Add production-ready shell features: tab completion, aliases, history search, chaining, and redirection

Commands/AboutCommand.cs

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+using NShell.Shell;
+using NShell.Shell.Commands;
+using Spectre.Console;
+
+namespace NShell.Commands;
+
+public class AboutCommand : ICustomCommand, IMetadataCommand
+{
+    public string Name => "about";
+    public string Description => "Display information about NShell.";
+
+    public void Execute(ShellContext context, string[] args)
+    {
+        AnsiConsole.Clear();
+
+        var panel = new Panel(new Markup(
+            $"[bold cyan]NShell[/] - A Custom C# Interactive Shell\n\n" +
+            $"[grey]Version:[/] [yellow]{Program.VERSION}[/]\n" +
+            $"[grey]GitHub:[/] [blue]{Program.GITHUB}[/]\n\n" +
+            $"[grey]Runtime:[/] [green].NET {Environment.Version}[/]\n" +
+            $"[grey]Platform:[/] [green]{Environment.OSVersion}[/]\n\n" +
+            $"[dim]Type [yellow]help[/] to see available commands.[/]"
+        ))
+        {
+            Header = new PanelHeader("[bold green] About NShell [/]"),
+            Border = BoxBorder.Rounded
+        };
+
+        AnsiConsole.Write(panel);
+        Console.WriteLine();
+    }
+}

Commands/AliasCommand.cs

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+using NShell.Shell;
+using NShell.Shell.Commands;
+using NShell.Shell.Config;
+using Spectre.Console;
+
+namespace NShell.Commands;
+
+public class AliasCommand : ICustomCommand, IMetadataCommand
+{
+    public string Name => "alias";
+    public string Description => "Create command aliases (e.g., alias ll='ls -la').";
+
+    // Static dictionary to store aliases
+    public static Dictionary<string, string> Aliases { get; } = new Dictionary<string, string>();
+    private static readonly ConfigManager _configManager = new ConfigManager();
+
+    static AliasCommand()
+    {
+        // Load saved aliases on first use
+        var savedAliases = _configManager.LoadAliases();
+        foreach (var alias in savedAliases)
+        {
+            Aliases[alias.Key] = alias.Value;
+        }
+    }
+
+    public void Execute(ShellContext context, string[] args)
+    {
+        if (args.Length == 0)
+        {
+            // List all aliases
+            if (Aliases.Count == 0)
+            {
+                AnsiConsole.MarkupLine("[[[yellow]*[/]]] - No aliases defined.");
+                return;
+            }
+
+            AnsiConsole.MarkupLine("[bold cyan]Current Aliases:[/]\n");
+            foreach (var alias in Aliases.OrderBy(a => a.Key))
+            {
+                AnsiConsole.MarkupLine($"[yellow]{alias.Key}[/]=[green]'{alias.Value}'[/]");
+            }
+            return;
+        }
+
+        // Join all args to handle aliases with spaces
+        var fullArg = string.Join(' ', args);
+        var parts = fullArg.Split('=', 2);
+
+        if (parts.Length != 2)
+        {
+            AnsiConsole.MarkupLine("[[[yellow]*[/]]] - Usage: alias name='command'");
+            return;
+        }
+
+        string aliasName = parts[0].Trim();
+        string aliasValue = parts[1].Trim();
+
+        // Remove quotes if present
+        if ((aliasValue.StartsWith("\"") && aliasValue.EndsWith("\"")) ||
+            (aliasValue.StartsWith("'") && aliasValue.EndsWith("'")))
+        {
+            aliasValue = aliasValue.Substring(1, aliasValue.Length - 2);
+        }
+
+        Aliases[aliasName] = aliasValue;
+        _configManager.SaveAliases(Aliases);
+        AnsiConsole.MarkupLine($"[[[green]+[/]]] - Alias created: [yellow]{aliasName}[/]=[green]'{aliasValue}'[/]");
+    }
+}

Commands/ClearCommand.cs

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+using NShell.Shell;
+using NShell.Shell.Commands;
+using Spectre.Console;
+
+namespace NShell.Commands;
+
+public class ClearCommand : ICustomCommand, IMetadataCommand
+{
+    public string Name => "clear";
+    public string Description => "Clear the terminal screen.";
+
+    public void Execute(ShellContext context, string[] args)
+    {
+        AnsiConsole.Clear();
+    }
+}

Commands/ExitCommand.cs

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+using NShell.Shell;
+using NShell.Shell.Commands;
+using Spectre.Console;
+
+namespace NShell.Commands;
+
+public class ExitCommand : ICustomCommand, IMetadataCommand
+{
+    public string Name => "exit";
+    public string Description => "Exit the shell.";
+
+    public void Execute(ShellContext context, string[] args)
+    {
+        // Save history before exiting
+        Shell.Readline.ReadLine.History.Save();
+
+        AnsiConsole.MarkupLine("[bold green]Goodbye![/]");
+        Environment.Exit(0);
+    }
+}

