Fix co-op error when using static helpers (#1353)

When playing co-op, if you view details for another player, the client
will make a call to /friend/get_support_chara_detail with their ID. If
you have static helpers enabled, this will fail. We should fall back to
real helper data to handle this case.

We expect this particular case to always hit this path rather than a
static helper shadowing a real
player, because all the static helper IDs are near ulong.MaxValue. So
there is a clear separation, unless
we get a LOT of new players.

Note: it shouldn't be necessary to do this for GetHelper above as that
is only called from
/friend/id_search.

Author: SapiensAnatis

DragaliaAPI/DragaliaAPI.Integration.Test/Features/Friends/SupportCharaTest.cs

@@ -291,6 +291,32 @@ await this.Client.PostMsgpack<FriendGetSupportCharaDetailResponse>(
         response.SupportUserDataDetail.IsFriend.Should().BeTrue();
     }
 
+    [Fact]
+    public async Task GetSupportCharaDetail_StaticEnabled_SendsRealViewerId_GetsCorrectCharacter()
+    {
+        // See comment in StaticHelperDataService explaining why this is a valid scenario
+
+        this.ApiContext.PlayerSettings.Add(
+            new()
+            {
+                ViewerId = this.ViewerId,
+                SettingsJson = new() { UseLegacyHelpers = true },
+            }
+        );
+        await this.ApiContext.SaveChangesAsync(TestContext.Current.CancellationToken);
+
+        DragaliaResponse<FriendGetSupportCharaDetailResponse> response = (
+            await this.Client.PostMsgpack<FriendGetSupportCharaDetailResponse>(
+                "/friend/get_support_chara_detail",
+                new FriendGetSupportCharaDetailRequest() { SupportViewerId = (ulong)this.ViewerId },
+                cancellationToken: TestContext.Current.CancellationToken,
+                ensureSuccessHeader: false
+            )
+        );
+
+        response.DataHeaders.ResultCode.Should().Be(ResultCode.Success);
+    }
+
     [Fact]
     public async Task GetSupportCharaDetail_RealViewerId_GetsSupportCharaDetail()
     {

DragaliaAPI/DragaliaAPI/Features/Friends/StaticHelperDataService.cs

@@ -4,7 +4,10 @@
 
 namespace DragaliaAPI.Features.Friends;
 
-public class StaticHelperDataService(IBonusService bonusService) : IHelperDataService
+internal sealed class StaticHelperDataService(
+    IBonusService bonusService,
+    RealHelperDataService realHelperDataService
+) : IHelperDataService
 {
     public Task<QuestGetSupportUserListResponse> GetHelperList(CancellationToken cancellationToken)
     {
@@ -32,7 +35,20 @@ CancellationToken cancellationToken
 
         if (staticHelperInfo is null)
         {
-            return null;
+            // When playing co-op, if you view details for another player, the client will make a call to
+            // /friend/get_support_chara_detail with their ID. If you have static helpers enabled, this will fail. We
+            // should fall back to real helper data to handle this case.
+            // We expect this particular case to always hit this path rather than a static helper shadowing a real
+            // player, because all the static helper IDs are near ulong.MaxValue. So there is a clear separation, unless
+            // we get a LOT of new players.
+            //
+            // Note: it shouldn't be necessary to do this for GetHelper above as that is only called from
+            // /friend/id_search.
+            //
+            return await realHelperDataService.GetHelperDataDetail(
+                helperViewerId,
+                cancellationToken
+            );
         }
 
         FortBonusList bonusList = await bonusService.GetBonusList(cancellationToken);