Add support for fake input in asciicast recordings

* Fixes a bug with `SelectionPrompt` and page size.
* Allow `IAnsiConsoleInput` to return `null`.

resources/scripts/Generator/Commands/AsciiCast/AsciiCastInput.cs

@@ -0,0 +1,81 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using Spectre.Console;
+
+namespace Generator.Commands
+{
+    public sealed class AsciiCastInput : IAnsiConsoleInput
+    {
+        private readonly Queue<(ConsoleKeyInfo?, int)> _input;
+        private readonly Random _random = new Random();
+
+        public AsciiCastInput()
+        {
+            _input = new Queue<(ConsoleKeyInfo?, int)>();
+        }
+
+        public void PushText(string input, int keypressDelayMs)
+        {
+            if (input is null)
+            {
+                throw new ArgumentNullException(nameof(input));
+            }
+
+            foreach (var character in input)
+            {
+                PushCharacter(character, keypressDelayMs);
+            }
+        }
+
+        public void PushTextWithEnter(string input, int keypressDelayMs)
+        {
+            PushText(input, keypressDelayMs);
+            PushKey(ConsoleKey.Enter, keypressDelayMs);
+        }
+
+        public void PushCharacter(char input, int keypressDelayMs)
+        {
+            var delay = keypressDelayMs + _random.Next((int)(keypressDelayMs * -.2), (int)(keypressDelayMs * .2));
+
+            switch (input)
+            {
+                case '↑':
+                    PushKey(ConsoleKey.UpArrow, keypressDelayMs);
+                    break;
+                case '↓':
+                    PushKey(ConsoleKey.DownArrow, keypressDelayMs);
+                    break;
+                case '↲':
+                    PushKey(ConsoleKey.Enter, keypressDelayMs);
+                    break;
+                case '¦':
+                    _input.Enqueue((null, delay));
+                    break;
+                default:
+                    var control = char.IsUpper(input);
+                    _input.Enqueue((new ConsoleKeyInfo(input, (ConsoleKey)input, false, false, control), delay));
+                    break;
+            }
+        }
+
+        public void PushKey(ConsoleKey input, int keypressDelayMs)
+        {
+            var delay = keypressDelayMs + _random.Next((int)(keypressDelayMs * -.2), (int)(keypressDelayMs * .2));
+            _input.Enqueue((new ConsoleKeyInfo((char)input, input, false, false, false), delay));
+        }
+
+        public ConsoleKeyInfo? ReadKey(bool intercept)
+        {
+            if (_input.Count == 0)
+            {
+                throw new InvalidOperationException("No input available.");
+            }
+
+            var result = _input.Dequeue();
+
+            Thread.Sleep(result.Item2);
+            return result.Item1;
+        }
+    }
+}