Convert the :navigation cluster to command types (#392)

src/Fallout.Cli/Commands/Navigation/GetNextDirectoryCommand.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Linq;
+using Fallout.Common;
+using Fallout.Common.IO;
+
+namespace Fallout.Cli.Commands.Navigation;
+
+/// <summary><c>fallout :GetNextDirectory</c>: prints (and consumes) the queued next directory.</summary>
+public sealed class GetNextDirectoryCommand : IFalloutCommand
+{
+    public string Name => "GetNextDirectory";
+
+    public int Execute(string[] args, AbsolutePath rootDirectory, AbsolutePath buildScript)
+    {
+        var content = NavigationSession.SessionFile.Existing()?.ReadAllLines();
+        if (content == null || string.IsNullOrWhiteSpace(content[0]))
+        {
+            Console.WriteLine(EnvironmentInfo.WorkingDirectory);
+            return 1;
+        }
+
+        var nextDirectory = content[0];
+        content[0] = string.Empty;
+        NavigationSession.SessionFile.WriteAllLines(content);
+        Console.WriteLine(nextDirectory);
+        return 0;
+    }
+}

src/Fallout.Cli/Commands/Navigation/NavigationSession.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Fallout.Common;
+using Fallout.Common.IO;
+using Fallout.Common.Utilities;
+using static Fallout.Common.Constants;
+
+namespace Fallout.Cli.Commands.Navigation;
+
+/// <summary>
+/// Shared per-terminal-session state for the directory-navigation commands. The companion shell
+/// functions invoke the commands by name (preserved on conversion):
+/// <code>
+/// function nuke- { nuke :PopDirectory; cd $(nuke :GetNextDirectory) }
+/// function nuke/ { nuke :PushWithChosenRootDirectory; cd $(nuke :GetNextDirectory) }
+/// function nuke. { nuke :PushWithCurrentRootDirectory; cd $(nuke :GetNextDirectory) }
+/// function nuke.. { nuke :PushWithParentRootDirectory; cd $(nuke :GetNextDirectory) }
+/// </code>
+/// </summary>
+internal static class NavigationSession
+{
+    public static string SessionId
+        => EnvironmentInfo.Platform switch
+        {
+            PlatformFamily.OSX => EnvironmentInfo.GetVariable("TERM_SESSION_ID").NotNull()[7..],
+            PlatformFamily.Windows => EnvironmentInfo.GetVariable("WT_SESSION").NotNull(),
+            _ => throw new NotSupportedException($"{EnvironmentInfo.Platform} has no session id selector.")
+        };
+
+    public static AbsolutePath SessionFile => GlobalTemporaryDirectory / $"nuke-{SessionId}.dat";
+
+    public static int PushAndSetNext(Func<string> directoryProvider)
+    {
+        try
+        {
+            var content = SessionFile.Existing()?.ReadAllLines().ToList() ?? new List<string> { null };
+            content[0] = directoryProvider.Invoke();
+            content.Insert(index: 1, EnvironmentInfo.WorkingDirectory);
+            SessionFile.WriteAllLines(content);
+            return 0;
+        }
+        catch (Exception exception)
+        {
+            Console.Error.WriteLine(exception.Message);
+            return 1;
+        }
+    }
+}

src/Fallout.Cli/Commands/Navigation/PopDirectoryCommand.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Linq;
+using Fallout.Common.IO;
+
+namespace Fallout.Cli.Commands.Navigation;
+
+/// <summary><c>fallout :PopDirectory</c>: pops the previous directory back to the front of the queue.</summary>
+public sealed class PopDirectoryCommand : IFalloutCommand
+{
+    public string Name => "PopDirectory";
+
+    public int Execute(string[] args, AbsolutePath rootDirectory, AbsolutePath buildScript)
+    {
+        var content = NavigationSession.SessionFile.Existing()?.ReadAllLines().ToList();
+        if (content == null || content.Count <= 1)
+        {
+            Console.Error.WriteLine("No previous directory");
+            return 1;
+        }
+
+        content[0] = content[1];
+        content.RemoveAt(1);
+        NavigationSession.SessionFile.WriteAllLines(content);
+        return 0;
+    }
+}

