#include <expected>
#include <memory>
#include <string>
#include <vector>

#include <catch2/catch_test_macros.hpp>
#include "serif/utils/dependencies/dependencies.hpp"

namespace
{
    namespace dependencies = serif::utils::dependencies;
    struct Source
    {
    };
    struct Result
    {
    };
    struct OtherResult
    {
    };
    struct FinalResult
    {
    };
} // namespace

TEST_CASE("Shared dependency results survive refresh rejection invalidation and cache destruction", "[unit][utils][dependencies]")
{
    std::shared_ptr<const std::vector<int>> first;
    std::shared_ptr<const std::vector<int>> second;
    std::weak_ptr<const std::vector<int>> released;
    {
        int value = 4;
        auto context = dependencies::make_dependency_context(dependencies::borrow<Source>(value));
        auto graph = dependencies::make_computation_graph(dependencies::make_computation<Result, dependencies::InputList<Source>>(
            [](const int& input) -> std::expected<std::vector<int>, std::string>
        {
            if (input < 0)
            {
                return std::unexpected("negative trial");
            }
            return std::vector<int>{input, input + 1};
        }));
        auto cache = dependencies::make_computation_cache<std::string>(std::move(graph), context);
        STATIC_CHECK(std::same_as<decltype(cache.share<Result>()), std::shared_ptr<const std::vector<int>>>);
        CHECK_THROWS(cache.share<Result>());
        REQUIRE(cache.try_prepare(context));
        first = cache.share<Result>();
        CHECK((*first == std::vector<int>{4, 5}));
        REQUIRE(cache.try_prepare(context));
        CHECK(cache.share<Result>() == first);
        value = 9;
        REQUIRE(cache.try_prepare(context));
        second = cache.share<Result>();
        CHECK(second != first);
        CHECK((*first == std::vector<int>{4, 5}));
        CHECK((*second == std::vector<int>{9, 10}));
        value = -1;
        CHECK_FALSE(cache.try_prepare(context));
        CHECK_FALSE(cache.ready());
        CHECK_THROWS(cache.share<Result>());
        CHECK((*first == std::vector<int>{4, 5}));
        CHECK((*second == std::vector<int>{9, 10}));
        value = 9;
        REQUIRE(cache.try_prepare(context));
        CHECK(cache.share<Result>() == second);
        cache.invalidate();
        CHECK_THROWS(cache.share<Result>());
        CHECK((*second == std::vector<int>{9, 10}));
        REQUIRE(cache.try_prepare(context));
        released = cache.share<Result>();
        CHECK_FALSE(released.expired());
    }
    CHECK(released.expired());
    CHECK((*first == std::vector<int>{4, 5}));
    CHECK((*second == std::vector<int>{9, 10}));
    released = first;
    first.reset();
    CHECK(released.expired());
}

TEST_CASE("Only currently requested dependency results can be shared while retained snapshots stay valid", "[unit][utils][dependencies]")
{
    const auto context = dependencies::make_dependency_context(dependencies::own<Source>(3));
    auto graph = dependencies::make_computation_graph(
        dependencies::make_computation<Result, dependencies::InputList<Source>>([](const int& value)
    {
        return value;
    }),
        dependencies::make_computation<OtherResult, dependencies::InputList<Source>>([](const int& value)
    {
        return 2 * value;
    }));
    auto cache = dependencies::make_computation_cache(std::move(graph), context);
    REQUIRE(cache.try_prepare(context));
    const auto previous = cache.share<OtherResult>();
    REQUIRE(cache.try_prepare(context, dependencies::KeyList<Result>{}));
    CHECK_THROWS(cache.share<OtherResult>());
    CHECK(*previous == 6);
    CHECK(*cache.share<Result>() == 3);
    auto moved = std::move(cache);
    CHECK_THROWS(cache.share<Result>());
    CHECK(*moved.share<Result>() == 3);
    CHECK(*previous == 6);
}

