PongFE/PongFE/Engines/GameStateEngine.cs

using Encompass;
using Microsoft.Xna.Framework.Input;
using MoonTools.Structs;
using PongFE.Components;
using PongFE.Enums;
using PongFE.Messages;
using SpriteFontPlus;

namespace PongFE.Engines
{
    [Reads(
        typeof(PositionComponent),
        typeof(GameStateComponent),
        typeof(PlayAreaComponent),
        typeof(UITextComponent)
    )]
    [Receives(typeof(ChangeGameStateMessage))]
    [Sends(
        typeof(BallSpawnMessage),
        typeof(PaddleSpawnMessage),
        typeof(BoundarySpawnMessage),
        typeof(GoalBoundarySpawnMessage),
        typeof(UITextSpawnMessage)
    )]
    [Writes(typeof(GameStateComponent))]
    public class GameStateEngine : Engine
    {
        private DynamicSpriteFont TitleFont { get; }
        private DynamicSpriteFont InstructionFont { get; }

        public GameStateEngine(DynamicSpriteFont titleFont, DynamicSpriteFont instructionFont)
        {
            TitleFont = titleFont;
            InstructionFont = instructionFont;
        }

        public override void Update(double dt)
        {
            ref readonly var gameStateEntity = ref ReadEntity<GameStateComponent>();
            ref readonly var gameStateComponent = ref GetComponent<GameStateComponent>(gameStateEntity);

            if (gameStateComponent.GameState == GameState.Title)
            {
                if (Keyboard.GetState().IsKeyDown(Keys.Enter))
                {
                    EndTitle();
                    StartGame();

                    SetComponent(gameStateEntity, new GameStateComponent(GameState.Game));
                }
            }

            if (SomeMessage<ChangeGameStateMessage>())
            {
                ref readonly var changeGameStateMessage = ref ReadMessage<ChangeGameStateMessage>();

                if (changeGameStateMessage.GameState == gameStateComponent.GameState)
                {
                    return;
                }

                if (changeGameStateMessage.GameState == GameState.Title)
                {
                    EndGame();
                    StartTitle();

                    SetComponent(gameStateEntity, new GameStateComponent(GameState.Title));
                }
            }
        }

        private void StartGame()
        {
            ref readonly var playAreaComponent = ref ReadComponent<PlayAreaComponent>();
            var playAreaWidth = playAreaComponent.Width;
            var playAreaHeight = playAreaComponent.Height;

            SendMessage(
                new PaddleSpawnMessage(
                    new MoonTools.Structs.Position2D(20, playAreaHeight / 2 - 40),
                    Enums.PlayerIndex.One,
                    PaddleControl.Player,
                    20,
                    80
                )
            );

            SendMessage(
                new PaddleSpawnMessage(
                    new MoonTools.Structs.Position2D(playAreaWidth - 45, playAreaHeight / 2 - 40),
                    Enums.PlayerIndex.Two,
                    PaddleControl.Computer,
                    20,
                    80
                )
            );

            SendMessage(
                new BallSpawnMessage(
                    new MoonTools.Structs.Position2D(playAreaWidth / 2, playAreaHeight / 2),
                    500,
                    16,
                    16
                ),
                0.5
            );

            // top boundary
            SendMessage(
                new BoundarySpawnMessage(
                    new MoonTools.Structs.Position2D(0, -6),
                    playAreaWidth,
                    6
                )
            );

            // bottom boundary
            SendMessage(
                new BoundarySpawnMessage(
                    new MoonTools.Structs.Position2D(0, playAreaHeight),
                    playAreaWidth,
                    6
                )
            );

            // right boundary
            SendMessage(
                new GoalBoundarySpawnMessage(
                    Enums.PlayerIndex.One,
                    new MoonTools.Structs.Position2D(playAreaWidth, 0),
                    6,
                    playAreaHeight
                )
            );

            // left boundary
            SendMessage(
                new GoalBoundarySpawnMessage(
                    Enums.PlayerIndex.Two,
                    new MoonTools.Structs.Position2D(-6, 0),
                    6,
                    playAreaHeight
                )
            );
        }

        private void EndGame()
        {
            DestroyAllWith<PositionComponent>();
        }

        private void StartTitle()
        {
            ref readonly var playAreaComponent = ref ReadComponent<PlayAreaComponent>();

            var titleDimensions = TitleFont.MeasureString("PongFE");
            var titlePosition = new Position2D(
                (playAreaComponent.Width - titleDimensions.X) / 2,
                (playAreaComponent.Height - titleDimensions.Y) / 4
            );

            SendMessage(new UITextSpawnMessage(
                titlePosition,
                TitleFont,
                "PongFE"
            ));

            var instructionDimensions = InstructionFont.MeasureString("Press Enter to begin");
            var instructionPosition = new Position2D(
                (playAreaComponent.Width - instructionDimensions.X) / 2,
                playAreaComponent.Height * 2 / 3
            );

            SendMessage(new UITextSpawnMessage(
                instructionPosition,
                InstructionFont,
                "Press Enter to play"
            ));
        }

        private void EndTitle()
        {
            DestroyAllWith<UITextComponent>();
        }
    }
}