#include <cpp_api.h>

void System_iter(void) {
    flecs::world world;

    auto entity = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    world.system<Position, Velocity>()
        .iter([](flecs::iter&it, Position *p, Velocity *v) {
            for (auto i : it) {
                p[i].x += v[i].x;
                p[i].y += v[i].y;
            }
        });

    world.progress();

    const Position *p = entity.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    const Velocity *v = entity.get<Velocity>();
    test_int(v->x, 1);
    test_int(v->y, 2);
}

void System_iter_const(void) {
    flecs::world world;

    auto entity = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    world.system<Position, const Velocity>()
        .iter([](flecs::iter&it, Position *p, const Velocity* v) {
            for (auto i : it) {
                p[i].x += v[i].x;
                p[i].y += v[i].y;
            }
        });

    world.progress();

    const Position *p = entity.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    const Velocity *v = entity.get<Velocity>();
    test_int(v->x, 1);
    test_int(v->y, 2);
}

void System_iter_shared(void) {
    flecs::world world;

    auto base = world.entity()
        .set<Velocity>({1, 2});

    auto e1 = world.entity()
        .set<Position>({10, 20})
        .add(flecs::IsA, base);

    auto e2 = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({3, 4});

    world.system<Position>().expr("Velocity(self|up)")
        .iter([](flecs::iter&it, Position *p) {
            auto v = it.field<const Velocity>(2);

            if (!it.is_self(2)) {
                for (auto i : it) {
                    p[i].x += v->x;
                    p[i].y += v->y;
                }
            } else {
                for (auto i : it) {
                    p[i].x += v[i].x;
                    p[i].y += v[i].y;
                }
            }
        });

    world.progress();

    const Position *p = e1.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    p = e2.get<Position>();
    test_int(p->x, 13);
    test_int(p->y, 24);
}

void System_iter_optional(void) {
    flecs::world world;
    flecs::component<Mass>(world, "Mass");

    auto e1 = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2})
        .set<Mass>({1});

    auto e2 = world.entity()
        .set<Position>({30, 40})
        .set<Velocity>({3, 4})
        .set<Mass>({1});

    auto e3 = world.entity()
        .set<Position>({50, 60});

    auto e4 = world.entity()
        .set<Position>({70, 80});

    world.system<Position, Velocity*, Mass*>()
        .iter([](flecs::iter& it, Position *p, Velocity *v, Mass *m) {
        if (it.is_set(2) && it.is_set(3)) {
            for (auto i : it) {
                p[i].x += v[i].x * m[i].value;
                p[i].y += v[i].y * m[i].value;
            }
        } else {
            for (auto i : it) {
                p[i].x ++;
                p[i].y ++;
            }
        }
    });

    world.progress();

    const Position *p = e1.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    p = e2.get<Position>();
    test_int(p->x, 33);
    test_int(p->y, 44);

    p = e3.get<Position>();
    test_int(p->x, 51);
    test_int(p->y, 61);

    p = e4.get<Position>();
    test_int(p->x, 71);
    test_int(p->y, 81);
}

void System_each(void) {
    flecs::world world;

    auto entity = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    world.system<Position, Velocity>()
        .each([](flecs::entity e, Position& p, Velocity& v) {
            p.x += v.x;
            p.y += v.y;
        });

    world.progress();

    const Position *p = entity.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);
}

void System_each_const(void) {
    flecs::world world;

    auto entity = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    world.system<Position, const Velocity>()
        .each([](flecs::entity e, Position& p, const Velocity& v) {
            p.x += v.x;
            p.y += v.y;
        });

    world.progress();

    const Position *p = entity.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);
}

void System_each_shared(void) {
    flecs::world world;

    auto base = world.entity()
        .set<Velocity>({1, 2});

    auto e1 = world.entity()
        .set<Position>({10, 20})
        .add(flecs::IsA, base);

    auto e2 = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({3, 4});

    world.system<Position, const Velocity>()
        .each([](flecs::entity e, Position& p, const Velocity& v) {
            p.x += v.x;
            p.y += v.y;
        });

    world.progress();

    const Position *p = e1.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    p = e2.get<Position>();
    test_int(p->x, 13);
    test_int(p->y, 24);
}

void System_each_optional(void) {
    flecs::world world;
    flecs::component<Mass>(world, "Mass");

    auto e1 = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2})
        .set<Mass>({1});

    auto e2 = world.entity()
        .set<Position>({30, 40})
        .set<Velocity>({3, 4})
        .set<Mass>({1});

    auto e3 = world.entity()
        .set<Position>({50, 60});

    auto e4 = world.entity()
        .set<Position>({70, 80});

    world.system<Position, Velocity*, Mass*>()
        .each([](flecs::entity e, Position& p, Velocity* v, Mass *m) {
        if (v && m) {
            p.x += v->x * m->value;
            p.y += v->y * m->value;
        } else {
            p.x ++;
            p.y ++;
        }
    });

    world.progress();

    const Position *p = e1.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    p = e2.get<Position>();
    test_int(p->x, 33);
    test_int(p->y, 44);

    p = e3.get<Position>();
    test_int(p->x, 51);
    test_int(p->y, 61);

    p = e4.get<Position>();
    test_int(p->x, 71);
    test_int(p->y, 81);
}


void System_signature(void) {
    flecs::world world;

    auto entity = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    world.system<>().expr("Position, Velocity")
        .iter([](flecs::iter&it) {
            flecs::column<Position> p(it, 1);
            flecs::column<Velocity> v(it, 2);

            for (auto i : it) {
                p[i].x += v[i].x;
                p[i].y += v[i].y;
            }
        });

    world.progress();

    const Position *p = entity.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    const Velocity *v = entity.get<Velocity>();
    test_int(v->x, 1);
    test_int(v->y, 2);
}

void System_signature_const(void) {
    flecs::world world;

    auto entity = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    world.system<>().expr("Position, [in] Velocity")
        .iter([](flecs::iter&it) {
            flecs::column<Position> p(it, 1);
            flecs::column<const Velocity> v(it, 2);

            for (auto i : it) {
                p[i].x += v[i].x;
                p[i].y += v[i].y;
            }
        });

    world.progress();

    const Position *p = entity.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    const Velocity *v = entity.get<Velocity>();
    test_int(v->x, 1);
    test_int(v->y, 2);
}

void System_signature_shared(void) {
    flecs::world world;

    auto base = world.entity()
        .set<Velocity>({1, 2});

    auto e1 = world.entity()
        .set<Position>({10, 20})
        .add(flecs::IsA, base);

    auto e2 = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({3, 4});

    world.system<>().expr("Position, [in] Velocity(self|up)")
        .iter([](flecs::iter&it) {
            flecs::column<Position> p(it, 1);
            flecs::column<const Velocity> v(it, 2);

            if (!it.is_self(2)) {
                for (auto i : it) {
                    p[i].x += v->x;
                    p[i].y += v->y;
                }
            } else {
                for (auto i : it) {
                    p[i].x += v[i].x;
                    p[i].y += v[i].y;
                }
            }
        });

    world.progress();

    const Position *p = e1.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    p = e2.get<Position>();
    test_int(p->x, 13);
    test_int(p->y, 24);
}