TEST_CASE("Owning computations retain the exact move-only prerequisite across cache generations and owner lifetimes", "[unit][utils][dependencies]")
{
    using Snapshot = std::shared_ptr<const std::unique_ptr<int>>;
    Snapshot first;
    Snapshot second;
    std::weak_ptr<const std::unique_ptr<int>> unretained;
    {
        int value = 4;
        auto context = dependencies::make_dependency_context(dependencies::borrow<Source>(value));
        auto graph = dependencies::make_computation_graph(
            dependencies::make_owning_computation<OtherResult, dependencies::InputList<Result>>([](Snapshot prerequisite)
        {
            return prerequisite;
        }),
            dependencies::make_computation<Result, dependencies::InputList<Source>>([](const int input)
        {
            return std::make_unique<int>(input);
        }),
            dependencies::make_computation<FinalResult, dependencies::InputList<OtherResult>>([](const Snapshot& input)
        {
            return **input + 1;
        }));
        auto cache = dependencies::make_computation_cache(std::move(graph), context);
        REQUIRE(cache.try_prepare(context));
        first = cache.get<OtherResult>();
        CHECK(first == cache.share<Result>());
        CHECK(cache.get<FinalResult>() == 5);

        const auto reused = cache.try_prepare(context);
        REQUIRE(reused);
        CHECK(reused->reused_count() == 3);
        CHECK(cache.get<OtherResult>() == first);

        value = 9;
        REQUIRE(cache.try_prepare(context));
        second = cache.get<OtherResult>();
        CHECK(second == cache.share<Result>());
        CHECK(second != first);
        CHECK(**first == 4);
        CHECK(**second == 9);
        CHECK(cache.get<FinalResult>() == 10);

        cache.invalidate();
        CHECK(**first == 4);
        CHECK(**second == 9);
        REQUIRE(cache.try_prepare(context));
        unretained = cache.share<Result>();
        CHECK_FALSE(unretained.expired());
    }
    CHECK(unretained.expired());
    CHECK(**first == 4);
    CHECK(**second == 9);
}

TEST_CASE("Rejected owning computations release candidate prerequisites and preserve the accepted generation", "[unit][utils][dependencies]")
{
    using Snapshot = std::shared_ptr<const std::unique_ptr<int>>;
    int value = 4;
    std::weak_ptr<const std::unique_ptr<int>> rejected;
    auto context = dependencies::make_dependency_context(dependencies::borrow<Source>(value));
    auto graph = dependencies::make_computation_graph(
        dependencies::make_computation<Result, dependencies::InputList<Source>>([](const int input)
    {
        return std::make_unique<int>(input);
    }),
        dependencies::make_owning_computation<OtherResult, dependencies::InputList<Result>>([&rejected](Snapshot prerequisite) -> std::expected<Snapshot, std::string>
    {
        if (**prerequisite < 0)
        {
            rejected = prerequisite;
            return std::unexpected("negative candidate");
        }
        return prerequisite;
    }));
    auto cache = dependencies::make_computation_cache(std::move(graph), context);
    REQUIRE(cache.try_prepare(context));
    const Snapshot accepted = cache.get<OtherResult>();

    value = -1;
    const auto failure = cache.try_prepare(context);
    REQUIRE_FALSE(failure);
    CHECK(failure.error().error == "negative candidate");
    CHECK(rejected.expired());
    CHECK_FALSE(cache.ready());
    CHECK(**accepted == 4);

    value = 4;
    const auto recovered = cache.try_prepare(context);
    REQUIRE(recovered);
    CHECK(recovered->reused_count() == 2);
    CHECK(cache.get<OtherResult>() == accepted);

    const auto rebuilt = cache.try_prepare(context, dependencies::KeyList<OtherResult>{}, dependencies::PreparationMode::rebuild);
    REQUIRE(rebuilt);
    CHECK(rebuilt->computed_count() == 2);
    CHECK(cache.get<OtherResult>() != accepted);
    CHECK(**accepted == 4);
}