PR E: ChartService cleanup

Remove the settings-mutating year-hopping in GetAccountExpensesPerMonth
that discarded the user's header year selection and silently forced
the Spendings-over-time chart back to DateTime.Now.Year. The chart
now honours settingsService.GetYear(), skips accounts with no
transactions instead of returning null, and no longer depends on
IAccountRepository or ISubclassRepository.

Also reorder the plan: async becomes PR F, tests PR G.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

IMPROVEMENT_PLAN.md

@@ -99,5 +99,6 @@ Analysis and phased plan produced 2026-07-02. See conversation history for full
 - **PR B** — Phase 1 item 8 (atomic writes + lock).
 - **PR C** — Phase 2 mechanical cleanup: items 11, 13, 15, 16, 17.
 - **PR D** — Phase 2 item 9: per-request unit of work / cache. Split off from PR C because it is invasive enough to warrant its own review.
-- **PR E** — Phase 3 (async).
-- **PR F** — Phase 4 (tests) — done alongside PR D to lock in behavior.
+- **PR E** — Phase 3 item 22: ChartService cleanup. Promoted ahead of async because it fixes an active correctness bug — `GetAccountExpensesPerMonth(accountId, year)` was mutating `ISettingsService` on the singleton to hop years, with the year parameter always hardcoded to `DateTime.Now.Year`, so the Spendings-over-time chart discarded the user's header year selection.
+- **PR F** — Phase 3 items 19 + 21: async I/O across the repository stack, and precomputed dictionaries for view assembly.
+- **PR G** — Phase 4 (tests) — locks in behavior for PR F.

Schaad.Accounting.Services/ChartService.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using Schaad.Accounting.Datasets;
 using Schaad.Accounting.Datasets.Charts;
 using Schaad.Accounting.Interfaces;
 
@@ -8,115 +9,88 @@ namespace Schaad.Accounting.Services
 {
     public class ChartService : IChartService
     {
-        private readonly IAccountRepository accountRepository;
         private readonly ISettingsService settingsService;
-        private readonly ISubclassRepository subclassRepository;
         private readonly IViewService viewService;
 
-        public ChartService(
-            ISettingsService settingsService,
-            IViewService viewService,
-            IAccountRepository accountRepository,
-            ISubclassRepository subclassRepository)
+        public ChartService(ISettingsService settingsService, IViewService viewService)
         {
             this.settingsService = settingsService;
             this.viewService = viewService;
-            this.accountRepository = accountRepository;
-            this.subclassRepository = subclassRepository;
         }
 
         public IReadOnlyList<DataSerie> GetExpensesPerMonth()
         {
-            var transactions = viewService.GetTransactionViewList().Where(a => a.TargetAccount.Class == ClassIds.Expenses);
+            var expenseTransactions = viewService.GetTransactionViewList()
+                .Where(t => t.TargetAccount.Class == ClassIds.Expenses)
+                .ToList();
 
-            // More than one subclass xx
-            if (transactions.Select(t => t.TargetAccount.SubClass).Distinct().Count() > 1)
-            {
-                return GetSubClassExpensesPerMonth();
+            var distinctSubClasses = expenseTransactions
+                .Select(t => t.TargetAccount.SubClass)
+                .Distinct()
+                .Count();
+
+            return distinctSubClasses > 1
+                ? GetSubClassExpensesPerMonth(expenseTransactions)
+                : GetAccountExpensesPerMonth();
         }
 
-            // only one subclass xx (z.B. Mandant Mannenbach)
-            return GetAccountExpensesPerMonth();
-        }
-
-        private List<DataSerie> GetSubClassExpensesPerMonth()
+        private List<DataSerie> GetSubClassExpensesPerMonth(List<TransactionDataset> expenseTransactions)
         {
-            //var subclasses = subclassRepository.GetSubClassList();
-            var transactions = viewService.GetTransactionViewList().Where(a => a.TargetAccount.Class == ClassIds.Expenses).ToList();
-            var list = new List<DataSerie>();
-
-            var newestTransaction = transactions.OrderByDescending(t => t.ValueDate).FirstOrDefault();
-            var maxMonth = newestTransaction?.ValueDate.Month ?? 12;
             var year = settingsService.GetYear();
+            var maxMonth = expenseTransactions
+                .OrderByDescending(t => t.ValueDate)
+                .FirstOrDefault()?.ValueDate.Month ?? 12;
 
