Pong/Assets/Scripts/GameUI.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Game;
using UnityEngine;
using UnityEngine.UIElements;

public class GameUI : MonoBehaviour {

	public delegate void ButtonDown(Side verticalSide, string horizontalSide);
	public delegate void ButtonUp(Side side, string direction);
	public static GameUI Singleton;
	public ButtonDown buttonDown;
	public ButtonUp buttonUp;

	private UIDocument document;

	private List<VisualElement> PlayerPanels => document.rootVisualElement.Children().Where(e => e.ClassListContains("player_panel")).ToList();

	private void Awake() {
		Singleton = this;
		document = GetComponent<UIDocument>();
		PreparePlayerPanels();
	}

	public VisualElement PlayerPanel(Side side) {
		return side switch {
			Side.Top => PlayerPanels[0],
			Side.Bottom => PlayerPanels[1],
			_ => throw new ArgumentOutOfRangeException(nameof(side), side, null)
		};
	}

	public static VisualElement AddModification(VisualElement playerPanel, ModificationProperties properties) {
		var listElement = ModsList(playerPanel, properties.type);

		VisualElement newElement = new() {
			style = {
				backgroundImage = Background.FromSprite(properties.image)
			}
		};
		listElement.Add(newElement);

		return newElement;
	}

	private static VisualElement ModsList(VisualElement player, ModType type) {
		return type switch {
			ModType.Buff => player.Children().First(e => e.ClassListContains("mods_list")),
			ModType.Nerf => player.Children().Last(e => e.ClassListContains("mods_list")),
			_ => throw new ArgumentOutOfRangeException(nameof(type), type, null)
		};
	}

	private void PreparePlayerPanels() {
		var pixelHeight = Dimensions.Singleton.PanelHeightPixels;
		PlayerPanel(Side.Top).style.height = PlayerPanel(Side.Bottom).style.height = new Length(pixelHeight, LengthUnit.Pixel);

		SetupGoButton(Side.Top, "left");
		SetupGoButton(Side.Top, "right");
		SetupGoButton(Side.Bottom, "left");
		SetupGoButton(Side.Bottom, "right");
	}

	private Label GetGoButton(Side sideVertical, string sideHorizontal) {
		return PlayerPanel(sideVertical).Q<Label>("go_" + sideHorizontal);
	}

	private void SetupGoButton(Side sideVertical, string sideHorizontal) {
		var element = GetGoButton(sideVertical, sideHorizontal);
		element.RegisterCallback<PointerDownEvent>(_ => buttonDown(sideVertical, sideHorizontal));
		element.RegisterCallback<PointerUpEvent>(_ => buttonUp(sideVertical, sideHorizontal));
		element.RegisterCallback<PointerLeaveEvent>(_ => buttonUp(sideVertical, sideHorizontal));
	}
}