Feat: Local Extension Registry (EXT-2)

lib/core/extensions/extension_paths.dart

@@ -0,0 +1,29 @@
+import 'dart:io';
+
+import 'package:path/path.dart' as p;
+import 'package:path_provider/path_provider.dart';
+
+/// Centralizes extension file locations.
+abstract final class ExtensionPaths {
+  static const _extensionsSegment = 'extensions';
+
+  /// Returns `~/.querya/extensions` on Linux/Mac, or equivalent `USERPROFILE\.querya\extensions` on Windows.
+  /// Falls back to application support directory if HOME is unavailable.
+  static Future<Directory> extensionsDirectory() async {
+    final home = Platform.environment['HOME'] ?? Platform.environment['USERPROFILE'];
+    if (home == null || home.isEmpty) {
+      final support = await getApplicationSupportDirectory();
+      return Directory(p.join(support.path, _extensionsSegment));
+    }
+    return Directory(p.join(home, '.querya', _extensionsSegment));
+  }
+
+  /// Creates the extensions directory if it doesn't exist.
+  static Future<Directory> ensureExtensionsDirectory() async {
+    final dir = await extensionsDirectory();
+    if (!await dir.exists()) {
+      await dir.create(recursive: true);
+    }
+    return dir;
+  }
+}

lib/core/extensions/local_extension_registry.dart

@@ -0,0 +1,61 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:path/path.dart' as p;
+
+import 'extension_paths.dart';
+import 'models/extension_manifest.dart';
+
+/// Scans the local filesystem for extensions and loads their manifests.
+class LocalExtensionRegistry {
+  LocalExtensionRegistry._();
+  static final LocalExtensionRegistry instance = LocalExtensionRegistry._();
+
+  List<ExtensionManifest> _manifests = [];
+  bool _loaded = false;
+
+  /// Returns an unmodifiable list of loaded manifests.
+  List<ExtensionManifest> get manifests => List.unmodifiable(_manifests);
+
+  /// Reloads manifests from the disk.
+  Future<void> reload() async {
+    _loaded = false;
+    await load();
+  }
+
+  /// Loads manifests from the extensions directory if not already loaded.
+  Future<List<ExtensionManifest>> load() async {
+    if (_loaded) return manifests;
+
+    final dir = await ExtensionPaths.extensionsDirectory();
+    final loadedManifests = <ExtensionManifest>[];
+
+    if (await dir.exists()) {
+      // Use list() rather than listSync() to prevent blocking the UI
+      final entities = await dir.list().toList();
+      for (final entity in entities) {
+        if (entity is Directory) {
+          final manifestFile = File(p.join(entity.path, 'manifest.json'));
+          if (await manifestFile.exists()) {
+            try {
+              final content = await manifestFile.readAsString();
+              final json = jsonDecode(content) as Map<String, dynamic>;
+              final manifest = ExtensionManifest.fromJson(
+                json, 
+                installPath: entity.path,
+              );
+              loadedManifests.add(manifest);
+            } catch (e) {
+              // Log or ignore invalid manifests
+              // In the future, we could report these to an error logging service
+            }
+          }
+        }
+      }
+    }
+
+    _manifests = loadedManifests;
+    _loaded = true;
+    return manifests;
+  }
+}

lib/core/extensions/models/extension_manifest.dart

@@ -10,6 +10,7 @@ class ExtensionManifest {
   final String? main;
   final String? icon;
   final String? description;
+  final String? installPath;
 
   const ExtensionManifest({
     required this.id,
@@ -21,9 +22,10 @@ class ExtensionManifest {
     this.main,
     this.icon,
     this.description,
+    this.installPath,
   });
 
-  factory ExtensionManifest.fromJson(Map<String, dynamic> json) {
+  factory ExtensionManifest.fromJson(Map<String, dynamic> json, {String? installPath}) {
     return ExtensionManifest(
       id: json['id'] as String,
       name: json['name'] as String,
@@ -34,6 +36,7 @@ class ExtensionManifest {
       main: json['main'] as String?,
       icon: json['icon'] as String?,
       description: json['description'] as String?,
+      installPath: installPath,
     );
   }