src/Fallout.Cli/Commands/Navigation/PushWithChosenRootDirectoryCommand.cs

@@ -0,0 +1,34 @@
+using System.Linq;
+using Fallout.Cli.Prompts;
+using Fallout.Common;
+using Fallout.Common.IO;
+using static Fallout.Common.Constants;
+
+namespace Fallout.Cli.Commands.Navigation;
+
+/// <summary>
+/// <c>fallout :PushWithChosenRootDirectory</c>: prompts for a discovered root directory and queues it.
+/// </summary>
+public sealed class PushWithChosenRootDirectoryCommand : IFalloutCommand
+{
+    private readonly IConsolePrompts _prompts;
+
+    public PushWithChosenRootDirectoryCommand(IConsolePrompts prompts) => _prompts = prompts;
+
+    public string Name => "PushWithChosenRootDirectory";
+
+    public int Execute(string[] args, AbsolutePath rootDirectory, AbsolutePath buildScript)
+    {
+        return NavigationSession.PushAndSetNext(() =>
+        {
+            var directories = EnvironmentInfo.WorkingDirectory.GlobDirectories($"**/{FalloutDirectoryName}")
+                .Concat(EnvironmentInfo.WorkingDirectory.GlobFiles($"**/{FalloutDirectoryName}"))
+                .Where(x => !x.Equals(EnvironmentInfo.WorkingDirectory))
+                .Select(x => x.Parent)
+                .Select(x => (x, EnvironmentInfo.WorkingDirectory.GetRelativePathTo(x).ToString()))
+                .OrderBy(x => x.Item2).ToArray();
+
+            return _prompts.PromptForChoice("Where to go next?", directories);
+        });
+    }
+}

src/Fallout.Cli/Commands/Navigation/PushWithCurrentRootDirectoryCommand.cs

@@ -0,0 +1,16 @@
+using Fallout.Common;
+using Fallout.Common.IO;
+using Fallout.Common.Utilities;
+
+namespace Fallout.Cli.Commands.Navigation;
+
+/// <summary><c>fallout :PushWithCurrentRootDirectory</c>: queues the current root directory.</summary>
+public sealed class PushWithCurrentRootDirectoryCommand : IFalloutCommand
+{
+    public string Name => "PushWithCurrentRootDirectory";
+
+    public int Execute(string[] args, AbsolutePath rootDirectory, AbsolutePath buildScript)
+    {
+        return NavigationSession.PushAndSetNext(() => rootDirectory.NotNull("No root directory"));
+    }
+}

src/Fallout.Cli/Commands/Navigation/PushWithParentRootDirectoryCommand.cs

@@ -0,0 +1,19 @@
+using System.IO;
+using Fallout.Common;
+using Fallout.Common.IO;
+using Fallout.Common.Utilities;
+using static Fallout.Common.Constants;
+
+namespace Fallout.Cli.Commands.Navigation;
+
+/// <summary><c>fallout :PushWithParentRootDirectory</c>: queues the parent repository's root directory.</summary>
+public sealed class PushWithParentRootDirectoryCommand : IFalloutCommand
+{
+    public string Name => "PushWithParentRootDirectory";
+
+    public int Execute(string[] args, AbsolutePath rootDirectory, AbsolutePath buildScript)
+    {
+        return NavigationSession.PushAndSetNext(() => TryGetRootDirectoryFrom(Path.GetDirectoryName(rootDirectory.NotNull("No root directory")))
+            .NotNull("No parent root directory"));
+    }
+}

src/Fallout.Cli/Program.cs

@@ -71,11 +71,14 @@ private static void RegisterCommands(IServiceCollection services)
 
         // Legacy handlers still living on Program, adapted until they are extracted into command
         // types. Each conversion deletes one line here plus its Program.X.cs partial.
-        services.AddSingleton<IFalloutCommand>(new DelegateCommand("GetNextDirectory", GetNextDirectory));
-        services.AddSingleton<IFalloutCommand>(new DelegateCommand("PopDirectory", PopDirectory));
-        services.AddSingleton<IFalloutCommand>(new DelegateCommand("PushWithCurrentRootDirectory", PushWithCurrentRootDirectory));
-        services.AddSingleton<IFalloutCommand>(new DelegateCommand("PushWithParentRootDirectory", PushWithParentRootDirectory));
-        services.AddSingleton<IFalloutCommand>(new DelegateCommand("PushWithChosenRootDirectory", PushWithChosenRootDirectory));
+        services.AddSingleton<IFalloutCommand, Commands.Navigation.GetNextDirectoryCommand>();
+        services.AddSingleton<IFalloutCommand, Commands.Navigation.PopDirectoryCommand>();
+        services.AddSingleton<IFalloutCommand, Commands.Navigation.PushWithCurrentRootDirectoryCommand>();
+        services.AddSingleton<IFalloutCommand, Commands.Navigation.PushWithParentRootDirectoryCommand>();
+        services.AddSingleton<IFalloutCommand, Commands.Navigation.PushWithChosenRootDirectoryCommand>();
+
+        // Legacy handlers still living on Program, adapted until they are extracted into command
+        // types. Each conversion deletes one line here plus its Program.X.cs partial.
     }
 
     internal static void PrintInfo()