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

#include <catch2/catch_test_macros.hpp>
#include <array>
#include <expected>
#include <memory>
#include <stdexcept>
#include <string>
#include <utility>

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

    struct Source {};
    struct OtherSource {};
    struct Shared {};
    struct Left {};
    struct Right {};
    struct Total {};
}

TEST_CASE("Named computations build a cache directly with general and custom keys", "[unit][utils][dependencies]") {
    namespace keys = dependencies::keys;
    struct Offset { double unused; };

    std::array<double, 3> a{1.0, 2.0, 3.0};
    double scale = 2.0;
    double offset = 0.5;
    std::array<int, 2> calls{};
    const auto context = dependencies::make_dependency_context(
        dependencies::borrow<keys::Input>(a), dependencies::borrow<keys::Scale>(scale), dependencies::borrow<Offset>(offset)
    );
    const auto multiply = dependencies::make_computation<keys::Output, dependencies::InputList<keys::Input, keys::Scale>>(
        [&calls](const std::array<double, 3>& input, double factor) {
            ++calls[0];
            return std::array<double, 3>{factor * input[0], factor * input[1], factor * input[2]};
        }
    );
    const auto sum = dependencies::make_computation<Total, dependencies::InputList<keys::Output, Offset>>(
        [&calls](const std::array<double, 3>& input, double shift) {
            ++calls[1];
            return input[0] + input[1] + input[2] + shift;
        }
    );

    // No explicit graph or ownership transfer is needed; prerequisites may be supplied last.
    auto cache = dependencies::make_computation_cache(context, sum, multiply);
    CHECK_FALSE(cache.ready());
    CHECK(calls == std::array<int, 2>{0, 0});
    auto report = cache.try_prepare(context, dependencies::RequestedResults<Total>{});
    REQUIRE(report);
    CHECK(report->computed_count() == 2);
    CHECK(cache.get<keys::Output>() == std::array<double, 3>{2.0, 4.0, 6.0});
    CHECK(cache.get<Total>() == 12.5);
    CHECK(calls == std::array<int, 2>{1, 1});

    report = cache.try_prepare(context);
    REQUIRE(report);
    CHECK(report->reused_count() == 2);
    CHECK(calls == std::array<int, 2>{1, 1});

    offset = 1.5;
    report = cache.try_prepare(context);
    REQUIRE(report);
    CHECK(report->status<keys::Output>() == dependencies::PreparationStatus::reused);
    CHECK(report->status<Total>() == dependencies::PreparationStatus::computed);
    CHECK(cache.get<Total>() == 13.5);
    CHECK(calls == std::array<int, 2>{1, 2});

    scale = 3.0;
    report = cache.try_prepare(context);
    REQUIRE(report);
    CHECK(report->computed_count() == 2);
    CHECK(cache.get<Total>() == 19.5);
    CHECK(calls == std::array<int, 2>{2, 3});
}

TEST_CASE("Direct cache construction transfers computations owning noncopyable state", "[unit][utils][dependencies]") {
    const auto context = dependencies::make_dependency_context(dependencies::own<Source>(4));
    auto computation = dependencies::make_computation<Total, dependencies::InputList<Source>>(
        [offset = std::make_unique<int>(3)](int input) { return input + *offset; }
    );
    auto cache = dependencies::make_computation_cache(context, std::move(computation));
    REQUIRE(cache.try_prepare(context));
    CHECK(cache.get<Total>() == 7);
    const auto report = cache.try_prepare(context);
    REQUIRE(report);
    CHECK(report->status<Total>() == dependencies::PreparationStatus::reused);
}

