PR D: per-scope repository cache

Add a Scoped RepositoryCache that memoizes deserialized XML lists,
keyed by absolute file path. Each XML file is loaded at most once per
SignalR circuit; Save invalidates the corresponding entry so
subsequent reads reload from disk.

BaseRepository gains a LoadList<T>(fileName) helper; each of the seven
repositories now defines Get*List() as a one-liner over that helper
and takes RepositoryCache via the constructor.

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

Schaad.Accounting.Db/Repositories/AccountRepository.cs

@@ -11,20 +11,16 @@ namespace Schaad.Accounting.Repositories
     {
         private readonly string ACCOUNTS = "Accounts.xml";
 
-        public AccountRepository(ISettingsService settingsService) : base(settingsService)
+        public AccountRepository(ISettingsService settingsService, RepositoryCache cache)
+            : base(settingsService, cache)
         {
             EnsureAccountsFile();
         }
 
-
         /// <summary>
         /// Load accounts
         /// </summary>
-        public List<Account> GetAccountList()
+        public List<Account> GetAccountList() => LoadList<Account>(ACCOUNTS);
-        {
-            var accounts = Load<List<Account>>(ACCOUNTS);
-            return accounts ?? new List<Account>();
-        }
 
         /// <summary>
         /// Save an account (insert/update)

Schaad.Accounting.Db/Repositories/BankTransactionRepository.cs

@@ -10,18 +10,15 @@ namespace Schaad.Accounting.Repositories
     {
         private readonly string BANK_TRANSACTIONS = "BankTransactions.xml";
 
-        public BankTransactionRepository(ISettingsService settingsService) : base(settingsService)
+        public BankTransactionRepository(ISettingsService settingsService, RepositoryCache cache)
+            : base(settingsService, cache)
         {
         }
 
         /// <summary>
         /// Load bank transactions
         /// </summary>
-        public List<BankTransaction> GetBankTransactionList()
+        public List<BankTransaction> GetBankTransactionList() => LoadList<BankTransaction>(BANK_TRANSACTIONS);
-        {
-            var transactions = Load<List<BankTransaction>>(BANK_TRANSACTIONS);
-            return transactions != null ? transactions : new List<BankTransaction>();
-        }
 
         /// <summary>
         /// Save new bank transactions, ignore existing ones (no update)

Schaad.Accounting.Db/Repositories/BaseRepository.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Concurrent;
+using System.Collections.Generic;
 using System.IO;
 using System.Text;
 using System.Xml;
@@ -16,10 +17,12 @@ namespace Schaad.Accounting.Repositories
             new(StringComparer.OrdinalIgnoreCase);
 
         protected readonly ISettingsService settingsService;
+        protected readonly RepositoryCache cache;
 
-        protected BaseRepository(ISettingsService settingsService)
+        protected BaseRepository(ISettingsService settingsService, RepositoryCache cache)
         {
             this.settingsService = settingsService;
+            this.cache = cache;
         }
 
         protected void EnsureFileExists(string fileName)
@@ -38,9 +41,20 @@ namespace Schaad.Accounting.Repositories
             }
         }
 
+        /// <summary>
+        /// Load a list, cached per scope. First call reads the XML file; subsequent calls in
+        /// the same scope return the cached list. <see cref="Save"/> invalidates the entry.
+        /// </summary>
+        protected List<T> LoadList<T>(string fileName)
+        {
+            var filePath = Path.Combine(settingsService.GetDbPath(), fileName);
+            return cache.GetOrLoad(filePath, () => Load<List<T>>(fileName) ?? new List<T>());
+        }
+
         /// <summary>
         /// Save an object to an xml file. Writes to a .tmp sibling and then atomically
-        /// renames it, so a crash mid-write leaves the previous file intact.
+        /// renames it, so a crash mid-write leaves the previous file intact. Invalidates
+        /// the corresponding cache entry.
         /// </summary>
         protected void Save<T>(T obj, string fileName)
         {
@@ -74,10 +88,13 @@ namespace Schaad.Accounting.Repositories
                     throw;
                 }
             }
+
+            cache.Invalidate(filePath);
         }
 
