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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.Key;
import com.intellij.openapi.vfs.VirtualFile;
import com.intellij.psi.PsiElement;
import com.intellij.psi.PsiNamedElement;
import com.intellij.psi.ResolveState;
import com.intellij.psi.scope.PsiScopeProcessor;
import com.intellij.psi.util.PsiTreeUtil;
import com.jetbrains.python.PyNames;
import com.jetbrains.python.psi.*;
import com.jetbrains.python.psi.impl.PyImportedModule;
import com.intellij.psi.util.QualifiedName;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

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

import static com.jetbrains.python.codeInsight.dataflow.scope.ScopeUtil.getScopeOwner;

public class ResolveProcessor implements PsiScopeProcessor {
  @NotNull private final String myName;
  private PsiElement myResult = null;
  private final List myDefiners;
  private boolean myLocalResolve = false;

  public ResolveProcessor(@NotNull final String name) {
    myName = name;
    myDefiners = new ArrayList(2); // 1 is typical, 2 is sometimes, more is rare.
  }

  public PsiElement getResult() {
    return myResult;
  }

  /**
   * Adds a NameDefiner point which is a secondary resolution target. E.g. import statement for imported name.
   *
   * @param definer
   */
  protected void addNameDefiner(PsiElement definer) {
    myDefiners.add(definer);
  }

  public List getDefiners() {
    return myDefiners;
  }

  public void setLocalResolve() {
    myLocalResolve = true;
  }

  public String toString() {
    return PyUtil.nvl(myName) + ", " + PyUtil.nvl(myResult);
  }

  @Override
  public boolean execute(@NotNull PsiElement element, @NotNull ResolveState substitutor) {
    if (element instanceof PyFile) {
      final VirtualFile file = ((PyFile)element).getVirtualFile();
      if (file != null) {
        if (myName.equals(file.getNameWithoutExtension())) {
          return setResult(element, null);
        }
        else if (PyNames.INIT_DOT_PY.equals(file.getName())) {
          VirtualFile dir = file.getParent();
          if ((dir != null) && myName.equals(dir.getName())) {
            return setResult(element, null);
          }
        }
      }
    }
    if (element instanceof PsiNamedElement) {
      if (myName.equals(((PsiNamedElement)element).getName())) {
        return setResult(element, null);
      }
    }
    if (element instanceof PyReferenceExpression) {
      PyReferenceExpression expr = (PyReferenceExpression)element;
      String referencedName = expr.getReferencedName();
      if (referencedName != null && referencedName.equals(myName)) {
        return setResult(element, null);
      }
    }
    if (element instanceof NameDefiner) {
      final NameDefiner definer = (NameDefiner)element;
      PsiElement byName = resolveFromNameDefiner(definer);
      if (byName != null) {
        // prefer more specific imported modules to less specific ones
        if (byName instanceof PyImportedModule && myResult instanceof PyImportedModule &&
            ((PyImportedModule)byName).isAncestorOf((PyImportedModule)myResult)) {
          return false;
        }

        setResult(byName, definer);
        if (!PsiTreeUtil.isAncestor(element, byName, true)) {
          addNameDefiner(definer);
        }
        // we can have same module imported directly and as part of chain (import os; import os.path)
        // direct imports always take precedence over imported modules
        // also, if some name is defined both in 'try' and 'except' parts of the same try/except statement,
        // we prefer the declaration in the 'try' part
        if (!(myResult instanceof PyImportedModule) && PsiTreeUtil.getParentOfType(element, PyExceptPart.class) == null) {
          return false;
        }
      }
      else if (element instanceof PyImportElement) {
        final PyImportElement importElement = (PyImportElement) element;
        final QualifiedName qName = importElement.getImportedQName();
        // http://stackoverflow.com/questions/6048786/from-module-import-in-init-py-makes-module-name-visible
        if (qName != null && qName.getComponentCount() > 1 && myName.equals(qName.getLastComponent()) &&
            PyNames.INIT_DOT_PY.equals(importElement.getContainingFile().getName())) {
          final PsiElement packageElement = ResolveImportUtil.resolveImportElement(importElement, qName.removeLastComponent());
          if (PyUtil.turnDirIntoInit(packageElement) == importElement.getContainingFile()) {
            myResult = PyUtil.turnDirIntoInit(importElement.resolve());
            addNameDefiner(importElement);
          }
        }

        // name is resolved to unresolved import (PY-956)
        String definedName = importElement.getAsName();
        if (definedName == null) {
          if (qName != null && qName.getComponentCount() == 1) {
            definedName = qName.getComponents().get(0);
          }
        }
        if (myName.equals(definedName)) {
          addNameDefiner(importElement);
        }
        element = importElement.getContainingImportStatement();
      }
    }
    if (element instanceof PyFromImportStatement && PyNames.INIT_DOT_PY.equals(element.getContainingFile().getName())) {
      final PyFromImportStatement fromImportStatement = (PyFromImportStatement)element;
      final QualifiedName qName = fromImportStatement.getImportSourceQName();
      if (qName != null && qName.endsWith(myName)) {
        final PsiElement source = PyUtil.turnInitIntoDir(fromImportStatement.resolveImportSource());
        if (source != null && source.getParent() == element.getContainingFile().getContainingDirectory()) {
          myResult = source;
          addNameDefiner(fromImportStatement);
        }
      }
    }

    return true;
  }

  @Nullable
  private PsiElement resolveFromNameDefiner(NameDefiner definer) {
    if (myLocalResolve) {
      if (definer instanceof PyImportElement) {
        return ((PyImportElement) definer).getElementNamed(myName, false);
      }
      else if (definer instanceof PyStarImportElement) {
        return null;
      }
    }
    return definer.getElementNamed(myName);
  }

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

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

  private boolean setResult(PsiElement result, @Nullable PsiElement definer) {
    if (myResult == null || getScopeOwner(myResult) == getScopeOwner(result) ||
        (definer != null && getScopeOwner(myResult) == getScopeOwner(definer))) {
      myResult = result;
    }
    return false;
  }
}