void System_signature_optional(void) {
    flecs::world world;
    flecs::component<Mass>(world, "Mass");

    auto e1 = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2})
        .set<Mass>({1});

    auto e2 = world.entity()
        .set<Position>({30, 40})
        .set<Velocity>({3, 4})
        .set<Mass>({1});

    auto e3 = world.entity()
        .set<Position>({50, 60});

    auto e4 = world.entity()
        .set<Position>({70, 80});

    world.system<>().expr("Position, ?Velocity, ?Mass")
        .iter([](flecs::iter& it) {
            flecs::column<Position> p(it, 1);
            flecs::column<Velocity> v(it, 2);
            flecs::column<Mass> m(it, 3);

            if (it.is_set(2) && it.is_set(3)) {
                for (auto i : it) {
                    p[i].x += v[i].x * m[i].value;
                    p[i].y += v[i].y * m[i].value;
                }
            } else {
                for (auto i : it) {
                    p[i].x ++;
                    p[i].y ++;
                }
            }
        });

    world.progress();

    const Position *p = e1.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    p = e2.get<Position>();
    test_int(p->x, 33);
    test_int(p->y, 44);

    p = e3.get<Position>();
    test_int(p->x, 51);
    test_int(p->y, 61);

    p = e4.get<Position>();
    test_int(p->x, 71);
    test_int(p->y, 81);
}


void System_copy_name_on_create(void) {
    flecs::world world;

    char name[6];
    strcpy(name, "Hello");

    auto system_1 = world.system<Position>(name)
        .iter([](flecs::iter&it, Position *p) {});

    strcpy(name, "World");
    auto system_2 = world.system<Position>(name)
        .iter([](flecs::iter&it, Position *p) {});

    test_assert(system_1.id() != system_2.id());
}

void System_nested_system(void) {
    flecs::world world;

    auto system_1 = world.system<Position>("foo::bar")
        .iter([](flecs::iter&it, Position *p) {});

    test_str(system_1.name().c_str(), "bar");

    auto e = world.lookup("foo");
    test_assert(e.id() != 0);
    test_str(e.name().c_str(), "foo");

    auto se = e.lookup("bar");
    test_assert(se.id() != 0);
    test_str(se.name().c_str(), "bar");
}

void System_empty_signature(void) {
    flecs::world world;

    int count = 0;

    world.system<>()
        .iter([&](flecs::iter it) {
            count ++;
        });

    world.progress();

    test_int(count, 1);
}

struct MyTag { };

void System_iter_tag(void) {
    flecs::world world;

    int invoked = 0;

    world.system<MyTag>()
        .iter([&](flecs::iter it, MyTag*) {
            invoked ++;
        });

    world.entity()
        .add<MyTag>();

    world.progress();

    test_int(invoked, 1);
}

void System_each_tag(void) {
    flecs::world world;

    int invoked = 0;

    world.system<MyTag>()
        .each([&](flecs::entity e, MyTag) {
            invoked ++;
        });

    world.entity()
        .add<MyTag>();

    world.progress();

    test_int(invoked, 1);
}

void System_set_interval(void) {
    flecs::world world;

    auto sys = world.system<>()
        .kind(0)
        .interval(1.0f)
        .iter([&](flecs::iter& it) { });

    float i = sys.interval();
    test_int(i, 1.0f);

    sys.interval(2.0f);

    i = sys.interval();
    test_int(i, 2.0f);
}

void System_order_by_type(void) {
    flecs::world world;

    world.entity().set<Position>({3, 0});
    world.entity().set<Position>({1, 0});
    world.entity().set<Position>({5, 0});
    world.entity().set<Position>({2, 0});
    world.entity().set<Position>({4, 0});

    float last_val = 0;
    int32_t count = 0;

    auto sys = world.system<const Position>()
        .order_by<Position>(
            [](flecs::entity_t e1, const Position *p1,
               flecs::entity_t e2, const Position *p2) {
                return (p1->x > p2->x) - (p1->x < p2->x);
            })
        .each([&](flecs::entity e, const Position& p) {
            test_assert(p.x > last_val);
            last_val = p.x;
            count ++;
        });

    sys.run();

    test_int(count, 5);
}

void System_order_by_id(void) {
    flecs::world world;

    auto pos = world.component<Position>();

    world.entity().set<Position>({3, 0});
    world.entity().set<Position>({1, 0});
    world.entity().set<Position>({5, 0});
    world.entity().set<Position>({2, 0});
    world.entity().set<Position>({4, 0});

    float last_val = 0;
    int32_t count = 0;

    auto sys = world.system<const Position>()
        .order_by(pos, [](flecs::entity_t e1, const void *p1,
                          flecs::entity_t e2, const void *p2)
            {
                return (static_cast<const Position*>(p1)->x >
                            static_cast<const Position*>(p2)->x) -
                       (static_cast<const Position*>(p1)->x <
                            static_cast<const Position*>(p2)->x);
            })
        .each([&](flecs::entity e, const Position& p) {
            test_assert(p.x > last_val);
            last_val = p.x;
            count ++;
        });

    sys.run();

    test_int(count, 5);
}

void System_order_by_type_after_create(void) {
    flecs::world world;

    world.entity().set<Position>({3, 0});
    world.entity().set<Position>({1, 0});
    world.entity().set<Position>({5, 0});
    world.entity().set<Position>({2, 0});
    world.entity().set<Position>({4, 0});

    float last_val = 0;
    int32_t count = 0;

    auto sys = world.system<const Position>()
        .order_by<Position>([](flecs::entity_t e1, const Position *p1,
            flecs::entity_t e2, const Position *p2) {
            return (p1->x > p2->x) - (p1->x < p2->x);
        })
        .each([&](flecs::entity e, const Position& p) {
            test_assert(p.x > last_val);
            last_val = p.x;
            count ++;
        });

    sys.run();

    test_int(count, 5);
}

void System_order_by_id_after_create(void) {
    flecs::world world;

    auto pos = world.component<Position>();

    world.entity().set<Position>({3, 0});
    world.entity().set<Position>({1, 0});
    world.entity().set<Position>({5, 0});
    world.entity().set<Position>({2, 0});
    world.entity().set<Position>({4, 0});

    float last_val = 0;
    int32_t count = 0;

    auto sys = world.system<const Position>()
        .order_by(pos, [](flecs::entity_t e1, const void *p1, flecs::entity_t e2, const void *p2) {
            return (static_cast<const Position*>(p1)->x > static_cast<const Position*>(p2)->x) -
                (static_cast<const Position*>(p1)->x < static_cast<const Position*>(p2)->x);
        })
        .each([&](flecs::entity e, const Position& p) {
            test_assert(p.x > last_val);
            last_val = p.x;
            count ++;
        });

    sys.run();

    test_int(count, 5);
}

void System_get_query(void) {
    flecs::world world;

    world.entity().set<Position>({0, 0});
    world.entity().set<Position>({1, 0});
    world.entity().set<Position>({2, 0});

    int32_t count = 0;

    auto sys = world.system<const Position>()
        .each([&](flecs::entity e, const Position& p) {
            // Not used
        });

    auto q = sys.query();

