feat: implement Stripe product configuration and add token-based input validation using Microsoft.ML.Tokenizers

src/NexusReader.Infrastructure/Services/BillingService.cs

@@ -1,7 +1,10 @@
 using Microsoft.AspNetCore.Identity;
 using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
 using NexusReader.Application.Abstractions.Services;
 using NexusReader.Domain.Entities;
+using NexusReader.Infrastructure.Configuration;
 using NexusReader.Infrastructure.Persistence;
 
 namespace NexusReader.Infrastructure.Services;
@@ -10,44 +13,83 @@ public class BillingService : IBillingService
 {
     private readonly AppDbContext _dbContext;
     private readonly UserManager<NexusUser> _userManager;
+    private readonly StripeSettings _stripeSettings;
+    private readonly ILogger<BillingService> _logger;
 
-    public BillingService(AppDbContext dbContext, UserManager<NexusUser> userManager)
+    public BillingService(
+        AppDbContext dbContext, 
+        UserManager<NexusUser> userManager,
+        IOptions<StripeSettings> stripeSettings,
+        ILogger<BillingService> logger)
     {
         _dbContext = dbContext;
         _userManager = userManager;
+        _stripeSettings = stripeSettings.Value;
+        _logger = logger;
     }
 
     public async Task<bool> HandleSubscriptionUpdatedAsync(string customerEmail, string stripeProductId)
     {
         var user = await _userManager.FindByEmailAsync(customerEmail);
-        if (user == null) return false;
+        if (user == null) 
+        {
+            _logger.LogWarning("Attempted to update subscription for non-existent user: {Email}", customerEmail);
+            return false;
+        }
 
-        // Map Stripe Product IDs to Nexus Plans
-        // These IDs would typically come from configuration
-        if (stripeProductId.Contains("pro")) 
+        if (stripeProductId == _stripeSettings.ProProductId)
         {
             user.CurrentPlan = "Pro";
             user.AITokenLimit = 50000;
         }
-        else if (stripeProductId.Contains("basic"))
+        else if (stripeProductId == _stripeSettings.BasicProductId)
         {
             user.CurrentPlan = "Basic";
             user.AITokenLimit = 10000;
         }
+        else if (stripeProductId == _stripeSettings.FreeProductId || string.IsNullOrEmpty(stripeProductId))
+        {
+            user.CurrentPlan = "Free";
+            user.AITokenLimit = 1000;
+        }
+        else
+        {
+            _logger.LogWarning("Unrecognized Stripe Product ID: {ProductId} for user {Email}. Falling back to Free tier.", stripeProductId, customerEmail);
+            user.CurrentPlan = "Free";
+            user.AITokenLimit = 1000;
+        }
+
+        var result = await _userManager.UpdateAsync(user);
+        if (!result.Succeeded)
+        {
+            _logger.LogError("Failed to update user {Email} after subscription change: {Errors}", 
+                customerEmail, string.Join(", ", result.Errors.Select(e => e.Description)));
+            return false;
+        }
 
-        await _userManager.UpdateAsync(user);
         return true;
     }
 
     public async Task<bool> HandleSubscriptionDeletedAsync(string customerEmail)
     {
         var user = await _userManager.FindByEmailAsync(customerEmail);
-        if (user == null) return false;
+        if (user == null)
+        {
+            _logger.LogWarning("Attempted to delete subscription for non-existent user: {Email}", customerEmail);
+            return false;
+        }
 
         user.CurrentPlan = "Free";
         user.AITokenLimit = 1000; // Reset to free limit
         
-        await _userManager.UpdateAsync(user);
+        var result = await _userManager.UpdateAsync(user);
+        if (!result.Succeeded)
+        {
+            _logger.LogError("Failed to reset user {Email} to Free tier after subscription deletion: {Errors}", 
+                customerEmail, string.Join(", ", result.Errors.Select(e => e.Description)));
+            return false;
+        }
+
         return true;
     }
 }