/**
 * 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.
 */

package org.apache.commons.cli;

import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

/** 
 * A formatter of help messages for the current command line options
 *
 * @author Slawek Zachcial
 * @author John Keyes (john at integralsource.com)
 * @version $Revision$, $Date$
 */
public class HelpFormatter
{
    // --------------------------------------------------------------- Constants

    /** default number of characters per line */
    public static final int DEFAULT_WIDTH = 74;

    /** default padding to the left of each line */
    public static final int DEFAULT_LEFT_PAD = 1;

    /**
     * the number of characters of padding to be prefixed
     * to each description line
     */
    public static final int DEFAULT_DESC_PAD = 3;

    /** the string to display at the beginning of the usage statement */
    public static final String DEFAULT_SYNTAX_PREFIX = "usage: ";

    /** default prefix for shortOpts */
    public static final String DEFAULT_OPT_PREFIX = "-";

    /** default prefix for long Option */
    public static final String DEFAULT_LONG_OPT_PREFIX = "--";

    /** default name for an argument */
    public static final String DEFAULT_ARG_NAME = "arg";

    // -------------------------------------------------------------- Attributes

    /**
     * number of characters per line
     *
     * @deprecated Scope will be made private for next major version
     * - use get/setWidth methods instead.
     */
    public int defaultWidth = DEFAULT_WIDTH;

    /**
     * amount of padding to the left of each line
     *
     * @deprecated Scope will be made private for next major version
     * - use get/setLeftPadding methods instead.
     */
    public int defaultLeftPad = DEFAULT_LEFT_PAD;

    /**
     * the number of characters of padding to be prefixed
     * to each description line
     *
     * @deprecated Scope will be made private for next major version
     * - use get/setDescPadding methods instead.
     */
    public int defaultDescPad = DEFAULT_DESC_PAD;

    /**
     * the string to display at the begining of the usage statement
     *
     * @deprecated Scope will be made private for next major version
     * - use get/setSyntaxPrefix methods instead.
     */
    public String defaultSyntaxPrefix = DEFAULT_SYNTAX_PREFIX;

    /**
     * the new line string
     *
     * @deprecated Scope will be made private for next major version
     * - use get/setNewLine methods instead.
     */
    public String defaultNewLine = System.getProperty("line.separator");

    /**
     * the shortOpt prefix
     *
     * @deprecated Scope will be made private for next major version
     * - use get/setOptPrefix methods instead.
     */
    public String defaultOptPrefix = DEFAULT_OPT_PREFIX;

    /**
     * the long Opt prefix
     *
     * @deprecated Scope will be made private for next major version
     * - use get/setLongOptPrefix methods instead.
     */
    public String defaultLongOptPrefix = DEFAULT_LONG_OPT_PREFIX;

    /**
     * the name of the argument
     *
     * @deprecated Scope will be made private for next major version
     * - use get/setArgName methods instead.
     */
    public String defaultArgName = DEFAULT_ARG_NAME;

    /**
     * Comparator used to sort the options when they output in help text
     * 
     * Defaults to case-insensitive alphabetical sorting by option key
     */
    protected Comparator optionComparator = new OptionComparator();

    /**
     * Sets the 'width'.
     *
     * @param width the new value of 'width'
     */
    public void setWidth(int width)
    {
        this.defaultWidth = width;
    }

    /**
     * Returns the 'width'.
     *
     * @return the 'width'
     */
    public int getWidth()
    {
        return defaultWidth;
    }

    /**
     * Sets the 'leftPadding'.
     *
     * @param padding the new value of 'leftPadding'
     */
    public void setLeftPadding(int padding)
    {
        this.defaultLeftPad = padding;
    }

    /**
     * Returns the 'leftPadding'.
     *
     * @return the 'leftPadding'
     */
    public int getLeftPadding()
    {
        return defaultLeftPad;
    }

    /**
     * Sets the 'descPadding'.
     *
     * @param padding the new value of 'descPadding'
     */
    public void setDescPadding(int padding)
    {
        this.defaultDescPad = padding;
    }

    /**
     * Returns the 'descPadding'.
     *
     * @return the 'descPadding'
     */
    public int getDescPadding()
    {
        return defaultDescPad;
    }

