/*
 *                 Sun Public License Notice
 * 
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 * 
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2003 Sun
 * Microsystems, Inc. All Rights Reserved.
 */

package org.netbeans.editor;

import java.io.IOException;
import java.io.Reader;
import javax.swing.text.Segment;

/**
 * Converters handling the various line separators.
 *
 * @author Miloslav Metelka
 * @version 1.00
 */

public class LineSeparatorConversion {
    
    /**
     * Default size of the conversion buffers.
     */
    private static final int DEFAULT_CONVERSION_BUFFER_SIZE = 16384;
        
    private LineSeparatorConversion() {
        // no instances
    }
    
    /**
     * Convert all the occurrences of '\r' and '\r\n' in the text to '\n'.
     * @param text text being converted
     * @return converted text with '\n' instead of '\r' and '\r\n'.
     */
    public static String convertToLineFeed(String text) {
        StringBuffer output = new StringBuffer();
        convertToLineFeed(text, 0, text.length(), output);
        return output.toString();
    }
    
    /**
     * Convert all the occurrences of '\r' and '\r\n' in the text to '\n'.
     * @param text text being converted
     * @param offset offset of the first character in the text to be converted.
     * @param length number of characters to be converted.
     * @param output output buffer to which the converted characters are added.
     */
    public static void convertToLineFeed(String text, int offset, int length,
    StringBuffer output) {

        int endOffset = offset + length;
        boolean lastCharCR = false; // whether last char was '\r'

        while (offset < endOffset) {
            char ch = text.charAt(offset++);
            if (lastCharCR && ch == '\n') { // found CRLF sequence
                lastCharCR = false;

            } else { // not CRLF sequence
                if (ch == '\r') {
                    output.append('\n');
                    lastCharCR = true;

                } else { // current char not '\r'
                    lastCharCR = false;
                    output.append(ch);
                }
            }
        }
    }

    /**
     * Convert all the occurrences of '\n' in the given text
     * to the requested line separator.
     * @param text text being converted
     * @param lineFeedReplace characters that replace the '\n' character
     *  in the converted text.
     * @return converted text with replaced '\n' by characters from lineFeedReplace string
     */
    public static String convertFromLineFeed(String text, String lineFeedReplace) {
        StringBuffer output = new StringBuffer();
        convertFromLineFeed(text, 0, text.length(), lineFeedReplace, output);
        return output.toString();
    }

    /**
     * Convert all the occurrences of '\n' in the given text
     * to the requested line separator.
     * @param text text being converted
     * @param offset offset of the first character in the text to be converted.
     * @param length number of characters to be converted.
     * @param lineFeedReplace characters that replace the '\n' character in the output
     * @param output output buffer to which the converted characters are added.
     */
    public static void convertFromLineFeed(String text, int offset, int length,
    String lineFeedReplace, StringBuffer output) {
        int lineFeedReplaceLength = lineFeedReplace.length();
        int endOffset = offset + length;
        while (offset < endOffset) {
            char ch = text.charAt(offset++);
            if (ch == '\n') {
                for (int i = 0; i < lineFeedReplaceLength; i++) {
                    output.append(lineFeedReplace.charAt(i));
                }
            } else {
                output.append(ch);
            }
        }
    }

    /**
     * Convert all the occurrences of '\r' and '\r\n' in the text to '\n'.
     * This class does conversion in chunks of fixed size
     * and is therefore suitable for conversion of readers
     * where the size is unknown.
     */
    public static class ToLineFeed {
        
        private Reader reader;
        
        private Segment convertedText;
        
        private boolean lastCharCR;

        public ToLineFeed(Reader reader) {
            this(reader, DEFAULT_CONVERSION_BUFFER_SIZE);
        }

        public ToLineFeed(Reader reader, int convertBufferSize) {
            this.reader = reader;
            convertedText = new Segment();
            convertedText.array = new char[convertBufferSize];
        }
        
        public Segment nextConverted() throws IOException {
            if (reader == null) { // no more chars to read
                return null;
            }

            int readOffset = 0;
            int readSize = readBuffer(reader, convertedText.array, readOffset, true);
            
            if (readSize == 0) { // no more chars in reader
                reader.close();
                reader = null;
                return null;
            }

            if (lastCharCR && readSize > 0 && convertedText.array[readOffset] == '\n') {
                /* the preceding '\r' was already converted to '\n'
                 * in the previous buffer so here just skip initial '\n'
                 */
                readOffset++;
                readSize--;
            }

            convertedText.offset = readOffset;
            convertedText.count = readSize;
            lastCharCR = convertSegmentToLineFeed(convertedText);
            return convertedText;
        }
        