    q.iter([&](flecs::iter &it) {
        auto pos = it.field<const Position>(1);
        for (auto i : it) {
            test_int(i, pos[i].x);
            count ++;
        }
    });

    test_int(count, 3);
}

void System_add_from_each(void) {
    flecs::world world;

    auto e1 = world.entity().set<Position>({0, 0});
    auto e2 = world.entity().set<Position>({1, 0});
    auto e3 = world.entity().set<Position>({2, 0});

    world.system<const Position>()
        .each([](flecs::entity e, const Position& p) {
            e.add<Velocity>();
            // Add is deferred
            test_assert(!e.has<Velocity>());
        });

    world.progress();

    test_assert(e1.has<Velocity>());
    test_assert(e2.has<Velocity>());
    test_assert(e3.has<Velocity>());
}

void System_delete_from_each(void) {
    flecs::world world;

    auto e1 = world.entity().set<Position>({0, 0});
    auto e2 = world.entity().set<Position>({1, 0});
    auto e3 = world.entity().set<Position>({2, 0});

    world.system<const Position>()
        .each([](flecs::entity e, const Position& p) {
            e.destruct();
            // Delete is deferred
            test_assert(e.is_alive());
        });

    world.progress();

    test_assert(!e1.is_alive());
    test_assert(!e2.is_alive());
    test_assert(!e3.is_alive());
}

struct Entity {
    flecs::entity e;
};

void System_add_from_each_world_handle(void) {
    flecs::world world;

    auto e1 = world.entity().set<Entity>({world.entity()});
    auto e2 = world.entity().set<Entity>({world.entity()});
    auto e3 = world.entity().set<Entity>({world.entity()});

    world.system<const Entity>()
        .each([](flecs::entity e, const Entity& c) {
            c.e.mut(e).add<Position>();
        });

    world.progress();

    test_assert(e1.get<Entity>()->e.has<Position>());
    test_assert(e2.get<Entity>()->e.has<Position>());
    test_assert(e3.get<Entity>()->e.has<Position>());
}

void System_new_from_each(void) {
    flecs::world world;

    auto e1 = world.entity().set<Position>({0, 0});
    auto e2 = world.entity().set<Position>({0, 0});
    auto e3 = world.entity().set<Position>({0, 0});

    world.system<const Position>()
        .each([](flecs::entity e, const Position& p) {
            e.set<Entity>({
                e.world().entity().add<Velocity>()
            });
        });

    world.progress();

    test_assert(e1.has<Entity>());
    test_assert(e2.has<Entity>());
    test_assert(e3.has<Entity>());

    test_assert(e1.get<Entity>()->e.has<Velocity>());
    test_assert(e2.get<Entity>()->e.has<Velocity>());
    test_assert(e3.get<Entity>()->e.has<Velocity>());
}

void System_add_from_iter(void) {
    flecs::world world;

    auto e1 = world.entity().set<Position>({0, 0});
    auto e2 = world.entity().set<Position>({1, 0});
    auto e3 = world.entity().set<Position>({2, 0});

    world.system<const Position>()
        .iter([](flecs::iter& it, const Position* p) {
            for (auto i : it) {
                it.entity(i).add<Velocity>();
                test_assert(!it.entity(i).has<Velocity>());
            }
        });

    world.progress();

    test_assert(e1.has<Velocity>());
    test_assert(e2.has<Velocity>());
    test_assert(e3.has<Velocity>());
}

void System_delete_from_iter(void) {
    flecs::world world;

    auto e1 = world.entity().set<Position>({0, 0});
    auto e2 = world.entity().set<Position>({1, 0});
    auto e3 = world.entity().set<Position>({2, 0});

    world.system<const Position>()
        .iter([](const flecs::iter& it, const Position* p) {
            for (auto i : it) {
                it.entity(i).destruct();
                // Delete is deferred
                test_assert(it.entity(i).is_alive());
            }
        });

    world.progress();

    test_assert(!e1.is_alive());
    test_assert(!e2.is_alive());
    test_assert(!e3.is_alive());
}

void System_add_from_iter_world_handle(void) {
    flecs::world world;

    auto e1 = world.entity().set<Entity>({world.entity()});
    auto e2 = world.entity().set<Entity>({world.entity()});
    auto e3 = world.entity().set<Entity>({world.entity()});

    world.system<const Entity>()
        .iter([](const flecs::iter& it, const Entity* c) {
            for (auto i : it) {
                c[i].e.mut(it).add<Position>();
            }
        });

    world.progress();

    test_assert(e1.get<Entity>()->e.has<Position>());
    test_assert(e2.get<Entity>()->e.has<Position>());
    test_assert(e3.get<Entity>()->e.has<Position>());
}

void System_new_from_iter(void) {
    flecs::world world;

    auto e1 = world.entity().set<Position>({0, 0});
    auto e2 = world.entity().set<Position>({0, 0});
    auto e3 = world.entity().set<Position>({0, 0});

    world.system<const Position>()
        .iter([](const flecs::iter& it, const Position* p) {
            for (auto i : it) {
                it.entity(i).set<Entity>({
                    it.world().entity().add<Velocity>()
                });
            }
        });

    world.progress();

    test_assert(e1.has<Entity>());
    test_assert(e2.has<Entity>());
    test_assert(e3.has<Entity>());

    test_assert(e1.get<Entity>()->e.has<Velocity>());
    test_assert(e2.get<Entity>()->e.has<Velocity>());
    test_assert(e3.get<Entity>()->e.has<Velocity>());
}

void System_each_w_mut_children_it(void) {
    flecs::world world;

    auto parent = world.entity().set<Position>({0, 0});
    auto e1 = world.entity().set<Position>({0, 0}).child_of(parent);
    auto e2 = world.entity().set<Position>({0, 0}).child_of(parent);
    auto e3 = world.entity().set<Position>({0, 0}).child_of(parent);

    int32_t count = 0;

    world.system<const Position>()
        .iter([&](const flecs::iter& it, const Position* p) {
            for (auto i : it) {
                it.entity(i).children([&](flecs::entity child) {
                    child.add<Velocity>();
                    count ++;
                });
            }
        });

    world.progress();

    test_int(count, 3);

    test_assert(e1.has<Velocity>());
    test_assert(e2.has<Velocity>());
    test_assert(e3.has<Velocity>());
}

void System_readonly_children_iter(void) {
    flecs::world world;

    auto parent = world.entity();
    world.entity().set<Entity>({ parent });
    world.entity().set<Position>({1, 0}).child_of(parent);
    world.entity().set<Position>({1, 0}).child_of(parent);
    world.entity().set<Position>({1, 0}).child_of(parent);

    int32_t count = 0;

    world.system<const Entity>()
        .iter([&](const flecs::iter& it, const Entity* c) {
            for (auto i : it) {
                c[i].e.children([&](flecs::entity child) {
                    // Dummy code to ensure we can access the entity
                    const Position *p = child.get<Position>();
                    test_int(p->x, 1);
                    test_int(p->y, 0);

                    count ++;
                });
            }
        });

    world.progress();

    test_int(count, 3);
}

void System_rate_filter(void) {
    flecs::world world;

