Add an RZ Coin slot machine

Adds a spend-coins-for-a-random-reward mini-game reachable from the shop. Backend mirrors the store's existing atomic/idempotent purchase pattern (SpinAsync in CreditStore.cs) with a server-authoritative, weighted reward roll and a rolling per-user spin-rate guard; odds are served from GET /api/credits/spin-config so the client never hardcodes numbers that could drift from the real payout table. The mockup's "Streak Protector" reward was swapped for a real Exam Simulation Token since streaks aren't currently a persisted, protectable concept. Also fixes two latent bugs surfaced while building this: - credits_service.gd's operation-id builder referenced a nonexistent AuthState.user_id (should be .username), throwing on every credit action. - _post() silently no-op'd with no signal when signed out, which combined with a GDScript closure gotcha (lambdas capture outer locals by value, so reassigning inside one never reached the caller) meant a spin attempted while unauthenticated could hang forever instead of surfacing an error.
2026-07-30 00:29:49 -05:00
parent 4909cf0b71
commit 1860e6ede6
8 changed files with 816 additions and 3 deletions
@@ -48,6 +48,27 @@ public sealed class CreditsController(CreditStore credits, ExamSimulationStore s
                { code = "reset_token_required", message = "A QBank Reset Token is required.", credits = result.Status });
    }

+    [HttpGet("spin-config")]
+    public IActionResult SpinConfig() => Ok(new SpinConfigResponse());
+
+    [HttpPost("spin")]
+    public async Task<IActionResult> Spin([FromBody] SpinRequest request)
+    {
+        if (!ValidOperationId(request.OperationId))
+            return BadRequest(new { code = "invalid_operation_id", message = "A valid operation ID is required." });
+        var result = await credits.SpinAsync(UserId(), request.OperationId);
+        return result.Result switch
+        {
+            CreditOperationResult.Succeeded => Ok(result),
+            CreditOperationResult.InsufficientCredits => Conflict(new
+                { code = "insufficient_coins", message = "Not enough Rz Coins.", credits = result.Status }),
+            CreditOperationResult.RateLimited => Conflict(new
+                { code = "rate_limited", message = "Too many spins - try again later.", credits = result.Status }),
+            _ => Conflict(new
+                { code = "operation_conflict", message = "That operation ID was already used.", credits = result.Status })
+        };
+    }
+
    private string UserId() => User.FindFirstValue(ClaimTypes.NameIdentifier)
        ?? User.FindFirstValue(ClaimTypes.Name)
        ?? User.Identity?.Name
@@ -36,7 +36,49 @@ public static class CreditEconomy
        Products.FirstOrDefault(value => value.Sku.Equals(sku, StringComparison.Ordinal));
 }

-public enum RzStoreGrant { ExamToken, QBankResetToken }
+public static class SlotMachineEconomy
+{
+    public const int SpinCost = 50;
+    public const int RollingSpinLimit = 200;
+    public static readonly TimeSpan SpinWindow = TimeSpan.FromHours(24);
+
+    public static readonly IReadOnlyList<SpinReward> Rewards =
+    [
+        new() { Key = "jackpot", Label = "10,000 RZ Coins", Description = "Jackpot!", Grant = RzStoreGrant.Coins, CoinAmount = 10000, Probability = 0.005 },
+        new() { Key = "epic", Label = "2,000 RZ Coins", Description = "Epic Reward", Grant = RzStoreGrant.Coins, CoinAmount = 2000, Probability = 0.02 },
+        new() { Key = "great", Label = "500 RZ Coins", Description = "Great Reward", Grant = RzStoreGrant.Coins, CoinAmount = 500, Probability = 0.10 },
+        new() { Key = "exam_token", Label = "Exam Simulation Token", Description = "Starts one new full exam simulation.", Grant = RzStoreGrant.ExamToken, Probability = 0.15 },
+        new() { Key = "qbank_reset", Label = "QBank Reset Token", Description = "Makes every QBank question eligible again.", Grant = RzStoreGrant.QBankResetToken, Probability = 0.20 },
+        new() { Key = "nice", Label = "100 RZ Coins", Description = "Nice!", Grant = RzStoreGrant.Coins, CoinAmount = 100, Probability = 0.30 },
+        new() { Key = "good_luck", Label = "50 RZ Coins", Description = "Good luck!", Grant = RzStoreGrant.Coins, CoinAmount = 50, Probability = 0.225 },
+    ];
+
+    public static SpinReward RollReward(double roll)
+    {
+        var cumulative = 0.0;
+        foreach (var reward in Rewards)
+        {
+            cumulative += reward.Probability;
+            if (roll < cumulative) return reward;
+        }
+        return Rewards[^1];
+    }
+
+    public static SpinReward? FindReward(string key) =>
+        Rewards.FirstOrDefault(value => value.Key.Equals(key, StringComparison.Ordinal));
+}
+
+public enum RzStoreGrant { ExamToken, QBankResetToken, Coins }
+
+public sealed class SpinReward
+{
+    public string Key { get; set; } = "";
+    public string Label { get; set; } = "";
+    public string Description { get; set; } = "";
+    public RzStoreGrant Grant { get; set; }
+    public int CoinAmount { get; set; }
+    public double Probability { get; set; }
+}

 public sealed class RzStoreProduct
 {
@@ -61,6 +103,14 @@ public sealed class CreditPurchaseEvent
    public DateTime CreatedUtc { get; set; }
 }

