////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2020 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 com.puppycrawl.tools.checkstyle.checks.naming;

import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;

/**
 * <p>
 * Checks lambda parameter names.
 * </p>
 * <ul>
 * <li>
 * Property {@code format} - Specifies valid identifiers.
 * Default value is {@code "^[a-z][a-zA-Z0-9]*$"}.
 * </li>
 * </ul>
 * <p>
 * An example of how to configure the check is:
 * </p>
 * <pre>
 * &lt;module name="LambdaParameterName"/&gt;
 * </pre>
 * <p>
 * An example of how to configure the check for names that begin
 * with a lower case letter, followed by letters is:
 * </p>
 * <pre>
 * &lt;module name="LambdaParameterName"&gt;
 *   &lt;property name="format" value="^[a-z]([a-zA-Z]+)*$"/&gt;
 * &lt;/module&gt;
 * </pre>
 * <p>
 * Example of checking with this config:
 * </p>
 * <pre>
 * public class TestClass {
 *
 *     Function&lt;String, String&gt; function1 = str -&gt; str.toUpperCase().trim();
 *
 *     Function&lt;String, String&gt; function2 = _s -&gt; _s.trim().toUpperCase(); // violation
 *
 *     public boolean testMethod(String sentence) {
 *         return Stream.of(sentence.split(" "))
 *             .map(word -&gt; word.trim())
 *             .anyMatch(Word -&gt; "in".equals(Word)); // violation
 *     }
 *
 * }
 *
 * </pre>
 *
 * @since 8.11
 */
public class LambdaParameterNameCheck extends AbstractNameCheck {

    /** Creates new instance of {@code LambdaParameterNameCheck}. */
    public LambdaParameterNameCheck() {
        super("^[a-z][a-zA-Z0-9]*$");
    }

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

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

    @Override
    public int[] getRequiredTokens() {
        return new int[] {
            TokenTypes.LAMBDA,
        };
    }

    @Override
    public void visitToken(DetailAST ast) {
        final DetailAST parametersNode = ast.findFirstToken(TokenTypes.PARAMETERS);
        if (parametersNode == null) {
            super.visitToken(ast);
        }
        else {
            for (DetailAST parameterDef = parametersNode.getFirstChild();
                 parameterDef != null;
                 parameterDef = parameterDef.getNextSibling()) {
                if (parameterDef.getType() == TokenTypes.PARAMETER_DEF) {
                    super.visitToken(parameterDef);
                }
            }
        }
    }

    @Override
    protected boolean mustCheckName(DetailAST ast) {
        return true;
    }

}