         /// <summary>
-        /// Load an object from an xml file
+        /// Load an object from an xml file (uncached; used for one-off reads such as file
+        /// existence bootstrapping). Prefer <see cref="LoadList{T}"/> for repository reads.
         /// </summary>
         protected T Load<T>(string fileName)
         {

Schaad.Accounting.Db/Repositories/BookingRuleRepository.cs

@@ -10,7 +10,8 @@ namespace Schaad.Accounting.Repositories
     {
         private readonly string BOOKING_RULES = "BookingRules.xml";
 
-        public BookingRuleRepository(ISettingsService settingsService) : base(settingsService)
+        public BookingRuleRepository(ISettingsService settingsService, RepositoryCache cache)
+            : base(settingsService, cache)
         {
             EnsureFileExists(BOOKING_RULES);
         }
@@ -18,11 +19,7 @@ namespace Schaad.Accounting.Repositories
         /// <summary>
         /// Load booking rules
         /// </summary>
-        public List<BookingRule> GetBookingRuleList()
+        public List<BookingRule> GetBookingRuleList() => LoadList<BookingRule>(BOOKING_RULES);
-        {
-            var bookingTexts = Load<List<BookingRule>>(BOOKING_RULES);
-            return bookingTexts ?? new List<BookingRule>();
-        }
 
         /// <summary>
         /// Save a booking rule (insert/update)

Schaad.Accounting.Db/Repositories/BookingTextRepository.cs

@@ -10,19 +10,16 @@ namespace Schaad.Accounting.Repositories
     {
         private readonly string BOOKING_TEXTS = "BookingTexts.xml";
 
-        public BookingTextRepository(ISettingsService settingsService) : base(settingsService)
+        public BookingTextRepository(ISettingsService settingsService, RepositoryCache cache)
+            : base(settingsService, cache)
         {
             EnsureFileExists(BOOKING_TEXTS);
         }
 
         /// <summary>
-        /// Load bokking texts
+        /// Load booking texts
         /// </summary>
-        public List<BookingText> GetBookingTextList()
+        public List<BookingText> GetBookingTextList() => LoadList<BookingText>(BOOKING_TEXTS);
-        {
-            var bookingTexts = Load<List<BookingText>>(BOOKING_TEXTS);
-            return bookingTexts ?? new List<BookingText>();
-        }
 
         /// <summary>
         /// Save a booking text (insert/update)

Schaad.Accounting.Db/Repositories/SplitPredefinitionRepository.cs

@@ -10,7 +10,8 @@ namespace Schaad.Accounting.Repositories
     {
         private readonly string SPLIT_PREDEFINITION = "SplitPredefinitions.xml";
 
-        public SplitPredefinitionRepository(ISettingsService settingsService) : base(settingsService)
+        public SplitPredefinitionRepository(ISettingsService settingsService, RepositoryCache cache)
+            : base(settingsService, cache)
         {
             EnsureFileExists(SPLIT_PREDEFINITION);
         }
@@ -18,11 +19,7 @@ namespace Schaad.Accounting.Repositories
         /// <summary>
         /// Load split predefinitions
         /// </summary>
-        public List<SplitPredefinition> GetSplitPredefinitionList()
+        public List<SplitPredefinition> GetSplitPredefinitionList() => LoadList<SplitPredefinition>(SPLIT_PREDEFINITION);
-        {
-            var definitions = Load<List<SplitPredefinition>>(SPLIT_PREDEFINITION);
-            return definitions ?? new List<SplitPredefinition>();
-        }
 
         /// <summary>
         /// Save a split predefinition (insert/update)

