Adds Snake Scenario (#2353)

* Add empty snake scenario

* Move snake head around

* Snake now has a tail

* Rest of logic implementation

* Ctrl K D layout fixes

* Game gets faster as you collect more apples

* Adjust speed increase rate down

* Use white on black for snake and border and red for apple

* Fix ScenarioTests not Disposing Scenario

* Add disposes and fix to use LineCanvas.GenerateImage

* Fix stack overflow, doh!

---------

Co-authored-by: Tig <[email protected]>

UICatalog/Scenarios/Animation.cs

@@ -71,7 +71,7 @@ namespace UICatalog.Scenarios {
 		protected override void Dispose(bool disposing)
 		{
 			isDisposed = true;
-			base.Dispose();
+			base.Dispose(disposing);
 		}
 
 		// This is a C# port of https://github.com/andraaspar/bitmap-to-braille by Andraaspar

UICatalog/Scenarios/Snake.cs

@@ -0,0 +1,353 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading.Tasks;
+using Terminal.Gui;
+using Terminal.Gui.Graphs;
+using Attribute = Terminal.Gui.Attribute;
+
+namespace UICatalog.Scenarios {
+	[ScenarioMetadata (Name: "Snake", Description: "The game of apple eating.")]
+	[ScenarioCategory ("Colors")]
+	public class Snake : Scenario {
+		private bool isDisposed;
+
+		public override void Setup ()
+		{
+			base.Setup ();
+
+			var state = new SnakeState ();
+
+			state.Reset (60, 20);
+
+			var snakeView = new SnakeView (state) {
+				Width = state.Width,
+				Height = state.Height
+			};
+
+
+			Win.Add (snakeView);
+
+			Stopwatch sw = new Stopwatch ();
+
+			Task.Run (() => {
+				while (!isDisposed) {
+
+					sw.Restart ();
+
+					if (state.AdvanceState ()) {
+
+						// When updating from a Thread/Task always use Invoke
+						Application.MainLoop?.Invoke (() => {
+							snakeView.SetNeedsDisplay ();
+						});
+					}
+
+					var wait = state.SleepAfterAdvancingState - sw.ElapsedMilliseconds;
+
+					if (wait > 0) {
+						Task.Delay ((int)wait).Wait ();
+					}
+				}
+			});
+		}
+
+		protected override void Dispose (bool disposing)
+		{
+			isDisposed = true;
+			base.Dispose (disposing);
+		}
+
+		private class SnakeView : View {
+
+			private Attribute red = new Terminal.Gui.Attribute (Color.Red,Color.Black);
+			private Attribute white = new Terminal.Gui.Attribute (Color.White, Color.Black);
+
+			public SnakeState State { get; }
+
+			public SnakeView (SnakeState state)
+			{
+				State = state;
+				CanFocus = true;
+
+				ColorScheme = new ColorScheme {
+					Normal = white,
+					Focus = white,
+					HotNormal = white,
+					HotFocus = white,
+					Disabled = white
+				};
+			}
+
+			public override void Redraw (Rect bounds)
+			{
+				base.Redraw (bounds);
+
+				Driver.SetAttribute (white);
+				Clear ();
+
+				var canvas = new LineCanvas ();
+
+				canvas.AddLine (new Point (0, 0), State.Width - 1, Orientation.Horizontal, BorderStyle.Double);
+				canvas.AddLine (new Point (0, 0), State.Height - 1, Orientation.Vertical, BorderStyle.Double);
+				canvas.AddLine (new Point (0, State.Height - 1), State.Width - 1, Orientation.Horizontal, BorderStyle.Double);
+				canvas.AddLine (new Point (State.Width - 1, 0), State.Height - 1, Orientation.Vertical, BorderStyle.Double);
+
+				for (int i = 1; i < State.Snake.Count; i++) {
+
+					var pt1 = State.Snake [i - 1];
+					var pt2 = State.Snake [i];
+
+					var orientation = pt1.X == pt2.X ? Orientation.Vertical : Orientation.Horizontal;
+					var length = orientation == Orientation.Horizontal
+						? pt1.X > pt2.X ? 1 : -1
+						: pt1.Y > pt2.Y ? 1 : -1;
+
+					canvas.AddLine (
+						pt2,
+						length,
+						orientation,
+						BorderStyle.Single);
+
+				}
+
+				foreach(var p in canvas.GenerateImage (bounds)) {
+					AddRune (p.Key.X, p.Key.Y, p.Value);
+				}
+
+
+				Driver.SetAttribute (red);
+				AddRune (State.Apple.X, State.Apple.Y, 'A');
+				Driver.SetAttribute (white);
+			}
+			public override bool OnKeyDown (KeyEvent keyEvent)
+			{
+				if (keyEvent.Key == Key.CursorUp) {
+					State.PlannedDirection = Direction.Up;
+					return true;
+				}
+				if (keyEvent.Key == Key.CursorDown) {
+					State.PlannedDirection = Direction.Down;
+					return true;
+				}
+				if (keyEvent.Key == Key.CursorLeft) {
+					State.PlannedDirection = Direction.Left;
+					return true;
+				}
+				if (keyEvent.Key == Key.CursorRight) {
+					State.PlannedDirection = Direction.Right;
+					return true;
+				}
+
+				return false;
+			}
+		}
+		private class SnakeState {
