riversong-code-showcase/Source/Riversong/Game/World/Agents/AgentsCleanUpSystem.cs

using UnityEngine;

namespace DanieleMarotta.RiversongCodeShowcase
{
    [GameSystemGroup(typeof(DefaultAgentsSystemGroup))]
    [UpdateAfter(typeof(AgentManagerSystem))]
    public class AgentsCleanUpSystem : GameSystem, IUpdatable
    {
        [InjectService]
        private IEntityCollection _entityCollection;

        public AgentsCleanUpSystem(IServiceLocator serviceLocator) : base(serviceLocator)
        {
        }

        public void Update()
        {
            foreach (IAgentSourceEntity agentSource in _entityCollection.GetInternalEntityList(typeof(ConstructionSite))) CleanUpAgentSource(agentSource);
            foreach (IAgentSourceEntity agentSource in _entityCollection.GetInternalEntityList(typeof(Building))) CleanUpAgentSource(agentSource);
            foreach (IAgentSourceEntity agentSource in _entityCollection.GetInternalEntityList(typeof(CritterHerd))) CleanUpAgentSource(agentSource);
        }

        private void CleanUpAgentSource(IAgentSourceEntity agentSource)
        {
            ref var agentSourceState = ref agentSource.GetAgentSourceStateRW();

            for (var i = agentSourceState.AgentIds.Length - 1; i >= 0; i--)
            {
                var id = agentSourceState.AgentIds[i];

                var agent = _entityCollection.Get<Agent>(id);
                if (agent is not { LifecycleState: AgentLifecycleState.DeSpawning }) continue;

                ref var jobState = ref agent.GetJobStateRW();
                var job = jobState.Job;

                var count = agentSourceState.AgentCount[(int)job];
                if (count > 0)
                {
                    agentSourceState.AgentCount[(int)job] = (byte)(count - 1);
                }
                else
                {
                    var home = _entityCollection.Get<Building>(agent.HomeId);
                    Debug.LogError($"Agent count <= 0 when de-spawning agent. Home: '{home.Definition.name}', Job: '{job}'");
                }

                agentSourceState.AgentIds.RemoveAtSwapBack(i);
            }
        }
    }
}