Give packs an identity so create can refuse missing deps and load in a stable order.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/HSchool.Server/Api/ModEndpoints.cs

@@ -11,8 +11,16 @@ internal static class ModEndpoints
 {
     public static void MapModEndpoints(this IEndpointRouteBuilder builder)
     {
-        builder.MapGet("/api/mods", (ModContent mods) =>
-            new ModsResponse(mods.ListPacks().Select(pack => new ModInfoResponse(pack.Id, pack.Required)).ToArray()))
+        builder.MapGet("/api/mods", (string? lang, ModContent mods) =>
+            {
+                var locale = string.Equals(lang, "en", StringComparison.OrdinalIgnoreCase) ? "en" : "ru";
+                return new ModsResponse(mods.ListPacks(locale).Select(pack => new ModInfoResponse(
+                    pack.Id,
+                    pack.Required,
+                    pack.Label,
+                    pack.Version,
+                    pack.Requires)).ToArray());
+            })
             .WithName("GetMods");
 
         builder.MapGet("/api/catalog", (string? lang, string? mods, ModContent content) =>
@@ -31,7 +39,19 @@ internal static class ModEndpoints
                 return Problem(StatusCodes.Status400BadRequest, "invalid-catalog", "The core pack is missing.");
             }
 
-            var packIds = content.NormalizePackIds(extras);
+            IReadOnlyList<string> packIds;
+            try
+            {
+                packIds = content.ResolveSelectedPacks(extras);
+            }
+            catch (PackDependencyException ex)
+            {
+                return PackProblem(ex);
+            }
+            catch (ContentLoadException ex)
+            {
+                return Problem(StatusCodes.Status400BadRequest, "invalid-catalog", ex.Message);
+            }
             DefCatalog catalog;
             MapLayout map;
             try
@@ -69,6 +89,17 @@ internal static class ModEndpoints
         return mods.Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
     }
 
+    private static IResult PackProblem(PackDependencyException ex) =>
+        Results.Problem(
+            detail: ex.Message,
+            statusCode: StatusCodes.Status400BadRequest,
+            title: ex.Code,
+            extensions: new Dictionary<string, object?>
+            {
+                ["code"] = ex.Code,
+                ["missing"] = ex.MissingPackId,
+            });
+
     private static IResult Problem(int statusCode, string code, string detail) =>
         Results.Problem(detail: detail, statusCode: statusCode, title: code, extensions: new Dictionary<string, object?>
         {
@@ -78,7 +109,12 @@ internal static class ModEndpoints
 
 internal sealed record ModsResponse(IReadOnlyList<ModInfoResponse> Mods);
 
-internal sealed record ModInfoResponse(string Id, bool Required);
+internal sealed record ModInfoResponse(
+    string Id,
+    bool Required,
+    string Label,
+    string Version,
+    IReadOnlyList<string> Requires);
 
 internal sealed record CatalogResponse(
     IReadOnlyList<DefInfoResponse> Territories,

src/HSchool.Server/Api/SchoolEndpoints.cs

@@ -80,6 +80,14 @@ internal static class SchoolEndpoints
                     Problem(StatusCodes.Status400BadRequest, "unknown-name-set", "The selected name set is not in the catalog."),
                 SchoolCreationError.UnknownNativeLanguage =>
                     Problem(StatusCodes.Status400BadRequest, "unknown-native-language", "The selected native language is not in that name set."),
+                SchoolCreationError.MissingMod =>
+                    Problem(
+                        StatusCodes.Status400BadRequest,
+                        "missing-mod",
+                        $"Mod '{outcome.MissingPackId}' is required but was not selected.",
+                        missing: outcome.MissingPackId),
+                SchoolCreationError.ModCycle =>
+                    Problem(StatusCodes.Status400BadRequest, "mod-cycle", "Selected mods have a cyclic dependency."),
                 _ => Results.Problem("Unknown error."),
             };
         })
@@ -468,7 +476,12 @@ internal static class SchoolEndpoints
         return true;
     }
 
-    private static IResult Problem(int statusCode, string code, string detail, StaffingOutcome? staffing = null)
+    private static IResult Problem(
+        int statusCode,
+        string code,
+        string detail,
+        StaffingOutcome? staffing = null,
+        string? missing = null)
     {
         var extensions = new Dictionary<string, object?> { ["code"] = code };
         if (staffing is not null)
@@ -479,6 +492,11 @@ internal static class SchoolEndpoints
             extensions["attempted"] = staffing.Attempted;
         }
 
+        if (missing is not null)
+        {
+            extensions["missing"] = missing;
+        }
+
         return Results.Problem(detail: detail, statusCode: statusCode, title: code, extensions: extensions);
     }
 }
@@ -492,10 +510,16 @@ internal sealed record CreateSchoolRequest(
     string? NameSetId,
     string? NativeLanguage);
 
