using Friflo.Engine.ECS.Systems;
using MrGameEng.Core;

namespace MrGameEng.Input;

/// <summary>Polls the <see cref="InputManager"/> once per frame. Registered first in the update phase.</summary>
public sealed class InputSystem : BaseSystem
{
    private readonly InputManager _input;

    /// <summary>Creates the system for <paramref name="input"/>.</summary>
    public InputSystem(InputManager input) => _input = input;

    /// <inheritdoc />
    protected override void OnUpdateGroup() => _input.Update();
}

/// <summary>Wires the input module into a <see cref="Scene"/>.</summary>
public static class SceneInputExtensions
{
    /// <summary>
    /// Returns the shared <see cref="InputManager"/> service (creating it on first use) and
    /// inserts <see cref="InputSystem"/> at the start of the scene's update phase.
    /// Call from <c>OnLoad</c> before adding gameplay systems.
    /// </summary>
    public static InputManager UseInput(this Scene scene)
    {
        var services = scene.Context.Services;
        var input = services.GetOrDefault<InputManager>();
        if (input is null)
        {
            var capture = services.GetOrDefault<InputCapture>();
            if (capture is null)
            {
                capture = new InputCapture();
                services.Add(capture);
            }

            input = new InputManager(capture);
            services.Add(input);
        }

        scene.UpdateSystems.Insert(0, new InputSystem(input));
        return input;
    }
}