TEST_CASE("A dependency diamond prepares shared work once in prerequisite order", "[unit][utils][dependencies]") {
    int source = 2;
    std::array<int, 4> calls{};
    auto context = dependencies::make_dependency_context(dependencies::borrow<Source>(source));
    auto graph = dependencies::make_computation_graph(
        dependencies::make_computation<Total, dependencies::InputList<Left, Right>>([&calls](int left, int right) { ++calls[3]; return left + right; }),
        dependencies::make_computation<Right, dependencies::InputList<Shared>>([&calls](int shared) { ++calls[2]; return 3 * shared; }),
        dependencies::make_computation<Shared, dependencies::InputList<Source>>([&calls](int input) { ++calls[0]; return 2 * input; }),
        dependencies::make_computation<Left, dependencies::InputList<Shared>>([&calls](int shared) { ++calls[1]; return shared + 1; })
    );
    auto cache = dependencies::make_computation_cache(graph, context);
    CHECK_FALSE(cache.ready());
    CHECK_THROWS_AS(cache.get<Total>(), std::logic_error);

    auto report = cache.try_prepare(context, dependencies::RequestedResults<Total>{});
    REQUIRE(report);
    CHECK(report->computed_count() == 4);
    CHECK(report->source_changed<Source>());
    CHECK(cache.get<Total>() == 17);
    CHECK(calls == std::array<int, 4>{1, 1, 1, 1});

    report = cache.try_prepare(context);
    REQUIRE(report);
    CHECK(report->reused_count() == 4);
    CHECK_FALSE(report->source_changed<Source>());
    CHECK(calls == std::array<int, 4>{1, 1, 1, 1});

    source = 3;
    report = cache.try_prepare(context);
    REQUIRE(report);
    CHECK(report->computed_count() == 4);
    CHECK(cache.get<Total>() == 25);
    CHECK(calls == std::array<int, 4>{2, 2, 2, 2});

    report = cache.try_prepare(context, dependencies::RequestedResults<Total>{}, dependencies::PreparationMode::rebuild);
    REQUIRE(report);
    CHECK(report->computed_count() == 4);
    CHECK(calls == std::array<int, 4>{3, 3, 3, 3});

    cache.invalidate();
    CHECK_FALSE(cache.ready());
    CHECK_THROWS_AS(cache.get<Left>(), std::logic_error);
    report = cache.try_prepare(context);
    REQUIRE(report);
    CHECK(report->computed_count() == 4);
    CHECK(calls == std::array<int, 4>{4, 4, 4, 4});
}

TEST_CASE("Partial dependency requests retain caches and propagate later changes", "[unit][utils][dependencies]") {
    int source = 2;
    int other_source = 3;
    std::array<int, 3> calls{};
    auto context = dependencies::make_dependency_context(dependencies::borrow<Source>(source), dependencies::borrow<OtherSource>(other_source));
    auto graph = dependencies::make_computation_graph(
        dependencies::make_computation<Total, dependencies::InputList<Left, Right>>([&calls](int left, int right) { ++calls[2]; return left + right; }),
        dependencies::make_computation<Left, dependencies::InputList<Source>>([&calls](int input) { ++calls[0]; return 2 * input; }),
        dependencies::make_computation<Right, dependencies::InputList<OtherSource>>([&calls](int input) { ++calls[1]; return 2 * input; })
    );
    auto cache = dependencies::make_computation_cache(std::move(graph), context);
    REQUIRE(cache.try_prepare(context));
    CHECK(cache.get<Total>() == 10);

    source = 4;
    auto report = cache.try_prepare(context, dependencies::RequestedResults<Left>{});
    REQUIRE(report);
    CHECK(calls == std::array<int, 3>{2, 1, 1});
    CHECK(report->status<Right>() == dependencies::PreparationStatus::not_required);
    CHECK_FALSE(cache.contains<Total>());
    CHECK_THROWS_AS(cache.get<Right>(), std::logic_error);

    report = cache.try_prepare(context, dependencies::RequestedResults<Total>{});
    REQUIRE(report);
    CHECK(cache.get<Total>() == 14);
    CHECK(report->computed_count() == 1);
    CHECK(report->reused_count() == 2);
    CHECK(calls == std::array<int, 3>{2, 1, 2});

