add FacetIndex for faster facet search in large projects like ours

platform/lang-api/src/com/intellij/facet/FacetIndex.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2000-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.facet;
+
+import com.intellij.openapi.module.Module;
+import com.intellij.openapi.module.ModuleManager;
+import com.intellij.openapi.project.Project;
+import com.intellij.openapi.roots.ProjectRootModificationTracker;
+import com.intellij.psi.util.CachedValueProvider;
+import com.intellij.psi.util.CachedValuesManager;
+import com.intellij.util.containers.ContainerUtil;
+import com.intellij.util.containers.MultiMap;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Allows to find modules with facets of specified types in amortized O(1) time, without iterating over all modules.
+ * 
+ * @see FacetManager
+ * @since 173.*
+ */
+public class FacetIndex {
+  private final MultiMap<FacetTypeId<?>, Module> myMap = MultiMap.createLinked();
+
+  private FacetIndex(Project project) {
+    for (Module module : ModuleManager.getInstance(project).getModules()) {
+      for (Facet facet : FacetManager.getInstance(module).getAllFacets()) {
+        myMap.putValue(facet.getTypeId(), module);
+      }
+    }
+  }
+
+  public boolean hasAnyModuleWithFacet(@NotNull FacetTypeId<?> type) {
+    return myMap.containsKey(type);
+  }
+
+  @Nullable
+  public Module findModuleWithFacet(@NotNull FacetTypeId<?> type) {
+    return ContainerUtil.getFirstItem(myMap.get(type));
+  }
+
+  @NotNull
+  public static FacetIndex getIndex(@NotNull Project project) {
+    return CachedValuesManager.getManager(project).getCachedValue(project, () -> CachedValueProvider.Result.create(
+      new FacetIndex(project), 
+      ProjectRootModificationTracker.getInstance(project)));
+  }
+}