Split API into phase-specific endpoint files

Endpoints/EndpointHelpers.cs

@@ -0,0 +1,56 @@
+using GameList.Data;
+using GameList.Domain;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+
+namespace GameList.Endpoints;
+
+internal static class EndpointHelpers
+{
+    public static async Task<Player> GetOrCreatePlayer(HttpContext ctx, AppDbContext db)
+    {
+        if (!ctx.Items.TryGetValue(Infrastructure.PlayerIdentityExtensions.PlayerCookieName, out var value) || value is not Guid playerId)
+        {
+            throw new InvalidOperationException("Player cookie missing.");
+        }
+
+        var existing = await db.Players.FindAsync(playerId);
+        if (existing != null) return existing;
+
+        var player = new Player { Id = playerId };
+        db.Players.Add(player);
+        await db.SaveChangesAsync();
+        return player;
+    }
+
+    public static async Task<Phase> GetPhase(AppDbContext db)
+    {
+        var state = await db.AppState.AsNoTracking().FirstAsync();
+        return state.CurrentPhase;
+    }
+
+    public static IResult PhaseMismatch(Phase required, Phase current) =>
+        Results.BadRequest(new { error = $"This endpoint is available in the {required} phase. Current phase is {current}." });
+
+    public static string? TrimTo(string? input, int max) =>
+        string.IsNullOrWhiteSpace(input)
+            ? null
+            : input.Trim() is var t && t.Length > 0
+                ? t[..Math.Min(t.Length, max)]
+                : null;
+
+    public static bool IsAuthorized(HttpContext ctx, IConfiguration config)
+    {
+        var provided = ctx.Request.Headers["X-Admin-Key"].FirstOrDefault()
+                       ?? ctx.Request.Query["key"].FirstOrDefault();
+        var expected = config["ADMIN_PASSWORD"];
+        return !string.IsNullOrWhiteSpace(expected) && provided == expected;
+    }
+
+    public static AppState NewAppState() => new()
+    {
+        Id = 1,
+        CurrentPhase = Phase.Suggest,
+        UpdatedAt = DateTimeOffset.UnixEpoch
+    };
+}