dynamic_compute_cell.hpp

/*
 * live_cells_cpp
 * Copyright (C) 2024  Alexander Gutev <alex.gutev@gmail.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you
 * may not use this file except in compliance with the License.  You
 * may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied.  See the License for the specific language governing
 * permissions and limitations under the License.
 */
 
#ifndef LIVE_CELLS_DYNAMIC_COMPUTE_CELL_HPP
#define LIVE_CELLS_DYNAMIC_COMPUTE_CELL_HPP
 
#include <unordered_set>
#include <functional>
#include <utility>
#include <concepts>
#include <type_traits>
 
#include "compute_state.hpp"
#include "stateful_cell.hpp"
#include "changes_only_state.hpp"
#include "tracker.hpp"
 
namespace live_cells {
 
    template <std::invocable F>
    class dynamic_compute_cell_state;
 
    template <std::invocable F>
    class dynamic_compute_state {
        const F compute;
 
        std::unordered_set<cell> arguments;
 
        friend class dynamic_compute_cell_state<F>;
 
    public:
        dynamic_compute_state(F compute) :
            compute(compute) {}
 
        auto operator()(observer::ref state) {
            auto t = argument_tracker::global().with_tracker([this, state] (auto cell) {
                if (!arguments.count(cell)) {
                    arguments.emplace(cell);
 
                    cell.add_observer(state);
                }
            });
 
            return compute();
        }
    };
 
    template <std::invocable F>
    class dynamic_compute_cell_state : public compute_cell_state<dynamic_compute_state<F>> {
        typedef compute_cell_state<dynamic_compute_state<F>> parent;
 
    public:
        dynamic_compute_cell_state(key_ref key, F compute) :
            parent(key, compute) {}
 
    protected:
        void init() override {
            parent::init();
 
            try {
                // Determine arguments and add observers
                this->value();
            }
            catch (...) {
                // Prevent exception from being propagated to caller
            }
        }
 
        void pause() override {
            parent::pause();
 
            for (auto arg : this->compute.arguments) {
                arg.remove_observer(this->observer_ptr());
            }
 
            this->compute.arguments.clear();
        }
    };
 
    template <std::invocable F>
    class dynamic_compute_changes_only_cell_state :
        public changes_only_cell_state<dynamic_compute_cell_state<F>> {
 
        typedef changes_only_cell_state<dynamic_compute_cell_state<F>> parent;
 
    public:
        using parent::parent;
 
    };
 
    template <std::invocable F, typename State = dynamic_compute_cell_state<F>>
    class dynamic_compute_cell : public stateful_cell<State> {
        typedef stateful_cell<State> parent;
 
    public:
        typedef std::invoke_result_t<F> value_type;
 
        dynamic_compute_cell(F compute) :
            dynamic_compute_cell(key_ref::create<unique_key>(), compute) {}
 
        dynamic_compute_cell(key_ref key, F compute) :
            parent(key, compute) {}
 
        value_type value() const {
            return this->state->value();
        }
 
        value_type operator()() const {
            argument_tracker::global().track_argument(*this);
            return value();
        }
    };
 
}  // live_cells
 
#endif /* LIVE_CELLS_DYNAMIC_COMPUTE_CELL_HPP */