////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2015 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
////////////////////////////////////////////////////////////////////////////////
package edu.cmu.cs.vbc.prog.checkstyle.checks.design;

import edu.cmu.cs.varex.annotation.VConditional;
import edu.cmu.cs.vbc.prog.checkstyle.api.Check;
import edu.cmu.cs.vbc.prog.checkstyle.api.DetailAST;
import edu.cmu.cs.vbc.prog.checkstyle.api.TokenTypes;

/**
 * Make sure that utility classes (classes that contain only static methods)
 * do not have a public constructor.
 * <p>
 * Rationale: Instantiating utility classes does not make sense.
 * A common mistake is forgetting to hide the default constructor.
 * </p>
 *
 * @author lkuehne
 */
public class HideUtilityClassConstructorCheck extends Check
{
	@VConditional
	private static boolean HideUtilityClassConstructor = true;
	
	@Override
	public boolean isEnabled() {
		return HideUtilityClassConstructor;
	}
    /**
     * A key is pointing to the warning message text in "messages.properties"
     * file.
     */
    public static final String MSG_KEY = "hide.utility.class";

    @Override
    public int[] getDefaultTokens()
    {
        return new int[] {TokenTypes.CLASS_DEF};
    }

    @Override
    public int[] getAcceptableTokens()
    {
        return new int[] {TokenTypes.CLASS_DEF};
    }

    @Override
    public void visitToken(DetailAST ast)
    {
        if (isAbstract(ast)) {
            // abstract class could not have private constructor
            return;
        }

        final DetailAST objBlock = ast.findFirstToken(TokenTypes.OBJBLOCK);
        DetailAST child = objBlock.getFirstChild();
        final boolean hasStaticModifier = isStatic(ast);
        boolean hasMethodOrField = false;
        boolean hasNonStaticMethodOrField = false;
        boolean hasNonPrivateStaticMethodOrField = false;
        boolean hasDefaultCtor = true;
        boolean hasPublicCtor = false;

        while (child != null) {
            final int type = child.getType();
            if (type == TokenTypes.METHOD_DEF
                    || type == TokenTypes.VARIABLE_DEF)
            {
                hasMethodOrField = true;
                final DetailAST modifiers =
                    child.findFirstToken(TokenTypes.MODIFIERS);
                final boolean isStatic =
                    modifiers.branchContains(TokenTypes.LITERAL_STATIC);
                final boolean isPrivate =
                    modifiers.branchContains(TokenTypes.LITERAL_PRIVATE);

                if (!isStatic && !isPrivate) {
                    hasNonStaticMethodOrField = true;
                }
                if (isStatic && !isPrivate) {
                    hasNonPrivateStaticMethodOrField = true;
                }
            }
            if (type == TokenTypes.CTOR_DEF) {
                hasDefaultCtor = false;
                final DetailAST modifiers =
                    child.findFirstToken(TokenTypes.MODIFIERS);
                if (!modifiers.branchContains(TokenTypes.LITERAL_PRIVATE)
                    && !modifiers.branchContains(TokenTypes.LITERAL_PROTECTED))
                {
                    // treat package visible as public
                    // for the purpose of this Check
                    hasPublicCtor = true;
                }

            }
            child = child.getNextSibling();
        }

        final boolean hasAccessibleCtor = (hasDefaultCtor || hasPublicCtor);

        // figure out if class extends java.lang.object directly
        // keep it simple for now and get a 99% solution
        // TODO: check for "extends java.lang.Object" and "extends Object"
        // consider "import org.omg.CORBA.*"
        final boolean extendsJLO = // J.Lo even made it into in our sources :-)
            ast.findFirstToken(TokenTypes.EXTENDS_CLAUSE) == null;

        final boolean isUtilClass = extendsJLO && hasMethodOrField
            && !hasNonStaticMethodOrField && hasNonPrivateStaticMethodOrField;

        if (isUtilClass && (hasAccessibleCtor && !hasStaticModifier)) {
            log(ast.getLineNo(), ast.getColumnNo(), MSG_KEY);
        }
    }

    /**
     * @param ast class definition for check.
     * @return true if a given class declared as abstract.
     */
    private boolean isAbstract(DetailAST ast)
    {
        return ast.findFirstToken(TokenTypes.MODIFIERS)
            .branchContains(TokenTypes.ABSTRACT);
    }

    /**
     * @param ast class definition for check.
     * @return true if a given class declared as static.
     */
    private boolean isStatic(DetailAST ast)
    {
        return ast.findFirstToken(TokenTypes.MODIFIERS)
            .branchContains(TokenTypes.LITERAL_STATIC);
    }
}
