/*
 * This file is part of Araknemu.
 *
 * Araknemu is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Araknemu is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Araknemu.  If not, see <https://www.gnu.org/licenses/>.
 *
 * Copyright (c) 2017-2021 Vincent Quatrevieux
 */

package fr.quatrevieux.araknemu.game.fight.ai.action.util;

import fr.quatrevieux.araknemu.game.fight.ai.AI;
import fr.quatrevieux.araknemu.game.fight.ai.action.ActionGenerator;
import fr.quatrevieux.araknemu.game.fight.ai.action.AiActionFactory;
import fr.quatrevieux.araknemu.game.fight.ai.memory.MemoryKey;
import fr.quatrevieux.araknemu.game.fight.ai.memory.TurnMemoryKey;
import fr.quatrevieux.araknemu.game.fight.ai.simulation.CastSimulation;
import fr.quatrevieux.araknemu.game.fight.ai.simulation.Simulator;
import fr.quatrevieux.araknemu.game.fight.ai.util.AIHelper;
import fr.quatrevieux.araknemu.game.fight.map.BattlefieldCell;
import fr.quatrevieux.araknemu.game.fight.turn.action.Action;
import fr.quatrevieux.araknemu.game.spell.Spell;

import java.util.Optional;

/**
 * Try to cast the best spell
 * When the action is generated, the cast spell is stored in the memory at key {@link #LAST_CAST}
 */
public final class CastSpell implements ActionGenerator {
    public static final MemoryKey<LastCast> LAST_CAST = new TurnMemoryKey<>();

    private final Simulator simulator;
    private final SimulationSelector selector;

    public CastSpell(Simulator simulator, SimulationSelector selector) {
        this.simulator = simulator;
        this.selector = selector;
    }

    @Override
    public void initialize(AI ai) {
    }

    @Override
    public <A extends Action> Optional<A> generate(AI ai, AiActionFactory<A> actions) {
        final AIHelper helper = ai.helper();

        if (!helper.canCast()) {
            return Optional.empty();
        }

        return helper.spells().caster(actions.castSpellValidator())
            .simulate(simulator)
            .filter(selector::valid)
            .reduce((s1, s2) -> selector.compare(s2, s1) ? s2 : s1)
            .map(simulation -> {
                ai.set(LAST_CAST, new LastCast(simulation.spell(), simulation.target()));

                return actions.cast(simulation.spell(), simulation.target());
            })
        ;
    }

    public interface SimulationSelector {
        /**
         * Check if the simulation is valid
         */
        public default boolean valid(CastSimulation simulation) {
            return score(simulation) > 0;
        }

        /**
         * Compare the two simulation
         * Return true if a is better than b
         *
         * Note: The simulations may be null
         */
        public default boolean compare(CastSimulation a, CastSimulation b) {
            return score(a) > score(b);
        }

        /**
         * Compute the score for the given simulation
         *
         * @param simulation The simulation result
         *
         * @return The score of the simulation. 0 is null
         */
        public double score(CastSimulation simulation);
    }

    /**
     * Store the last generated cast spell action
     */
    public static final class LastCast {
        private final Spell spell;
        private final BattlefieldCell target;

        public LastCast(Spell spell, BattlefieldCell target) {
            this.spell = spell;
            this.target = target;
        }

        /**
         * Get the selected spell
         */
        public Spell spell() {
            return spell;
        }

        /**
         * Get the selected target
         */
        public BattlefieldCell target() {
            return target;
        }
    }
}