    /**
     * Sets the 'syntaxPrefix'.
     *
     * @param prefix the new value of 'syntaxPrefix'
     */
    public void setSyntaxPrefix(String prefix)
    {
        this.defaultSyntaxPrefix = prefix;
    }

    /**
     * Returns the 'syntaxPrefix'.
     *
     * @return the 'syntaxPrefix'
     */
    public String getSyntaxPrefix()
    {
        return defaultSyntaxPrefix;
    }

    /**
     * Sets the 'newLine'.
     *
     * @param newline the new value of 'newLine'
     */
    public void setNewLine(String newline)
    {
        this.defaultNewLine = newline;
    }

    /**
     * Returns the 'newLine'.
     *
     * @return the 'newLine'
     */
    public String getNewLine()
    {
        return defaultNewLine;
    }

    /**
     * Sets the 'optPrefix'.
     *
     * @param prefix the new value of 'optPrefix'
     */
    public void setOptPrefix(String prefix)
    {
        this.defaultOptPrefix = prefix;
    }

    /**
     * Returns the 'optPrefix'.
     *
     * @return the 'optPrefix'
     */
    public String getOptPrefix()
    {
        return defaultOptPrefix;
    }

    /**
     * Sets the 'longOptPrefix'.
     *
     * @param prefix the new value of 'longOptPrefix'
     */
    public void setLongOptPrefix(String prefix)
    {
        this.defaultLongOptPrefix = prefix;
    }

    /**
     * Returns the 'longOptPrefix'.
     *
     * @return the 'longOptPrefix'
     */
    public String getLongOptPrefix()
    {
        return defaultLongOptPrefix;
    }

    /**
     * Sets the 'argName'.
     *
     * @param name the new value of 'argName'
     */
    public void setArgName(String name)
    {
        this.defaultArgName = name;
    }

    /**
     * Returns the 'argName'.
     *
     * @return the 'argName'
     */
    public String getArgName()
    {
        return defaultArgName;
    }

    /**
     * Comparator used to sort the options when they output in help text
     * 
     * Defaults to case-insensitive alphabetical sorting by option key
     */
    public Comparator getOptionComparator()
    {
        return optionComparator;
    }

    /**
     * Set the comparator used to sort the options when they output in help text
     * 
     * Passing in a null parameter will set the ordering to the default mode
     */
    public void setOptionComparator(Comparator comparator)
    {
        if (comparator == null)
        {
            this.optionComparator = new OptionComparator();
        }
        else
        {
            this.optionComparator = comparator;
        }
    }

    /**
     * Print the help for <code>options</code> with the specified
     * command line syntax.  This method prints help information to
     * System.out.
     *
     * @param cmdLineSyntax the syntax for this application
     * @param options the Options instance
     */
    public void printHelp(String cmdLineSyntax, Options options)
    {
        printHelp(defaultWidth, cmdLineSyntax, null, options, null, false);
    }

    /**
     * Print the help for <code>options</code> with the specified
     * command line syntax.  This method prints help information to 
     * System.out.
     *
     * @param cmdLineSyntax the syntax for this application
     * @param options the Options instance
     * @param autoUsage whether to print an automatically generated
     * usage statement
     */
    public void printHelp(String cmdLineSyntax, Options options, boolean autoUsage)
    {
        printHelp(defaultWidth, cmdLineSyntax, null, options, null, autoUsage);
    }

    /**
     * Print the help for <code>options</code> with the specified
     * command line syntax.  This method prints help information to
     * System.out.
     *
     * @param cmdLineSyntax the syntax for this application
     * @param header the banner to display at the begining of the help
     * @param options the Options instance
     * @param footer the banner to display at the end of the help
     */
    public void printHelp(String cmdLineSyntax, String header, Options options, String footer)
    {
        printHelp(cmdLineSyntax, header, options, footer, false);
    }