Commands/ExportCommand.cs

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+using NShell.Shell;
+using NShell.Shell.Commands;
+using Spectre.Console;
+
+namespace NShell.Commands;
+
+public class ExportCommand : ICustomCommand, IMetadataCommand
+{
+    public string Name => "export";
+    public string Description => "Set environment variables (e.g., export VAR=value).";
+
+    public void Execute(ShellContext context, string[] args)
+    {
+        if (args.Length == 0)
+        {
+            // Display all environment variables
+            var envVars = Environment.GetEnvironmentVariables();
+            var sortedKeys = envVars.Keys.Cast<string>().OrderBy(k => k);
+
+            foreach (var key in sortedKeys)
+            {
+                AnsiConsole.MarkupLine($"[cyan]{key}[/]=[yellow]{envVars[key]}[/]");
+            }
+            return;
+        }
+
+        foreach (var arg in args)
+        {
+            var parts = arg.Split('=', 2);
+            if (parts.Length != 2)
+            {
+                AnsiConsole.MarkupLine($"[[[yellow]*[/]]] - Invalid format: {arg}. Use: export VAR=value");
+                continue;
+            }
+
+            string varName = parts[0].Trim();
+            string varValue = parts[1].Trim();
+
+            // Remove quotes if present
+            if ((varValue.StartsWith("\"") && varValue.EndsWith("\"")) ||
+                (varValue.StartsWith("'") && varValue.EndsWith("'")))
+            {
+                varValue = varValue.Substring(1, varValue.Length - 2);
+            }
+
+            Environment.SetEnvironmentVariable(varName, varValue);
+            AnsiConsole.MarkupLine($"[[[green]+[/]]] - Set [cyan]{varName}[/]=[yellow]{varValue}[/]");
+        }
+    }
+}

Commands/HelpCommand.cs

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+using NShell.Shell;
+using NShell.Shell.Commands;
+using Spectre.Console;
+
+namespace NShell.Commands;
+
+public class HelpCommand : ICustomCommand, IMetadataCommand
+{
+    public string Name => "help";
+    public string Description => "Display help information about available commands.";
+
+    public void Execute(ShellContext context, string[] args)
+    {
+        AnsiConsole.MarkupLine("[bold cyan]NShell - Available Commands[/]\n");
+
+        var table = new Table();
+        table.AddColumn("[bold]Command[/]");
+        table.AddColumn("[bold]Description[/]");
+
+        // Add custom commands with descriptions
+        foreach (var cmd in CommandParser.CustomCommands.Values.OrderBy(c => c.Name))
+        {
+            string description = "No description available";
+            if (cmd is IMetadataCommand metaCmd)
+            {
+                description = metaCmd.Description;
+            }
+
+            table.AddRow($"[yellow]{cmd.Name}[/]", description);
+        }
+
+        AnsiConsole.Write(table);
+
+        AnsiConsole.MarkupLine($"\n[grey]Total custom commands: {CommandParser.CustomCommands.Count}[/]");
+        AnsiConsole.MarkupLine($"[grey]Total system commands: {CommandParser.SystemCommands.Count}[/]");
+        AnsiConsole.MarkupLine("\n[grey]Type a command name to execute it, or use Tab for auto-completion.[/]");
+    }
+}

Commands/HistoryCommand.cs

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+using NShell.Shell;
+using NShell.Shell.Commands;
+using NShell.Shell.Readline;
+using Spectre.Console;
+
+namespace NShell.Commands;
+
+public class HistoryCommand : ICustomCommand, IMetadataCommand
+{
+    public string Name => "history";
+    public string Description => "Display command history.";
+
+    public void Execute(ShellContext context, string[] args)
+    {
+        int displayCount = 20; // Default to last 20 commands
+        int historyCount = ReadLine.History.Count;
+
+        if (args.Length > 0)
+        {
+            if (args[0] == "-c" || args[0] == "--clear")
+            {
+                // Clear history - not implemented as it would require HistoryManager changes
+                AnsiConsole.MarkupLine("[[[yellow]*[/]]] - History clearing not yet implemented.");
+                return;
+            }
+            else if (int.TryParse(args[0], out int count))
+            {
+                displayCount = count;
+            }
+            else
+            {
+                AnsiConsole.MarkupLine("[[[yellow]*[/]]] - Usage: history [number] or history -c");
+                return;
+            }
+        }
+
+        // Display the last N commands
+        int startIndex = Math.Max(0, historyCount - displayCount);
+
+        if (historyCount == 0)
+        {
+            AnsiConsole.MarkupLine("[[[yellow]*[/]]] - No commands in history.");
+            return;
+        }
+
+        AnsiConsole.MarkupLine($"[bold cyan]Command History (last {Math.Min(displayCount, historyCount)} commands):[/]\n");
+
+        for (int i = startIndex; i < historyCount; i++)
+        {
+            var command = ReadLine.History.GetAt(i);
+            if (command != null)
+            {
+                AnsiConsole.MarkupLine($"  [grey]{i + 1,4}[/]  {command}");
+            }
+        }
+    }
+}

Commands/PrintEnvCommand.cs

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+using NShell.Shell;
+using NShell.Shell.Commands;
+using Spectre.Console;
+
+namespace NShell.Commands;
+
+public class PrintEnvCommand : ICustomCommand, IMetadataCommand
+{
+    public string Name => "printenv";
+    public string Description => "Print environment variables.";
+
+    public void Execute(ShellContext context, string[] args)
+    {
+        if (args.Length == 0)
+        {
+            // Display all environment variables
+            var envVars = Environment.GetEnvironmentVariables();
+            var sortedKeys = envVars.Keys.Cast<string>().OrderBy(k => k);
+
+            foreach (var key in sortedKeys)
+            {
+                AnsiConsole.MarkupLine($"[cyan]{key}[/]=[yellow]{envVars[key]}[/]");
+            }
+        }
+        else
+        {
+            // Display specific environment variables
+            foreach (var varName in args)
+            {
+                var value = Environment.GetEnvironmentVariable(varName);
+                if (value != null)
+                {
+                    AnsiConsole.MarkupLine($"[cyan]{varName}[/]=[yellow]{value}[/]");
+                }
+                else
+                {
+                    AnsiConsole.MarkupLine($"[[[yellow]*[/]]] - Variable [cyan]{varName}[/] is not set.");
+                }
+            }
+        }
+    }
+}