riversong-code-showcase/Source/Riversong/Game/Vfx/ProjectileManagerSystem.cs

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

namespace DanieleMarotta.RiversongCodeShowcase
{
    [Service(typeof(IProjectileManager))]
    public class ProjectileManagerSystem : GameSystem, IProjectileManager
    {
        private const float ProjectileSpeed = 4;

        [InjectService]
        private IIntentLogicExecutor _intentLogicExecutor;

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

        public float ComputeProjectileTravelTime(Agent source, Agent target)
        {
            return math.distance(source.Position, target.Position) / ProjectileSpeed;
        }

        public void FireProjectile(Agent source, Agent target)
        {
            _ = FireProjectileAsync(source, target, ComputeProjectileTravelTime(source, target));
        }

        private async UniTask FireProjectileAsync(Agent source, Agent target, float travelTime)
        {
            var prefabRef = source.Definition.Projectile;
            var projectile = await prefabRef.InstantiateAsync();

            var p0 = (Vector3)source.Position;
            var p1 = (Vector3)target.Position;

            // const float peakHeightPerMeter = 0.1f;
            // var peak = Vector3.Distance(p0, p1) * peakHeightPerMeter;

            var t = 0f;
            while (t < 1)
            {
                t = Mathf.Clamp01(t + Time.deltaTime / travelTime);

                var position = Vector3.Lerp(p0, p1, t);
                //position.y += 4 * peak * t * (1 - t);

                var rotation = Quaternion.LookRotation((position - projectile.transform.position).normalized);

                projectile.transform.SetPositionAndRotation(position, rotation);

                await UniTask.NextFrame();
            }

            Addressables.ReleaseInstance(projectile);

            _intentLogicExecutor.CancelRemainingIntents(target);
        }
    }
}