Fix read-only open semantics, Studio prompt localization, and multi-process config docs (#125)

* Initial plan

* Fix read-only open behavior, Studio prompts, and multiprocess docs

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

Author: Copilot

README-5.0.0-preview.0.md

@@ -528,7 +528,7 @@ This feature is **opt-in** — all existing single-process behaviour is preserve
 ```csharp
 var config = new PageFileConfig
 {
-    EnableMultiProcessAccess = true,
+    AllowMultiProcessAccess = true,
 };
 
 // Process A (writer)
@@ -539,7 +539,7 @@ using var db = new AppDb("shared.db", config);
 ```
 
 > [!IMPORTANT]
-> Multi-process WAL requires all cooperating processes to open the database with `EnableMultiProcessAccess = true`. A process that opens with `EnableMultiProcessAccess = false` will hold `FileShare.None` and block other processes.
+> Multi-process WAL requires all cooperating processes to open the database with `AllowMultiProcessAccess = true`. A process that opens with `AllowMultiProcessAccess = false` will hold `FileShare.None` and block other processes.
 
 ---
 
@@ -628,7 +628,7 @@ v5.0.0-preview.0 is **fully backwards-compatible** with v4.4.2 databases. No fil
 | Add audit trail | Call `ConfigureAudit(...)` after construction |
 | Add GDPR annotations | Annotate properties with `[PersonalData]` and rebuild |
 | Enable Strict mode | Add `HasGdprMode(GdprMode.Strict)` + configure encryption + audit |
-| Enable multi-process access | Set `PageFileConfig.EnableMultiProcessAccess = true` on all processes |
+| Enable multi-process access | Set `PageFileConfig.AllowMultiProcessAccess = true` on all processes |
 
 ---
 
@@ -706,7 +706,7 @@ v5.0.0-preview.0 is **fully backwards-compatible** with v4.4.2 databases. No fil
 ## Known limitations in this preview
 
 - `RotateEncryptionKeyAsync` is implemented but not yet stress-tested under concurrent write load. Use it during a maintenance window.
-- Multi-process WAL (`EnableMultiProcessAccess`) is not yet supported on WASM/Browser targets (tracked in [WASM_SUPPORT.md](WASM_SUPPORT.md)).
+- Multi-process WAL (`AllowMultiProcessAccess`) is not yet supported on WASM/Browser targets (tracked in [WASM_SUPPORT.md](WASM_SUPPORT.md)).
 - Argon2id KDF is reserved for a future release. PBKDF2-SHA256 (600 000 iterations) and HKDF-SHA256 are the only supported KDFs in this preview.
 - Source-generator GDPR metadata emission (`PersonalDataFields`) requires .NET SDK 9+ (Roslyn 4.x). Fallback reflection path is fully functional on all supported runtimes.
 

README.md

@@ -302,7 +302,7 @@ await db.VacuumAsync();
 A `.wal-shm` sidecar enables **N-reader / 1-writer** access across OS processes (opt-in):
 
 ```csharp
-var config = new PageFileConfig { EnableMultiProcessAccess = true };
+var config = new PageFileConfig { AllowMultiProcessAccess = true };
 using var db = new AppDb("shared.db", config); // open from multiple processes
 ```
 
@@ -1082,7 +1082,7 @@ We are actively building the core. Here is where we stand:
 - ✅ **GDPR Compliance Primitives (v5.0.0)**: `[PersonalData]` annotation, `DataSensitivity` levels, Subject Export (`ExportSubjectDataAsync` — Art. 15/20), Database Inspection (`InspectDatabase` — Art. 30), CDC Field Masking (WP2 — `RevealPersonalData`, `IncludeOnlyFields`, `ExcludeFields`), and `GdprMode.Strict` (Art. 25 privacy-by-default orchestration).
 - ✅ **Generalized Retention Policy (v5.0.0)**: `HasRetentionPolicy` now applies to any typed collection (not only `TimeSeries`). Supports `maxAge`, `maxDocumentCount`, and configurable `RetentionTrigger` (on-insert or scheduled).
 - ✅ **Secure Erase & VACUUM (v5.0.0)**: `HasSecureErase(true)` zeros the storage slot on delete for GDPR Art. 17. `VacuumAsync()` compacts the database and reclaims free space.
-- ✅ **Multi-Process WAL (v5.0.0)**: `.wal-shm` sidecar enables N-reader / 1-writer access across OS processes. Opt in via `PageFileConfig.EnableMultiProcessAccess = true`.
+- ✅ **Multi-Process WAL (v5.0.0)**: `.wal-shm` sidecar enables N-reader / 1-writer access across OS processes. Opt in via `PageFileConfig.AllowMultiProcessAccess = true`.
 
 ## 🔮 Future Vision
 
@@ -1127,4 +1127,3 @@ Special thanks to the community members who helped improve BLite:
 
 Licensed under the MIT License. Use it freely in personal and commercial projects.
 
