/*******************************************************************************
 * Copyright (c) 2000, 2006 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.erlide.ui.util.eclipse.text;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.text.BreakIterator;

import org.eclipse.swt.graphics.GC;

/*
 * Not a real reader. Could change if requested
 */
public class LineBreakingReader {

    private final BufferedReader fReader;
    private final GC fGC;
    private final int fMaxWidth;

    private String fLine;
    private int fOffset;

    private final BreakIterator fLineBreakIterator;
    private final boolean fBreakWords;

    /**
     * Creates a reader that breaks an input text to fit in a given width.
     *
     * @param reader
     *            Reader of the input text
     * @param gc
     *            The graphic context that defines the currently used font sizes
     * @param maxLineWidth
     *            The max width (pixels) where the text has to fit in
     */
    public LineBreakingReader(final Reader reader, final GC gc, final int maxLineWidth) {
        fReader = new BufferedReader(reader);
        fGC = gc;
        fMaxWidth = maxLineWidth;
        fOffset = 0;
        fLine = null;
        fLineBreakIterator = BreakIterator.getLineInstance();
        fBreakWords = true;
    }

    public boolean isFormattedLine() {
        return fLine != null;
    }

    /**
     * Reads the next line. The lengths of the line will not exceed the given
     * maximum width.
     *
     * @return the next line
     * @throws IOException
     */
    public String readLine() throws IOException {
        if (fLine == null) {
            final String line = fReader.readLine();
            if (line == null) {
                return null;
            }

            final int lineLen = fGC.textExtent(line).x;
            if (lineLen < fMaxWidth) {
                return line;
            }
            fLine = line;
            fLineBreakIterator.setText(line);
            fOffset = 0;
        }
        final int breakOffset = findNextBreakOffset(fOffset);
        String res;
        if (breakOffset != BreakIterator.DONE) {
            res = fLine.substring(fOffset, breakOffset);
            fOffset = findWordBegin(breakOffset);
            if (fOffset == fLine.length()) {
                fLine = null;
            }
        } else {
            res = fLine.substring(fOffset);
            fLine = null;
        }
        return res;
    }

    private int findNextBreakOffset(final int currOffset0) {
        int currOffset = currOffset0;
        int currWidth = 0;
        int nextOffset = fLineBreakIterator.following(currOffset);
        while (nextOffset != BreakIterator.DONE) {
            String word = fLine.substring(currOffset, nextOffset);
            int wordWidth = fGC.textExtent(word).x;
            final int nextWidth = wordWidth + currWidth;
            if (nextWidth > fMaxWidth) {
                if (currWidth > 0) {
                    return currOffset;
                }

                if (!fBreakWords) {
                    return nextOffset;
                }

                // need to fit into fMaxWidth
                int length = word.length();
                while (length >= 0) {
                    length--;
                    word = word.substring(0, length);
                    wordWidth = fGC.textExtent(word).x;
                    if (wordWidth + currWidth < fMaxWidth) {
                        return currOffset + length;
                    }
                }
                return nextOffset;
            }
            currWidth = nextWidth;
            currOffset = nextOffset;
            nextOffset = fLineBreakIterator.next();
        }
        return nextOffset;
    }

    private int findWordBegin(final int idx0) {
        int idx = idx0;
        while (idx < fLine.length() && Character.isWhitespace(fLine.charAt(idx))) {
            idx++;
        }
        return idx;
    }
}