    runSpawn([&](boost::asio::yield_context yield) {
        std::expected<ValueType, ErrorType> result;
        {
            EXPECT_CALL(mockUpdater, Call).WillOnce(Return(value));
            EXPECT_CALL(mockVerifier, Call(value)).WillOnce(Return(false));

            result =
                cache->asyncGet(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());

            ASSERT_TRUE(result.has_value());
            EXPECT_EQ(result.value(), value);
        }

        int const newValue = 24;
        {
            EXPECT_CALL(mockUpdater, Call).WillOnce(Return(newValue));
            EXPECT_CALL(mockVerifier, Call(newValue)).WillOnce(Return(true));

            result =
                cache->asyncGet(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());

            ASSERT_TRUE(result.has_value());
            EXPECT_EQ(result.value(), newValue);
        }

        result = cache->asyncGet(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());

        ASSERT_TRUE(result.has_value());
        EXPECT_EQ(result.value(), newValue);
    });
}

TEST_F(BlockingCacheTest, asyncGet_HasValueCacheReturnsValue)
{
    cache = std::make_unique<Cache>(value);

    runSpawn([&](boost::asio::yield_context yield) {
        auto result =
            cache->asyncGet(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());

        ASSERT_TRUE(result.has_value());
        EXPECT_EQ(result.value(), value);
    });
}

struct BlockingCacheWaitTestBundle {
    bool updateSuccessful;
    bool verifierAccepts;
    std::string testName;
};

struct BlockingCacheWaitTest : BlockingCacheTest,
                               testing::WithParamInterface<BlockingCacheWaitTestBundle> {};

TEST_P(BlockingCacheWaitTest, WaitForUpdate)
{
    bool waitingCoroutineFinished = false;

    auto waitingCoroutine = [&](boost::asio::yield_context yield) {
        auto result =
            cache->asyncGet(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());

        if (GetParam().updateSuccessful) {
            ASSERT_TRUE(result.has_value());
            EXPECT_EQ(result.value(), value);
        } else {
            ASSERT_FALSE(result.has_value());
            EXPECT_EQ(result.error(), error);
        }
        waitingCoroutineFinished = true;
    };

    EXPECT_CALL(mockUpdater, Call)
        .WillOnce(
            [this, &waitingCoroutine](
                boost::asio::yield_context yield
            ) -> std::expected<ValueType, ErrorType> {
                util::spawn(yield, waitingCoroutine);
                if (GetParam().updateSuccessful) {
                    return value;
                }
                return std::unexpected{error};
            }
        );

    if (GetParam().updateSuccessful)
        EXPECT_CALL(mockVerifier, Call(value)).WillOnce(Return(GetParam().verifierAccepts));

    runSpawn([&](boost::asio::yield_context yield) {
        auto result =
            cache->asyncGet(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());

        if (GetParam().updateSuccessful) {
            ASSERT_TRUE(result.has_value());
            EXPECT_EQ(result.value(), value);
        } else {
            ASSERT_FALSE(result.has_value());
            EXPECT_EQ(result.error(), error);
        }
        ASSERT_FALSE(waitingCoroutineFinished);
    });
}

INSTANTIATE_TEST_SUITE_P(
    BlockingCacheTest,
    BlockingCacheWaitTest,
    testing::Values(
        BlockingCacheWaitTestBundle{
            .updateSuccessful = true,
            .verifierAccepts = true,
            .testName = "UpdateSucceedsVerifierAccepts"
        },
        BlockingCacheWaitTestBundle{
            .updateSuccessful = true,
            .verifierAccepts = false,
            .testName = "UpdateSucceedsVerifierRejects"
        },
        BlockingCacheWaitTestBundle{
            .updateSuccessful = false,
            .verifierAccepts = false,
            .testName = "UpdateFails"
        }
    ),
    tests::util::kNAME_GENERATOR
);

TEST_F(BlockingCacheTest, InvalidateWhenStateIsNoValue)
{
    ASSERT_EQ(cache->state(), Cache::State::NoValue);
    cache->invalidate();
    ASSERT_EQ(cache->state(), Cache::State::NoValue);
}

TEST_F(BlockingCacheTest, InvalidateWhenStateIsUpdating)
{
    EXPECT_CALL(mockUpdater, Call).WillOnce([this](auto&&) {
        EXPECT_EQ(cache->state(), Cache::State::Updating);
        cache->invalidate();
        EXPECT_EQ(cache->state(), Cache::State::Updating);
        return value;
    });
    EXPECT_CALL(mockVerifier, Call(value)).WillOnce(Return(true));

    runSpawn([&](boost::asio::yield_context yield) {
        auto result =
            cache->asyncGet(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());
        ASSERT_TRUE(result.has_value());
        ASSERT_EQ(result.value(), value);
        ASSERT_EQ(cache->state(), Cache::State::HasValue);
    });
}

TEST_F(BlockingCacheTest, InvalidateWhenStateIsHasValue)
{
    cache = std::make_unique<Cache>(value);
    ASSERT_EQ(cache->state(), Cache::State::HasValue);
    cache->invalidate();
    EXPECT_EQ(cache->state(), Cache::State::NoValue);
}

TEST_F(BlockingCacheTest, UpdateFromTwoCoroutinesHappensOnlyOnce)
{
    auto waitingCoroutine = [&](boost::asio::yield_context yield) {
        auto result =
            cache->update(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());
        ASSERT_TRUE(result.has_value());
        ASSERT_EQ(result.value(), value);
    };

    EXPECT_CALL(mockUpdater, Call)
        .WillOnce(
            [this, &waitingCoroutine](
                boost::asio::yield_context yield
            ) -> std::expected<ValueType, ErrorType> {
                util::spawn(yield, waitingCoroutine);
                return value;
            }
        );
    EXPECT_CALL(mockVerifier, Call(value)).WillOnce(Return(true));

    auto updatingCoroutine = [&](boost::asio::yield_context yield) {
        auto const result =
            cache->update(yield, mockUpdater.AsStdFunction(), mockVerifier.AsStdFunction());
        EXPECT_TRUE(result.has_value());
        ASSERT_EQ(result.value(), value);
    };

    runSpawn([&](boost::asio::yield_context yield) { util::spawn(yield, updatingCoroutine); });
}