+
+			public const int StartingLength = 10;
+			public const int AppleGrowRate = 5;
+			public const int StartingSpeed = 50;
+			public const int MaxSpeed = 20;
+
+			public int Width { get; private set; }
+			public int Height { get; private set; }
+
+			/// <summary>
+			/// Position of the snakes head
+			/// </summary>
+			public Point Head => Snake.Last ();
+
+			/// <summary>
+			/// Current position of the Apple that the snake has to eat.
+			/// </summary>
+			public Point Apple { get; private set; }
+
+			public Direction CurrentDirection { get; private set; }
+			public Direction PlannedDirection { get; set; }
+
+			public List<Point> Snake { get; private set; }
+
+			public int SleepAfterAdvancingState { get; private set; } = StartingSpeed;
+
+			int step;
+
+			internal bool AdvanceState ()
+			{
+				step++;
+
+				if (step < GetStepVelocity ()) {
+					return false;
+				}
+
+				step = 0;
+
+				UpdateDirection ();
+
+				var newHead = GetNewHeadPoint ();
+
+				Snake.RemoveAt (0);
+				Snake.Add (newHead);
+
+				if (IsDeath (newHead)) {
+					GameOver ();
+				}
+
+				if (newHead == Apple) {
+					GrowSnake (AppleGrowRate);
+					Apple = GetNewRandomApplePoint ();
+
+					var delta = 5;
+					if(SleepAfterAdvancingState < 40) {
+						delta = 3;
+					}
+					if (SleepAfterAdvancingState < 30) {
+						delta = 2;
+					}
+					SleepAfterAdvancingState = Math.Max (MaxSpeed, SleepAfterAdvancingState - delta);
+				}
+
+				return true;
+			}
+
+			private int GetStepVelocity ()
+			{
+				if (CurrentDirection == Direction.Left || CurrentDirection == Direction.Right) {
+					return 1;
+				}
+
+				return 2;
+			}
+
+			public void GrowSnake ()
+			{
+				var tail = Snake.First ();
+				Snake.Insert (0, tail);
+			}
+			public void GrowSnake (int amount)
+			{
+				for (int i = 0; i < amount; i++) {
+					GrowSnake ();
+				}
+			}
+
+			private void UpdateDirection ()
+			{
+				if (!AreOpposites (CurrentDirection, PlannedDirection)) {
+					CurrentDirection = PlannedDirection;
+				}
+			}
+
+			private bool AreOpposites (Direction a, Direction b)
+			{
+				switch (a) {
+				case Direction.Left: return b == Direction.Right;
+				case Direction.Right: return b == Direction.Left;
+				case Direction.Up: return b == Direction.Down;
+				case Direction.Down: return b == Direction.Up;
+				}
+
+				return false;
+			}
+
+			private void GameOver ()
+			{
+				Reset (Width, Height);
+			}
+
+			private Point GetNewHeadPoint ()
+			{
+				switch (CurrentDirection) {
+				case Direction.Left:
+					return new Point (Head.X - 1, Head.Y);
+
+				case Direction.Right:
+					return new Point (Head.X + 1, Head.Y);
+
+				case Direction.Up:
+					return new Point (Head.X, Head.Y - 1);
+
+				case Direction.Down:
+					return new Point (Head.X, Head.Y + 1);
+				}
+
+				throw new Exception ("Unknown direction");
+			}
+
+			/// <summary>
+			/// Restarts the game with the given canvas size
+			/// </summary>
+			/// <param name="width"></param>
+			/// <param name="height"></param>
+			internal void Reset (int width, int height)
+			{
+				if (width < 5 || height < 5) {
+					return;
+				}
+
+				Width = width;
+				Height = height;
+
+				var middle = new Point (width / 2, height / 2);
+
+				// Start snake with a length of 2
+				Snake = new List<Point> { middle, middle };
+				Apple = GetNewRandomApplePoint ();
+
+				SleepAfterAdvancingState = StartingSpeed;
+
+				GrowSnake (StartingLength);
+			}
+
+			private Point GetNewRandomApplePoint ()
+			{
+				Random r = new Random ();
+
+				for (int i = 0; i < 1000; i++) {
+					var x = r.Next (0, Width);
+					var y = r.Next (0, Height);
+
+					var p = new Point (x, y);
+
+					if (p == Head) {
+						continue;
+					}
+
+					if (IsDeath (p)) {
+						continue;
+					}
+
+					return p;
+				}
+
+				// Game is won or we are unable to generate a valid apple
+				// point after 1000 attempts.  Maybe screen size is very small
+				// or something.  Either way restart the game.
+				Reset (Width, Height);
+				return Apple;
+			}
+
+			private bool IsDeath (Point p)
+			{
+				if (p.X <= 0 || p.X >= Width - 1) {
+					return true;
+				}
+
+				if (p.Y <= 0 || p.Y >= Height - 1) {
+					return true;
+				}
+
+				if (Snake.Take (Snake.Count - 1).Contains (p))
+					return true;
+
+				return false;
+			}
+		}
+		private enum Direction {
+			Up,
+			Down,
+			Left,
+			Right
+		}
+	}
+}

