MTECSPS.cs

using MoonTools.ECS;
using MoonToolsECSTest.Components;
using MoonToolsECSTest.Messages;

namespace MoonToolsECSTest.Systems
{
    public sealed class ParticleSystem : MoonTools.ECS.System
    {
        readonly Dictionary<string, ParticleSystemTemplate> _particleSystemResources;
        readonly Dictionary<int, List<string>> _entityClassificationsToParticleSystems;
        
        public ParticleSystem(
            World world,
            Dictionary<string, ParticleSystemTemplate> particleSystemResources,
            Dictionary<int, List<string>> entityClassificationsToParticleSystems
        ) : base(world) 
        {
            _particleSystemResources = particleSystemResources;
            _entityClassificationsToParticleSystems = entityClassificationsToParticleSystems;
        }

        public override void Update(TimeSpan delta)
        {
            //NOTE - random memory access here looking up items in mapping table and resource table.
            //Is this a 'problem'? Do we care? Our games are 'simple' and update / draw in a couple of ms
            //I do think I like the architecture - maybe
            
            //You could instead build a simple array as the lookup with offset index and count with the downside of some data duplication

            //A bunch of things may have died this frame
            foreach (var message in ReadMessages<DeathMessage>())
            {
                //If any of the dead entities have the ExplosionComponent we can create particle explosions for them
                if (Has<ExplosionComponent>(message.Entity))
                {
                    var explosionComponent = Get<ExplosionComponent>(message.Entity);

                    //We look up the name(s) of the particle system(s) to create from the mapping table
                    //This will tell us the name(s) of the systems to create.
                    //e.g.
                    //Entities of 'type' PLAYER should create "GenericBoom", "PlayerBigBoom", "PlayerSparkles"
                    var particleSystemNames = _entityClassificationsToParticleSystems[explosionComponent.ClassificationId];

                    //Now we know the names we can lookup the templates and create particle systems based on them
                    foreach (var name in particleSystemNames)
                    {
                        var template = _particleSystemResources[name];
                        Console.WriteLine($"Template: {name}, {template.Color}, { template.Count}");
                    }
                }
            }
        }
    }
}