package org.apache.maven.svnlib;

/* ====================================================================
 *   Copyright 2001-2004 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.
 * ====================================================================
 */

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import java.text.ParseException;
import java.text.SimpleDateFormat;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;

// commons imports
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

// maven
import org.apache.maven.changelog.ChangeLog;
import org.apache.maven.changelog.ChangeLogEntry;
import org.apache.maven.changelog.ChangeLogFile;
import org.apache.maven.changelog.ChangeLogParser;

// regexp
import org.apache.regexp.RE;
import org.apache.regexp.RESyntaxException;


/**
 * A class to parse the log output from Subversion.
 *
 * @author <a href="mailto:dion@multitask.com.au">dIon Gillard</a>
 * @author <a href="mailto:pete-apache-dev@kazmier.com">Pete Kazmier</a>
 * @author Daniel Rall
 * @version $Id$
 */
public class SvnChangeLogParser implements ChangeLogParser
{
    /** Date formatter for svn timestamp (after a little massaging) */
    private static final SimpleDateFormat SVN_TIMESTAMP =
        new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss zzzzzzzzz" );

    /** Log */
    private static final Log LOG =
        LogFactory.getLog( SvnChangeLogParser.class );

    /** State machine constant: expecting header */
    private static final int GET_HEADER = 1;

    /** State machine constant: expecting file information */
    private static final int GET_FILE = 2;

    /** State machine constant: expecting comments */
    private static final int GET_COMMENT = 3;

    /** A file line begins with a space character */
    private static final String FILE_BEGIN_TOKEN = " ";

    /** The file section ends with a blank line */
    private static final String FILE_END_TOKEN = "";

    /** The filename starts after 5 characters */
    private static final int FILE_START_INDEX = 5;

    /** The comment section ends with a dashed line */
    private static final String COMMENT_END_TOKEN =
        "------------------------------------"
        + "------------------------------------";

    /** The pattern used to match svn header lines */
    private static final String pattern =
        "^r(\\d+)\\s+\\|\\s+" // revision number
        + "([^|]+)\\|\\s+" // author username
        + "(\\d+-\\d+-\\d+ " // date 2002-08-24
        + "\\d+:\\d+:\\d+) " // time 16:01:00
        + "([\\-+])(\\d\\d)(\\d\\d)"; // gmt offset -0400 

    /** Current status of the parser */
    private int status = GET_HEADER;

    /** List of change log entries */
    private Collection entries = new ArrayList();

    /** The current log entry being processed by the parser */
    private ChangeLogEntry currentLogEntry;

    /** The current revision of the entry being processed by the parser */
    private String currentRevision;

    /** The current comment of the entry being processed by the parser */
    private StringBuffer currentComment;

    /** The regular expression used to match header lines */
    private RE headerRegexp;

    /** The invoking changelog controller (useful to log messages) */
    private ChangeLog changeLog;

    /**
     * Default constructor.
     */
    public SvnChangeLogParser()
    {
        try
        {
            headerRegexp = new RE( pattern );
        }
        catch ( RESyntaxException ignored )
        {
            LOG.error( "Could not create regexp to parse svn log file", ignored );
        }
    }

    /**
     * Initialize the parser from the change log.
     *
     * @param changeLog The controlling task
     * @see ChangeLogParser#init(ChangeLog)
     */
    public void init( ChangeLog changeLog )
    {
        this.changeLog = changeLog;
    }

    /**
     * Clean up any parser resources.
     *
     * @see ChangeLogParser#cleanup()
     */
    public void cleanup()
    {
    }

    /**
     * Parse the input stream into a collection.
     *
     * @param anInputStream An input stream containing svn log output
     * @return A collection of ChangeLogEntry's
     * @throws IOException When there are errors reading the provided stream
     */
    public Collection parse( InputStream anInputStream )
        throws IOException
    {
        BufferedReader stream =
            new BufferedReader( new InputStreamReader( anInputStream ) );

        // Current state transitions in the parser's state machine:
        //      Get Header     -> Get File
        //      Get File       -> Get Comment or Get (another) File
        //      Get Comment    -> Get (another) Comment
        String line = null;

        while ( ( line = stream.readLine() ) != null )
        {
            switch ( status )
            {
            case GET_HEADER :
                processGetHeader( line );

                break;

            case GET_FILE :
                processGetFile( line );

                break;

            case GET_COMMENT :
                processGetComment( line );

                break;

            default :
                throw new IllegalStateException( "Unknown state: " + status );
            }
        }

        return entries;
    }

    /**
     * Process the current input line in the GET_HEADER state.  The
     * author, date, and the revision of the entry are gathered.  Note,
     * Subversion does not have per-file revisions, instead, the entire
     * repository is given a single revision number, which is used for
     * the revision number of each file.
     *
     * @param line A line of text from the svn log output
     */
    private void processGetHeader( String line )
    {
        if ( !headerRegexp.match( line ) )
        {
            return;
        }

        currentRevision = headerRegexp.getParen( 1 );
        currentLogEntry = new ChangeLogEntry();

        /* set author to be trimmed author field */
        currentLogEntry.setAuthor( headerRegexp.getParen( 2 ).trim() );
        currentLogEntry.setDate( parseDate() );

        status = GET_FILE;
    }

    /**
     * Process the current input line in the GET_FILE state.  This state
     * adds each file entry line to the current change log entry.  Note,
     * the revision number for the entire entry is used for the revision
     * number of each file.
     *
     * @param line A line of text from the svn log output
     */
    private void processGetFile( String line )
    {
        if ( line.startsWith( FILE_BEGIN_TOKEN ) )
        {
            // Skip the status flags and just get the name of the file
            String name = line.substring( FILE_START_INDEX );

            currentLogEntry.addFile( new ChangeLogFile( name, currentRevision ) );

            status = GET_FILE;
        }
        else if ( line.equals( FILE_END_TOKEN ) )
        {
            // Create a buffer for the collection of the comment now
            // that we are leaving the GET_FILE state.
            currentComment = new StringBuffer();

            status = GET_COMMENT;
        }
    }

    /**
     * Process the current input line in the GET_COMMENT state.  This
     * state gathers all of the comments that are part of a log entry.
     *
     * @param line a line of text from the svn log output
     */
    private void processGetComment( String line )
    {
        if ( line.equals( COMMENT_END_TOKEN ) )
        {
            currentLogEntry.setComment( currentComment.toString() );
            entries.add( currentLogEntry );

            status = GET_HEADER;
        }
        else
        {
            currentComment.append( line ).append( '\n' );
        }
    }

    /**
     * Converts the date timestamp from the svn output into a date
     * object.
     *
     * @return A date representing the timestamp of the log entry.
     */
    private Date parseDate()
    {
        try
        {
            StringBuffer date =
                new StringBuffer().append( headerRegexp.getParen( 3 ) )
                                    .append( " GMT" )
                                    .append( headerRegexp.getParen( 4 ) )
                                    .append( headerRegexp.getParen( 5 ) )
                                    .append( ':' ).append( headerRegexp
                    .getParen( 6 ) );

            return SVN_TIMESTAMP.parse( date.toString() );
        }
        catch ( ParseException e )
        {
            LOG.error( "ParseException Caught", e );

            return null;
        }
    }

    public void setDateFormatInFile( String dateFormat )
    {
    }
}