    int32_t
    root_count = 0, root_mult = 1,
    l1_a_count = 0, l1_a_mult = 1,
    l1_b_count = 0, l1_b_mult = 2,
    l1_c_count = 0, l1_c_mult = 3,
    l2_a_count = 0, l2_a_mult = 2,
    l2_b_count = 0, l2_b_mult = 4,
    frame_count = 0;

    auto root = world.system<>("root")
        .iter([&](flecs::iter& it) {
            root_count ++;
        });

    auto l1_a = world.system<>("l1_a")
        .rate(root, 1)
        .iter([&](flecs::iter& it) {
            l1_a_count ++;
        });

    auto l1_b = world.system<>("l1_b")
        .rate(root, 2)
        .iter([&](flecs::iter& it) {
            l1_b_count ++;
        });

    world.system<>("l1_c")
        .rate(root, 3)
        .iter([&](flecs::iter& it) {
            l1_c_count ++;
        });

    world.system<>("l2_a")
        .rate(l1_a, 2)
        .iter([&](flecs::iter& it) {
            l2_a_count ++;
        });

    world.system<>("l2_b")
        .rate(l1_b, 2)
        .iter([&](flecs::iter& it) {
            l2_b_count ++;
        });

    for (int i = 0; i < 30; i ++) {
        world.progress(); frame_count ++;
        test_int(root_count, frame_count / root_mult);
        test_int(l1_a_count, frame_count / l1_a_mult);
        test_int(l1_b_count, frame_count / l1_b_mult);
        test_int(l1_c_count, frame_count / l1_c_mult);
        test_int(l2_a_count, frame_count / l2_a_mult);
        test_int(l2_b_count, frame_count / l2_b_mult);
    }
}

void System_update_rate_filter(void) {
    flecs::world world;

    int32_t
    root_count = 0, root_mult = 1,
    l1_count = 0, l1_mult = 2,
    l2_count = 0, l2_mult = 6,
    frame_count = 0;

    auto root = world.system<>("root")
        .iter([&](flecs::iter& it) {
            root_count ++;
        });

    auto l1 = world.system<>("l1")
        .rate(root, 2)
        .iter([&](flecs::iter& it) {
            l1_count ++;
        });

    world.system<>("l2")
        .rate(l1, 3)
        .iter([&](flecs::iter& it) {
            l2_count ++;
        });

    for (int i = 0; i < 12; i ++) {
        world.progress(); frame_count ++;
        test_int(root_count, frame_count / root_mult);
        test_int(l1_count, frame_count / l1_mult);
        test_int(l2_count, frame_count / l2_mult);
    }

    l1.rate(4); // Run twice as slow
    l1_mult *= 2;
    l2_mult *= 2;

    frame_count = 0;
    l1_count = 0;
    l2_count = 0;
    root_count = 0;

    for (int i = 0; i < 32; i ++) {
        world.progress(); frame_count ++;
        test_int(root_count, frame_count / root_mult);
        test_int(l1_count, frame_count / l1_mult);
        test_int(l2_count, frame_count / l2_mult);
    }
}

void System_test_auto_defer_each(void) {
    flecs::world world;

    struct Value { int value; };

    auto e1 = world.entity().add<Tag>().set<Value>({10});
    auto e2 = world.entity().add<Tag>().set<Value>({20});
    auto e3 = world.entity().add<Tag>().set<Value>({30});

    auto s = world.system<Value>()
        .term<Tag>()
        .each([](flecs::entity e, Value& v) {
            v.value ++;
            e.remove<Tag>();
        });

    s.run();

    test_assert(!e1.has<Tag>());
    test_assert(!e2.has<Tag>());
    test_assert(!e3.has<Tag>());

    test_assert(e1.has<Value>());
    test_assert(e2.has<Value>());
    test_assert(e3.has<Value>());

    test_int(e1.get<Value>()->value, 11);
    test_int(e2.get<Value>()->value, 21);
    test_int(e3.get<Value>()->value, 31);
}

void System_test_auto_defer_iter(void) {
    flecs::world world;

    struct Value { int value; };

    auto e1 = world.entity().add<Tag>().set<Value>({10});
    auto e2 = world.entity().add<Tag>().set<Value>({20});
    auto e3 = world.entity().add<Tag>().set<Value>({30});

    auto s = world.system<Value>()
        .term<Tag>()
        .iter([](flecs::iter& it, Value *v) {
            for (auto i : it) {
                v[i].value ++;
                it.entity(i).remove<Tag>();
            }
        });

    s.run();

    test_assert(!e1.has<Tag>());
    test_assert(!e2.has<Tag>());
    test_assert(!e3.has<Tag>());

    test_assert(e1.has<Value>());
    test_assert(e2.has<Value>());
    test_assert(e3.has<Value>());

    test_int(e1.get<Value>()->value, 11);
    test_int(e2.get<Value>()->value, 21);
    test_int(e3.get<Value>()->value, 31);
}

void System_custom_pipeline(void) {
    flecs::world world;

    auto PreFrame = world.entity().add(flecs::Phase);
    auto OnFrame = world.entity().add(flecs::Phase).depends_on(PreFrame);
    auto PostFrame = world.entity().add(flecs::Phase).depends_on(OnFrame);
    auto Tag = world.entity();

    flecs::entity pip = world.pipeline()
        .term(flecs::System)
        .term(flecs::Phase).cascade(flecs::DependsOn)
        .term(Tag)
        .build();

    int count = 0;

    world.system()
        .kind(PostFrame)
        .iter([&](flecs::iter it) {
            test_int(count, 2);
            count ++;
        })
        .add(Tag);

    world.system()
        .kind(OnFrame)
        .iter([&](flecs::iter it) {
            test_int(count, 1);
            count ++;
        })
        .add(Tag);

    world.system()
        .kind(PreFrame)
        .iter([&](flecs::iter it) {
            test_int(count, 0);
            count ++;
        })
        .add(Tag);

    test_int(count, 0);

    world.set_pipeline(pip);

    world.progress();

    test_int(count, 3);
}

void System_custom_pipeline_w_kind(void) {
    flecs::world world;

    auto Tag = world.entity();

    flecs::entity pip = world.pipeline()
        .term(flecs::System)
        .term(Tag)
        .build();

    int count = 0;

    world.system()
        .kind(Tag)
        .iter([&](flecs::iter it) {
            test_int(count, 0);
            count ++;
        });

    world.system()
        .kind(Tag)
        .iter([&](flecs::iter it) {
            test_int(count, 1);
            count ++;
        });

    world.system()
        .kind(Tag)
        .iter([&](flecs::iter it) {
            test_int(count, 2);
            count ++;
        });

    test_int(count, 0);

    world.set_pipeline(pip);

    world.progress();

    test_int(count, 3);
}

void System_instanced_query_w_singleton_each(void) {
    flecs::world ecs;

    ecs.set<Velocity>({1, 2});

    auto e1 = ecs.entity().set<Position>({10, 20}); e1.set<Self>({e1});
    auto e2 = ecs.entity().set<Position>({20, 30}); e2.set<Self>({e2});
    auto e3 = ecs.entity().set<Position>({30, 40}); e3.set<Self>({e3});
    auto e4 = ecs.entity().set<Position>({40, 50}); e4.set<Self>({e4});
    auto e5 = ecs.entity().set<Position>({50, 60}); e5.set<Self>({e5});