-

src/BLite.Core/Storage/PageFile.cs

@@ -354,10 +354,14 @@ public void Open()
 
             var fileExists = File.Exists(_filePath);
 
+            var isReadOnlyAccess = _config.Access == MemoryMappedFileAccess.Read;
+            var fileMode = isReadOnlyAccess ? FileMode.Open : FileMode.OpenOrCreate;
+            var fileAccess = isReadOnlyAccess ? FileAccess.Read : FileAccess.ReadWrite;
+
             _fileStream = new FileStream(
                 _filePath,
-                FileMode.OpenOrCreate,
-                FileAccess.ReadWrite,
+                fileMode,
+                fileAccess,
                 _config.AllowMultiProcessAccess ? FileShare.ReadWrite : FileShare.None,
                 bufferSize: 4096,
 #if NET6_0_OR_GREATER

tests/BLite.Tests/MultiProcessAccessConfigTests.cs

@@ -102,4 +102,51 @@ public void StorageEngine_ForwardsAllowMultiProcessAccess_ToOwnedWal()
             try { Directory.Delete(dir, recursive: true); } catch { /* best-effort */ }
         }
     }
+
+    [Fact]
+    public void StorageEngine_ReadOnlyReader_CanOpenAlongsideWriter_WhenMultiProcessEnabled()
+    {
+        var dir = Path.Combine(Path.GetTempPath(), $"blite_mpread_{Guid.NewGuid():N}");
+        Directory.CreateDirectory(dir);
+        try
+        {
+            var dbPath = Path.Combine(dir, "shared.db");
+            var writerConfig = PageFileConfig.Default with { AllowMultiProcessAccess = true };
+            var readerConfig = writerConfig with { Access = System.IO.MemoryMappedFiles.MemoryMappedFileAccess.Read };
+
+            using var writer = new StorageEngine(dbPath, writerConfig);
+            using var reader = new StorageEngine(dbPath, readerConfig);
+
+            Assert.NotNull(writer.SharedMemory);
+            Assert.NotNull(reader.SharedMemory);
+        }
+        finally
+        {
+            try { Directory.Delete(dir, recursive: true); } catch { /* best-effort */ }
+        }
+    }
+
+    [Fact]
+    public void PageFile_ReadOnlyMode_DoesNotCreateMissingFile()
+    {
+        var dir = Path.Combine(Path.GetTempPath(), $"blite_readonly_{Guid.NewGuid():N}");
+        Directory.CreateDirectory(dir);
+        try
+        {
+            var dbPath = Path.Combine(dir, "missing.db");
+            var config = PageFileConfig.Default with
+            {
+                Access = System.IO.MemoryMappedFiles.MemoryMappedFileAccess.Read,
+                AllowMultiProcessAccess = true
+            };
+
+            using var pageFile = new PageFile(dbPath, config);
+            Assert.Throws<FileNotFoundException>(() => pageFile.Open());
+            Assert.False(File.Exists(dbPath));
+        }
+        finally
+        {
+            try { Directory.Delete(dir, recursive: true); } catch { /* best-effort */ }
+        }
+    }
 }

tools/BLite.Studio/ViewModels/MainWindowViewModel.cs

@@ -262,10 +262,13 @@ private async Task TryOpen(string path, int presetValue, bool readOnly)
                 if (string.IsNullOrEmpty(EncryptionPassphrase))
                     throw new InvalidOperationException("A passphrase is required when encryption is enabled.");
 
+                var access = IsReadOnly
+                    ? MemoryMappedFileAccess.Read
+                    : MemoryMappedFileAccess.ReadWrite;
                 var crypto      = new CryptoOptions(EncryptionPassphrase);
-                var baseConfig  = new PageFileConfig { AllowMultiProcessAccess = true };
+                var baseConfig  = new PageFileConfig { AllowMultiProcessAccess = true, Access = access };
                 _engine       = new BLiteEngine(path, crypto, baseConfig: baseConfig);
-                _openedConfig = PageFileConfig.Default with { AllowMultiProcessAccess = true };
+                _openedConfig = PageFileConfig.Default with { AllowMultiProcessAccess = true, Access = access };
             }
             else
             {
@@ -308,7 +311,7 @@ private async Task TryOpen(string path, int presetValue, bool readOnly)
         }
         catch (Exception ex)
         {
-            StatusMessage  = $"Errore: {ex.Message}";
+            StatusMessage  = $"Error: {ex.Message}";
             IsDatabaseOpen = false;
         }
     }

tools/BLite.Studio/Views/MainWindow.axaml.cs

@@ -20,13 +20,13 @@ private async void Browse_Click(object? sender, RoutedEventArgs e)
 
         var files = await topLevel.StorageProvider.OpenFilePickerAsync(new FilePickerOpenOptions
         {
-            Title = "Apri database BLite",
+            Title = "Open BLite database",
             AllowMultiple = false,
-            // Nessun filtro: qualsiasi estensione è accettata
+            // Keep broad filters so users can open existing files with custom extensions.
             FileTypeFilter =
             [
                 new FilePickerFileType("Database BLite") { Patterns = ["*.db", "*.blite", "*.blt"] },
-                new FilePickerFileType("Tutti i file")   { Patterns = ["*.*"] },
+                new FilePickerFileType("All files")      { Patterns = ["*.*"] },
             ]
         });