refactor: move services and AITools to MoneyMap.Core

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

MoneyMap.Core/Services/CardService.cs

@@ -0,0 +1,123 @@
+using Microsoft.EntityFrameworkCore;
+using MoneyMap.Data;
+using MoneyMap.Models;
+
+namespace MoneyMap.Services;
+
+/// <summary>
+/// Service for card management including retrieval, validation, and deletion.
+/// </summary>
+public interface ICardService
+{
+    /// <summary>
+    /// Gets a card by ID with optional related data.
+    /// </summary>
+    Task<Card?> GetCardByIdAsync(int id, bool includeRelated = false);
+
+    /// <summary>
+    /// Gets all cards with transaction statistics.
+    /// </summary>
+    Task<List<CardWithStats>> GetAllCardsWithStatsAsync();
+
+    /// <summary>
+    /// Checks if a card can be deleted (no transactions exist).
+    /// </summary>
+    Task<DeleteValidationResult> CanDeleteCardAsync(int id);
+
+    /// <summary>
+    /// Deletes a card if it has no associated transactions.
+    /// </summary>
+    Task<DeleteResult> DeleteCardAsync(int id);
+}
+
+public class CardService : ICardService
+{
+    private readonly MoneyMapContext _db;
+
+    public CardService(MoneyMapContext db)
+    {
+        _db = db;
+    }
+
+    public async Task<Card?> GetCardByIdAsync(int id, bool includeRelated = false)
+    {
+        var query = _db.Cards.AsQueryable();
+
+        if (includeRelated)
+        {
+            query = query
+                .Include(c => c.Account)
+                .Include(c => c.Transactions);
+        }
+
+        return await query.FirstOrDefaultAsync(c => c.Id == id);
+    }
+
+    public async Task<List<CardWithStats>> GetAllCardsWithStatsAsync()
+    {
+        // Single query with projection to avoid N+1
+        return await _db.Cards
+            .Include(c => c.Account)
+            .OrderBy(c => c.Owner)
+            .ThenBy(c => c.Last4)
+            .Select(c => new CardWithStats
+            {
+                Card = c,
+                TransactionCount = c.Transactions.Count
+            })
+            .ToListAsync();
+    }
+
+    public async Task<DeleteValidationResult> CanDeleteCardAsync(int id)
+    {
+        var card = await _db.Cards.FindAsync(id);
+        if (card == null)
+            return new DeleteValidationResult
+            {
+                CanDelete = false,
+                Reason = "Card not found."
+            };
+
+        var transactionCount = await _db.Transactions.CountAsync(t => t.CardId == id);
+        if (transactionCount > 0)
+            return new DeleteValidationResult
+            {
+                CanDelete = false,
+                Reason = $"Cannot delete card. It has {transactionCount} transaction(s) associated with it."
+            };
+
+        return new DeleteValidationResult { CanDelete = true };
+    }
+
+    public async Task<DeleteResult> DeleteCardAsync(int id)
+    {
+        var validation = await CanDeleteCardAsync(id);
+        if (!validation.CanDelete)
+        {
+            return new DeleteResult
+            {
+                Success = false,
+                Message = validation.Reason ?? "Cannot delete card."
+            };
+        }
+
+        var card = await _db.Cards.FindAsync(id);
+        if (card == null)
+        {
+            return new DeleteResult
+            {
+                Success = false,
+                Message = "Card not found."
+            };
+        }
+
+        _db.Cards.Remove(card);
+        await _db.SaveChangesAsync();
+
+        return new DeleteResult
+        {
+            Success = true,
+            Message = "Card deleted successfully."
+        };
+    }
+}