riversong-code-showcase/Source/Riversong/Game/World/Population/PopulationUpdateSystem.cs

using Cysharp.Threading.Tasks;
using Unity.Mathematics;
using UnityEngine;

namespace DanieleMarotta.RiversongCodeShowcase
{
    [UpdateAfter(typeof(PopulationNeedsSystem))]
    public class PopulationUpdateSystem : GameSystem, IInitializable, IUpdatable
    {
        [InjectService]
        private ISignalBus _signalBus;

        [InjectService]
        private World _world;

        [InjectService]
        private IEntityCache _entityCache;

        [InjectService]
        private GameConfig _config;

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

        public UniTask InitializeAsync()
        {
            _world.PopulationState.Happiness = _config.Population.InitialeOverallHappiness;

            return UniTask.CompletedTask;
        }

        public void Update()
        {
            if (_world.TimeState.DayNightCycleStep != DayNightCycleStep.Day) return;

            UpdateOverallHappiness();
            UpdatePopulation();
        }

        private void UpdateOverallHappiness()
        {
            var targetHappiness = 0f;
            var totalWeight = 0f;

            foreach (var house in _entityCache.GetHouses())
            {
                ref var needsState = ref house.GetNeedsStateRW();
                targetHappiness += needsState.OverallHappinessWeight * needsState.Happiness;
                totalWeight += needsState.OverallHappinessWeight;
            }

            if (totalWeight > 0) targetHappiness = math.saturate(targetHappiness / totalWeight);

            var grace = _world.TimeState.TotalWeeks < _config.Population.GraceWeekCount;
            if (grace) targetHappiness = math.max(targetHappiness, _config.Population.GraceMinHappiness);

            var populationState = _world.PopulationState;
            var delta = math.abs(targetHappiness - populationState.Happiness);
            const float halfOnePercent = 0.005f;
            populationState.Sentiment = delta > halfOnePercent ? math.sign(targetHappiness - populationState.Happiness) : 0;
            populationState.Happiness = Mathf.MoveTowards(populationState.Happiness, targetHappiness, _config.Population.OverallHappinessChangeRate * Time.deltaTime);
            populationState.Happiness = math.saturate(populationState.Happiness);
        }

        private void UpdatePopulation()
        {
            var populationState = _world.PopulationState;

            populationState.PopulationCapacity = 0;
            foreach (var house in _entityCache.GetHouses()) populationState.PopulationCapacity += house.PopulationCapacity;

            var growthRate = _config.Population.GrowthRatePeakValue * _config.Population.GrowthRateCurve.Evaluate(populationState.Happiness);
            if (populationState.Sentiment > 0) growthRate = math.max(growthRate, 0);

            populationState.GrowthAccumulator += growthRate * Time.deltaTime;
            if (math.abs(populationState.GrowthAccumulator) < 1) return;

            var delta = (int)math.sign(populationState.GrowthAccumulator);
            populationState.GrowthAccumulator -= delta;

            var updatedPopulation = math.clamp(populationState.Population + delta, 0, populationState.PopulationCapacity);
            if (updatedPopulation == populationState.Population) return;

            populationState.Population = updatedPopulation;
            _signalBus.Raise(new PopulationChangedSignal(updatedPopulation));
        }
    }
}