#include "serif/utils/dependencies/dependencies.hpp"

#include <catch2/catch_test_macros.hpp>
#include <memory>
#include <numeric>
#include <utility>
#include <vector>

namespace {
    namespace dependencies = serif::utils::dependencies;

    struct Source {};
    struct Unused {};
    struct Result {};
    struct OtherResult {};
    struct Untrackable {};

    struct View {
        const int& binding;
        const int& value;
    };
    struct ViewTracking {
        /// Snapshot content without retaining the temporary view.
        int capture(const View& view) const { return view.value; }
        /// Vector storage may move or be copied without changing its value.
        bool matches(const int& captured, const View& view) const { return captured == view.value; }
        /// The persistent role, rather than its temporary wrapper, defines identity.
        const void* identity(const View& view) const { return &view.binding; }
    };

    struct RevisionedSource {
        std::unique_ptr<int> value;
        unsigned revision{0};
    };

    struct OwnedSnapshot {
        int& captures;
        int& comparisons;

        /// Exercise an owning snapshot that cannot itself be copied.
        std::unique_ptr<int> capture(const RevisionedSource& source) const {
            ++captures;
            return std::make_unique<int>(*source.value);
        }

        /// Compare the frozen content, independent of source revision counters.
        bool matches(const std::unique_ptr<int>& captured, const RevisionedSource& source) const {
            ++comparisons;
            return *captured == *source.value;
        }
    };
}

TEST_CASE("Dependency views can preserve underlying identity across temporary wrappers", "[unit][utils][dependencies]") {
    int binding = 1, other_binding = 1, value = 4, copied_value = 4;
    const auto context = dependencies::make_dependency_context(dependencies::own<Source>(View{binding, value}, ViewTracking{}));
    auto graph = dependencies::make_computation_graph(dependencies::make_computation<Result, dependencies::InputList<Source>>([](const View& view) { return view.value; }));
    auto cache = dependencies::make_computation_cache(std::move(graph), context);
    REQUIRE(cache.try_prepare(context));
    const auto copied = dependencies::make_dependency_context(dependencies::own<Source>(View{binding, copied_value}, ViewTracking{}));
    auto report = cache.try_prepare(copied);
    REQUIRE(report);
    CHECK(report->reused_count() == 1);

    const auto rebound = dependencies::make_dependency_context(dependencies::own<Source>(View{other_binding, copied_value}, ViewTracking{}));
    report = cache.try_prepare(rebound);
    REQUIRE(report);
    CHECK(report->computed_count() == 1);
    copied_value = 8;
    REQUIRE(cache.try_prepare(rebound));
    CHECK(cache.get<Result>() == 8);
}

TEST_CASE("Dependency value snapshots detect in-place container changes", "[unit][utils][dependencies]") {
    std::vector<int> values{2, 3};
    int calls = 0;
    auto context = dependencies::make_dependency_context(dependencies::borrow<Source>(values), dependencies::own<Unused>(Untrackable{}));
    auto graph = dependencies::make_computation_graph(dependencies::make_computation<Result, dependencies::InputList<Source>>([&calls](const std::vector<int>& input) { ++calls; return std::accumulate(input.begin(), input.end(), 0); }));
    auto cache = dependencies::make_computation_cache(std::move(graph), context);
    REQUIRE(cache.try_prepare(context));
    CHECK(cache.get<Result>() == 5);

    values[1] = 7;
    REQUIRE(cache.try_prepare(context));
    CHECK(cache.get<Result>() == 9);
    CHECK(calls == 2);
    values.push_back(4);
    REQUIRE(cache.try_prepare(context));
    CHECK(cache.get<Result>() == 13);
    CHECK(calls == 3);
    REQUIRE(cache.try_prepare(context));
    CHECK(calls == 3);
}

TEST_CASE("A dependency projection tracks noncopyable sources by revision", "[unit][utils][dependencies]") {
    RevisionedSource source{.value = std::make_unique<int>(2)};
    int calls = 0;
    auto context = dependencies::make_dependency_context(dependencies::borrow<Source>(source,
        dependencies::track_by([](const RevisionedSource& input) { return input.revision; })));
    auto graph = dependencies::make_computation_graph(dependencies::make_computation<Result, dependencies::InputList<Source>>([&calls](const RevisionedSource& input) { ++calls; return *input.value; }));
    auto cache = dependencies::make_computation_cache(std::move(graph), context);

    REQUIRE(cache.try_prepare(context));
    REQUIRE(cache.try_prepare(context));
    CHECK(calls == 1);
    *source.value = 8;
    ++source.revision;
    REQUIRE(cache.try_prepare(context));
    CHECK(calls == 2);
    CHECK(cache.get<Result>() == 8);
}

TEST_CASE("Required sources are inspected once and can use move-only snapshot state", "[unit][utils][dependencies]") {
    RevisionedSource source{.value = std::make_unique<int>(2)};
    int captures = 0;
    int comparisons = 0;
    auto context = dependencies::make_dependency_context(dependencies::borrow<Source>(source,
        OwnedSnapshot{.captures = captures, .comparisons = comparisons}));
    auto graph = dependencies::make_computation_graph(
        dependencies::make_computation<Result, dependencies::InputList<Source>>([](const RevisionedSource& input) { return *input.value; }),
        dependencies::make_computation<OtherResult, dependencies::InputList<Source>>([](const RevisionedSource& input) { return 2 * *input.value; })
    );
    auto cache = dependencies::make_computation_cache(std::move(graph), context);
    REQUIRE(cache.try_prepare(context));
    CHECK(captures == 1);
    CHECK(comparisons == 0);
    REQUIRE(cache.try_prepare(context));
    CHECK(captures == 1);
    CHECK(comparisons == 1);

    *source.value = 9;
    REQUIRE(cache.try_prepare(context));
    CHECK(captures == 2);
    CHECK(comparisons == 2);
    CHECK(cache.get<Result>() == 9);
    CHECK(cache.get<OtherResult>() == 18);
}