-internal sealed record SchoolResponse(int Id, string Name, DateTime GameTime, bool Running, byte SpeedIndex)
+internal sealed record SchoolResponse(
+    int Id,
+    string Name,
+    DateTime GameTime,
+    bool Running,
+    byte SpeedIndex,
+    IReadOnlyList<string> ModIds)
 {
     public static SchoolResponse From(SchoolState school) =>
-        new(school.Id, school.Name, school.GameTime, school.Running, school.SpeedIndex);
+        new(school.Id, school.Name, school.GameTime, school.Running, school.SpeedIndex, school.ModIds);
 }
 
 /// <summary>Everything the main menu needs in one request.</summary>

src/HSchool.Server/Game/GameLoopService.cs

@@ -303,7 +303,30 @@ internal sealed class GameLoopService(
                 }
             }
 
-            var packIds = mods.NormalizePackIds(extras);
+            IReadOnlyList<string> packIds;
+            try
+            {
+                packIds = mods.ResolveSelectedPacks(extras);
+            }
+            catch (PackDependencyException ex) when (ex.Code == PackDependencyException.MissingCode)
+            {
+                command.Result.TrySetResult(new SchoolCreationOutcome(
+                    null,
+                    SchoolCreationError.MissingMod,
+                    ex.MissingPackId));
+                return;
+            }
+            catch (PackDependencyException)
+            {
+                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.ModCycle));
+                return;
+            }
+            catch (ContentLoadException)
+            {
+                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.InvalidCatalog));
+                return;
+            }
+
             if (!mods.PackExists(CatalogLoader.CorePackId))
             {
                 command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.InvalidCatalog));

src/HSchool.Server/Game/ModContent.cs

@@ -51,9 +51,9 @@ internal sealed class ModContent
         return true;
     }
 
-    public IReadOnlyList<ModPackInfo> ListPacks()
+    public IReadOnlyList<ModPackInfo> ListPacks(string locale)
     {
-        var packs = new List<ModPackInfo> { new(CatalogLoader.CorePackId, Required: true) };
+        var packs = new List<ModPackInfo> { Describe(CatalogLoader.CorePackId, required: true, locale) };
         if (!Directory.Exists(Root))
         {
             return packs;
@@ -67,7 +67,7 @@ internal sealed class ModContent
                 continue;
             }
 
-            packs.Add(new ModPackInfo(id, Required: false));
+            packs.Add(Describe(id, required: false, locale));
         }
 
         return packs;
@@ -76,6 +76,30 @@ internal sealed class ModContent
     public IReadOnlyList<string> NormalizePackIds(IReadOnlyList<string>? extraModIds) =>
         CatalogLoader.NormalizePackOrder(extraModIds ?? []);
 
+    /// <summary>
+    /// Player extras plus <c>core</c>, reordered so each pack's <c>requires</c> load first.
+    /// Missing dependencies and cycles throw <see cref="PackDependencyException"/>.
+    /// </summary>
+    public IReadOnlyList<string> ResolveSelectedPacks(IReadOnlyList<string>? extraModIds)
+    {
+        var selected = NormalizePackIds(extraModIds);
+        var manifests = new Dictionary<string, PackManifest>(StringComparer.OrdinalIgnoreCase);
+        foreach (var packId in selected)
+        {
+            manifests[packId] = ReadManifest(packId);
+        }
+
+        return PackLoadOrder.Resolve(selected, manifests);
+    }
+
+    public PackManifest ReadManifest(string packId)
+    {
+        var jsonc = Path.Combine(PackPath(packId), "pack.jsonc");
+        var json = Path.Combine(PackPath(packId), "pack.json");
+        var path = File.Exists(jsonc) ? jsonc : File.Exists(json) ? json : null;
+        return path is null ? PackManifest.Empty : PackManifest.Parse(packId, File.ReadAllText(path));
+    }
+
     public IReadOnlyList<ContentDocument> ReadDocuments(IReadOnlyList<string> packIds)
     {
         var documents = new List<ContentDocument>();
@@ -136,7 +160,50 @@ internal sealed class ModContent
 
     public DefCatalog LoadCatalog(IReadOnlyList<string> packIds) => LoadCatalog(packIds, _logger);
 
+    private ModPackInfo Describe(string packId, bool required, string locale)
+    {
+        PackManifest manifest;
+        try
+        {
+            manifest = PackExists(packId) ? ReadManifest(packId) : PackManifest.Empty;
+        }
+        catch (ContentLoadException ex)
+        {
+            _logger.LogWarning(ex, "Could not read pack.jsonc for {PackId}.", packId);
+            manifest = PackManifest.Empty;
+        }
+
+        return new ModPackInfo(packId, required, ReadPackLabel(packId, locale), manifest.Version, manifest.Requires);
+    }
+
+    private string ReadPackLabel(string packId, string locale)
+    {
+        var jsonc = Path.Combine(PackPath(packId), "localizations", $"{locale}.jsonc");
+        var json = Path.Combine(PackPath(packId), "localizations", $"{locale}.json");
+        var path = File.Exists(jsonc) ? jsonc : File.Exists(json) ? json : null;
+        if (path is null)
+        {
+            return packId;
+        }
+
+        try
+        {
+            var table = PackManifest.ReadLocaleTable(File.ReadAllText(path), $"{packId}:localizations/{locale}");
+            return table.TryGetValue(packId, out var label) ? label : packId;
+        }
+        catch (ContentLoadException ex)
+        {
+            _logger.LogWarning(ex, "Could not read pack label for {PackId}.", packId);
+            return packId;
+        }
+    }
+
     private string PackPath(string packId) => Path.Combine(Root, packId);
 }
 