        /**
         * Convert all the '\r\n' or '\r' to '\n' (linefeed).
         * This method 
         * @param text the text to be converted. Text is converted
         *  in the original array of the given segment.
         *  The count field
         *  of the text parameter will possibly be changed by the conversion
         *  if '\r\n' sequences are present.
         * @return whether the last character in the text was the '\r' character.
         *  That character was already converted to '\n' and is present
         *  in the segment. However this notification is important
         *  because if there would be '\n' at the begining
         *  of the next buffer then that character should be skipped.
         */
        private static boolean convertSegmentToLineFeed(Segment text) {
            char[] chars = text.array;
            int storeOffset = text.offset; // offset at which chars are stored
            int endOffset = storeOffset + text.count;
            boolean storeChar = false; // to prevent copying same chars to same offsets
            boolean lastCharCR = false; // whether last char was '\r'

            for (int offset = storeOffset; offset < endOffset; offset++) {
                char ch = chars[offset];

                if (lastCharCR && ch == '\n') { // found CRLF sequence
                    lastCharCR = false;
                    storeChar = true; // storeOffset now differs from offset

                } else { // not CRLF sequence
                    if (ch == '\r') {
                        lastCharCR = true;
                        chars[storeOffset++] = '\n'; // convert it to '\n'

                    } else { // current char not '\r'
                        lastCharCR = false;
                        if (storeChar) {
                            chars[storeOffset] = ch;
                        }
                        storeOffset++;
                    }
                }
            }

            text.count = storeOffset - text.offset;

            return lastCharCR;
        }

        private static int readBuffer(Reader reader, char[] buffer, int offset,
        boolean joinReads) throws IOException {
            int maxReadSize = buffer.length - offset;
            int totalReadSize = 0;

            do {
                int readSize = 0;
                while (readSize == 0) { // eliminate empty reads
                    readSize = reader.read(buffer, offset, maxReadSize);
                }

                if (readSize == -1) {
                    break; // no more chars in reader
                }

                totalReadSize += readSize;
                offset += readSize;
                maxReadSize -= readSize;

            } while (joinReads && maxReadSize > 0);

            return totalReadSize;
        }

    }

    /**
     * Convert all the occurrences of '\n' in the given text
     * to the requested line separator.
     * This class does conversion in chunks of fixed size
     * and is therefore suitable for conversion of large
     * texts.
     */
    public static class FromLineFeed {
        
        private Object charArrayOrSequence;
        
        private int offset;
        
        private int endOffset;
        
        private String lineFeedReplace;

        private Segment convertedText;
        
        public FromLineFeed(char[] source, int offset, int length,
        String lineFeedReplace) {
            this(source, offset, length, lineFeedReplace, DEFAULT_CONVERSION_BUFFER_SIZE);
        }

        public FromLineFeed(char[] source, int offset, int length,
        String lineFeedReplace, int conversionSegmentSize) {
            this((Object)source, offset, length, lineFeedReplace, conversionSegmentSize);
        }

        public FromLineFeed(String text, int offset, int length,
        String lineFeedReplace) {
            this(text, offset, length, lineFeedReplace, DEFAULT_CONVERSION_BUFFER_SIZE);
        }

        public FromLineFeed(String text, int offset, int length,
        String lineFeedReplace, int conversionSegmentSize) {
            this((Object)text, offset, length, lineFeedReplace, conversionSegmentSize);
        }

        private FromLineFeed(Object charArrayOrSequence, int offset, int length,
        String lineFeedReplace, int conversionSegmentSize) {
            
            if (conversionSegmentSize < lineFeedReplace.length()) {
                throw new IllegalArgumentException("conversionSegmentSize=" // NOI18N
                    + conversionSegmentSize + " < lineFeedReplace.length()=" // NOI18N
                    + lineFeedReplace.length()
                );
            }

            this.charArrayOrSequence = charArrayOrSequence;
            this.offset = offset;
            this.endOffset = offset + length;
            this.lineFeedReplace = lineFeedReplace;

            convertedText = new Segment();
            convertedText.array = new char[conversionSegmentSize];
        }

        public Segment nextConverted() {
            if (offset == endOffset) { // no more chars to convert
                return null;
            }