    /**
     * Print the help for <code>options</code> with the specified
     * command line syntax.  This method prints help information to 
     * System.out.
     *
     * @param cmdLineSyntax the syntax for this application
     * @param header the banner to display at the begining of the help
     * @param options the Options instance
     * @param footer the banner to display at the end of the help
     * @param autoUsage whether to print an automatically generated
     * usage statement
     */
    public void printHelp(String cmdLineSyntax, String header, Options options, String footer, boolean autoUsage)
    {
        printHelp(defaultWidth, cmdLineSyntax, header, options, footer, autoUsage);
    }

    /**
     * Print the help for <code>options</code> with the specified
     * command line syntax.  This method prints help information to
     * System.out.
     *
     * @param width the number of characters to be displayed on each line
     * @param cmdLineSyntax the syntax for this application
     * @param header the banner to display at the beginning of the help
     * @param options the Options instance
     * @param footer the banner to display at the end of the help
     */
    public void printHelp(int width, String cmdLineSyntax, String header, Options options, String footer)
    {
        printHelp(width, cmdLineSyntax, header, options, footer, false);
    }

    /**
     * Print the help for <code>options</code> with the specified
     * command line syntax.  This method prints help information to
     * System.out.
     *
     * @param width the number of characters to be displayed on each line
     * @param cmdLineSyntax the syntax for this application
     * @param header the banner to display at the begining of the help
     * @param options the Options instance
     * @param footer the banner to display at the end of the help
     * @param autoUsage whether to print an automatically generated 
     * usage statement
     */
    public void printHelp(int width, String cmdLineSyntax, String header,
                          Options options, String footer, boolean autoUsage)
    {
        PrintWriter pw = new PrintWriter(System.out);

        printHelp(pw, width, cmdLineSyntax, header, options, defaultLeftPad, defaultDescPad, footer, autoUsage);
        pw.flush();
    }

    /**
     * Print the help for <code>options</code> with the specified
     * command line syntax.
     *
     * @param pw the writer to which the help will be written
     * @param width the number of characters to be displayed on each line
     * @param cmdLineSyntax the syntax for this application
     * @param header the banner to display at the begining of the help
     * @param options the Options instance
     * @param leftPad the number of characters of padding to be prefixed
     * to each line
     * @param descPad the number of characters of padding to be prefixed
     * to each description line
     * @param footer the banner to display at the end of the help
     *
     * @throws IllegalStateException if there is no room to print a line
     */
    public void printHelp(PrintWriter pw, int width, String cmdLineSyntax, 
                          String header, Options options, int leftPad, 
                          int descPad, String footer)
    {
        printHelp(pw, width, cmdLineSyntax, header, options, leftPad, descPad, footer, false);
    }


    /**
     * Print the help for <code>options</code> with the specified
     * command line syntax.
     *
     * @param pw the writer to which the help will be written
     * @param width the number of characters to be displayed on each line
     * @param cmdLineSyntax the syntax for this application
     * @param header the banner to display at the begining of the help
     * @param options the Options instance
     * @param leftPad the number of characters of padding to be prefixed
     * to each line
     * @param descPad the number of characters of padding to be prefixed
     * to each description line
     * @param footer the banner to display at the end of the help
     * @param autoUsage whether to print an automatically generated
     * usage statement
     *
     * @throws IllegalStateException if there is no room to print a line
     */
    public void printHelp(PrintWriter pw, int width, String cmdLineSyntax,
                          String header, Options options, int leftPad,
                          int descPad, String footer, boolean autoUsage)
    {
        if ((cmdLineSyntax == null) || (cmdLineSyntax.length() == 0))
        {
            throw new IllegalArgumentException("cmdLineSyntax not provided");
        }

        if (autoUsage)
        {
            printUsage(pw, width, cmdLineSyntax, options);
        }
        else
        {
            printUsage(pw, width, cmdLineSyntax);
        }

        if ((header != null) && (header.trim().length() > 0))
        {
            printWrapped(pw, width, header);
        }

        printOptions(pw, width, options, leftPad, descPad);

        if ((footer != null) && (footer.trim().length() > 0))
        {
            printWrapped(pw, width, footer);
        }
    }

