KT-1426 Implement "Optimize Imports" in plugin - get collection of used references in file

idea/src/META-INF/plugin.xml

@@ -66,6 +66,7 @@
       <internalFileTemplate name="Kotlin Trait"/>
 
       <gotoSymbolContributor implementation="org.jetbrains.jet.plugin.caches.GotoSymbolContributor"/>
+      <lang.importOptimizer language="jet" implementationClass="org.jetbrains.jet.plugin.editor.importOptimizer.JetImportOptimizer"/>
 
       <fileTypeFactory implementation="org.jetbrains.jet.plugin.JetFileFactory"/>
 
@@ -166,5 +167,7 @@
                   anchor="right"
                   icon="/org/jetbrains/jet/plugin/icons/kotlin16x16.png"
               />
+
+
   </extensions>
 </idea-plugin>

idea/src/org/jetbrains/jet/plugin/editor/importOptimizer/JetImportOptimizer.java

@@ -0,0 +1,138 @@
+/*
+ * Copyright 2000-2012 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 org.jetbrains.jet.plugin.editor.importOptimizer;
+
+import com.intellij.lang.ImportOptimizer;
+import com.intellij.openapi.progress.ProgressIndicatorProvider;
+import com.intellij.psi.*;
+import com.intellij.psi.util.PsiTreeUtil;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.jet.lang.psi.*;
+import org.jetbrains.jet.lang.resolve.java.JvmAbi;
+import org.jetbrains.jet.util.QualifiedNamesUtil;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * @author Nikolay Krasko
+ */
+public class JetImportOptimizer implements ImportOptimizer {
+    @Override
+    public boolean supports(PsiFile file) {
+        return file instanceof JetFile;
+    }
+
+    @NotNull
+    @Override
+    public Runnable processFile(final PsiFile file) {
+        return new Runnable() {
+
+            @Override
+            public void run() {
+                JetFile jetFile = (JetFile) file;
+                Set<String> usedQualifiedNames = extractUsedQualifiedNames(jetFile);
+
+            }
+        };
+
+    }
+
+    public static Set<String> extractUsedQualifiedNames(JetFile jetFile) {
+
+        final Set<String> usedQualifiedNames = new HashSet<String>();
+        jetFile.accept(new JetVisitorVoid() {
+            @Override
+            public void visitElement(PsiElement element) {
+                ProgressIndicatorProvider.checkCanceled();
+                element.acceptChildren(this);
+            }
+
+            @Override
+            public void visitReferenceExpression(JetReferenceExpression expression) {
+                if (PsiTreeUtil.getParentOfType(expression, JetQualifiedExpression.class) == null) {
+                    PsiReference reference = expression.getReference();
+                    if (reference != null) {
+                        List<PsiElement> references = new ArrayList<PsiElement>();
+                        PsiElement resolve = reference.resolve();
+                        if (resolve != null) {
+                            references.add(resolve);
+                        }
+
+                        if (references.isEmpty() && reference instanceof PsiPolyVariantReference) {
+                            for (ResolveResult resolveResult : ((PsiPolyVariantReference) reference).multiResolve(true)) {
+                                references.add(resolveResult.getElement());
+                            }
+                        }
+
+                        for (PsiElement psiReference : references) {
+                            String fqName = getElementFQName(psiReference);
+                            if (fqName != null) {
+                                usedQualifiedNames.add(fqName);
+                            }
+                        }
+                    }
+
+                }
+
+                super.visitReferenceExpression(expression);
+            }
+        });
+
+        return usedQualifiedNames;
+    }
+
+
+    @Nullable
+    public static String getElementFQName(PsiElement element) {
+        if (element instanceof JetClassOrObject) {
+            return JetPsiUtil.getFQName((JetClassOrObject) element);
+        }
+        if (element instanceof JetNamedFunction) {
+            return JetPsiUtil.getFQName((JetNamedFunction) element);
+        }
+        if (element instanceof PsiClass) {
+            return ((PsiClass) element).getQualifiedName();
+        }
+        if (element instanceof PsiMethod) {
+            PsiMethod method = (PsiMethod) element;
+
+            PsiClass containingClass = method.getContainingClass();
+
+            if (containingClass != null) {
+                String classFQN = containingClass.getQualifiedName();
+
+                if (classFQN != null) {
+                    if (QualifiedNamesUtil.fqnToShortName(classFQN).equals(JvmAbi.PACKAGE_CLASS)) {
+                        String classParentFQN = QualifiedNamesUtil.withoutLastSegment(classFQN);
+                        return QualifiedNamesUtil.combine(classParentFQN, method.getName());
+                    }
+                    else {
+                        return QualifiedNamesUtil.combine(containingClass.getQualifiedName(), method.getName());
+                    }
+                }
+            }
+        }
+
+        return null;
+    }
+
+
+}