Schaad.Accounting.Db/Repositories/SubclassRepository.cs

@@ -11,7 +11,8 @@ namespace Schaad.Accounting.Repositories
         private readonly Dictionary<int, string> classes = new Dictionary<int, string>();
         private readonly string SUBCLASSES = "SubClasses.xml";
 
-        public SubclassRepository(ISettingsService settingsService) : base(settingsService)
+        public SubclassRepository(ISettingsService settingsService, RepositoryCache cache)
+            : base(settingsService, cache)
         {
             EnsureFileExists(SUBCLASSES);
 
@@ -22,13 +23,9 @@ namespace Schaad.Accounting.Repositories
         }
 
         /// <summary>
-        /// Load bokking texts
+        /// Load subclasses
         /// </summary>
-        public List<SubClass> GetSubClassList()
+        public List<SubClass> GetSubClassList() => LoadList<SubClass>(SUBCLASSES);
-        {
-            var subclasses = Load<List<SubClass>>(SUBCLASSES);
-            return subclasses ?? new List<SubClass>();
-        }
 
         /// <summary>
         /// Save a booking text (insert/update)

Schaad.Accounting.Db/Repositories/TransactionRepository.cs

@@ -11,7 +11,8 @@ namespace Schaad.Accounting.Repositories
         private readonly IAccountRepository accountRepository;
         private readonly string TRANSACTIONS = "Transactions.xml";
 
-        public TransactionRepository(ISettingsService settingsService, IAccountRepository accountRepository) : base(settingsService)
+        public TransactionRepository(ISettingsService settingsService, RepositoryCache cache, IAccountRepository accountRepository)
+            : base(settingsService, cache)
         {
             this.accountRepository = accountRepository;
         }
@@ -19,11 +20,7 @@ namespace Schaad.Accounting.Repositories
         /// <summary>
         /// Get transaction list
         /// </summary>
-        public List<Transaction> GetTransactionList()
+        public List<Transaction> GetTransactionList() => LoadList<Transaction>(TRANSACTIONS);
-        {
-            var transactionList = Load<List<Transaction>>(TRANSACTIONS);
-            return transactionList ?? new List<Transaction>();
-        }
 
         /// <summary>
         /// Save a transaction (insert/update)

Schaad.Accounting.Db/RepositoryCache.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+
+namespace Schaad.Accounting.Repositories
+{
+    /// <summary>
+    /// Per-scope cache of deserialized XML lists, keyed by absolute file path.
+    ///
+    /// Registered as Scoped so it lives for the SignalR circuit; each XML file is
+    /// then loaded at most once per circuit. Writes go through <see cref="BaseRepository.Save"/>,
+    /// which invalidates the corresponding entry so the next read reloads from disk.
+    ///
+    /// Not thread-safe — callers within a single Blazor Server circuit run serialized on the
+    /// circuit's synchronization context, so no locking is needed.
+    /// </summary>
+    public class RepositoryCache
+    {
+        private readonly Dictionary<string, object> entries =
+            new(StringComparer.OrdinalIgnoreCase);
+
+        public List<T> GetOrLoad<T>(string cacheKey, Func<List<T>> loader)
+        {
+            if (entries.TryGetValue(cacheKey, out var cached))
+            {
+                return (List<T>)cached;
+            }
+
+            var list = loader();
+            entries[cacheKey] = list;
+            return list;
+        }
+
+        public void Invalidate(string cacheKey)
+        {
+            entries.Remove(cacheKey);
+        }
+    }
+}

Schaad.Accounting.UI/Extensions.cs

@@ -16,6 +16,7 @@ namespace Schaad.Accounting.UI
             // can safely become Scoped (see IMPROVEMENT_PLAN.md).
             services.AddSingleton<ISettingsService, SettingsService>();
 
+            services.AddScoped<RepositoryCache>();
             services.AddScoped<IAccountRepository, AccountRepository>();
             services.AddScoped<IBankTransactionRepository, BankTransactionRepository>();
             services.AddScoped<IBookingRuleRepository, BookingRuleRepository>();