    /**
     * <p>Prints the usage statement for the specified application.</p>
     *
     * @param pw The PrintWriter to print the usage statement 
     * @param width The number of characters to display per line
     * @param app The application name
     * @param options The command line Options
     *
     */
    public void printUsage(PrintWriter pw, int width, String app, Options options)
    {
        // initialise the string buffer
        StringBuffer buff = new StringBuffer(defaultSyntaxPrefix).append(app).append(" ");

        // create a list for processed option groups
        final Collection processedGroups = new ArrayList();

        // temp variable
        Option option;

        List optList = new ArrayList(options.getOptions());
        Collections.sort(optList, getOptionComparator());
        // iterate over the options
        for (Iterator i = optList.iterator(); i.hasNext();)
        {
            // get the next Option
            option = (Option) i.next();

            // check if the option is part of an OptionGroup
            OptionGroup group = options.getOptionGroup(option);

            // if the option is part of a group 
            if (group != null)
            {
                // and if the group has not already been processed
                if (!processedGroups.contains(group))
                {
                    // add the group to the processed list
                    processedGroups.add(group);


                    // add the usage clause
                    appendOptionGroup(buff, group);
                }

                // otherwise the option was displayed in the group
                // previously so ignore it.
            }

            // if the Option is not part of an OptionGroup
            else
            {
                appendOption(buff, option, option.isRequired());
            }

            if (i.hasNext())
            {
                buff.append(" ");
            }
        }


        // call printWrapped
        printWrapped(pw, width, buff.toString().indexOf(' ') + 1, buff.toString());
    }

    /**
     * Appends the usage clause for an OptionGroup to a StringBuffer.  
     * The clause is wrapped in square brackets if the group is required.
     * The display of the options is handled by appendOption
     * @param buff the StringBuffer to append to
     * @param group the group to append
     * @see #appendOption(StringBuffer,Option,boolean)
     */
    private void appendOptionGroup(final StringBuffer buff, final OptionGroup group)
    {
        if (!group.isRequired())
        {
            buff.append("[");
        }

        List optList = new ArrayList(group.getOptions());
        Collections.sort(optList, getOptionComparator());
        // for each option in the OptionGroup
        for (Iterator i = optList.iterator(); i.hasNext();)
        {
            // whether the option is required or not is handled at group level
            appendOption(buff, (Option) i.next(), true);

            if (i.hasNext())
            {
                buff.append(" | ");
            }
        }

        if (!group.isRequired())
        {
            buff.append("]");
        }
    }

    /**
     * Appends the usage clause for an Option to a StringBuffer.  
     *
     * @param buff the StringBuffer to append to
     * @param option the Option to append
     * @param required whether the Option is required or not
     */
    private static void appendOption(final StringBuffer buff, final Option option, final boolean required)
    {
        if (!required)
        {
            buff.append("[");
        }

        if (option.getOpt() != null)
        {
            buff.append("-").append(option.getOpt());
        }
        else
        {
            buff.append("--").append(option.getLongOpt());
        }

        // if the Option has a value
        if (option.hasArg() && option.hasArgName())
        {
            buff.append(" <").append(option.getArgName()).append(">");
        }

        // if the Option is not a required option
        if (!required)
        {
            buff.append("]");
        }
    }

    /**
     * Print the cmdLineSyntax to the specified writer, using the
     * specified width.
     *
     * @param pw The printWriter to write the help to
     * @param width The number of characters per line for the usage statement.
     * @param cmdLineSyntax The usage statement.
     */
    public void printUsage(PrintWriter pw, int width, String cmdLineSyntax)
    {
        int argPos = cmdLineSyntax.indexOf(' ') + 1;

        printWrapped(pw, width, defaultSyntaxPrefix.length() + argPos, defaultSyntaxPrefix + cmdLineSyntax);
    }

    /**
     * <p>Print the help for the specified Options to the specified writer, 
     * using the specified width, left padding and description padding.</p>
     *
     * @param pw The printWriter to write the help to
     * @param width The number of characters to display per line
     * @param options The command line Options
     * @param leftPad the number of characters of padding to be prefixed
     * to each line
     * @param descPad the number of characters of padding to be prefixed
     * to each description line
     */
    public void printOptions(PrintWriter pw, int width, Options options, 
                             int leftPad, int descPad)
    {
        StringBuffer sb = new StringBuffer();

        renderOptions(sb, width, options, leftPad, descPad);
        pw.println(sb.toString());
    }