-            // Group by subclass
-            foreach (var grp in transactions.GroupBy(a => a.TargetAccount.SubClass).Select(a => new {Key = a.Key, List = a.ToList()}))
+            var list = new List<DataSerie>();
+            foreach (var grp in expenseTransactions.GroupBy(t => t.TargetAccount.SubClass))
             {
-                // Sum subclass transactions per month
-                var groupedByMonth = grp.List.GroupBy(g => g.ValueDate.Month).ToDictionary(g => g.Key, g => g.ToList().Sum(s => s.Value));
+                var groupedByMonth = grp
+                    .GroupBy(t => t.ValueDate.Month)
+                    .ToDictionary(g => g.Key, g => g.Sum(t => t.Value));
                 EnsureEntryForEveryMonth(groupedByMonth, maxMonth);
 
-                //var subClass = subclasses.FirstOrDefault(s => s.Number == grp.List.First().TargetAccount.SubClass);
-                list.Add(
-                    new DataSerie(
-                        Id: grp.List.First().TargetAccount.SubClass.ToString(),
-                        Name: grp.List.First().TargetAccount.Name,
+                list.Add(new DataSerie(
+                    Id: grp.Key.ToString(),
+                    Name: grp.First().TargetAccount.Name,
                     X: groupedByMonth.OrderBy(g => g.Key).Select(g => new DateOnly(year, g.Key, 1)).ToList(),
                     Y: groupedByMonth.OrderBy(g => g.Key).Select(g => g.Value).ToList()
-                    )
-                );
+                ));
             }
             return list;
         }
 
         private List<DataSerie> GetAccountExpensesPerMonth()
         {
+            var year = settingsService.GetYear();
+            var allTransactions = viewService.GetTransactionViewList();
+            var expenseAccounts = viewService.GetAccountViewList().Where(a => a.Class == ClassIds.Expenses);
+
             var list = new List<DataSerie>();
-            var expensesAccounts = viewService.GetAccountViewList().Where(a => a.Class == ClassIds.Expenses);
-            foreach (var account in expensesAccounts)
+            foreach (var account in expenseAccounts)
             {
-                var serie = GetAccountExpensesPerMonth(account.Id, DateTime.Now.Year);
-                if (serie != null)
+                var transactions = allTransactions.Where(t => t.TargetAccountId == account.Id).ToList();
+                if (transactions.Count == 0)
                 {
-                    list.Add(serie);
+                    continue;
                 }
+
+                var maxMonth = transactions.Max(t => t.ValueDate.Month);
+                var groupedByMonth = transactions
+                    .GroupBy(t => t.ValueDate.Month)
+                    .ToDictionary(g => g.Key, g => g.Sum(t => t.Value));
+                EnsureEntryForEveryMonth(groupedByMonth, maxMonth);
+
+                list.Add(new DataSerie(
+                    Id: account.Id,
+                    Name: account.Name,
+                    X: groupedByMonth.OrderBy(g => g.Key).Select(g => new DateOnly(year, g.Key, 1)).ToList(),
+                    Y: groupedByMonth.OrderBy(g => g.Key).Select(g => g.Value).ToList()
+                ));
             }
             return list;
         }
 
-        private DataSerie GetAccountExpensesPerMonth(string accountId, int year)
-        {
-            if (settingsService.TrySetYear(year))
-            {
-                var accountList = accountRepository.GetAccountList();
-                var account = accountList.SingleOrDefault(a => a.Id == accountId);
-                // perhaps we dont have the account for last year
-                if (account == null)
-                {
-                    return null;
-                }
-                var transactions = viewService.GetTransactionViewList().Where(t => t.TargetAccountId == accountId).ToList();
-
-                var newestTransaction = transactions.OrderByDescending(t => t.ValueDate).FirstOrDefault();
-                var maxMonth = newestTransaction?.ValueDate.Month ?? 12;
-
-                var groupedByMonth = transactions.GroupBy(g => g.ValueDate.Month).ToDictionary(g => g.Key, g => g.ToList().Sum(s => s.Value));
-                EnsureEntryForEveryMonth(groupedByMonth, maxMonth);
-
-                settingsService.SetYear(DateTime.Now.Year);
-
-                return new DataSerie(
-                    Id: accountId,
-                    Name: account.Name,
-                    X: groupedByMonth.OrderBy(g => g.Key).Select(g => new DateOnly(year, g.Key, 1)).ToList(), 
-                    Y: groupedByMonth.OrderBy(g => g.Key).Select(g => g.Value).ToList()
-                );
-            }
-            
-            return null;
-        }
-
-        private void EnsureEntryForEveryMonth(Dictionary<int, decimal> values, int maxMonth = 12)
+        private static void EnsureEntryForEveryMonth(Dictionary<int, decimal> values, int maxMonth = 12)
         {
             for (int i = 1; i <= maxMonth; i++)
             {