UICatalog/UICatalog.cs

@@ -72,6 +72,7 @@ namespace UICatalog {
 				_selectedScenario.Init (_colorScheme);
 				_selectedScenario.Setup ();
 				_selectedScenario.Run ();
+				_selectedScenario.Dispose ();
 				_selectedScenario = null;
 				Application.Shutdown ();
 				return;
@@ -95,6 +96,7 @@ namespace UICatalog {
 				scenario.Init (_colorScheme);
 				scenario.Setup ();
 				scenario.Run ();
+				scenario.Dispose ();
 
 				// This call to Application.Shutdown brackets the Application.Init call
 				// made by Scenario.Init() above

UnitTests/UICatalog/ScenarioTests.cs

@@ -69,6 +69,9 @@ namespace UICatalog.Tests {
 				scenario.Init (Colors.Base);
 				scenario.Setup ();
 				scenario.Run ();
+
+				scenario.Dispose();
+
 				Application.Shutdown ();
 #if DEBUG_IDISPOSABLE
 				foreach (var inst in Responder.Instances) {
@@ -136,6 +139,8 @@ namespace UICatalog.Tests {
 			// Using variable in the left side of Assert.Equal/NotEqual give error. Must be used literals values.
 			//Assert.Equal (stackSize, iterations);
 
+			generic.Dispose();
+
 			// Shutdown must be called to safely clean up Application if Init has been called
 			Application.Shutdown ();