Create a new class for managing the set of analysis roots.

pkg/analysis_server/lib/src/context_directory_manager.dart

Index: pkg/analysis_server/lib/src/context_directory_manager.dart
diff --git a/pkg/analysis_server/lib/src/context_directory_manager.dart b/pkg/analysis_server/lib/src/context_directory_manager.dart
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+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library context.directory.manager;
+
+import 'package:analysis_server/src/resource.dart';
+
+/**
+ * Class that maintains a mapping from included/excluded paths to a set of
+ * folders that should correspond to analysis contexts.
+ */
+abstract class ContextDirectoryManager {
+  /**
+   * The set of included folders in the most recent successful call to
+   * [setRoots].
+   */
+  Set<Folder> currentFolders = new Set<Folder>();
+
+  /**
+   * The [ResourceProvider] using which paths are converted into [Resource]s.
+   */
+  final ResourceProvider resourceProvider;
+
+  ContextDirectoryManager(this.resourceProvider);
+
+  /**
+   * Change the set of paths which should be used as starting points to
+   * determine the context directories.
+   */
+  void setRoots(List<String> includedPaths,
+                List<String> excludedPaths) {
+    // included
+    Set<Folder> includedFolders = new Set<Folder>();
+    for (int i = 0; i < includedPaths.length; i++) {
+      String path = includedPaths[i];
+      Resource resource = resourceProvider.getResource(path);
+      if (resource is Folder) {
+        includedFolders.add(resource);
+      } else {
+        // TODO(scheglov) implemented separate files analysis
+        throw new UnimplementedError(
+            '$path is not a folder. '
+            'Only support for folder analysis is implemented currently.');
+      }
+    }
+    // excluded
+    // TODO(scheglov) remove when implemented
+    if (excludedPaths.isNotEmpty) {
+      throw new UnimplementedError(
+          'Excluded paths are not supported yet');
+    }
+    Set<Folder> excludedFolders = new Set<Folder>();
+    // diff
+    Set<Folder> newFolders = includedFolders.difference(currentFolders);
+    Set<Folder> oldFolders = currentFolders.difference(includedFolders);
+    // remove old contexts
+    for (Folder folder in oldFolders) {
+      // TODO(scheglov) implement
+    }
+    // add new contexts
+    for (Folder folder in newFolders) {
+      addContext(folder);
+    }
+    currentFolders = new Set<Folder>.from(includedFolders);
+  }
+
+  /**
+   * Called when a new context needs to be created.
+   */
+  void addContext(Folder folder);
+}