UtiltiyAIExample

using UnityEngine;

using System.Collections.Generic;

namespace AIScripts.UtilityAI
{
    public interface IAction
    {
        void Execute();

        float GetUtility();
    }

    public class AnimalAI : MonoBehaviour
    {
        [SerializeField] private float _hunger;

        [SerializeField] private float _thirst;

        [SerializeField] private float _fatigue;

        private List<IAction> _actions;

        private void Start()
        {
            _actions = new List<IAction>
            {
                new SleepAction(this),
                new EatAction(this),
                new DrinkAction(this),
                new HuntAction(this)
            };
        }

        private void Update()
        {
            IAction bestAction = GetBestAction();
            bestAction.Execute();
        }

        private IAction GetBestAction()
        {
            float bestUtility = float.MinValue;
            IAction bestAction = null;

            foreach(IAction action in _actions)
            {
                float utility = action.GetUtility();

                if (utility > bestUtility)
                {
                    bestUtility = utility;
                    bestAction = action;
                }
            }

            return bestAction;
        }

        private class SleepAction : IAction
        {
            private readonly AnimalAI _animal;

            public SleepAction(AnimalAI animal) =>
                _animal = animal;

            public void Execute()
            {
                Debug.Log("Sleeping");
                _animal._fatigue -= Time.deltaTime;
                _animal._hunger += Time.deltaTime * 0.5f;
                _animal._thirst += Time.deltaTime * 0.5f;
            }

            public float GetUtility()
            {
                return _animal._fatigue;
            }
        }

        private class EatAction : IAction
        {
            private readonly AnimalAI _animal;

            public EatAction(AnimalAI animal) =>
                _animal = animal;

            public void Execute()
            {
                _animal._hunger -= Time.deltaTime;
                _animal._fatigue += Time.deltaTime * 0.5f;
                _animal._thirst += Time.deltaTime * 0.5f;
            }

            public float GetUtility() => _animal._hunger;
        }

        private class DrinkAction : IAction
        {
            private readonly AnimalAI _animal;

            public DrinkAction(AnimalAI animal) =>
                _animal = animal;

            public void Execute()
            {
                _animal._thirst -= Time.deltaTime;
                _animal._fatigue += Time.deltaTime * 0.5f;
                _animal._hunger += Time.deltaTime * 0.5f;
            }

            public float GetUtility() => _animal._thirst;
        }

        private class HuntAction : IAction
        {
            private readonly AnimalAI _animal;

            public HuntAction(AnimalAI animal) =>
                _animal = animal;

            public void Execute()
            {
                _animal._fatigue += Time.deltaTime * 0.5f;
                _animal._hunger -= Time.deltaTime;
                _animal._thirst += Time.deltaTime * 0.5f;
            }

            public float GetUtility() =>
                _animal._hunger;
        }
    }
}