    e4.add<Tag>();
    e5.add<Tag>();

    int32_t count = 0;

    auto s = ecs.system<Self, Position, const Velocity>()
        .arg(3).singleton()
        .instanced()
        .each([&](flecs::entity e, Self& s, Position&p, const Velocity& v) {
            test_assert(e == s.value);
            p.x += v.x;
            p.y += v.y;
            count ++;
        });

    s.run();

    test_int(count, 5);

    test_assert(e1.get([](const Position& p) {
        test_int(p.x, 11);
        test_int(p.y, 22);
    }));

    test_assert(e2.get([](const Position& p) {
        test_int(p.x, 21);
        test_int(p.y, 32);
    }));

    test_assert(e3.get([](const Position& p) {
        test_int(p.x, 31);
        test_int(p.y, 42);
    }));

    test_assert(e4.get([](const Position& p) {
        test_int(p.x, 41);
        test_int(p.y, 52);
    }));

    test_assert(e5.get([](const Position& p) {
        test_int(p.x, 51);
        test_int(p.y, 62);
    }));
}

void System_instanced_query_w_base_each(void) {
    flecs::world ecs;

    auto base = ecs.entity().set<Velocity>({1, 2});

    auto e1 = ecs.entity().is_a(base).set<Position>({10, 20}); e1.set<Self>({e1});
    auto e2 = ecs.entity().is_a(base).set<Position>({20, 30}); e2.set<Self>({e2});
    auto e3 = ecs.entity().is_a(base).set<Position>({30, 40}); e3.set<Self>({e3});
    auto e4 = ecs.entity().is_a(base).set<Position>({40, 50}).add<Tag>(); e4.set<Self>({e4});
    auto e5 = ecs.entity().is_a(base).set<Position>({50, 60}).add<Tag>(); e5.set<Self>({e5});
    auto e6 = ecs.entity().set<Position>({60, 70}).set<Velocity>({2, 3}); e6.set<Self>({e6});
    auto e7 = ecs.entity().set<Position>({70, 80}).set<Velocity>({4, 5}); e7.set<Self>({e7});

    int32_t count = 0;
    auto s = ecs.system<Self, Position, const Velocity>()
        .instanced()
        .each([&](flecs::entity e, Self& s, Position&p, const Velocity& v) {
            test_assert(e == s.value);
            p.x += v.x;
            p.y += v.y;
            count ++;
        });

    s.run();

    test_int(count, 7);

    test_assert(e1.get([](const Position& p) {
        test_int(p.x, 11);
        test_int(p.y, 22);
    }));

    test_assert(e2.get([](const Position& p) {
        test_int(p.x, 21);
        test_int(p.y, 32);
    }));

    test_assert(e3.get([](const Position& p) {
        test_int(p.x, 31);
        test_int(p.y, 42);
    }));

    test_assert(e4.get([](const Position& p) {
        test_int(p.x, 41);
        test_int(p.y, 52);
    }));

    test_assert(e5.get([](const Position& p) {
        test_int(p.x, 51);
        test_int(p.y, 62);
    }));

    test_assert(e6.get([](const Position& p) {
        test_int(p.x, 62);
        test_int(p.y, 73);
    }));

    test_assert(e7.get([](const Position& p) {
        test_int(p.x, 74);
        test_int(p.y, 85);
    }));
}

void System_un_instanced_query_w_singleton_each(void) {
    flecs::world ecs;

    ecs.set<Velocity>({1, 2});

    auto e1 = ecs.entity().set<Position>({10, 20}); e1.set<Self>({e1});
    auto e2 = ecs.entity().set<Position>({20, 30}); e2.set<Self>({e2});
    auto e3 = ecs.entity().set<Position>({30, 40}); e3.set<Self>({e3});
    auto e4 = ecs.entity().set<Position>({40, 50}); e4.set<Self>({e4});
    auto e5 = ecs.entity().set<Position>({50, 60}); e5.set<Self>({e5});

    e4.add<Tag>();
    e5.add<Tag>();

    int32_t count = 0;

    auto s = ecs.system<Self, Position, const Velocity>()
        .arg(3).singleton()
        .each([&](flecs::entity e, Self& s, Position&p, const Velocity& v) {
            test_assert(e == s.value);
            p.x += v.x;
            p.y += v.y;
            count ++;
        });

    s.run();

    test_int(count, 5);

    test_assert(e1.get([](const Position& p) {
        test_int(p.x, 11);
        test_int(p.y, 22);
    }));

    test_assert(e2.get([](const Position& p) {
        test_int(p.x, 21);
        test_int(p.y, 32);
    }));

    test_assert(e3.get([](const Position& p) {
        test_int(p.x, 31);
        test_int(p.y, 42);
    }));

    test_assert(e4.get([](const Position& p) {
        test_int(p.x, 41);
        test_int(p.y, 52);
    }));

    test_assert(e5.get([](const Position& p) {
        test_int(p.x, 51);
        test_int(p.y, 62);
    }));
}

void System_un_instanced_query_w_base_each(void) {
    flecs::world ecs;

    auto base = ecs.entity().set<Velocity>({1, 2});

    auto e1 = ecs.entity().is_a(base).set<Position>({10, 20}); e1.set<Self>({e1});
    auto e2 = ecs.entity().is_a(base).set<Position>({20, 30}); e2.set<Self>({e2});
    auto e3 = ecs.entity().is_a(base).set<Position>({30, 40}); e3.set<Self>({e3});
    auto e4 = ecs.entity().is_a(base).set<Position>({40, 50}).add<Tag>(); e4.set<Self>({e4});
    auto e5 = ecs.entity().is_a(base).set<Position>({50, 60}).add<Tag>(); e5.set<Self>({e5});
    auto e6 = ecs.entity().set<Position>({60, 70}).set<Velocity>({2, 3}); e6.set<Self>({e6});
    auto e7 = ecs.entity().set<Position>({70, 80}).set<Velocity>({4, 5}); e7.set<Self>({e7});

    int32_t count = 0;

    auto s = ecs.system<Self, Position, const Velocity>()
        .each([&](flecs::entity e, Self& s, Position&p, const Velocity& v) {
            test_assert(e == s.value);
            p.x += v.x;
            p.y += v.y;
            count ++;
        });

    s.run();

    test_int(count, 7);

    test_assert(e1.get([](const Position& p) {
        test_int(p.x, 11);
        test_int(p.y, 22);
    }));

    test_assert(e2.get([](const Position& p) {
        test_int(p.x, 21);
        test_int(p.y, 32);
    }));

    test_assert(e3.get([](const Position& p) {
        test_int(p.x, 31);
        test_int(p.y, 42);
    }));

    test_assert(e4.get([](const Position& p) {
        test_int(p.x, 41);
        test_int(p.y, 52);
    }));

    test_assert(e5.get([](const Position& p) {
        test_int(p.x, 51);
        test_int(p.y, 62);
    }));

    test_assert(e6.get([](const Position& p) {
        test_int(p.x, 62);
        test_int(p.y, 73);
    }));

