feat(startup): add configurable game root

engine/Age.Engine/Sys4/GameRootSelection.cs

@@ -0,0 +1,99 @@
+namespace Age.Engine.Sys4;
+
+public enum GameRootSource
+{
+    LaunchArgument,
+    ExecutableDirectory,
+    CurrentDirectory,
+}
+
+/// <summary>
+/// Resolves the installed game's root independently of repository/development paths.
+/// A valid root is anchored by the game's authoritative SYS4INI catalog.
+/// </summary>
+public readonly record struct GameRootSelection(string Root, GameRootSource Source)
+{
+    public const string OptionName = "--game-root";
+
+    public string Sys4IniPath => Path.Combine(Root, "SYS4INI.BIN");
+
+    public string SourceName => Source switch
+    {
+        GameRootSource.LaunchArgument => "launch-argument",
+        GameRootSource.ExecutableDirectory => "executable-directory",
+        GameRootSource.CurrentDirectory => "current-directory",
+        _ => throw new InvalidOperationException($"unknown game-root source: {Source}"),
+    };
+
+    public static GameRootSelection Resolve(
+        IReadOnlyList<string> arguments, string? executablePath, string currentDirectory)
+    {
+        ArgumentNullException.ThrowIfNull(arguments);
+        ArgumentException.ThrowIfNullOrWhiteSpace(currentDirectory);
+
+        string cwd = Path.GetFullPath(currentDirectory);
+        string? overridePath = null;
+        for (int index = 0; index < arguments.Count; index++)
+        {
+            if (arguments[index] != OptionName) continue;
+            if (index + 1 >= arguments.Count || arguments[index + 1].StartsWith("--", StringComparison.Ordinal))
+                throw new ArgumentException($"{OptionName} requires a directory path");
+            overridePath = arguments[++index];
+        }
+
+        if (overridePath != null)
+        {
+            string root = Path.GetFullPath(overridePath, cwd);
+            RequireCatalog(root, $"{OptionName} '{overridePath}'");
+            return new GameRootSelection(root, GameRootSource.LaunchArgument);
+        }
+
+        var candidates = new List<(string Root, GameRootSource Source)>();
+        string? executableDirectory = TryGetExecutableDirectory(executablePath, cwd);
+        if (executableDirectory != null)
+            candidates.Add((executableDirectory, GameRootSource.ExecutableDirectory));
+        if (!candidates.Any(candidate => SamePath(candidate.Root, cwd)))
+            candidates.Add((cwd, GameRootSource.CurrentDirectory));
+
+        foreach ((string root, GameRootSource source) in candidates)
+            if (File.Exists(Path.Combine(root, "SYS4INI.BIN")))
+                return new GameRootSelection(root, source);
+
+        string searched = string.Join(", ", candidates.Select(candidate => $"'{candidate.Root}'"));
+        throw new ArgumentException(
+            $"game root not found: SYS4INI.BIN was not present in {searched}; " +
+            $"pass {OptionName} <directory>");
+    }
+
+    private static string? TryGetExecutableDirectory(string? executablePath, string cwd)
+    {
+        if (string.IsNullOrWhiteSpace(executablePath)) return null;
+        try
+        {
+            return Path.GetDirectoryName(Path.GetFullPath(executablePath, cwd));
+        }
+        catch (Exception error) when (
+            error is ArgumentException or NotSupportedException or PathTooLongException)
+        {
+            return null;
+        }
+    }
+
+    private static void RequireCatalog(string root, string description)
+    {
+        if (!File.Exists(Path.Combine(root, "SYS4INI.BIN")))
+            throw new ArgumentException(
+                $"{description} does not contain SYS4INI.BIN (resolved to '{root}')");
+    }
+
+    private static bool SamePath(string left, string right)
+    {
+        StringComparison comparison = OperatingSystem.IsWindows()
+            ? StringComparison.OrdinalIgnoreCase
+            : StringComparison.Ordinal;
+        return string.Equals(
+            Path.TrimEndingDirectorySeparator(left),
+            Path.TrimEndingDirectorySeparator(right),
+            comparison);
+    }
+}

engine/Age.Engine/Sys4/Paths.cs

@@ -5,7 +5,7 @@ public static class Paths
     public static string Workspace => Directory.GetParent(Repo)!.FullName;
     public static string Extracted => Path.Combine(Workspace, "extracted");
     public static string Data1 => Path.Combine(Extracted, "DATA1");
-    public static string GameDir => Path.Combine(Workspace, "姫狩りダンジョンマイスター");
+    public static string GameDir => Path.Combine(Workspace, "Himegari_Game");
     public static string Build => Path.Combine(Repo, "build");
     public static string OpcodesJson => Path.Combine(Build, "opcodes.json");
     public static string AssetSectionsJson => Path.Combine(Build, "asset-sections.json");