    /**
     * Print the specified text to the specified PrintWriter.
     *
     * @param pw The printWriter to write the help to
     * @param width The number of characters to display per line
     * @param text The text to be written to the PrintWriter
     */
    public void printWrapped(PrintWriter pw, int width, String text)
    {
        printWrapped(pw, width, 0, text);
    }

    /**
     * Print the specified text to the specified PrintWriter.
     *
     * @param pw The printWriter to write the help to
     * @param width The number of characters to display per line
     * @param nextLineTabStop The position on the next line for the first tab.
     * @param text The text to be written to the PrintWriter
     */
    public void printWrapped(PrintWriter pw, int width, int nextLineTabStop, String text)
    {
        StringBuffer sb = new StringBuffer(text.length());

        renderWrappedText(sb, width, nextLineTabStop, text);
        pw.println(sb.toString());
    }

    // --------------------------------------------------------------- Protected

    /**
     * Render the specified Options and return the rendered Options
     * in a StringBuffer.
     *
     * @param sb The StringBuffer to place the rendered Options into.
     * @param width The number of characters to display per line
     * @param options The command line Options
     * @param leftPad the number of characters of padding to be prefixed
     * to each line
     * @param descPad the number of characters of padding to be prefixed
     * to each description line
     *
     * @return the StringBuffer with the rendered Options contents.
     */
    protected StringBuffer renderOptions(StringBuffer sb, int width, Options options, int leftPad, int descPad)
    {
        final String lpad = createPadding(leftPad);
        final String dpad = createPadding(descPad);

        // first create list containing only <lpad>-a,--aaa where 
        // -a is opt and --aaa is long opt; in parallel look for 
        // the longest opt string this list will be then used to 
        // sort options ascending
        int max = 0;
        StringBuffer optBuf;
        List prefixList = new ArrayList();

        List optList = options.helpOptions();

        Collections.sort(optList, getOptionComparator());

        for (Iterator i = optList.iterator(); i.hasNext();)
        {
            Option option = (Option) i.next();
            optBuf = new StringBuffer(8);

            if (option.getOpt() == null)
            {
                optBuf.append(lpad).append("   " + defaultLongOptPrefix).append(option.getLongOpt());
            }
            else
            {
                optBuf.append(lpad).append(defaultOptPrefix).append(option.getOpt());

                if (option.hasLongOpt())
                {
                    optBuf.append(',').append(defaultLongOptPrefix).append(option.getLongOpt());
                }
            }

            if (option.hasArg())
            {
                if (option.hasArgName())
                {
                    optBuf.append(" <").append(option.getArgName()).append(">");
                }
                else
                {
                    optBuf.append(' ');
                }
            }

            prefixList.add(optBuf);
            max = (optBuf.length() > max) ? optBuf.length() : max;
        }

        int x = 0;

        for (Iterator i = optList.iterator(); i.hasNext();)
        {
            Option option = (Option) i.next();
            optBuf = new StringBuffer(prefixList.get(x++).toString());

            if (optBuf.length() < max)
            {
                optBuf.append(createPadding(max - optBuf.length()));
            }

            optBuf.append(dpad);

            int nextLineTabStop = max + descPad;

            if (option.getDescription() != null)
            {
                optBuf.append(option.getDescription());
            }

            renderWrappedText(sb, width, nextLineTabStop, optBuf.toString());

            if (i.hasNext())
            {
                sb.append(defaultNewLine);
            }
        }

        return sb;
    }

    /**
     * Render the specified text and return the rendered Options
     * in a StringBuffer.
     *
     * @param sb The StringBuffer to place the rendered text into.
     * @param width The number of characters to display per line
     * @param nextLineTabStop The position on the next line for the first tab.
     * @param text The text to be rendered.
     *
     * @return the StringBuffer with the rendered Options contents.
     */
    protected StringBuffer renderWrappedText(StringBuffer sb, int width, 
                                             int nextLineTabStop, String text)
    {
        int pos = findWrapPos(text, width, 0);

        if (pos == -1)
        {
            sb.append(rtrim(text));

            return sb;
        }
        sb.append(rtrim(text.substring(0, pos))).append(defaultNewLine);

        if (nextLineTabStop >= width)
        {
            // stops infinite loop happening
            nextLineTabStop = 1;
        }