    test_assert(e7.get([](const Position& p) {
        test_int(p.x, 74);
        test_int(p.y, 85);
    }));
}

void System_instanced_query_w_singleton_iter(void) {
    flecs::world ecs;

    ecs.set<Velocity>({1, 2});

    auto e1 = ecs.entity().set<Position>({10, 20}); e1.set<Self>({e1});
    auto e2 = ecs.entity().set<Position>({20, 30}); e2.set<Self>({e2});
    auto e3 = ecs.entity().set<Position>({30, 40}); e3.set<Self>({e3});
    auto e4 = ecs.entity().set<Position>({40, 50}); e4.set<Self>({e4});
    auto e5 = ecs.entity().set<Position>({50, 60}); e5.set<Self>({e5});

    e4.add<Tag>();
    e5.add<Tag>();

    int32_t count = 0;

    auto s = ecs.system<Self, Position, const Velocity>()
        .arg(3).singleton()
        .instanced()
        .iter([&](flecs::iter it, Self* s, Position* p, const Velocity* v) {
            test_assert(it.count() > 1);

            for (auto i : it) {
                p[i].x += v->x;
                p[i].y += v->y;
                test_assert(it.entity(i) == s[i].value);
                count ++;
            }
        });

    s.run();

    test_int(count, 5);

    test_assert(e1.get([](const Position& p) {
        test_int(p.x, 11);
        test_int(p.y, 22);
    }));

    test_assert(e2.get([](const Position& p) {
        test_int(p.x, 21);
        test_int(p.y, 32);
    }));

    test_assert(e3.get([](const Position& p) {
        test_int(p.x, 31);
        test_int(p.y, 42);
    }));

    test_assert(e4.get([](const Position& p) {
        test_int(p.x, 41);
        test_int(p.y, 52);
    }));

    test_assert(e5.get([](const Position& p) {
        test_int(p.x, 51);
        test_int(p.y, 62);
    }));
}

void System_instanced_query_w_base_iter(void) {
    flecs::world ecs;

    auto base = ecs.entity().set<Velocity>({1, 2});

    auto e1 = ecs.entity().is_a(base).set<Position>({10, 20}); e1.set<Self>({e1});
    auto e2 = ecs.entity().is_a(base).set<Position>({20, 30}); e2.set<Self>({e2});
    auto e3 = ecs.entity().is_a(base).set<Position>({30, 40}); e3.set<Self>({e3});
    auto e4 = ecs.entity().is_a(base).set<Position>({40, 50}).add<Tag>(); e4.set<Self>({e4});
    auto e5 = ecs.entity().is_a(base).set<Position>({50, 60}).add<Tag>(); e5.set<Self>({e5});
    auto e6 = ecs.entity().set<Position>({60, 70}).set<Velocity>({2, 3}); e6.set<Self>({e6});
    auto e7 = ecs.entity().set<Position>({70, 80}).set<Velocity>({4, 5}); e7.set<Self>({e7});

    int32_t count = 0;

    auto s = ecs.system<Self, Position, const Velocity>()
        .instanced()
        .iter([&](flecs::iter it, Self* s, Position* p, const Velocity* v) {
            test_assert(it.count() > 1);

            for (auto i : it) {
                if (it.is_self(3)) {
                    p[i].x += v[i].x;
                    p[i].y += v[i].y;
                } else {
                    p[i].x += v->x;
                    p[i].y += v->y;
                }

                test_assert(it.entity(i) == s[i].value);
                count ++;
            }
        });

    s.run();

    test_int(count, 7);

    test_assert(e1.get([](const Position& p) {
        test_int(p.x, 11);
        test_int(p.y, 22);
    }));

    test_assert(e2.get([](const Position& p) {
        test_int(p.x, 21);
        test_int(p.y, 32);
    }));

    test_assert(e3.get([](const Position& p) {
        test_int(p.x, 31);
        test_int(p.y, 42);
    }));

    test_assert(e4.get([](const Position& p) {
        test_int(p.x, 41);
        test_int(p.y, 52);
    }));

    test_assert(e5.get([](const Position& p) {
        test_int(p.x, 51);
        test_int(p.y, 62);
    }));

    test_assert(e6.get([](const Position& p) {
        test_int(p.x, 62);
        test_int(p.y, 73);
    }));

    test_assert(e7.get([](const Position& p) {
        test_int(p.x, 74);
        test_int(p.y, 85);
    }));
}

void System_un_instanced_query_w_singleton_iter(void) {
    flecs::world ecs;

    ecs.set<Velocity>({1, 2});

    auto e1 = ecs.entity().set<Position>({10, 20}); e1.set<Self>({e1});
    auto e2 = ecs.entity().set<Position>({20, 30}); e2.set<Self>({e2});
    auto e3 = ecs.entity().set<Position>({30, 40}); e3.set<Self>({e3});
    auto e4 = ecs.entity().set<Position>({40, 50}); e4.set<Self>({e4});
    auto e5 = ecs.entity().set<Position>({50, 60}); e5.set<Self>({e5});

    e4.add<Tag>();
    e5.add<Tag>();

    int32_t count = 0;

    auto s = ecs.system<Self, Position, const Velocity>()
        .arg(3).singleton()
        .iter([&](flecs::iter it, Self* s, Position* p, const Velocity* v) {
            test_assert(it.count() == 1);

            for (auto i : it) {
                p[i].x += v[i].x;
                p[i].y += v[i].y;
                test_assert(it.entity(i) == s[i].value);
                count ++;
            }
        });

    s.run();

    test_int(count, 5);

    test_assert(e1.get([](const Position& p) {
        test_int(p.x, 11);
        test_int(p.y, 22);
    }));

    test_assert(e2.get([](const Position& p) {
        test_int(p.x, 21);
        test_int(p.y, 32);
    }));

    test_assert(e3.get([](const Position& p) {
        test_int(p.x, 31);
        test_int(p.y, 42);
    }));

    test_assert(e4.get([](const Position& p) {
        test_int(p.x, 41);
        test_int(p.y, 52);
    }));

    test_assert(e5.get([](const Position& p) {
        test_int(p.x, 51);
        test_int(p.y, 62);
    }));
}

void System_un_instanced_query_w_base_iter(void) {
    flecs::world ecs;

    auto base = ecs.entity().set<Velocity>({1, 2});

    auto e1 = ecs.entity().is_a(base).set<Position>({10, 20}); e1.set<Self>({e1});
    auto e2 = ecs.entity().is_a(base).set<Position>({20, 30}); e2.set<Self>({e2});
    auto e3 = ecs.entity().is_a(base).set<Position>({30, 40}); e3.set<Self>({e3});
    auto e4 = ecs.entity().is_a(base).set<Position>({40, 50}).add<Tag>(); e4.set<Self>({e4});
    auto e5 = ecs.entity().is_a(base).set<Position>({50, 60}).add<Tag>(); e5.set<Self>({e5});
    auto e6 = ecs.entity().set<Position>({60, 70}).set<Velocity>({2, 3}); e6.set<Self>({e6});
    auto e7 = ecs.entity().set<Position>({70, 80}).set<Velocity>({4, 5}); e7.set<Self>({e7});