            // [PENDING-PERF] optimization for '\n' -> arraycopy

            char[] convertedArray = convertedText.array;
            int convertedArrayLength = convertedArray.length;
            int convertedOffset = 0;

            /* Determine whether the source is char-sequence
             * or char buffer.
             * Assign either sourceText or sourceArray but not both.
             */
            String sourceText;
            char[] sourceArray;
            if (charArrayOrSequence instanceof String) {
                sourceText = (String)charArrayOrSequence;
                sourceArray = null;

            } else {
                sourceArray = (char[])charArrayOrSequence;
                sourceText = null;
            }

            int lineFeedReplaceLength = lineFeedReplace.length();
            while (offset < endOffset
                && convertedArrayLength - convertedOffset >= lineFeedReplaceLength
            ) {
                char ch = (sourceText != null)
                    ? sourceText.charAt(offset++)
                    : sourceArray[offset++];

                if (ch == '\n') {
                    for (int i = 0; i < lineFeedReplaceLength; i++) {
                        convertedArray[convertedOffset++] = lineFeedReplace.charAt(i);
                    }
                    

                } else {
                    convertedArray[convertedOffset++] = ch;
                }
            }

            convertedText.offset = 0;
            convertedText.count = convertedOffset;

            return convertedText;
        }
        
    }
    
    public static class InitialSeparatorReader extends Reader {
        
        private static final int AFTER_CR_STATUS = -1;
        
        private static final int INITIAL_STATUS = 0;
        
        private static final int CR_SEPARATOR = 1;
        
        private static final int LF_SEPARATOR = 2;
        
        private static final int CRLF_SEPARATOR = 3;
        
        private Reader delegate;
        
        private int status = INITIAL_STATUS;
        
        public InitialSeparatorReader(Reader delegate) {
            this.delegate = delegate;
        }
        
        public String getInitialSeparator() {
            String separator;
            switch (status) {
                case CR_SEPARATOR:
                    separator = "\r"; // NOI18N
                    break;
                    
                case LF_SEPARATOR:
                    separator = "\n"; // NOI18N
                    break;
                    
                case CRLF_SEPARATOR:
                    separator = "\r\n"; // NOI18N
                    break;
                    
                case AFTER_CR_STATUS: // '\r' was last char
                    separator = "\r"; // NOI18N
                    break;
                    
                default:
                    separator = "\n"; // default // NOI18N
                    break;
            }

            return separator;
        }
        
        private void resolveSeparator(char ch) {
            switch (status) {
                case INITIAL_STATUS:
                    switch (ch) {
                        case '\r':
                            status = AFTER_CR_STATUS;
                            break;
                        case '\n':
                            status = LF_SEPARATOR;
                            break;
                    }
                    break;
                    
                case AFTER_CR_STATUS:
                    switch (ch) {
                        case '\n':
                            status = CRLF_SEPARATOR;
                            break;
                        default:
                            status = CR_SEPARATOR;
                            break;
                    }
                    break;

                default:
                    switch (ch) {
                        case '\r':
                            status = AFTER_CR_STATUS;
                            break;
                        case '\n':
                            status = LF_SEPARATOR;
                            break;
                    }
                    break;
            }
        }
        
        private boolean isSeparatorResolved() {
            return (status > 0);
        }
        
        public void close() throws IOException {
            if (delegate == null) {
                return;
            }

            delegate.close();
            delegate = null;
        }        
        
        public int read(char[] cbuf, int off, int len) throws IOException {
            if (delegate == null) {
                throw new IOException("Reader already closed."); // NOI18N
            }

            int readLen = delegate.read(cbuf, off, len);

            for (int endOff = off + readLen;
                off < endOff && !isSeparatorResolved();
                off++
            ) {
                resolveSeparator(cbuf[off]);
            }

            return readLen;
        }

        public int read() throws IOException {
            if (delegate == null) {
                throw new IOException("Reader already closed."); // NOI18N
            }

            int r = delegate.read();
            if (r != -1 && !isSeparatorResolved()) {
                resolveSeparator((char)r);
            }
            
            return r;
        }

    }

}