////////////////////////////////////////////////////////////////////////////////
// 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.coding;

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.FastStack;
import edu.cmu.cs.vbc.prog.checkstyle.api.TokenTypes;

import java.util.HashSet;
import java.util.Set;

/**
 * <p>
 * Disallow assignment of parameters.
 * </p>
 * <p>
 * Rationale:
 * Parameter assignment is often considered poor
 * programming practice. Forcing developers to declare
 * parameters as final is often onerous. Having a check
 * ensure that parameters are never assigned would give
 * the best of both worlds.
 * </p>
 * @author <a href="mailto:simon@redhillconsulting.com.au">Simon Harris</a>
 */
public final class ParameterAssignmentCheck extends Check
{
	@VConditional
	private static boolean ParameterAssignment = true;
	
	@Override
	public boolean isEnabled() {
		return ParameterAssignment;
	}
    /**
     * A key is pointing to the warning message text in "messages.properties"
     * file.
     */
    public static final String MSG_KEY = "parameter.assignment";

    /** Stack of methods' parameters. */
    private final FastStack<Set<String>> parameterNamesStack =
        FastStack.newInstance();
    /** Current set of perameters. */
    private Set<String> parameterNames;

    @Override
    public int[] getDefaultTokens()
    {
        return new int[] {
            TokenTypes.CTOR_DEF,
            TokenTypes.METHOD_DEF,
            TokenTypes.ASSIGN,
            TokenTypes.PLUS_ASSIGN,
            TokenTypes.MINUS_ASSIGN,
            TokenTypes.STAR_ASSIGN,
            TokenTypes.DIV_ASSIGN,
            TokenTypes.MOD_ASSIGN,
            TokenTypes.SR_ASSIGN,
            TokenTypes.BSR_ASSIGN,
            TokenTypes.SL_ASSIGN,
            TokenTypes.BAND_ASSIGN,
            TokenTypes.BXOR_ASSIGN,
            TokenTypes.BOR_ASSIGN,
            TokenTypes.INC,
            TokenTypes.POST_INC,
            TokenTypes.DEC,
            TokenTypes.POST_DEC,
        };
    }

    @Override
    public int[] getRequiredTokens()
    {
        return getDefaultTokens();
    }

    @Override
    public int[] getAcceptableTokens()
    {
        return new int[] {
            TokenTypes.CTOR_DEF,
            TokenTypes.METHOD_DEF,
            TokenTypes.ASSIGN,
            TokenTypes.PLUS_ASSIGN,
            TokenTypes.MINUS_ASSIGN,
            TokenTypes.STAR_ASSIGN,
            TokenTypes.DIV_ASSIGN,
            TokenTypes.MOD_ASSIGN,
            TokenTypes.SR_ASSIGN,
            TokenTypes.BSR_ASSIGN,
            TokenTypes.SL_ASSIGN,
            TokenTypes.BAND_ASSIGN,
            TokenTypes.BXOR_ASSIGN,
            TokenTypes.BOR_ASSIGN,
            TokenTypes.INC,
            TokenTypes.POST_INC,
            TokenTypes.DEC,
            TokenTypes.POST_DEC,
        };
    }

    @Override
    public void beginTree(DetailAST rootAST)
    {
        // clear data
        parameterNamesStack.clear();
        parameterNames = null;
    }

    @Override
    public void visitToken(DetailAST ast)
    {
        switch (ast.getType()) {
            case TokenTypes.CTOR_DEF:
            case TokenTypes.METHOD_DEF:
                visitMethodDef(ast);
                break;
            case TokenTypes.ASSIGN:
            case TokenTypes.PLUS_ASSIGN:
            case TokenTypes.MINUS_ASSIGN:
            case TokenTypes.STAR_ASSIGN:
            case TokenTypes.DIV_ASSIGN:
            case TokenTypes.MOD_ASSIGN:
            case TokenTypes.SR_ASSIGN:
            case TokenTypes.BSR_ASSIGN:
            case TokenTypes.SL_ASSIGN:
            case TokenTypes.BAND_ASSIGN:
            case TokenTypes.BXOR_ASSIGN:
            case TokenTypes.BOR_ASSIGN:
                visitAssign(ast);
                break;
            case TokenTypes.INC:
            case TokenTypes.POST_INC:
            case TokenTypes.DEC:
            case TokenTypes.POST_DEC:
                visitIncDec(ast);
                break;
            default:
                throw new IllegalStateException(ast.toString());
        }
    }

    @Override
    public void leaveToken(DetailAST ast)
    {
        switch (ast.getType()) {
            case TokenTypes.CTOR_DEF:
            case TokenTypes.METHOD_DEF:
                leaveMethodDef();
                break;
            case TokenTypes.ASSIGN:
            case TokenTypes.PLUS_ASSIGN:
            case TokenTypes.MINUS_ASSIGN:
            case TokenTypes.STAR_ASSIGN:
            case TokenTypes.DIV_ASSIGN:
            case TokenTypes.MOD_ASSIGN:
            case TokenTypes.SR_ASSIGN:
            case TokenTypes.BSR_ASSIGN:
            case TokenTypes.SL_ASSIGN:
            case TokenTypes.BAND_ASSIGN:
            case TokenTypes.BXOR_ASSIGN:
            case TokenTypes.BOR_ASSIGN:
            case TokenTypes.INC:
            case TokenTypes.POST_INC:
            case TokenTypes.DEC:
            case TokenTypes.POST_DEC:
                // Do nothing
                break;
            default:
                throw new IllegalStateException(ast.toString());
        }
    }

    /**
     * Ckecks if this is assignments of parameter.
     * @param ast assignment to check.
     */
    private void visitAssign(DetailAST ast)
    {
        checkIdent(ast);
    }

    /**
     * Checks if this is increment/decrement of parameter.
     * @param ast dec/inc to check.
     */
    private void visitIncDec(DetailAST ast)
    {
        checkIdent(ast);
    }

    /**
     * Check if ident is parameter.
     * @param ast ident to check.
     */
    private void checkIdent(DetailAST ast)
    {
        if ((parameterNames != null) && !parameterNames.isEmpty()) {
            final DetailAST identAST = ast.getFirstChild();

            if ((identAST != null)
                && (identAST.getType() == TokenTypes.IDENT)
                && parameterNames.contains(identAST.getText()))
            {
                log(ast.getLineNo(), ast.getColumnNo(),
                    MSG_KEY, identAST.getText());
            }
        }
    }

    /**
     * Creates new set of parameters and store old one in stack.
     * @param ast a method to process.
     */
    private void visitMethodDef(DetailAST ast)
    {
        parameterNamesStack.push(parameterNames);
        parameterNames = new HashSet<>();

        visitMethodParameters(ast.findFirstToken(TokenTypes.PARAMETERS));
    }

    /** Restores old set of parameters. */
    private void leaveMethodDef()
    {
        parameterNames = parameterNamesStack.pop();
    }

    /**
     * Creates new parameter set for given method.
     * @param ast a method for process.
     */
    private void visitMethodParameters(DetailAST ast)
    {
        DetailAST parameterDefAST =
            ast.findFirstToken(TokenTypes.PARAMETER_DEF);

        for (; parameterDefAST != null;
             parameterDefAST = parameterDefAST.getNextSibling())
        {
            if (parameterDefAST.getType() == TokenTypes.PARAMETER_DEF) {
                final DetailAST param =
                    parameterDefAST.findFirstToken(TokenTypes.IDENT);
                parameterNames.add(param.getText());
            }
        }
    }
}