-internal sealed record ModPackInfo(string Id, bool Required);
+internal sealed record ModPackInfo(
+    string Id,
+    bool Required,
+    string Label,
+    string Version,
+    IReadOnlyList<string> Requires);

src/HSchool.Server/Game/SchoolCreationOutcome.cs

@@ -3,7 +3,10 @@ using HSchool.Simulation;
 namespace HSchool.Server.Game;
 
 /// <summary>What the supervisor reports back after trying to create a school.</summary>
-internal readonly record struct SchoolCreationOutcome(SchoolState? School, SchoolCreationError Error)
+internal readonly record struct SchoolCreationOutcome(
+    SchoolState? School,
+    SchoolCreationError Error,
+    string? MissingPackId = null)
 {
     public bool Succeeded => Error == SchoolCreationError.None && School is not null;
 }

src/HSchool.Server/Game/SchoolState.cs

@@ -4,7 +4,13 @@ namespace HSchool.Server.Game;
 /// Immutable copy of a school, safe to hand to request threads. The live <c>School</c> object
 /// never leaves its worker thread.
 /// </summary>
-internal sealed record SchoolState(int Id, string Name, DateTime GameTime, bool Running, byte SpeedIndex);
+internal sealed record SchoolState(
+    int Id,
+    string Name,
+    DateTime GameTime,
+    bool Running,
+    byte SpeedIndex,
+    IReadOnlyList<string> ModIds);
 
 /// <summary>Everything the main menu needs in one read.</summary>
 internal sealed record SchoolsState(int MaxSchools, IReadOnlyList<SchoolState> Schools);

src/HSchool.Server/Game/SchoolWorker.cs

@@ -94,7 +94,7 @@ internal sealed class SchoolWorker
         _mods = mods;
         _onFailed = onFailed;
         _logger = logger;
-        _snapshot = new SchoolState(id, name, time, running, (byte)speedIndex);
+        _snapshot = new SchoolState(id, name, time, running, (byte)speedIndex, modIds ?? []);
     }
 
     public int Id => _id;
@@ -203,6 +203,7 @@ internal sealed class SchoolWorker
     private void RunLoop(CancellationToken cancellationToken)
     {
         var packIds = _mods.NormalizePackIds(_modIds);
+        _logger.LogInformation("School {SchoolId} loading packs [{Packs}].", _id, string.Join(", ", packIds));
         foreach (var packId in packIds)
         {
             if (!_mods.PackExists(packId))
@@ -577,7 +578,8 @@ internal sealed class SchoolWorker
                 school.Name,
                 school.Clock.Time,
                 school.Clock.IsRunning,
-                (byte)school.Clock.SpeedIndex));
+                (byte)school.Clock.SpeedIndex,
+                school.Catalog?.PackIds ?? _modIds ?? []));
         Volatile.Write(ref _rosterSnapshot, school.Roster);
         Volatile.Write(ref _applicantSnapshot, school.Applicants);
         Volatile.Write(ref _timetableSnapshot, school.Timetable);

src/HSchool.Server/Program.cs

@@ -73,6 +73,9 @@ if (app.Configuration.GetValue("HSchool:AllowSaveReload", false))
 
     app.MapGet("/api/dev/saves-directory", (SchoolStore store) => Results.Json(new { path = store.DirectoryPath }))
         .WithName("GetSavesDirectory");
+
+    app.MapGet("/api/dev/mods-directory", (ModContent mods) => Results.Json(new { path = mods.Root }))
+        .WithName("GetModsDirectory");
 }
 
 // The realtime channel: one binary frame per protocol message, see docs/protocol.md.

src/HSchool.Server/mods/core/localizations/en.jsonc

@@ -116,4 +116,5 @@
   "WinterBreak": "Winter break",
   "SpringBreak": "Spring break",
   "SummerBreak": "Summer break",
+  "core": "Core",
 }

src/HSchool.Server/mods/core/localizations/ru.jsonc

@@ -116,4 +116,5 @@
   "WinterBreak": "Зимние каникулы",
   "SpringBreak": "Весенние каникулы",
   "SummerBreak": "Летние каникулы",
+  "core": "Базовая игра",
 }

src/HSchool.Server/mods/core/pack.jsonc

@@ -0,0 +1,4 @@
+{
+  "version": "1.0",
+  "requires": [],
+}