+public sealed class SpinEvent
+{
+    public string OperationId { get; set; } = "";
+    public string RewardKey { get; set; } = "";
+    public int CoinsWon { get; set; }
+    public DateTime CreatedUtc { get; set; }
+}
+
 public sealed class UserCreditAccount
 {
    [BsonId]
@@ -74,6 +124,8 @@ public sealed class UserCreditAccount
    public bool InitialExamGrantApplied { get; set; }
    public List<CreditEvent> RecentEarnings { get; set; } = [];
    public List<CreditPurchaseEvent> Purchases { get; set; } = [];
+    public List<SpinEvent> Spins { get; set; } = [];
+    public List<CreditEvent> RecentSpins { get; set; } = [];
    public List<string> AppliedOperations { get; set; } = [];
    public DateTime UpdatedUtc { get; set; } = DateTime.UtcNow;
 }
@@ -102,10 +154,30 @@ public sealed class QBankResetRequest
    public string OperationId { get; set; } = "";
 }

-public enum CreditOperationResult { Succeeded, InsufficientCredits, InsufficientTokens, OperationConflict }
+public sealed class SpinRequest
+{
+    public string OperationId { get; set; } = "";
+}
+
+public enum CreditOperationResult { Succeeded, InsufficientCredits, InsufficientTokens, OperationConflict, RateLimited }

 public sealed class CreditOperationResponse
 {
    public CreditOperationResult Result { get; set; }
    public CreditStatusResponse Status { get; set; } = new();
 }
+
+public sealed class SpinConfigResponse
+{
+    public int SpinCost { get; set; } = SlotMachineEconomy.SpinCost;
+    public IReadOnlyList<SpinReward> Rewards { get; set; } = SlotMachineEconomy.Rewards;
+}
+
+public sealed class SpinResponse
+{
+    public CreditOperationResult Result { get; set; }
+    public string RewardKey { get; set; } = "";
+    public string RewardLabel { get; set; } = "";
+    public int CoinsWon { get; set; }
+    public CreditStatusResponse Status { get; set; } = new();
+}
@@ -130,6 +130,65 @@ public sealed class CreditStore
        return Response(CreditOperationResult.InsufficientTokens, account);
    }

