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A packaging of the IntelliJ Community Edition python-community library. This is release number 1 of trunk branch 142.
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/*
 * Copyright 2000-2014 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.jetbrains.python.psi.resolve;

import com.intellij.openapi.util.Condition;
import com.intellij.openapi.util.Key;
import com.intellij.openapi.util.io.FileUtil;
import com.intellij.psi.PsiElement;
import com.intellij.psi.PsiInvalidElementAccessException;
import com.intellij.psi.PsiNamedElement;
import com.intellij.psi.ResolveState;
import com.intellij.psi.scope.PsiScopeProcessor;
import com.jetbrains.python.psi.*;
import com.intellij.psi.util.QualifiedName;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.util.ArrayList;
import java.util.List;

public abstract class VariantsProcessor implements PsiScopeProcessor {
  protected final PsiElement myContext;
  protected Condition myNodeFilter;
  protected Condition myNameFilter;

  protected boolean myPlainNamesOnly = false; // if true, add insert handlers to known things like functions
  private List myAllowedNames;
  private final List mySeenNames = new ArrayList();

  public VariantsProcessor(PsiElement context) {
    // empty
    myContext = context;
  }

  public VariantsProcessor(PsiElement context, @Nullable final Condition nodeFilter, @Nullable final Condition nameFilter) {
    myContext = context;
    myNodeFilter = nodeFilter;
    myNameFilter = nameFilter;
  }

  public boolean isPlainNamesOnly() {
    return myPlainNamesOnly;
  }

  public void setPlainNamesOnly(boolean plainNamesOnly) {
    myPlainNamesOnly = plainNamesOnly;
  }


  @Override
  public boolean execute(@NotNull PsiElement element, @NotNull ResolveState substitutor) {
    if (myNodeFilter != null && !myNodeFilter.value(element)) return true; // skip whatever the filter rejects
    // TODO: refactor to look saner; much code duplication
    if (element instanceof PsiNamedElement) {
      final PsiNamedElement psiNamedElement = (PsiNamedElement)element;
      final String name = PyUtil.getElementNameWithoutExtension(psiNamedElement);
      if (name != null && nameIsAcceptable(name)) {
        addElement(name, psiNamedElement);
      }
    }
    else if (element instanceof PyReferenceExpression) {
      PyReferenceExpression expr = (PyReferenceExpression)element;
      String referencedName = expr.getReferencedName();
      if (nameIsAcceptable(referencedName)) {
        addElement(referencedName, expr);
      }
    }
    else if (element instanceof NameDefiner) {
      boolean handledAsImported = false;
      if (element instanceof PyImportElement) {
        final PyImportElement importElement = (PyImportElement)element;
        handledAsImported = handleImportElement(importElement);
      }
      if (! handledAsImported) {
        final NameDefiner definer = (NameDefiner)element;
        for (PyElement expr : definer.iterateNames()) {
          if (expr != null && expr != myContext) { // NOTE: maybe rather have SingleIterables skip nulls outright?
            if (!expr.isValid()) {
              throw new PsiInvalidElementAccessException(expr, "Definer: " + definer);
            }
            String referencedName = expr instanceof PyFile ? FileUtil.getNameWithoutExtension(((PyFile)expr).getName()) : expr.getName();
            if (referencedName != null && nameIsAcceptable(referencedName)) {
              addImportedElement(referencedName, definer, expr);
            }
          }
        }
      }
    }

    return true;
  }

  protected boolean handleImportElement(PyImportElement importElement) {
    final QualifiedName qName = importElement.getImportedQName();
    if (qName != null && qName.getComponentCount() == 1) {
      String name = importElement.getAsName() != null ? importElement.getAsName() : qName.getLastComponent();
      if (name != null && nameIsAcceptable(name)) {
        final PsiElement resolved = importElement.resolve();
        if (resolved instanceof PsiNamedElement) {
          addElement(name, resolved);
          return true;
        }
      }
    }
    return false;
  }

  protected void addElement(String name, PsiElement psiNamedElement) {
    mySeenNames.add(name);
  }

  protected void addImportedElement(String referencedName, NameDefiner definer, PyElement expr) {
    addElement(referencedName, expr);
  }

  private boolean nameIsAcceptable(String name) {
    if (name == null) {
      return false;
    }
    if (mySeenNames.contains(name)) {
      return false;
    }
    if (myNameFilter != null && !myNameFilter.value(name)) {
      return false;
    }
    if (myAllowedNames != null && !myAllowedNames.contains(name)) {
      return false;
    }
    return true;
  }

  @Override
  @Nullable
  public  T getHint(@NotNull Key hintKey) {
    return null;
  }

  @Override
  public void handleEvent(@NotNull Event event, Object associated) {
  }

  public void setAllowedNames(List namesFilter) {
    myAllowedNames = namesFilter;
  }
}