Add Rz Coin utility store

api/QuestionsApi/Models/CreditModels.cs

@@ -7,6 +7,44 @@ public static class CreditEconomy
 {
     public const int RollingEarningLimit = 20;
     public static readonly TimeSpan EarningWindow = TimeSpan.FromHours(24);
+    public const string ExamTokenSku = "exam_token_1";
+    public const string QBankResetTokenSku = "qbank_reset_1";
+    public const int ExamTokenPrice = 100;
+    public const int QBankResetTokenPrice = 300;
+
+    public static readonly IReadOnlyList<RzStoreProduct> Products =
+    [
+        new()
+        {
+            Sku = ExamTokenSku,
+            Name = "Exam Simulation Token",
+            Description = "Starts one new full exam simulation.",
+            CoinPrice = ExamTokenPrice,
+            Grant = RzStoreGrant.ExamToken
+        },
+        new()
+        {
+            Sku = QBankResetTokenSku,
+            Name = "QBank Reset Token",
+            Description = "Makes every QBank question eligible again without erasing progress.",
+            CoinPrice = QBankResetTokenPrice,
+            Grant = RzStoreGrant.QBankResetToken
+        }
+    ];
+
+    public static RzStoreProduct? FindProduct(string sku) =>
+        Products.FirstOrDefault(value => value.Sku.Equals(sku, StringComparison.Ordinal));
+}
+
+public enum RzStoreGrant { ExamToken, QBankResetToken }
+
+public sealed class RzStoreProduct
+{
+    public string Sku { get; set; } = "";
+    public string Name { get; set; } = "";
+    public string Description { get; set; } = "";
+    public int CoinPrice { get; set; }
+    public RzStoreGrant Grant { get; set; }
 }
 
 public sealed class CreditEvent
@@ -15,6 +53,14 @@ public sealed class CreditEvent
     public DateTime CreatedUtc { get; set; }
 }
 
+public sealed class CreditPurchaseEvent
+{
+    public string OperationId { get; set; } = "";
+    public string Sku { get; set; } = "";
+    public int CoinCost { get; set; }
+    public DateTime CreatedUtc { get; set; }
+}
+
 public sealed class UserCreditAccount
 {
     [BsonId]
@@ -22,7 +68,13 @@ public sealed class UserCreditAccount
     public string? Id { get; set; }
     public string UserId { get; set; } = "";
     public int Credits { get; set; }
+    public int ExamTokens { get; set; }
+    public int QBankResetTokens { get; set; }
+    public int BankCycle { get; set; }
+    public bool InitialExamGrantApplied { get; set; }
     public List<CreditEvent> RecentEarnings { get; set; } = [];
+    public List<CreditPurchaseEvent> Purchases { get; set; } = [];
+    public List<string> AppliedOperations { get; set; } = [];
     public DateTime UpdatedUtc { get; set; } = DateTime.UtcNow;
 }
 
@@ -32,4 +84,28 @@ public sealed class CreditStatusResponse
     public int EarnedInRollingWindow { get; set; }
     public int RemainingEarningCapacity { get; set; }
     public int RollingWindowHours { get; set; } = 24;
+    public int ExamTokens { get; set; }
+    public int QBankResetTokens { get; set; }
+    public int BankCycle { get; set; }
+    public IReadOnlyList<RzStoreProduct> Products { get; set; } = CreditEconomy.Products;
+}
+
+public sealed class CreditPurchaseRequest
+{
+    public string Sku { get; set; } = "";
+    public string OperationId { get; set; } = "";
+}
+
+public sealed class QBankResetRequest
+{
+    public string Confirmation { get; set; } = "";
+    public string OperationId { get; set; } = "";
+}
+
+public enum CreditOperationResult { Succeeded, InsufficientCredits, InsufficientTokens, OperationConflict }
+
+public sealed class CreditOperationResponse
+{
+    public CreditOperationResult Result { get; set; }
+    public CreditStatusResponse Status { get; set; } = new();
 }