    int32_t count = 0;

    auto s = ecs.system<Self, Position, const Velocity>()
        .iter([&](flecs::iter it, Self* s, Position* p, const Velocity* v) {
            for (auto i : it) {
                p[i].x += v[i].x;
                p[i].y += v[i].y;
                test_assert(it.entity(i) == s[i].value);
                count ++;
            }
        });

    s.run();

    test_int(count, 7);

    test_assert(e1.get([](const Position& p) {
        test_int(p.x, 11);
        test_int(p.y, 22);
    }));

    test_assert(e2.get([](const Position& p) {
        test_int(p.x, 21);
        test_int(p.y, 32);
    }));

    test_assert(e3.get([](const Position& p) {
        test_int(p.x, 31);
        test_int(p.y, 42);
    }));

    test_assert(e4.get([](const Position& p) {
        test_int(p.x, 41);
        test_int(p.y, 52);
    }));

    test_assert(e5.get([](const Position& p) {
        test_int(p.x, 51);
        test_int(p.y, 62);
    }));

    test_assert(e6.get([](const Position& p) {
        test_int(p.x, 62);
        test_int(p.y, 73);
    }));

    test_assert(e7.get([](const Position& p) {
        test_int(p.x, 74);
        test_int(p.y, 85);
    }));
}

void System_create_w_no_template_args(void) {
    flecs::world world;

    auto entity = world.entity()
        .set<Position>({10, 20});

    int32_t count = 0;

    auto s = world.system()
        .term<Position>()
        .each([&](flecs::entity e) {
            test_assert(e == entity);
            count ++;
        });

    s.run();

    test_int(count, 1);
}

struct PipelineType {};
struct First {};
struct Second {};

void System_system_w_type_kind_type_pipeline(void) {
    flecs::world world;

    world.component<Second>()
        .add(flecs::Phase)
        .depends_on(
            world.component<First>()
                .add(flecs::Phase)
        );

    world.pipeline<PipelineType>()
        .term(flecs::System)
        .term(flecs::Phase).cascade(flecs::DependsOn)
        .build();

    world.set_pipeline<PipelineType>();

    auto entity = world.entity().add<Tag>();

    int32_t s1_count = 0;
    int32_t s2_count = 0;

    world.system<Tag>()
        .kind<Second>()
        .each([&](flecs::entity e, Tag) {
            test_assert(e == entity);
            test_int(s1_count, 0);
            test_int(s2_count, 1);
            s1_count ++;
        });

    world.system<Tag>()
        .kind<First>()
        .each([&](flecs::entity e, Tag) {
            test_assert(e == entity);
            test_int(s1_count, 0);
            s2_count ++;
        });

    world.progress();

    test_int(s1_count, 1);
    test_int(s2_count, 1);
}

void System_default_ctor(void) {
    flecs::world world;

    flecs::system sys_var;

    int count = 0;
    auto sys = world.system<Position>()
        .each([&](flecs::entity e, Position& p) {
            test_int(p.x, 10);
            test_int(p.y, 20);
            count ++;
        });

    world.entity().set<Position>({10, 20});

    sys_var = sys;

    sys_var.run();

    test_int(count, 1);
}

void System_entity_ctor(void) {
    flecs::world world;

    uint32_t invoked = 0;

    flecs::entity sys = world.system<>()
        .iter([&](flecs::iter& it) {
            invoked ++;
        });

    auto sys_from_id = world.system(sys);

    sys_from_id.run();
    test_int(invoked, 1);
}

void System_ensure_instanced_w_each(void) {
    flecs::world world;

    flecs::entity e1 = world.entity().set<Position>({10, 20});

    int32_t count = 0;
    auto sys = world.system<Position>()
        .each([&](flecs::iter& it, size_t i, Position&) {
            test_assert(it.c_ptr()->flags & EcsIterIsInstanced);
            test_assert(it.entity(i) == e1);
            count ++;
        });

    auto q = sys.query();
    auto f = q.filter();
    const ecs_filter_t *c_f = f;
    test_assert(c_f->flags & EcsIterIsInstanced);

    test_int(count, 0);
    sys.run();
    test_int(count, 1);
}

void System_multithread_system_w_query_each(void) {
    flecs::world world;

    world.set_threads(2);

    flecs::entity e = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    auto q = world.query<Velocity>();

    world.system<Position>()
        .multi_threaded()
        .each([&](flecs::entity e, Position& p) {
            q.each(e, [&](Velocity& v) {
                p.x += v.x;
                p.y += v.y;
            });
        });

    world.progress();

    const Position *p = e.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);
}

void System_multithread_system_w_query_each_w_iter(void) {
    flecs::world world;

    world.set_threads(2);

    flecs::entity e = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    auto q = world.query<Velocity>();

    world.system<Position>()
        .multi_threaded()
        .each([&](flecs::iter& it, size_t, Position& p) {
            q.each(it, [&](Velocity& v) {
                p.x += v.x;
                p.y += v.y;
            });
        });

    world.progress();

    const Position *p = e.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);
}

void System_multithread_system_w_query_each_w_world(void) {
    flecs::world world;

    world.set_threads(2);

    flecs::entity e = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    auto q = world.query<Velocity>();

    world.system<Position>()
        .multi_threaded()
        .each([&](flecs::iter& it, size_t, Position& p) {
            q.each(it.world(), [&](Velocity& v) {
                p.x += v.x;
                p.y += v.y;
            });
        });

    world.progress();

    const Position *p = e.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);
}

void System_multithread_system_w_query_iter(void) {
    flecs::world world;

    world.set_threads(2);

    flecs::entity e = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    auto q = world.query<Velocity>();

    world.system<Position>()
        .multi_threaded()
        .each([&](flecs::entity e, Position& p) {
            q.iter(e, [&](flecs::iter& it, Velocity* v) {
                for (auto i : it) {
                    p.x += v[i].x;
                    p.y += v[i].y;
                }
            });
        });

    world.progress();

    const Position *p = e.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);
}

void System_multithread_system_w_query_iter_w_iter(void) {
    flecs::world world;

    world.set_threads(2);

    flecs::entity e = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    auto q = world.query<Velocity>();

    world.system<Position>()
        .multi_threaded()
        .each([&](flecs::iter& it, size_t, Position& p) {
            q.iter(it, [&](flecs::iter& it, Velocity* v) {
                for (auto i : it) {
                    p.x += v[i].x;
                    p.y += v[i].y;
                }
            });
        });

    world.progress();

    const Position *p = e.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);
}

void System_multithread_system_w_query_iter_w_world(void) {
    flecs::world world;

    world.set_threads(2);

    flecs::entity e = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    auto q = world.query<Velocity>();

    world.system<Position>()
        .multi_threaded()
        .each([&](flecs::iter& it, size_t, Position& p) {
            q.iter(it.world(), [&](flecs::iter& it, Velocity* v) {
                for (auto i : it) {
                    p.x += v[i].x;
                    p.y += v[i].y;
                }
            });
        });

    world.progress();

    const Position *p = e.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);
}

void System_run_callback(void) {
    flecs::world world;

    auto entity = world.entity()
        .set<Position>({10, 20})
        .set<Velocity>({1, 2});

