ParametersHints.java

/*******************************************************************************
 * Copyright (c) 2012-2017 Codenvy, S.A.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   Codenvy, S.A. - initial API and implementation
 *******************************************************************************/
package org.eclipse.che.plugin.java.server;

import com.google.inject.Singleton;

import org.eclipse.che.dto.server.DtoFactory;
import org.eclipse.che.ide.ext.java.shared.dto.model.MethodParameters;
import org.eclipse.core.runtime.NullProgressMonitor;
import org.eclipse.jdt.core.Flags;
import org.eclipse.jdt.core.ICompilationUnit;
import org.eclipse.jdt.core.IJavaElement;
import org.eclipse.jdt.core.IJavaProject;
import org.eclipse.jdt.core.ILocalVariable;
import org.eclipse.jdt.core.IMethod;
import org.eclipse.jdt.core.IType;
import org.eclipse.jdt.core.ITypeHierarchy;
import org.eclipse.jdt.core.JavaModelException;
import org.eclipse.jdt.ui.JavaElementLabels;

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

import static org.eclipse.jdt.core.IJavaElement.METHOD;

/**
 * The class provides business logic which allows to find hints of method's parameters. Also it finds methods parameter hints in
 * super classes. The class represents founded parameters as ordinary string. Parameters in string separated by coma from each other.
 * Example:
 * <pre>
 *      class Test{
 *          void x(int x, double y);
 *      }
 *
 *      class Test2 extends Test {
 *          void x(String y);
 *      }
 *
 *      Test2 test2 = new Test2();
 *      test2.x();
 * </pre>
 * <p/>
 * When we call method {@link ParametersHints#findHints(IJavaProject, String, int, int)} for test2.x()
 * we will get following:
 * ________
 * int x, double y
 * String y
 * --------
 *
 * @author Dmitry Shnurenko
 */
@Singleton
public class ParametersHints {

    public List<MethodParameters> findHints(IJavaProject project, String fqn, int offset, int lineStartOffset) throws JavaModelException {
        IType type = project.findType(fqn);
        if (type.isBinary()) {
            return Collections.emptyList();
        }

        IJavaElement element = getSelectedElement(type, offset, lineStartOffset);
        if (element == null) {
            return Collections.emptyList();
        }

        IJavaElement parent = element.getParent();
        if (!(parent instanceof IType) || !(element.getElementType() == METHOD)) {
            return Collections.emptyList();
        }

        List<MethodParameters> result = new ArrayList<>();
        findHintsRecursive(element, parent, result);

        return result;
    }

    private IJavaElement getSelectedElement(IType type, int offset, int lineStartOffset) throws JavaModelException {
        if (offset <= lineStartOffset) {
            return null;
        }
        ICompilationUnit compilationUnit = type.getCompilationUnit();
        IJavaElement[] javaElements = compilationUnit.codeSelect(offset, 0);

        if (javaElements.length == 0) {
            return getSelectedElement(type, --offset, lineStartOffset);
        }

        IJavaElement element = javaElements[0];

        if (element.getElementType() == METHOD) {
            return element;
        }

        return getSelectedElement(type, --offset, lineStartOffset);
    }

    private void findHintsRecursive(IJavaElement method, IJavaElement parent, List<MethodParameters> result) throws JavaModelException {
        findHints(method, parent, result);

        IType type = (IType)parent;
        ITypeHierarchy typeHierarchy = type.newTypeHierarchy(new NullProgressMonitor());
        IType[] superTypes = typeHierarchy.getAllSupertypes(type);

        for (IType iType : superTypes) {
            findHintsRecursive(method, iType, result);
        }
    }

    private void findHints(IJavaElement method, IJavaElement parent, List<MethodParameters> result) throws JavaModelException {
        String methodName = method.getElementName();

        for (IMethod iMethod : ((IType)parent).getMethods()) {
            int methodFlag = iMethod.getFlags();
            if (Flags.isPrivate(methodFlag) || !methodName.equals(iMethod.getElementName())) {
                continue;
            }

            MethodParameters methodParameters = DtoFactory.newDto(MethodParameters.class);

            String parameters = getMethodParametersAsString(iMethod);

            methodParameters.setMethodName(methodName);
            methodParameters.setParameters(parameters);

            if (!result.contains(methodParameters)) {
                result.add(methodParameters);
            }
        }
    }

    private String getMethodParametersAsString(IMethod method) throws JavaModelException {
        ILocalVariable[] parameters = method.getParameters();

        int paramsLength = parameters.length;
        int index = 0;

        StringBuffer buffer = new StringBuffer();

        for (ILocalVariable parameter : parameters) {
            JavaElementLabels.getLocalVariableLabel(parameter, JavaElementLabels.F_PRE_TYPE_SIGNATURE, buffer);
            index++;

            if (index < paramsLength) {
                buffer.append(", ");
            }
        }

        return buffer.toString();
    }
}