encompass-cs/encompass-cs/Engines/Detector.cs

using System;
using System.Reflection;
using System.Collections.Generic;
using Encompass.Exceptions;

namespace Encompass.Engines
{
    public abstract class Detector : Engine, IEntityTracker
    {
        private readonly List<Type> componentTypes = new List<Type>();
        private readonly EntityTracker entityTracker = new EntityTracker();

        public IEnumerable<Type> ComponentTypes { get { return componentTypes; } }

        protected Detector()
        {
            var detectsAttribute = GetType().GetCustomAttribute<Detects>(false);
            if (detectsAttribute != null)
            {
                componentTypes = detectsAttribute.componentTypes;
            }
            else
            {
                throw new DetectorWithoutComponentTypesException("Detector {0} does not have any component types declared. Use the Detects attribute to declare component types", GetType().Name);
            }
        }

        public override void Update(double dt)
        {
            foreach (var id in entityTracker.TrackedEntityIDs)
            {
                Detect(GetEntity(id), dt);
            }
        }

        public abstract void Detect(Entity entity, double dt);

        public bool CheckAndTrackEntity(Guid entityID)
        {
            var entity = GetEntity(entityID);
            var shouldTrack = CheckEntity(entity);
            if (shouldTrack) { entityTracker.TrackEntity(entityID); }
            return shouldTrack;
        }

        public bool CheckAndUntrackEntity(Guid entityID)
        {
            var entity = GetEntity(entityID);
            var shouldUntrack = !CheckEntity(entity);
            if (shouldUntrack) { entityTracker.UntrackEntity(entityID); }
            return shouldUntrack;
        }

        private bool CheckEntity(Entity entity)
        {
            return EntityChecker.CheckEntity(entity, componentTypes);
        }
    }
}