using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace scare2D
{
    // define some component
    public struct PingPongComponent : IComponentData
    {
        public float2 velocity;
    }

    // define a component system
    public class PingPongSystem : IComponentSystem
    {
        // define a Group of Components processed by the system
        public class PingPong : IComponentGroup
        {
            public Transform transform;
            public BoxCollider collider;
            public PingPongComponent ball;
        }

        // this collection will be automagically filled by the engine during runtime
        IComponentCollection<PingPong> items;

        // all arguments will be automagically be provided by the engine
        // the runtime model makes sur that before calling update, rect and deltaTime will be provided to the entity system
        public void Update(float4 rect, float deltaTime)
        {
            float4 window = rect;
            // iterate through all component group
            foreach (ref var item in items)
            {
                var origin = item.collider.origin;
                rect = window + new float4(origin.X, origin.Y, origin.X, origin.Y);

                var position = item.transform.position;
                var velocity = item.ball.velocity;
                var p = new float2(position.X + velocity.X * deltaTime, position.Y + velocity.Y * deltaTime);
                var half = item.collider.halfExtends;

                if (p.X - half.X < rect.X || rect.Z < p.X + half.X)
                {
                    item.ball.velocity.X = -item.ball.velocity.X;
                    p.X = p.X.Clamp(rect.X + half.X, rect.Z - half.X);
                }
                if (p.Y - half.Y < rect.Y || rect.W < p.Y + half.Y)
                {
                    item.ball.velocity.Y = -item.ball.velocity.Y;
                    p.Y = p.Y.Clamp(rect.Y + half.Y, rect.W - half.Y);
                }

                item.transform.position = p;
                // at the end of the loop iteration the enumerator will check what components have changed
                // and update these components
            }
        }
    }
}