+    public async Task<SpinResponse> SpinAsync(string userId, string operationId)
+    {
+        var now = _clock.GetUtcNow().UtcDateTime;
+        await EnsureAndCleanAsync(userId, now);
+        var existing = await _accounts.Find(value => value.UserId == userId).FirstAsync();
+        var priorSpin = existing.Spins.FirstOrDefault(value => value.OperationId == operationId);
+        if (priorSpin is not null)
+            return SpinResult(CreditOperationResult.Succeeded, existing, priorSpin);
+
+        var reward = SlotMachineEconomy.RollReward(Random.Shared.NextDouble());
+        var netCreditDelta = reward.Grant == RzStoreGrant.Coins
+            ? reward.CoinAmount - SlotMachineEconomy.SpinCost
+            : -SlotMachineEconomy.SpinCost;
+        var spinEvent = new SpinEvent
+        {
+            OperationId = operationId,
+            RewardKey = reward.Key,
+            CoinsWon = reward.Grant == RzStoreGrant.Coins ? reward.CoinAmount : 0,
+            CreatedUtc = now
+        };
+
+        var belowSpinCap = new BsonDocumentFilterDefinition<UserCreditAccount>(
+            new BsonDocument("$expr", new BsonDocument("$lt", new BsonArray
+            {
+                new BsonDocument("$size", new BsonDocument("$ifNull", new BsonArray { "$RecentSpins", new BsonArray() })),
+                SlotMachineEconomy.RollingSpinLimit
+            })));
+        var filter = Builders<UserCreditAccount>.Filter.Eq(value => value.UserId, userId) &
+            Builders<UserCreditAccount>.Filter.Gte(value => value.Credits, SlotMachineEconomy.SpinCost) &
+            Builders<UserCreditAccount>.Filter.Not(
+                Builders<UserCreditAccount>.Filter.ElemMatch(
+                    value => value.Spins, spin => spin.OperationId == operationId)) &
+            belowSpinCap;
+        var update = Builders<UserCreditAccount>.Update
+            .Inc(value => value.Credits, netCreditDelta)
+            .Push(value => value.Spins, spinEvent)
+            .Push(value => value.RecentSpins, new CreditEvent { OperationId = operationId, CreatedUtc = now })
+            .Set(value => value.UpdatedUtc, now);
+        update = reward.Grant switch
+        {
+            RzStoreGrant.ExamToken => update.Inc(value => value.ExamTokens, 1),
+            RzStoreGrant.QBankResetToken => update.Inc(value => value.QBankResetTokens, 1),
+            _ => update
+        };
+        var account = await _accounts.FindOneAndUpdateAsync(
+            filter, update, new FindOneAndUpdateOptions<UserCreditAccount>
+            {
+                ReturnDocument = ReturnDocument.After
+            });
+        if (account is not null) return SpinResult(CreditOperationResult.Succeeded, account, spinEvent);
+
+        account = await _accounts.Find(value => value.UserId == userId).FirstAsync();
+        priorSpin = account.Spins.FirstOrDefault(value => value.OperationId == operationId);
+        if (priorSpin is not null) return SpinResult(CreditOperationResult.Succeeded, account, priorSpin);
+        if (account.Credits < SlotMachineEconomy.SpinCost)
+            return SpinResult(CreditOperationResult.InsufficientCredits, account, null);
+        return SpinResult(CreditOperationResult.RateLimited, account, null);
+    }
+
    public async Task<bool> TryConsumeExamTokenAsync(string userId, string operationId)
    {
        var now = _clock.GetUtcNow().UtcDateTime;
@@ -166,6 +225,8 @@ public sealed class CreditStore
                .SetOnInsert(value => value.InitialExamGrantApplied, true)
                .SetOnInsert(value => value.RecentEarnings, [])
                .SetOnInsert(value => value.Purchases, [])
+                .SetOnInsert(value => value.Spins, [])
+                .SetOnInsert(value => value.RecentSpins, [])
                .SetOnInsert(value => value.AppliedOperations, [])
                .SetOnInsert(value => value.UpdatedUtc, now),
            new UpdateOptions { IsUpsert = true });
@@ -183,6 +244,14 @@ public sealed class CreditStore
            Builders<UserCreditAccount>.Filter.Eq(value => value.UserId, userId) &
            Builders<UserCreditAccount>.Filter.Exists(nameof(UserCreditAccount.Purchases), false),
            Builders<UserCreditAccount>.Update.Set(value => value.Purchases, []));
+        await _accounts.UpdateOneAsync(
+            Builders<UserCreditAccount>.Filter.Eq(value => value.UserId, userId) &
+            Builders<UserCreditAccount>.Filter.Exists(nameof(UserCreditAccount.Spins), false),
+            Builders<UserCreditAccount>.Update.Set(value => value.Spins, []));
+        await _accounts.UpdateOneAsync(
+            Builders<UserCreditAccount>.Filter.Eq(value => value.UserId, userId) &
+            Builders<UserCreditAccount>.Filter.Exists(nameof(UserCreditAccount.RecentSpins), false),
+            Builders<UserCreditAccount>.Update.Set(value => value.RecentSpins, []));
        await _accounts.UpdateOneAsync(
            Builders<UserCreditAccount>.Filter.Eq(value => value.UserId, userId) &
            Builders<UserCreditAccount>.Filter.Exists(nameof(UserCreditAccount.AppliedOperations), false),
@@ -193,6 +262,12 @@ public sealed class CreditStore
            Builders<UserCreditAccount>.Update.PullFilter(
                value => value.RecentEarnings,
                earning => earning.CreatedUtc <= cutoff));
+        var spinCutoff = now - SlotMachineEconomy.SpinWindow;
+        await _accounts.UpdateOneAsync(
+            value => value.UserId == userId,
+            Builders<UserCreditAccount>.Update.PullFilter(
+                value => value.RecentSpins,
+                spin => spin.CreatedUtc <= spinCutoff));
    }

    private static CreditStatusResponse ToStatus(UserCreditAccount account) => new()
@@ -212,4 +287,14 @@ public sealed class CreditStore
            Result = result,
            Status = ToStatus(account)
        };
+
+    private static SpinResponse SpinResult(
+        CreditOperationResult result, UserCreditAccount account, SpinEvent? spinEvent) => new()
+        {
+            Result = result,
+            RewardKey = spinEvent?.RewardKey ?? "",
+            RewardLabel = spinEvent is null ? "" : SlotMachineEconomy.FindReward(spinEvent.RewardKey)?.Label ?? "",
+            CoinsWon = spinEvent?.CoinsWon ?? 0,
+            Status = ToStatus(account)
+        };
 }