/*
 *			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 Terminal Emulator.
 * The Initial Developer of the Original Code is Sun Microsystems, Inc..
 * Portions created by Sun Microsystems, Inc. are Copyright (C) 2001.
 * All Rights Reserved.
 *
 * Contributor(s): Ivan Soleimanipour.
 */

/*
 * "MyFontMetrics"
 * MyFontMetrics.java 1.5 01/07/10
 */

package org.netbeans.lib.terminalemulator;

import java.awt.*;
import java.util.AbstractMap;
import java.util.HashMap;

class MyFontMetrics {

    /**
     * WidthCache contains a byte array that maps a character to it's cell width.
     * It also keeps track of whether we've discovered that we're dealing with a
     * font that has wide characters. This information is kept with WidthCache
     * because the caches are shared between MyFontMetrics and we test for
     * multi-cellnes only on a cache miss. So we got into a situation where one
     * Term got a wide character, missed the cache, figured that it's multi-cell,
     * then another Term got the same character didn't miss the cache and didn't
     * set it's own multi-cell bit.
     *
     * The reference counting stuff is explained with CacheFactory.
     */

    static class WidthCache {
	byte [] cache = new byte[Character.MAX_VALUE+1];
	int reference_count = 1;

	public void up() {
	    reference_count ++;
	    if (reference_count == 1)
		cache = new byte[Character.MAX_VALUE+1];
	} 

	public void down() {
	    if (reference_count == 0)
		return;
	    reference_count --;
	    if (reference_count == 0)
		cache = null;
	}

	public boolean isMultiCell() {
	    return multiCell;
	} 
	public void setMultiCell(boolean multiCell) {
	    this.multiCell = multiCell;
	} 
	private boolean multiCell = false;
    }

    /**
     *
     * CacheFactory doles out WidthCaches.
     *
     * These caches are 64Kb (Character.MAX_VALUE+1) and we don't really want 
     * Each interp to have it's own. So we share them in a map using FontMetrics
     * as a key. Unfortunately stuff will accumulate in the map. A WeakHashMap
     * is no good because the keys (FontMetrics) are usually alive. For all I
     * know Jave might be cacheing them in turn. I actually tried using a
     * WeakHashMap and wouldn't see things going away, even after System.gc().
     * 

     * So we get this slightly more involved manager.
     * 

     * A WidthCache holds on to the actual WidthCache and reference counts it.
     * When the count goes to 0 the actual cache array is "free"d be nulling
     * it's reference. To make the reference count go down CacheFactory.disposeBy()
     * is used. And that is called from MyFontMetrics.finalize().
     *
     * NOTE: The actual WidthCache's instances _will_ accumulate, but they are small and 
     * there are only so many font variations an app can go through. As I
     * mentioned above using a WeakHashMap doesn't help much because WidthCache's
     * are keyed by relatively persistent FontMetrics.
     */

    private static class CacheFactory {
	static synchronized WidthCache cacheForFontMetrics(FontMetrics fm) {
	    WidthCache entry = (WidthCache) map.get(fm);
	    if (entry == null) {
		entry = new WidthCache();
		map.put(fm, entry);
	    } else {
		entry.up();
	    }
	    return entry;
	}

	static synchronized void disposeBy(FontMetrics fm) {
	    WidthCache entry = (WidthCache) map.get(fm);
	    if (entry != null)
		entry.down();
	}

	private static AbstractMap map = new HashMap();
    }


    public MyFontMetrics(Component component, Font font) {
	fm = component.getFontMetrics(font);
	width = fm.charWidth('a');
	height = fm.getHeight();
	ascent = fm.getAscent();
	leading = fm.getLeading();

	// HACK
	// From all I can tell both xterm and DtTerm ignore the leading.
	// Maybe X font's don't have a leading and Java sets it to one
	// artificially? Because unless I do the below I get one extra pixel
	// between my lines.
	// 
	// Some code takes the leading into account and some code doesn't.
	// the following makes things match up, but if we ever undo this
	// we'll have to go and adjust how everything is drawn (cursor,
	// reverse-video attribute, underscore, bg stripe, selection etc.

	height -= leading;
	leading = 0;

	cwidth_cache = CacheFactory.cacheForFontMetrics(fm);
    }

    protected void finalize() {
	CacheFactory.disposeBy(fm);
    }


    public int width;
    public int height;
    public int ascent;
    public int leading;
    public FontMetrics fm;

    private WidthCache cwidth_cache;

    public boolean isMultiCell() {
	return cwidth_cache.isMultiCell();
    } 

    /*
     * Called 'wcwidth' for historical reasons. (see wcwidth(3) on unix.)
     * Return how many cells this character occupies.
     */

    public int wcwidth(char c) {
	int cell_width = cwidth_cache.cache[c];	// how many cells wide

	if (cell_width == 0) {
	    // width not cached yet so figure it out
	    int pixel_width = fm.charWidth(c);

	    if (pixel_width == width) {
		cell_width = 1;

	    } else if (pixel_width == 0) { 
		cell_width = 1;

	    } else {
		// round up pixel width to multiple of cell size
		// then distill into a width in terms of cells.
		int mod = pixel_width % width;
		int rounded_width = pixel_width;
		if (mod != 0)
		    rounded_width = pixel_width + (width - mod);
		cell_width = rounded_width/width;
		if (cell_width == 0)
		    cell_width = 1;

		cwidth_cache.setMultiCell(true);
	    }

	    cwidth_cache.cache[c] = (byte) cell_width;
	}
	return cell_width;
    }

    /*
     * Shift to the multi-cell character regime as soon as we spot one.
     * The actual work is done in wcwidth() itself.
     */
    void checkForMultiCell(char c) {
	wcwidth(c);
    }
}