/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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
 *
 *      https://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 org.apache.tools.ant.util;

import java.util.List;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.util.regexp.RegexpMatcher;
import org.apache.tools.ant.util.regexp.RegexpMatcherFactory;
import org.apache.tools.ant.util.regexp.RegexpUtil;

/**
 * Implementation of FileNameMapper that does regular expression
 * replacements.
 *
 */
public class RegexpPatternMapper implements FileNameMapper {

    private static final int DECIMAL = 10;

    // CheckStyle:VisibilityModifier OFF - bc
    protected RegexpMatcher reg = null;
    protected char[] to = null;
    protected StringBuffer result = new StringBuffer();
    // CheckStyle:VisibilityModifier ON

    /**
     * Constructor for RegexpPatternMapper.
     * @throws BuildException on error.
     */
    public RegexpPatternMapper() throws BuildException {
        reg = (new RegexpMatcherFactory()).newRegexpMatcher();
    }

    private boolean handleDirSep = false;
    private int     regexpOptions = 0;

    /**
     * Attribute specifying whether to ignore the difference
     * between / and \ (the two common directory characters).
     * @param handleDirSep a boolean, default is false.
     * @since Ant 1.6.3
     */
    public void setHandleDirSep(boolean handleDirSep) {
        this.handleDirSep = handleDirSep;
    }

    /**
     * Attribute specifying whether to ignore the case difference
     * in the names.
     *
     * @param caseSensitive a boolean, default is false.
     * @since Ant 1.6.3
     */
    public void setCaseSensitive(boolean caseSensitive) {
        regexpOptions = RegexpUtil.asOptions(caseSensitive);
    }

    /**
     * Sets the &quot;from&quot; pattern. Required.
     * @param from the from pattern.
     * @throws BuildException on error.
     */
    @Override
    public void setFrom(String from) throws BuildException {
        if (from == null) {
            throw new BuildException("this mapper requires a 'from' attribute");
        }
        try {
            reg.setPattern(from);
        } catch (NoClassDefFoundError e) {
            // depending on the implementation the actual RE won't
            // get instantiated in the constructor.
            throw new BuildException("Cannot load regular expression matcher",
                e);
        }
    }

    /**
     * Sets the &quot;to&quot; pattern. Required.
     * @param to the to pattern.
     * @throws BuildException on error.
     */
    @Override
    public void setTo(String to) {
        if (to == null) {
            throw new BuildException("this mapper requires a 'to' attribute");
        }
        this.to = to.toCharArray();
    }

    /**
     * Returns null if the source file name doesn't match the
     * &quot;from&quot; pattern, an one-element array containing the
     * translated file otherwise.
     * @param sourceFileName the source file name
     * @return a one-element array containing the translated file or
     *         null if the to pattern did not match
     */
    @Override
    public String[] mapFileName(String sourceFileName) {
        if (sourceFileName == null) {
            return null;
        }
        if (handleDirSep) {
            if (sourceFileName.contains("\\")) {
                sourceFileName = sourceFileName.replace('\\', '/');
            }
        }
        if (reg == null  || to == null
            || !reg.matches(sourceFileName, regexpOptions)) {
            return null;
        }
        return new String[] {replaceReferences(sourceFileName)};
    }

    /**
     * Replace all backreferences in the to pattern with the matched
     * groups of the source.
     * @param source the source file name.
     * @return the translated file name.
     */
    protected String replaceReferences(String source) {
        List<String> v = reg.getGroups(source, regexpOptions);

        result.setLength(0);
        for (int i = 0; i < to.length; i++) {
            if (to[i] == '\\') {
                final int nextCharIndex = i + 1;
                if (nextCharIndex < to.length) {
                    int value = Character.digit(to[nextCharIndex], DECIMAL);
                    if (value > -1) {
                        i++; // mark that the next digit (after the backslash) has been consumed
                        result.append(v.get(value));
                    } else {
                        result.append(to[i]); // append the backslash character
                    }
                } else {
                    // TODO - should throw an exception instead?
                    result.append('\\');
                }
            } else {
                result.append(to[i]);
            }
        }
        return result.substring(0);
    }

}
