FutureEntityTurn.java

package com.carterza.entity;

import com.artemis.Entity;
import com.carterza.action.Action;

/**
 * Created by zachcarter on 11/19/16.
 */
public class FutureEntityTurn implements Comparable<FutureEntityTurn> {
    private Entity entity;
    private int time;

    public FutureEntityTurn(Entity entity, int time) {
        this.entity = entity;
        this.time = time;
    }

    public int getTime() {
        return time;
    }

    public void setTime(int time) {
        this.time = time;
    }

    public Entity getEntity() {
        return entity;
    }

    @Override
    public int compareTo(FutureEntityTurn o) {
        return Integer.compare(this.time, o.time);
    }
}

PerformActionEvent.java

package com.carterza.event;

import com.artemis.Entity;
import com.carterza.action.Action;
import net.mostlyoriginal.api.event.common.Event;

/**
 * Created by zachcarter on 11/19/16.
 */
public class PerformActionEvent implements Event {
    private Entity entity;
    private int actionCost;
    private Action action;

    public Entity getEntity() {
        return entity;
    }

    public void setEntity(Entity entity) {
        this.entity = entity;
    }

    public int getActionCost() {
        return actionCost;
    }

    public void setActionCost(int actionCost) {
        this.actionCost = actionCost;
    }

    public Action getAction() {
        return action;
    }

    public void setAction(Action action) {
        this.action = action;
    }
}

TurnComponent.java

package com.carterza.component;

import com.artemis.Component;

/**
 * Created by zachcarter on 11/9/16.
 */
public class TurnComponent extends Component {

    private int speed;

    public TurnComponent(int speed) {
        this.speed = speed;
    }

    public int getSpeed() {
        return speed;
    }

    public TurnComponent() {

    }
}

TurnSystem.java

package com.carterza.system.turn;

import com.artemis.Aspect;
import com.artemis.BaseEntitySystem;
import com.artemis.ComponentMapper;
import com.artemis.Entity;
import com.artemis.annotations.Wire;
import com.carterza.component.TurnComponent;
import com.carterza.entity.FutureEntityTurn;
import com.carterza.event.PerformActionEvent;
import net.mostlyoriginal.api.event.common.Subscribe;

import java.util.Iterator;
import java.util.PriorityQueue;

@Wire
public class TurnSystem extends BaseEntitySystem {

    private static final int BASE_DELAY_VALUE = 10;
    PriorityQueue<FutureEntityTurn> turnQueue;

    private Entity entityWhoseTurnItIs;

    ComponentMapper<TurnComponent> turnComponentMapper;

    public TurnSystem() {
        super(Aspect.all(TurnComponent.class));
        turnQueue = new PriorityQueue<FutureEntityTurn>();
    }

    @Override
    protected void processSystem() {
        if(entityWhoseTurnItIs == null) {
            FutureEntityTurn futureEntityTurn = turnQueue.remove();
            entityWhoseTurnItIs = futureEntityTurn.getEntity();
            adjustActionQueue(futureEntityTurn.getTime());
        }

    }

    private void adjustActionQueue(int time) {
        Iterator<FutureEntityTurn> actionQueueIterator = turnQueue.iterator();
        while(actionQueueIterator.hasNext()) {
            FutureEntityTurn futureEntityAction = actionQueueIterator.next();
            futureEntityAction.setTime(futureEntityAction.getTime()-time);
        }
    }

    public Entity getEntityWhoseTurnItIs() {
        return entityWhoseTurnItIs;
    }

    @Override
    protected void inserted(int entityId) {
        TurnComponent turnComponent = turnComponentMapper.get(entityId);
        turnQueue.add(new FutureEntityTurn(world.getEntity(entityId), BASE_DELAY_VALUE/turnComponent.getSpeed()));
    }

    @Subscribe
    void handleEvent(PerformActionEvent event) {
        if(entityWhoseTurnItIs != null) {
            if (entityWhoseTurnItIs.equals(event.getEntity())) {
                event.getAction().execute();
                entityWhoseTurnItIs = null;
                turnQueue.add(new FutureEntityTurn(event.getEntity(), event.getActionCost()));
            }
        }
    }
}