/*
 * Copyright  2002-2004 The Apache Software Foundation
 *
 *  Licensed 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
 *
 *      http://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.filters;

import java.io.IOException;
import java.io.Reader;
import java.util.Vector;
import org.apache.tools.ant.types.Parameter;
import org.apache.tools.ant.types.RegularExpression;
import org.apache.tools.ant.util.regexp.Regexp;

/**
 * Filter which includes only those lines that contain the user-specified
 * regular expression matching strings.
 *
 * Example:
 * <pre><linecontainsregexp>
 *   <regexp pattern="foo*">
 * </linecontainsregexp></pre>
 *
 * Or:
 *
 * <pre><filterreader classname="org.apache.tools.ant.filters.LineContainsRegExp">
 *    <param type="regexp" value="foo*"/>
 * </filterreader></pre>
 *
 * This will fetch all those lines that contain the pattern <code>foo</code>
 *
 */
public final class LineContainsRegExp
    extends BaseParamFilterReader
    implements ChainableReader {
    /** Parameter name for the regular expression to filter on. */
    private static final String REGEXP_KEY = "regexp";

    /** Vector that holds the expressions that input lines must contain. */
    private Vector regexps = new Vector();

    /**
     * Remaining line to be read from this filter, or <code>null</code> if
     * the next call to <code>read()</code> should read the original stream
     * to find the next matching line.
     */
    private String line = null;

    /**
     * Constructor for "dummy" instances.
     *
     * @see BaseFilterReader#BaseFilterReader()
     */
    public LineContainsRegExp() {
        super();
    }

    /**
     * Creates a new filtered reader.
     *
     * @param in A Reader object providing the underlying stream.
     *           Must not be <code>null</code>.
     */
    public LineContainsRegExp(final Reader in) {
        super(in);
    }

    /**
     * Returns the next character in the filtered stream, only including
     * lines from the original stream which match all of the specified
     * regular expressions.
     *
     * @return the next character in the resulting stream, or -1
     * if the end of the resulting stream has been reached
     *
     * @exception IOException if the underlying stream throws an IOException
     * during reading
     */
    public final int read() throws IOException {
        if (!getInitialized()) {
            initialize();
            setInitialized(true);
        }

        int ch = -1;

        if (line != null) {
            ch = line.charAt(0);
            if (line.length() == 1) {
                line = null;
            } else {
                line = line.substring(1);
            }
        } else {
            line = readLine();
            final int regexpsSize = regexps.size();

            while (line != null) {
                for (int i = 0; i < regexpsSize; i++) {
                    RegularExpression regexp = (RegularExpression)
                                                        regexps.elementAt(i);
                    Regexp re = regexp.getRegexp(getProject());
                    boolean matches = re.matches(line);
                    if (!matches) {
                        line = null;
                        break;
                    }
                }

                if (line == null) {
                    // line didn't match
                    line = readLine();
                } else {
                    break;
                }
            }

            if (line != null) {
                return read();
            }
        }

        return ch;
    }

    /**
     * Adds a <code>regexp</code> element.
     *
     * @param regExp The <code>regexp</code> element to add.
     *               Must not be <code>null</code>.
     */
    public final void addConfiguredRegexp(final RegularExpression regExp) {
        this.regexps.addElement(regExp);
    }

    /**
     * Sets the vector of regular expressions which must be contained within
     * a line read from the original stream in order for it to match this
     * filter.
     *
     * @param regexps A vector of regular expressions which must be contained
     * within a line in order for it to match in this filter. Must not be
     * <code>null</code>.
     */
    private void setRegexps(final Vector regexps) {
        this.regexps = regexps;
    }

    /**
     * Returns the vector of regular expressions which must be contained within
     * a line read from the original stream in order for it to match this
     * filter.
     *
     * @return the vector of regular expressions which must be contained within
     * a line read from the original stream in order for it to match this
     * filter. The returned object is "live" - in other words, changes made to
     * the returned object are mirrored in the filter.
     */
    private final Vector getRegexps() {
        return regexps;
    }

    /**
     * Creates a new LineContainsRegExp using the passed in
     * Reader for instantiation.
     *
     * @param rdr A Reader object providing the underlying stream.
     *            Must not be <code>null</code>.
     *
     * @return a new filter based on this configuration, but filtering
     *         the specified reader
     */
    public final Reader chain(final Reader rdr) {
        LineContainsRegExp newFilter = new LineContainsRegExp(rdr);
        newFilter.setRegexps(getRegexps());
        newFilter.setInitialized(true);
        return newFilter;
    }

    /**
     * Parses parameters to add user defined regular expressions.
     */
    private final void initialize() {
        Parameter[] params = getParameters();
        if (params != null) {
            for (int i = 0; i < params.length; i++) {
                if (REGEXP_KEY.equals(params[i].getType())) {
                    String pattern = params[i].getValue();
                    RegularExpression regexp = new RegularExpression();
                    regexp.setPattern(pattern);
                    regexps.addElement(regexp);
                }
            }
        }
    }
}