/*
 * Copyright 1999,2004 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.catalina.util;

import java.text.SimpleDateFormat;
import java.util.Properties;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/**
 * Converts dates to strings using the same format specifiers as strftime
 *
 * Note: This does not mimic strftime perfectly.  Certain strftime commands, 
 *       are not supported, and will convert as if they were literals.
 *
 *       Certain complicated commands, like those dealing with the week of the year
 *       probably don't have exactly the same behavior as strftime.
 *
 *       These limitations are due to use SimpleDateTime.  If the conversion was done
 *       manually, all these limitations could be eliminated.
 *
 *       The interface looks like a subset of DateFormat.  Maybe someday someone will make this class
 *       extend DateFormat.
 *
 * @author Bip Thelin
 * @author Dan Sandberg
 * @version $Revision$, $Date$
 */
public class Strftime {
    protected static Properties translate;
    protected SimpleDateFormat simpleDateFormat;

    /**
     * Initialize our pattern translation
     */
    static {
        translate = new Properties();
        translate.put("a","EEE");
        translate.put("A","EEEE");
        translate.put("b","MMM");
        translate.put("B","MMMM");
        translate.put("c","EEE MMM d HH:mm:ss yyyy");

        //There's no way to specify the century in SimpleDateFormat.  We don't want to hard-code
        //20 since this could be wrong for the pre-2000 files.
        //translate.put("C", "20");
        translate.put("d","dd");
        translate.put("D","MM/dd/yy");
        translate.put("e","dd"); //will show as '03' instead of ' 3'
        translate.put("F","yyyy-MM-dd");
        translate.put("g","yy");
        translate.put("G","yyyy");
        translate.put("H","HH");
        translate.put("h","MMM");
        translate.put("I","hh");
        translate.put("j","DDD");
        translate.put("k","HH"); //will show as '07' instead of ' 7'
        translate.put("l","hh"); //will show as '07' instead of ' 7'
        translate.put("m","MM");
        translate.put("M","mm");
        translate.put("n","\n");
        translate.put("p","a");
        translate.put("P","a");  //will show as pm instead of PM
        translate.put("r","hh:mm:ss a");
        translate.put("R","HH:mm");
        //There's no way to specify this with SimpleDateFormat
        //translate.put("s","seconds since ecpoch");
        translate.put("S","ss");
        translate.put("t","\t");
        translate.put("T","HH:mm:ss");
        //There's no way to specify this with SimpleDateFormat
        //translate.put("u","day of week ( 1-7 )");

        //There's no way to specify this with SimpleDateFormat
        //translate.put("U","week in year with first sunday as first day...");

        translate.put("V","ww"); //I'm not sure this is always exactly the same

        //There's no way to specify this with SimpleDateFormat
        //translate.put("W","week in year with first monday as first day...");

        //There's no way to specify this with SimpleDateFormat
        //translate.put("w","E");
        translate.put("X","HH:mm:ss");
        translate.put("x","MM/dd/yy");
        translate.put("y","yy");
        translate.put("Y","yyyy");
        translate.put("Z","z");
        translate.put("z","Z");
        translate.put("%","%");
    }


    /**
     * Create an instance of this date formatting class
     *
     * @see #Strftime( String, Locale )
     */
    public Strftime( String origFormat ) {
        String convertedFormat = convertDateFormat( origFormat );
        simpleDateFormat = new SimpleDateFormat( convertedFormat );
    }

    /**
     * Create an instance of this date formatting class
     * 
     * @param origFormat the strftime-style formatting string
     * @param locale the locale to use for locale-specific conversions
     */
    public Strftime( String origFormat, Locale locale ) {
        String convertedFormat = convertDateFormat( origFormat );
        simpleDateFormat = new SimpleDateFormat( convertedFormat, locale );
    }

    /**
     * Format the date according to the strftime-style string given in the constructor.
     *
     * @param date the date to format
     * @return the formatted date
     */
    public String format( Date date ) {
        return simpleDateFormat.format( date );
    }

    /**
     * Get the timezone used for formatting conversions
     *
     * @return the timezone
     */
    public TimeZone getTimeZone() {
        return simpleDateFormat.getTimeZone();
    }

    /**
     * Change the timezone used to format dates
     *
     * @see SimpleDateFormat#setTimeZone
     */
    public void setTimeZone( TimeZone timeZone ) {
        simpleDateFormat.setTimeZone( timeZone );
    }

    /**
     * Search the provided pattern and get the C standard
     * Date/Time formatting rules and convert them to the
     * Java equivalent.
     *
     * @param pattern The pattern to search
     * @return The modified pattern
     */
    protected String convertDateFormat( String pattern ) {
        boolean inside = false;
        boolean mark = false;
        boolean modifiedCommand = false;

        StringBuffer buf = new StringBuffer();

        for(int i = 0; i < pattern.length(); i++) {
            char c = pattern.charAt(i);

            if ( c=='%' && !mark ) {
                mark=true;
            } else {
                if ( mark ) {
                    if ( modifiedCommand ) {
                        //don't do anything--we just wanted to skip a char
                        modifiedCommand = false;
                        mark = false;
                    } else {
                        inside = translateCommand( buf, pattern, i, inside );
                        //It's a modifier code
                        if ( c=='O' || c=='E' ) {
                            modifiedCommand = true;
                        } else {
                            mark=false;
                        }
                    }
                } else {
                    if ( !inside && c != ' ' ) {
                        //We start a literal, which we need to quote
                        buf.append("'");
                        inside = true;
                    }
                    
                    buf.append(c);
                }
            }
        }

        if ( buf.length() > 0 ) {
            char lastChar = buf.charAt( buf.length() - 1 );

            if( lastChar!='\'' && inside ) {
                buf.append('\'');
            }
        }
        return buf.toString();
    }

    protected String quote( String str, boolean insideQuotes ) {
        String retVal = str;
        if ( !insideQuotes ) {
            retVal = '\'' + retVal + '\'';
        }
        return retVal;
    }

    /**
     * Try to get the Java Date/Time formatting associated with
     * the C standard provided.
     *
     * @param buf The buffer
     * @param pattern The date/time pattern
     * @param index The char index
     * @param oldInside Flag value
     * @return True if new is inside buffer
     */
    protected boolean translateCommand( StringBuffer buf, String pattern, int index, boolean oldInside ) {
        char firstChar = pattern.charAt( index );
        boolean newInside = oldInside;

        //O and E are modifiers, they mean to present an alternative representation of the next char
        //we just handle the next char as if the O or E wasn't there
        if ( firstChar == 'O' || firstChar == 'E' ) {
            if ( index + 1 < pattern.length() ) {               
                newInside = translateCommand( buf, pattern, index + 1, oldInside );
            } else {
                buf.append( quote("%" + firstChar, oldInside ) );
            }
        } else {
            String command = translate.getProperty( String.valueOf( firstChar ) );
            
            //If we don't find a format, treat it as a literal--That's what apache does
            if ( command == null ) {
                buf.append( quote( "%" + firstChar, oldInside ) );
            } else {
                //If we were inside quotes, close the quotes
                if ( oldInside ) {
                    buf.append( '\'' );
                }
                buf.append( command );
                newInside = false;
            }
        }
        return newInside;
    }
}