/*
 * [CollapseBlankLines.java]
 *
 * Summary: Collapse multiple blank lines to one.
 *
 * Copyright: (c) 2002-2017 Roedy Green, Canadian Mind Products, http://mindprod.com
 *
 * Licence: This software may be copied and used freely for any purpose but military.
 *          http://mindprod.com/contact/nonmil.html
 *
 * Requires: JDK 1.8+
 *
 * Created with: JetBrains IntelliJ IDEA IDE http://www.jetbrains.com/idea/
 *
 * Version History:
 *  4.5 2009-02-26 add both Java string quoting and plain for Java search/regexes.
 */
package com.mindprod.quoter;

/**
 * Collapse multiple blank lines to one.
 *
 * @author Roedy Green, Canadian Mind Products
 * @version 4.5 2009-02-26 add both Java string quoting and plain for Java search/regexes.
 * @since 2002-06-19
 */
final class CollapseBlankLines extends TextProcessor
    {
    /**
     * Collapse runs of blank lines to a single blank line. Leave leading and trailing spaces on each line as is.
     *
     * @param raw String to process, may contain embedded \ns.
     *
     * @return String with blank lines collapsed.
     */
    String process( String raw )
        {
        if ( raw == null )
            {
            return null;
            }
        char[] ca = new char[ raw.length() ];
        int j = 0;
        // true if next blank line should be suppressed
        boolean suppressBlankLines = false;
        // true if we are in the leading spaces of a line
        boolean inLeading = true;
        // count of how many spaces we recently suppressed
        int spacesSuppressed = 0;
        for ( int i = 0; i < raw.length(); i++ )
            {
            char c = raw.charAt( i );
            switch ( c )
                {
                case '\t':
                case ' ':
                    spacesSuppressed++;
                    break;
                case '\n':
                    if ( inLeading )
                        {
                        // end of blank line
                        if ( suppressBlankLines )
                            {
                            spacesSuppressed = 0;
                            }
                        else
                            {
                            // We may have suppressed some trailing spaces we
                            // should
                            // not have.
                            // put them back.
                            for ( ; spacesSuppressed > 0; spacesSuppressed-- )
                                {
                                ca[ j++ ] = ' ';
                                }
                            ca[ j++ ] = c;
                            suppressBlankLines = true;
                            }
                        }
                    else
                        {
                        // end end of normal line
                        // We may have suppressed some trailing spaces we should
                        // not
                        // have.
                        // put them back.
                        for ( ; spacesSuppressed > 0; spacesSuppressed-- )
                            {
                            ca[ j++ ] = ' ';
                            }
                        ca[ j++ ] = c;
                        suppressBlankLines = false;
                        } // end else
                    inLeading = true;
                    break;
                default:
                    // ordinary character
                    // We may have suppressed some spaces we should not have.
                    // put them back.
                    for ( ; spacesSuppressed > 0; spacesSuppressed-- )
                        {
                        ca[ j++ ] = ' ';
                        }
                    ca[ j++ ] = c;
                    inLeading = false;
                    break;
                } // end switch
            } // end for
        // If there was no trailing \n,
        // we may have suppressed some trailing spaces we should not have.
        // put them back.
        if ( !( inLeading && suppressBlankLines ) )
            {
            for ( ; spacesSuppressed > 0; spacesSuppressed-- )
                {
                ca[ j++ ] = ' ';
                }
            }
        if ( j != raw.length() )
            {
            raw = new String( ca, 0/* offset */, j/* count */ );
            }
        return raw;
        } // end process
    } // end CollapseBlankLines