refactor: move services and AITools to MoneyMap.Core

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

MoneyMap.Core/Services/TransactionStatisticsService.cs

@@ -0,0 +1,105 @@
+using Microsoft.EntityFrameworkCore;
+using MoneyMap.Data;
+using MoneyMap.Models;
+
+namespace MoneyMap.Services;
+
+/// <summary>
+/// Service for calculating transaction statistics and aggregates.
+/// </summary>
+public interface ITransactionStatisticsService
+{
+    /// <summary>
+    /// Calculates statistics for a filtered set of transactions.
+    /// </summary>
+    Task<TransactionStats> CalculateStatsAsync(IQueryable<Transaction> query);
+
+    /// <summary>
+    /// Gets categorization statistics for the entire database.
+    /// </summary>
+    Task<CategorizationStats> GetCategorizationStatsAsync();
+
+    /// <summary>
+    /// Gets card statistics for a specific account.
+    /// </summary>
+    Task<List<CardStats>> GetCardStatsForAccountAsync(int accountId);
+}
+
+public class TransactionStatisticsService : ITransactionStatisticsService
+{
+    private readonly MoneyMapContext _db;
+
+    public TransactionStatisticsService(MoneyMapContext db)
+    {
+        _db = db;
+    }
+
+    public async Task<TransactionStats> CalculateStatsAsync(IQueryable<Transaction> query)
+    {
+        // Calculate stats at database level instead of loading all transactions into memory
+        var stats = await query
+            .GroupBy(_ => 1) // Group all into one group to aggregate
+            .Select(g => new TransactionStats
+            {
+                Count = g.Count(),
+                TotalDebits = g.Where(t => t.Amount < 0).Sum(t => t.Amount),
+                TotalCredits = g.Where(t => t.Amount > 0).Sum(t => t.Amount),
+                NetAmount = g.Sum(t => t.Amount)
+            })
+            .FirstOrDefaultAsync();
+
+        return stats ?? new TransactionStats();
+    }
+
+    public async Task<CategorizationStats> GetCategorizationStatsAsync()
+    {
+        var totalTransactions = await _db.Transactions.CountAsync();
+        var uncategorized = await _db.Transactions
+            .CountAsync(t => string.IsNullOrWhiteSpace(t.Category));
+        var categorized = totalTransactions - uncategorized;
+
+        return new CategorizationStats
+        {
+            TotalTransactions = totalTransactions,
+            Categorized = categorized,
+            Uncategorized = uncategorized
+        };
+    }
+
+    public async Task<List<CardStats>> GetCardStatsForAccountAsync(int accountId)
+    {
+        // Single query with projection to avoid N+1
+        return await _db.Cards
+            .Where(c => c.AccountId == accountId)
+            .OrderBy(c => c.Owner)
+            .ThenBy(c => c.Last4)
+            .Select(c => new CardStats
+            {
+                Card = c,
+                TransactionCount = c.Transactions.Count
+            })
+            .ToListAsync();
+    }
+}
+
+// DTOs
+public class TransactionStats
+{
+    public int Count { get; set; }
+    public decimal TotalDebits { get; set; }
+    public decimal TotalCredits { get; set; }
+    public decimal NetAmount { get; set; }
+}
+
+public class CategorizationStats
+{
+    public int TotalTransactions { get; set; }
+    public int Categorized { get; set; }
+    public int Uncategorized { get; set; }
+}
+
+public class CardStats
+{
+    public Card Card { get; set; } = null!;
+    public int TransactionCount { get; set; }
+}