    other_source = 5;
    report = cache.try_prepare(context, dependencies::RequestedResults<Left>{});
    REQUIRE(report);
    CHECK_FALSE(report->source_changed<OtherSource>()); // This source was outside the request and was not inspected.
    CHECK(report->reused_count() == 1);
    report = cache.try_prepare(context, dependencies::RequestedResults<Right>{});
    REQUIRE(report);
    CHECK(report->source_changed<OtherSource>());
    CHECK(cache.get<Right>() == 10);

    report = cache.try_prepare(context);
    REQUIRE(report);
    CHECK(report->computed_count() == 1);
    CHECK(cache.get<Total>() == 18);
    CHECK(calls == std::array<int, 3>{2, 2, 3});

    report = cache.try_prepare(context, dependencies::RequestedResults<>{});
    REQUIRE(report);
    CHECK(cache.ready());
    CHECK_FALSE(cache.contains<Total>());
    CHECK(report->computed_count() == 0);
    CHECK(report->reused_count() == 0);
}

TEST_CASE("Empty dependency graphs and constant calculations need no sources", "[unit][utils][dependencies]") {
    const auto context = dependencies::make_dependency_context();
    auto empty = dependencies::make_computation_cache(dependencies::make_computation_graph(), context);
    const auto empty_report = empty.try_prepare(context);
    REQUIRE(empty_report);
    CHECK(empty.ready());
    CHECK(empty_report->computed_count() == 0);

    int calls = 0;
    auto graph = dependencies::make_computation_graph(dependencies::make_computation<Total, dependencies::InputList<>>([&calls] { ++calls; return 42; }));
    auto cache = dependencies::make_computation_cache(std::move(graph), context);
    REQUIRE(cache.try_prepare(context));
    REQUIRE(cache.try_prepare(context));
    CHECK(calls == 1);
    CHECK(cache.get<Total>() == 42);
    REQUIRE(cache.try_prepare(context, dependencies::RequestedResults<Total>{}, dependencies::PreparationMode::rebuild));
    CHECK(calls == 2);
}

TEST_CASE("Move-only results retain accepted generations across rebuilds and rejection", "[unit][utils][dependencies]") {
    using Value = std::unique_ptr<int>;
    int source = 4;
    int calls = 0;
    const auto context = dependencies::make_dependency_context(dependencies::borrow<Source>(source));
    const auto computation = dependencies::make_computation<Total, dependencies::InputList<Source>>(
        [&calls](int input) -> std::expected<Value, std::string> {
            ++calls;
            if (input < 0) {
                return std::unexpected("negative input");
            }
            return std::make_unique<int>(input);
        }
    );
    auto cache = dependencies::make_computation_cache(context, computation);

    REQUIRE(cache.try_prepare(context));
    const auto first = cache.share<Total>();
    CHECK(**first == 4);
    const auto reused = cache.try_prepare(context);
    REQUIRE(reused);
    CHECK(reused->status<Total>() == dependencies::PreparationStatus::reused);
    CHECK(cache.share<Total>() == first);
    CHECK(calls == 1);

    const auto forced = cache.try_prepare(context, dependencies::RequestedResults<Total>{}, dependencies::PreparationMode::rebuild);
    REQUIRE(forced);
    CHECK(forced->status<Total>() == dependencies::PreparationStatus::computed);
    const auto accepted = cache.share<Total>();
    CHECK(accepted != first);
    CHECK(calls == 2);
    CHECK(**accepted == 4);
    CHECK(**first == 4);

    source = -1;
    const auto rejected = cache.try_prepare(context);
    REQUIRE_FALSE(rejected);
    CHECK(rejected.error().error == "negative input");
    CHECK_FALSE(cache.contains<Total>());
    CHECK(calls == 3);
    CHECK(**accepted == 4);
    CHECK(**first == 4);

    source = 4;
    const auto recovered = cache.try_prepare(context);
    REQUIRE(recovered);
    CHECK(recovered->status<Total>() == dependencies::PreparationStatus::reused);
    CHECK(cache.share<Total>() == accepted);
    CHECK(calls == 3);
}