using System;
using Friflo.Engine.ECS;
using Friflo.Engine.ECS.Systems;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using MrGameEng.Core;

namespace KniWebSpike
{
    // Компоненты симуляции — платформо-независимые, как в LittleSim.
    public struct DotPosition : IComponent
    {
        public float X;
        public float Y;
    }

    public struct DotVelocity : IComponent
    {
        public float X;
        public float Y;
    }

    public struct DotTint : IComponent
    {
        public byte R;
        public byte G;
        public byte B;
    }

    /// <summary>
    /// Сцена спайка: 300 «спрайтов» в Friflo EntityStore, движение в Update-фазе
    /// (детерминированный seed, отскок от краёв), отрисовка в Draw-фазе через
    /// KNI SpriteBatch (WebGL). Сцена и системные корни — из MrGameEng.Core.
    /// </summary>
    public sealed class SpikeScene : Scene
    {
        private readonly Func<SpriteBatch> _spriteBatch;
        private readonly Func<Texture2D> _pixel;
        private readonly float _width;
        private readonly float _height;

        public SpikeScene(Func<SpriteBatch> spriteBatch, Func<Texture2D> pixel, float width, float height)
        {
            _spriteBatch = spriteBatch;
            _pixel = pixel;
            _width = width;
            _height = height;
        }

        protected override void OnLoad()
        {
            var random = new Random(42);
            for (var i = 0; i < 300; i++)
            {
                var angle = (float)(random.NextDouble() * Math.Tau);
                var speed = 40f + (float)random.NextDouble() * 160f;
                Store.CreateEntity(
                    new DotPosition
                    {
                        X = (float)random.NextDouble() * _width,
                        Y = (float)random.NextDouble() * _height,
                    },
                    new DotVelocity
                    {
                        X = MathF.Cos(angle) * speed,
                        Y = MathF.Sin(angle) * speed,
                    },
                    new DotTint
                    {
                        R = (byte)random.Next(64, 256),
                        G = (byte)random.Next(64, 256),
                        B = (byte)random.Next(64, 256),
                    }
                );
            }

            UpdateSystems.Add(new BounceSystem(_width, _height));
            DrawSystems.Add(new DotDrawSystem(_spriteBatch, _pixel));
        }

        private sealed class BounceSystem : QuerySystem<DotPosition, DotVelocity>
        {
            private readonly float _width;
            private readonly float _height;

            public BounceSystem(float width, float height)
            {
                _width = width;
                _height = height;
            }

            protected override void OnUpdate()
            {
                var delta = Tick.deltaTime;
                var width = _width;
                var height = _height;
                Query.ForEachEntity(
                    (ref DotPosition pos, ref DotVelocity vel, Entity _) =>
                    {
                        pos.X += vel.X * delta;
                        pos.Y += vel.Y * delta;
                        if (pos.X < 0f || pos.X > width)
                        {
                            vel.X = -vel.X;
                            pos.X = Math.Clamp(pos.X, 0f, width);
                        }

                        if (pos.Y < 0f || pos.Y > height)
                        {
                            vel.Y = -vel.Y;
                            pos.Y = Math.Clamp(pos.Y, 0f, height);
                        }
                    }
                );
            }
        }

        private sealed class DotDrawSystem : QuerySystem<DotPosition, DotTint>
        {
            private readonly Func<SpriteBatch> _spriteBatch;
            private readonly Func<Texture2D> _pixel;

            public DotDrawSystem(Func<SpriteBatch> spriteBatch, Func<Texture2D> pixel)
            {
                _spriteBatch = spriteBatch;
                _pixel = pixel;
            }

            protected override void OnUpdate()
            {
                var batch = _spriteBatch();
                var pixel = _pixel();
                batch.Begin();
                Query.ForEachEntity(
                    (ref DotPosition pos, ref DotTint tint, Entity _) =>
                    {
                        batch.Draw(
                            pixel,
                            new Rectangle((int)pos.X, (int)pos.Y, 6, 6),
                            new Color(tint.R, tint.G, tint.B)
                        );
                    }
                );
                batch.End();
            }
        }
    }
}