/*
 * 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
 *
 *      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.
 *
 */

/* $Id: Grep.java 152682 2005-02-08 18:13:39Z gregor $  */

package org.apache.lenya.search;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.CharBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.avalon.framework.logger.ConsoleLogger;
import org.apache.avalon.framework.logger.Logger;

/**
 * Utility class to provide a subset of the grep functionality. 
 */
public class Grep {
    
    private static Charset charset = Charset.forName("UTF-8");
    private static CharsetDecoder decoder = charset.newDecoder();

    /**
     * Check if the given file contains the pattern
     * @param file the file which is to be searched for the pattern
     * @param pattern the pattern that is being searched.
     * @return true if the file contains the string, false otherwise.
     * @throws IOException
     */
    public static boolean containsPattern(File file, Pattern pattern) throws IOException {
        
        Logger log = new ConsoleLogger();

        FileChannel fc = null;
		// Open the file and then get a channel from the stream
        FileInputStream fis = null;
		boolean result = false;

		try {
			fis = new FileInputStream(file);
			fc = fis.getChannel();

			// Get the file's size and then map it into memory
			int sz = (int)fc.size();
			MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, sz);

			// Decode the file into a char buffer
			CharBuffer cb = decoder.decode(bb);

			// Perform the search
			Matcher pm = pattern.matcher(cb); // Pattern matcher

			result = pm.find();
		} catch (FileNotFoundException e) {
			log.error("File not found: " +e.toString());
		} catch (CharacterCodingException e) {
			log.error("Problem with encoding: " +e.toString());
		} catch (IOException e) {
			log.error("IO Exception: " +e.toString());
		} finally {
	        // Close the channel and the stream
	        if (fc != null)
	            fc.close();
	        if (fis != null)
	            fis.close();
		}
        return result;
    }

    /**
     * Find all occurences of pattern in a file.
     * @param file the file to search for occurences of pattern
     * @param pattern the pattern to search for
     * @param group which group in the pattern to return
     * @return an <code>array</code> of occurences of pattern 
     * (i.e. the groupth group of the match)
     * @throws IOException if the file could not be read.
     */
    public static String[] findPattern(File file, Pattern pattern, int group) throws IOException {

        Logger log = new ConsoleLogger();

        ArrayList occurences = new ArrayList();
        FileInputStream fis = null;
        FileChannel fc = null;

        try {
            // Open the file and then get a channel from the stream
            fis = new FileInputStream(file);
            fc = fis.getChannel();

            // Get the file's size and then map it into memory
            int sz = (int)fc.size();
            MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, sz);

            // Decode the file into a char buffer
            CharBuffer cb = decoder.decode(bb);

            // Perform the search
            Matcher pm = pattern.matcher(cb); // Pattern matcher

            while (pm.find()) {
                occurences.add(pm.group(group));
            }
        } catch (FileNotFoundException e) {
            log.error("file not found " +e.toString());
        } catch (CharacterCodingException e) {
            log.error("encoding problem " +e.toString());
        } catch (IOException e) {
            log.error("IO exception" +e.toString());
        } finally {
	        // Close the channel and the stream
	        if (fc != null)
	            fc.close();
	        if (fis != null)
	            fis.close();
        }
        return (String[])occurences.toArray(new String[occurences.size()]);

    }

    /**
     * Find all files below the given file which contain the given pattern.
     * @param file the file where to start the search for the pattern.
     * @param pattern the pattern to search for.
     * @return an array of files which contain the pattern
     * @throws IOException if any of the files could not be opened.
     */
    private static List find_internal(File file, Pattern pattern) throws IOException {
        ArrayList fileList = new ArrayList();

        if (file.isDirectory()) {
            String[] children = file.list();
            for (int i = 0; i < children.length; i++) {
                fileList.addAll(
                    find_internal(
                        new File(file.getAbsolutePath(), children[i]),
                        pattern));
            }
        } else if (file.isFile() && containsPattern(file, pattern)) {
            fileList.add(file);
        }
        return fileList;
    }

    /**
     * Find all files below the given file which contain the given search string.
     * 
     * @param file the where to start the search
     * @param searchString the string to search for.
     * 
     * @return an array of files which contain the search string.
     * 
     * @throws IOException if any of the files could not be opened.
     */
    public static File[] find(File file, String searchString) throws IOException {
        Pattern pattern = Pattern.compile(searchString);
        List fileList = find_internal(file, pattern);
        return (File[])fileList.toArray(new File[fileList.size()]);
    }
}