Seeding reorg

SVSim.EmulatedEntrypoint/Services/GameConfigService.cs

@@ -0,0 +1,74 @@
+using System.Collections.Concurrent;
+using System.Reflection;
+using System.Text.Json;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Configuration;
+using SVSim.Database;
+using SVSim.Database.Models.Config;
+using SVSim.Database.Services;
+
+namespace SVSim.EmulatedEntrypoint.Services;
+
+/// <summary>
+/// Three-tier resolver for <see cref="IGameConfigService"/>: GameConfigs row → IConfiguration
+/// section under "GameConfig:&lt;name&gt;" → <c>T.ShippedDefaults()</c> (via reflection) → <c>new T()</c>.
+/// <para>
+/// Atomic per section: the first tier that has the section wins entirely; no per-property merging.
+/// Scoped lifetime — one DB read per request — matches today's <c>GameConfigRoot</c> behavior.
+/// </para>
+/// </summary>
+public class GameConfigService : IGameConfigService
+{
+    private static readonly ConcurrentDictionary<Type, SectionMetadata> _metaCache = new();
+
+    private readonly SVSimDbContext _db;
+    private readonly IConfiguration _appSettings;
+
+    public GameConfigService(SVSimDbContext db, IConfiguration appSettings)
+    {
+        _db = db;
+        _appSettings = appSettings;
+    }
+
+    public T Get<T>() where T : class, new()
+    {
+        var meta = GetMeta(typeof(T));
+
+        // Tier 1: DB row
+        var row = _db.GameConfigs.AsNoTracking().FirstOrDefault(s => s.SectionName == meta.SectionName);
+        if (row is not null)
+        {
+            return (T?)JsonSerializer.Deserialize(row.ValueJson, typeof(T))
+                ?? throw new InvalidOperationException(
+                    $"GameConfigs row '{meta.SectionName}' deserialised to null — corrupt jsonb?");
+        }
+
+        // Tier 2: appsettings.json under "GameConfig:<name>"
+        var configSection = _appSettings.GetSection($"GameConfig:{meta.SectionName}");
+        if (configSection.Exists())
+        {
+            var fromAppsettings = configSection.Get<T>();
+            if (fromAppsettings is not null) return fromAppsettings;
+        }
+
+        // Tier 3: ShippedDefaults() if present, else parameterless ctor
+        if (meta.ShippedDefaultsFactory is not null)
+        {
+            return (T)meta.ShippedDefaultsFactory.Invoke(null, null)!;
+        }
+        return new T();
+    }
+
+    private static SectionMetadata GetMeta(Type t) => _metaCache.GetOrAdd(t, static type =>
+    {
+        var attr = type.GetCustomAttribute<ConfigSectionAttribute>(inherit: false)
+            ?? throw new InvalidOperationException(
+                $"{type.FullName} is not marked with [ConfigSection(...)] — IGameConfigService can't resolve it.");
+        var factory = type.GetMethod("ShippedDefaults",
+            BindingFlags.Public | BindingFlags.Static,
+            binder: null, types: Type.EmptyTypes, modifiers: null);
+        return new SectionMetadata(attr.Name, factory);
+    });
+
+    private sealed record SectionMetadata(string SectionName, MethodInfo? ShippedDefaultsFactory);
+}