feat(bp): /battle_pass/buy — crystal-cost + retroactive premium grants

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.EmulatedEntrypoint/Services/BattlePassService.cs

@@ -1,8 +1,10 @@
 using System.Globalization;
+using Microsoft.EntityFrameworkCore;
 using SVSim.Database;
 using SVSim.Database.Enums;
 using SVSim.Database.Models;
 using SVSim.Database.Repositories.BattlePass;
+using SVSim.Database.Services;
 using SVSim.EmulatedEntrypoint.Models.Dtos;
 using SVSim.EmulatedEntrypoint.Models.Dtos.BattlePass;
 
@@ -20,17 +22,20 @@ public sealed class BattlePassService : IBattlePassService
     private readonly IViewerBattlePassRepository _viewerBp;
     private readonly TimeProvider _time;
     private readonly SVSimDbContext _db;
+    private readonly RewardGrantService _rewards;
 
     public BattlePassService(
         IBattlePassRepository bp,
         IViewerBattlePassRepository viewerBp,
         TimeProvider time,
-        SVSimDbContext db)
+        SVSimDbContext db,
+        RewardGrantService rewards)
     {
         _bp = bp;
         _viewerBp = viewerBp;
         _time = time;
         _db = db;
+        _rewards = rewards;
     }
 
     public async Task<IReadOnlyDictionary<string, BattlePassLevel>?> GetLevelCurveAsync(CancellationToken ct)
@@ -132,6 +137,77 @@ public sealed class BattlePassService : IBattlePassService
         return response;
     }
 
+    public async Task<BattlePassBuyOutcome> BuyPremiumAsync(
+        long viewerId, int seasonId, int productId, CancellationToken ct)
+    {
+        var now = _time.GetUtcNow();
+        var season = await _bp.GetActiveSeasonAsync(now, ct);
+
+        // 24: outside BP period, season mismatch, or season not currently purchasable.
+        if (season is null || season.Id != seasonId || !season.CanPurchase)
+            return new BattlePassBuyOutcome(24, Array.Empty<GrantedReward>(), Array.Empty<GrantedReward>());
+
+        if (productId != season.Id * 1000)
+            return new BattlePassBuyOutcome(0, Array.Empty<GrantedReward>(), Array.Empty<GrantedReward>());
+
+        var viewer = await _db.Viewers
+            .Include(v => v.Cards).ThenInclude(c => c.Card)
+            .Include(v => v.Sleeves).Include(v => v.Emblems).Include(v => v.LeaderSkins)
+            .Include(v => v.Degrees).Include(v => v.MyPageBackgrounds).Include(v => v.Items).ThenInclude(i => i.Item)
+            .AsSplitQuery()                  // per memory project_ef_split_query
+            .FirstOrDefaultAsync(v => v.Id == viewerId, ct);
+        if (viewer is null)
+            return new BattlePassBuyOutcome(0, Array.Empty<GrantedReward>(), Array.Empty<GrantedReward>());
+
+        var progress = await _viewerBp.GetOrCreateProgressAsync(viewerId, season.Id, ct);
+        if (progress.IsPremium)
+            return new BattlePassBuyOutcome(23, Array.Empty<GrantedReward>(), Array.Empty<GrantedReward>());
+
+        if (viewer.Currency.Crystals < (ulong)season.PriceCrystal)
+            return new BattlePassBuyOutcome(22, Array.Empty<GrantedReward>(), Array.Empty<GrantedReward>());
+
+        // BeginTransactionAsync is a no-op on the SQLite in-memory test DB but is safe to call.
+        await using var tx = await _db.Database.BeginTransactionAsync(ct);
+
+        viewer.Currency.Crystals -= (ulong)season.PriceCrystal;
+        progress.IsPremium = true;
+
+        // Retroactive grants: every premium reward at level <= current_level not already claimed.
+        var rewards = await _bp.GetSeasonRewardsAsync(season.Id, ct);
+        var claims = await _viewerBp.GetClaimsAsync(viewerId, season.Id, ct);
+        var claimSet = claims.Select(c => (c.Track, c.Level)).ToHashSet();
+
+        var curve = await _bp.GetLevelCurveAsync(ct);
+        int currentLevel = ComputeLevel(curve, progress.CurrentPoint);
+
+        // achieved = delta list (the original reward spec amounts — what was just granted).
+        // postState = post-state totals from RewardGrantService (what goes in reward_list).
+        var achieved = new List<GrantedReward>();
+        var postState = new List<GrantedReward>();
+        foreach (var r in rewards.Where(r => r.Track == BattlePassTrack.Premium && r.Level <= currentLevel))
+        {
+            if (claimSet.Contains((r.Track, r.Level))) continue;
+            _viewerBp.AddClaim(viewerId, season.Id, r.Track, r.Level, now);
+            var granted = await _rewards.ApplyAsync(
+                viewer, (UserGoodsType)r.RewardType, r.RewardDetailId, r.RewardNumber, ct);
+            // achieved_info uses the original reward spec (delta), not post-state.
+            achieved.Add(new GrantedReward(r.RewardType, r.RewardDetailId, r.RewardNumber));
+            postState.AddRange(granted);
+        }
+
+        await _db.SaveChangesAsync(ct);
+        await tx.CommitAsync(ct);
+
+        // Post-state reward_list must also include the crystal balance after the deduction.
+        if (!postState.Any(r => r.RewardType == (int)UserGoodsType.Crystal))
+        {
+            postState.Add(new GrantedReward(
+                (int)UserGoodsType.Crystal, 0, checked((int)viewer.Currency.Crystals)));
+        }
+
+        return new BattlePassBuyOutcome(1, achieved, postState);
+    }
+
     internal static int ComputeLevel(IReadOnlyList<BattlePassLevelEntry> curve, int point)
     {
         if (curve.Count == 0) return 1;