WIP - next step: update 'GenerateRender'

Author: daxian-dbw

PSReadLine/BasicEditing.cs

@@ -31,30 +31,33 @@ public static void SelfInsert(ConsoleKeyInfo? key = null, object arg = null)
             {
                 if (count <= 0)
                     return;
-                if (count > 1)
-                {
-                    var toInsert = new string(keyChar, count);
-                    if (_singleton._visualSelectionCommandCount > 0)
-                    {
-                        _singleton.GetRegion(out var start, out var length);
-                        Replace(start, length, toInsert);
-                    }
-                    else
-                    {
-                        Insert(toInsert);
-                    }
-                    return;
-                }
+            }
+            else
+            {
+                count = 1;
             }
 
-            if (_singleton._visualSelectionCommandCount > 0)
+            try
             {
-                _singleton.GetRegion(out var start, out var length);
-                Replace(start, length, new string(keyChar, 1));
+                _singleton._showSuggestion = true;
+
+                if (_singleton._visualSelectionCommandCount > 0)
+                {
+                    _singleton.GetRegion(out var start, out var length);
+                    Replace(start, length, new string(keyChar, count));
+                }
+                else if (count > 1)
+                {
+                    Insert(new string(keyChar, count));
+                }
+                else
+                {
+                    Insert(keyChar);
+                }
             }
-            else
+            finally
             {
-                Insert(keyChar);
+                _singleton._showSuggestion = false;
             }
         }
 

PSReadLine/DummySuggestion.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+
+namespace Pseudo
+{
+    internal class DummySuggestion
+    {
+        private static readonly Dictionary<string, string> s_suggestions = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+        internal static string GetCommandLineSuggestion(string text)
+        {
+            if (s_suggestions.TryGetValue(text, out string suggestion))
+            {
+                return suggestion;
+            }
+
+            return null;
+        }
+    }
+}

PSReadLine/ReadLine.cs

@@ -63,6 +63,8 @@ public partial class PSConsoleReadLine : IPSConsoleReadLineMockableMethods
 
         private readonly StringBuilder _buffer;
         private readonly StringBuilder _statusBuffer;
+        private string _suggestionText;
+        private bool _showSuggestion;
         private bool _statusIsErrorMessage;
         private string _statusLinePrompt;
         private List<EditItem> _edits;

PSReadLine/Render.cs

@@ -91,6 +91,28 @@ private string ParseInput()
             return text;
         }
 
+        private string GetSuggestion(string text)
+        {
+            if (!_showSuggestion || LineIsMultiLine())
+            {
+                _suggestionText = null;
+            }
+            else
+            {
+                bool reuseSuggestionBuffer =
+                    _suggestionText != null &&
+                    _suggestionText.Length >= text.Length &&
+                    _suggestionText.StartsWith(text, StringComparison.OrdinalIgnoreCase);
+
+                if (!reuseSuggestionBuffer)
+                {
+                    _suggestionText = Pseudo.DummySuggestion.GetCommandLineSuggestion(text);
+                }
+            }
+
+            return _suggestionText == null ? null : _suggestionText.Substring(text.Length);
+        }
+
         private void ClearStatusMessage(bool render)
         {
             _statusBuffer.Clear();
@@ -156,6 +178,7 @@ private void ForceRender()
         private int GenerateRender(string defaultColor)
         {
             var text = ParseInput();
+            var suggestion = GetSuggestion(text);
 
             string color = defaultColor;
             string activeColor = string.Empty;