        // all following lines must be padded with nextLineTabStop space 
        // characters
        final String padding = createPadding(nextLineTabStop);

        while (true)
        {
            text = padding + text.substring(pos).trim();
            pos = findWrapPos(text, width, 0);

            if (pos == -1)
            {
                sb.append(text);

                return sb;
            }
            
            if ( (text.length() > width) && (pos == nextLineTabStop - 1) ) 
            {
                pos = width;
            }

            sb.append(rtrim(text.substring(0, pos))).append(defaultNewLine);
        }
    }

    /**
     * Finds the next text wrap position after <code>startPos</code> for the
     * text in <code>text</code> with the column width <code>width</code>.
     * The wrap point is the last postion before startPos+width having a 
     * whitespace character (space, \n, \r).
     *
     * @param text The text being searched for the wrap position
     * @param width width of the wrapped text
     * @param startPos position from which to start the lookup whitespace
     * character
     * @return postion on which the text must be wrapped or -1 if the wrap
     * position is at the end of the text
     */
    protected int findWrapPos(String text, int width, int startPos)
    {
        int pos = -1;

        // the line ends before the max wrap pos or a new line char found
        if (((pos = text.indexOf('\n', startPos)) != -1 && pos <= width)
                || ((pos = text.indexOf('\t', startPos)) != -1 && pos <= width))
        {
            return pos + 1;
        }
        else if (startPos + width >= text.length())
        {
            return -1;
        }


        // look for the last whitespace character before startPos+width
        pos = startPos + width;

        char c;

        while ((pos >= startPos) && ((c = text.charAt(pos)) != ' ')
                && (c != '\n') && (c != '\r'))
        {
            --pos;
        }

        // if we found it - just return
        if (pos > startPos)
        {
            return pos;
        }
        
        // must look for the first whitespace chearacter after startPos 
        // + width
        pos = startPos + width;

        while ((pos <= text.length()) && ((c = text.charAt(pos)) != ' ')
               && (c != '\n') && (c != '\r'))
        {
            ++pos;
        }

        return (pos == text.length()) ? (-1) : pos;
    }

    /**
     * Return a String of padding of length <code>len</code>.
     *
     * @param len The length of the String of padding to create.
     *
     * @return The String of padding
     */
    protected String createPadding(int len)
    {
        StringBuffer sb = new StringBuffer(len);

        for (int i = 0; i < len; ++i)
        {
            sb.append(' ');
        }

        return sb.toString();
    }

    /**
     * Remove the trailing whitespace from the specified String.
     *
     * @param s The String to remove the trailing padding from.
     *
     * @return The String of without the trailing padding
     */
    protected String rtrim(String s)
    {
        if ((s == null) || (s.length() == 0))
        {
            return s;
        }

        int pos = s.length();

        while ((pos > 0) && Character.isWhitespace(s.charAt(pos - 1)))
        {
            --pos;
        }

        return s.substring(0, pos);
    }

    // ------------------------------------------------------ Package protected
    // ---------------------------------------------------------------- Private
    // ---------------------------------------------------------- Inner classes
    /**
     * This class implements the <code>Comparator</code> interface
     * for comparing Options.
     */
    private static class OptionComparator implements Comparator
    {

        /**
         * Compares its two arguments for order. Returns a negative
         * integer, zero, or a positive integer as the first argument
         * is less than, equal to, or greater than the second.
         *
         * @param o1 The first Option to be compared.
         * @param o2 The second Option to be compared.
         * @return a negative integer, zero, or a positive integer as
         *         the first argument is less than, equal to, or greater than the
         *         second.
         */
        public int compare(Object o1, Object o2)
        {
            Option opt1 = (Option) o1;
            Option opt2 = (Option) o2;

            return opt1.getKey().compareToIgnoreCase(opt2.getKey());
        }
    }
}