    world.system<Position, const Velocity>()
        .run([](flecs::iter_t *it) {
            while (ecs_iter_next(it)) {
                it->callback(it);
            }
        })
        .iter([](flecs::iter&it, Position *p, const Velocity* v) {
            for (auto i : it) {
                p[i].x += v[i].x;
                p[i].y += v[i].y;
            }
        });

    world.progress();

    const Position *p = entity.get<Position>();
    test_int(p->x, 11);
    test_int(p->y, 22);

    const Velocity *v = entity.get<Velocity>();
    test_int(v->x, 1);
    test_int(v->y, 2);
}

void System_startup_system(void) {
    flecs::world ecs;

    int32_t count_a = 0, count_b = 0;

    ecs.system()
        .kind(flecs::OnStart)
        .iter([&](flecs::iter& it) {
            test_assert(it.delta_time() == 0);
            count_a ++;
        });

    ecs.system()
        .kind(flecs::OnUpdate)
        .iter([&](flecs::iter& it) {
            test_assert(it.delta_time() != 0);
            count_b ++;
        });

    ecs.progress();
    test_int(count_a, 1);
    test_int(count_b, 1);

    ecs.progress();
    test_int(count_a, 1);
    test_int(count_b, 2);
}

void System_interval_tick_source(void) {
    flecs::world ecs;

    flecs::timer t = ecs.timer().interval(2.1);

    flecs::Timer *timer = t.get_mut<flecs::Timer>();
    timer->time = 0;

    int32_t sys_a_invoked = 0, sys_b_invoked = 0;

    ecs.system()
        .tick_source(t)
        .iter([&](flecs::iter& it) {
            sys_a_invoked ++;
        });

    ecs.system()
        .tick_source(t)
        .iter([&](flecs::iter& it) {
            sys_b_invoked ++;
        });

    ecs.progress(1.0);
    test_int(0, sys_a_invoked);
    test_int(0, sys_b_invoked);

    ecs.progress(1.0);
    test_int(0, sys_a_invoked);
    test_int(0, sys_b_invoked);

    ecs.progress(1.0);
    test_int(1, sys_a_invoked);
    test_int(1, sys_b_invoked);
}

void System_rate_tick_source(void) {
    flecs::world ecs;

    flecs::timer t = ecs.timer().rate(3);

    int32_t sys_a_invoked = 0, sys_b_invoked = 0;

    ecs.system()
        .tick_source(t)
        .iter([&](flecs::iter& it) {
            sys_a_invoked ++;
        });

    ecs.system()
        .tick_source(t)
        .iter([&](flecs::iter& it) {
            sys_b_invoked ++;
        });

    ecs.progress(1.0);
    test_int(0, sys_a_invoked);
    test_int(0, sys_b_invoked);

    ecs.progress(1.0);
    test_int(0, sys_a_invoked);
    test_int(0, sys_b_invoked);

    ecs.progress(1.0);
    test_int(1, sys_a_invoked);
    test_int(1, sys_b_invoked);
}

void System_nested_rate_tick_source(void) {
    flecs::world ecs;

    flecs::timer t_3 = ecs.timer().rate(3);
    flecs::timer t_6 = ecs.timer().rate(2, t_3);

    int32_t sys_a_invoked = 0, sys_b_invoked = 0;

    ecs.system()
        .tick_source(t_3)
        .iter([&](flecs::iter& it) {
            sys_a_invoked ++;
        });

    ecs.system()
        .tick_source(t_6)
        .iter([&](flecs::iter& it) {
            sys_b_invoked ++;
        });

    ecs.progress(1.0);
    test_int(0, sys_a_invoked);
    test_int(0, sys_b_invoked);

    ecs.progress(1.0);
    test_int(0, sys_a_invoked);
    test_int(0, sys_b_invoked);

    ecs.progress(1.0);
    test_int(1, sys_a_invoked);
    test_int(0, sys_b_invoked);

    ecs.progress(1.0);
    test_int(1, sys_a_invoked);
    test_int(0, sys_b_invoked);

    ecs.progress(1.0);
    test_int(1, sys_a_invoked);
    test_int(0, sys_b_invoked);

    ecs.progress(1.0);
    test_int(2, sys_a_invoked);
    test_int(1, sys_b_invoked);
}

void System_table_get(void) {
    flecs::world ecs;

    flecs::entity e1 = ecs.entity().set<Position>({10, 20});
    flecs::entity e2 = ecs.entity().set<Position>({20, 30});

    auto s = ecs.system()
        .with<Position>()
        .each([&](flecs::iter& iter, size_t index) {
            flecs::entity e = iter.entity(index);
            const Position *p = &iter.table().get<Position>()[index];
            test_assert(p != nullptr);
            test_assert(e == e1 || e == e2);
            if (e == e1) {
                test_int(p->x, 10);
                test_int(p->y, 20);
            } else if (e == e2) {
                test_int(p->x, 20);
                test_int(p->y, 30);
            }
        });

    s.run();
}

void System_range_get(void) {
    flecs::world ecs;

    flecs::entity e1 = ecs.entity().set<Position>({10, 20});
    flecs::entity e2 = ecs.entity().set<Position>({20, 30});

    auto s = ecs.system()
        .with<Position>()
        .each([&](flecs::iter& iter, size_t index) {
            flecs::entity e = iter.entity(index);
            const Position *p = &iter.range().get<Position>()[index];
            test_assert(p != nullptr);
            test_assert(e == e1 || e == e2);
            if (e == e1) {
                test_int(p->x, 10);
                test_int(p->y, 20);
            } else if (e == e2) {
                test_int(p->x, 20);
                test_int(p->y, 30);
            }
        });

    s.run();
}

void System_randomize_timers(void) {
    flecs::world ecs;

    flecs::entity s1 = ecs.system()
        .interval(1.0)
        .iter([](flecs::iter& it) { });

    {
        const flecs::Timer *t = s1.get<flecs::Timer>();
        test_assert(t != nullptr);
        test_assert(t->time == 0);
    }

    ecs.randomize_timers();

    flecs::entity s2 = ecs.system()
        .interval(1.0)
        .iter([](flecs::iter& it) { });

    {
        const flecs::Timer *t = s1.get<flecs::Timer>();
        test_assert(t != nullptr);
        test_assert(t->time != 0);
    }

    {
        const flecs::Timer *t = s2.get<flecs::Timer>();
        test_assert(t != nullptr);
        test_assert(t->time != 0);
    }
}

void System_optional_pair_term(void) {
    flecs::world ecs;

    ecs.entity()
        .add<TagA>()
        .emplace<Position, Tag>(1.0f, 2.0f);
    ecs.entity()
        .add<TagA>();

    int32_t with_pair = 0, without_pair = 0;

    ecs.system<flecs::pair<Position, Tag>*>()
        .with<TagA>()
        .each([&](flecs::entity e, Position* p)
        {
            if (p)
            {
                with_pair++;
                test_flt(1.0f, p->x);
                test_flt(2.0f, p->y);
            }
            else
            {
                without_pair++;
            }
        });

    ecs.progress(1.0);

    test_int(1, with_pair);
    test_int(1, without_pair);
}