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

namespace MrGameEng.Sample;

/// <summary>Управление игроком (WASD/стрелки) и прыжок-писк на пробел.</summary>
public sealed class PlayerControlSystem(
    Entity player, ActionMap<SampleAction> actions, AudioManager audio, SoundEffect beep,
    MrGameEng.DevConsole.DevConsole console) : BaseSystem
{
    protected override void OnUpdateGroup()
    {
        if (console.IsOpen)
        {
            return;
        }

        ref var transform = ref player.GetComponent<Transform2D>();
        var move = new Vector2(
            actions.GetAxis(SampleAction.MoveLeft, SampleAction.MoveRight),
            actions.GetAxis(SampleAction.MoveUp, SampleAction.MoveDown));

        if (move != Vector2.Zero)
        {
            move.Normalize();
            transform.Position += move * 260f * Tick.deltaTime;
        }

        if (actions.IsPressed(SampleAction.Jump))
        {
            audio.Play(beep);
        }
    }
}

/// <summary>Камера следует за игроком; колесо — зум, Q/E — поворот.</summary>
public sealed class CameraControlSystem(Entity cameraEntity, Entity player, InputManager input) : BaseSystem
{
    protected override void OnUpdateGroup()
    {
        ref var camera = ref cameraEntity.GetComponent<Camera>();
        var target = player.GetComponent<Transform2D>().Position;

        camera.Position = Vector2.Lerp(camera.Position, target, Math.Min(1f, 6f * Tick.deltaTime));
        camera.Zoom = Math.Clamp(camera.Zoom * (1f + input.WheelDelta * 0.001f), 0.2f, 5f);

        var rotate = (input.IsKeyDown(Keys.E) ? 1f : 0f) - (input.IsKeyDown(Keys.Q) ? 1f : 0f);
        camera.Rotation += rotate * 1.2f * Tick.deltaTime;
    }
}

/// <summary>
/// Отскок сущностей со скоростью от границ мира. На больших количествах работа режется
/// на сегменты по всем ядрам (чанк Friflo держит весь архетип — сам по себе он слишком крупный).
/// </summary>
public sealed class BounceSystem(RectF bounds) : QuerySystem<Transform2D, Velocity>
{
    private const int ParallelThreshold = 8192;
    private const int SegmentSize = 8192;

    private readonly List<(Chunk<Transform2D> Transforms, Chunk<Velocity> Velocities)> _chunks = [];
    private readonly List<(int Chunk, int Start, int Length)> _segments = [];

    protected override void OnUpdate()
    {
        var delta = Tick.deltaTime;
        _chunks.Clear();
        var total = 0;
        foreach (var (transforms, velocities, _) in Query.Chunks)
        {
            _chunks.Add((transforms, velocities));
            total += transforms.Length;
        }

        if (total < ParallelThreshold)
        {
            foreach (var (transforms, velocities) in _chunks)
            {
                Move(transforms, velocities, 0, transforms.Length, delta);
            }

            return;
        }

        _segments.Clear();
        for (var c = 0; c < _chunks.Count; c++)
        {
            var length = _chunks[c].Transforms.Length;
            for (var start = 0; start < length; start += SegmentSize)
            {
                _segments.Add((c, start, Math.Min(SegmentSize, length - start)));
            }
        }

        Parallel.For(0, _segments.Count, i =>
        {
            var (chunk, start, length) = _segments[i];
            Move(_chunks[chunk].Transforms, _chunks[chunk].Velocities, start, length, delta);
        });
    }

    private void Move(Chunk<Transform2D> transforms, Chunk<Velocity> velocities, int start, int length, float delta)
    {
        var t = transforms.Span.Slice(start, length);
        var v = velocities.Span.Slice(start, length);
        for (var i = 0; i < t.Length; i++)
        {
            ref var position = ref t[i].Position;
            ref var velocity = ref v[i].Value;
            position += velocity * delta;

            if (position.X < bounds.Left || position.X > bounds.Right)
            {
                velocity.X = -velocity.X;
                position.X = Math.Clamp(position.X, bounds.Left, bounds.Right);
            }

            if (position.Y < bounds.Top || position.Y > bounds.Bottom)
            {
                velocity.Y = -velocity.Y;
                position.Y = Math.Clamp(position.Y, bounds.Top, bounds.Bottom);
            }
        }
    }
}

/// <summary>Пауза (P), музыка (M), переключение сцены с переходом (Tab).</summary>
public sealed class SceneHotkeysSystem(
    EngineContext context, ActionMap<SampleAction> actions, Func<Scene> nextScene, Transition transition) : BaseSystem
{
    protected override void OnUpdateGroup()
    {
        if (context.Services.Get<MrGameEng.DevConsole.DevConsole>().IsOpen)
        {
            return;
        }

        if (actions.IsPressed(SampleAction.Pause))
        {
            context.Clock.TimeScale = context.Clock.TimeScale > 0f ? 0f : 1f;
        }

        if (actions.IsPressed(SampleAction.ToggleMusic))
        {
            var music = context.Services.Get<AudioManager>().Music;
            if (music.IsPlaying)
            {
                music.Pause();
            }
            else
            {
                music.Resume();
            }
        }

        if (actions.IsPressed(SampleAction.SwitchScene) && !context.Scenes.IsTransitioning)
        {
            context.Scenes.Switch(nextScene(), transition);
        }
    }
}

/// <summary>FPS и статистика рендера: в HUD-лейбл и в заголовок окна (4 раза в секунду).</summary>
public sealed class StatsSystem(
    EngineContext context, Renderer2D renderer, string sceneName, Myra.Graphics2D.UI.Label? hudLabel = null) : BaseSystem
{
    private float _accumulated;
    private int _frames;

    protected override void OnUpdateGroup()
    {
        _accumulated += context.Clock.UnscaledDeltaTime;
        _frames++;
        if (_accumulated < 0.25f)
        {
            return;
        }

        var fps = _frames / _accumulated;
        _accumulated = 0f;
        _frames = 0;
        var stats =
            $"{fps:F0} FPS | sprites: {renderer.SubmittedSprites} | culled: {renderer.CulledSprites} | draw calls: {renderer.DrawCalls}";
        context.Services.Get<GameWindow>().Title = $"MrGameEng Sample — {sceneName} | {stats}";
        if (hudLabel is not null)
        {
            hudLabel.Text =
                $"{sceneName}\n{stats}\n" +
                $"submit {renderer.SubmitMs:F2} | sort {renderer.SortMs:F2} | build {renderer.BuildMs:F2} | " +
                $"upload {renderer.UploadMs:F2} | draw {renderer.DrawMs:F2} (ms)";
        }
    }
}

/// <summary>Общая настройка ввода для сцен сэмпла.</summary>
public static class SampleInput
{
    public static ActionMap<SampleAction> CreateActions(InputManager input) =>
        new ActionMap<SampleAction>(input)
            .Bind(SampleAction.MoveLeft, Keys.A)
            .Bind(SampleAction.MoveLeft, Keys.Left)
            .Bind(SampleAction.MoveRight, Keys.D)
            .Bind(SampleAction.MoveRight, Keys.Right)
            .Bind(SampleAction.MoveUp, Keys.W)
            .Bind(SampleAction.MoveUp, Keys.Up)
            .Bind(SampleAction.MoveDown, Keys.S)
            .Bind(SampleAction.MoveDown, Keys.Down)
            .Bind(SampleAction.Jump, Keys.Space)
            .Bind(SampleAction.Pause, Keys.P)
            .Bind(SampleAction.ToggleMusic, Keys.M)
            .Bind(SampleAction.SwitchScene, Keys.Tab);
}