python/src/com/jetbrains/python/debugger/PyDebugSupportUtils.java

/*
 * Copyright 2000-2013 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.debugger;

import com.intellij.openapi.application.ApplicationManager;
import com.intellij.openapi.editor.Document;
import com.intellij.openapi.project.Project;
import com.intellij.openapi.util.Computable;
import com.intellij.openapi.util.TextRange;
import com.intellij.psi.PsiDocumentManager;
import com.intellij.psi.PsiElement;
import com.intellij.psi.PsiFile;
import com.intellij.psi.util.PsiTreeUtil;
import com.jetbrains.python.PyTokenTypes;
import com.jetbrains.python.psi.*;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;


public class PyDebugSupportUtils {

  private PyDebugSupportUtils() {
  }

  // can expression be evaluated, or should be executed
  public static boolean isExpression(final Project project, final String expression) {
    return ApplicationManager.getApplication().runReadAction(new Computable<Boolean>() {
      public Boolean compute() {

        final PsiFile file = PyElementGenerator.getInstance(project).createDummyFile(LanguageLevel.getDefault(), expression);
        return file.getFirstChild() instanceof PyExpressionStatement && file.getFirstChild() == file.getLastChild();
      }
    });
  }

  @Nullable
  public static TextRange getExpressionRangeAtOffset(final Project project, final Document document, final int offset) {
    return ApplicationManager.getApplication().runReadAction(new Computable<TextRange>() {
      @Nullable
      public TextRange compute() {

        final PsiFile psiFile = PsiDocumentManager.getInstance(project).getPsiFile(document);
        if (psiFile != null) {
          PsiElement element = psiFile.findElementAt(offset);
          if (!(element instanceof PyExpression) || element instanceof PyLiteralExpression) {
            element = PsiTreeUtil.getParentOfType(element, PyExpression.class);
          }
          if (element != null && element instanceof PyLiteralExpression) {
            return null;
          }
          if (element != null && isSimpleEnough(element) && isExpression(project, document.getText(element.getTextRange()))) {
            return element.getTextRange();
          }
        }
        return null;
      }
    });
  }

  // is expression suitable to quick evaluate/display tooltip
  private static boolean isSimpleEnough(final PsiElement element) {
    return element instanceof PyLiteralExpression ||
           element instanceof PyQualifiedExpression ||
           element instanceof PyBinaryExpression ||
           element instanceof PyPrefixExpression ||
           element instanceof PySliceExpression ||
           element instanceof PyNamedParameter;
  }

  // is expression a variable reference and can be evaluated
  // todo: use patterns (?)
  public static boolean canSaveToTemp(final Project project, final String expression) {
    return ApplicationManager.getApplication().runReadAction(new Computable<Boolean>() {
      public Boolean compute() {

        final PsiFile file = PyElementGenerator.getInstance(project).createDummyFile(LanguageLevel.getDefault(), expression);
        final PsiElement root = file.getFirstChild();
        return !isVariable(root) && (root instanceof PyExpressionStatement);
      }
    });
  }

  private static Boolean isVariable(PsiElement root) {
    return root instanceof PyExpressionStatement &&
           root.getFirstChild() instanceof PyReferenceExpression &&
           root.getFirstChild() == root.getLastChild() &&
           root.getFirstChild().getFirstChild() != null &&
           root.getFirstChild().getFirstChild().getNode().getElementType() == PyTokenTypes.IDENTIFIER &&
           root.getFirstChild().getFirstChild() == root.getFirstChild().getLastChild() &&
           root.getFirstChild().getFirstChild().getFirstChild() == null;
  }

  @Nullable
  private static String getLineText(@NotNull Document document, int line) {
    if (line > 0 && line < document.getLineCount()) {
      return document.getText(TextRange.create(document.getLineStartOffset(line), document.getLineEndOffset(line)));
    }
    return null;
  }

  public static boolean isContinuationLine(@NotNull Document document, int line) {
    String text = getLineText(document, line);
    if (text != null && text.trim().endsWith("\\")) {
      return true;
    }

    return false;
  }
}