/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

/*

 *

 * (C) Copyright IBM Corp. 2003 - All Rights Reserved

 */

package sun.font;

/**

 * Iterates over runs of fonts in a CompositeFont, optionally taking script runs into account.

 */

public final class FontRunIterator {

    CompositeFont font;

    char[] text;

    int start;

    int limit;

    CompositeGlyphMapper mapper; // handy cache

    int slot = -1;

    int pos;

    public void init(CompositeFont font, char[] text, int start, int limit) {

        if (font == null || text == null || start < 0 || limit < start || limit > text.length) {

            throw new IllegalArgumentException();

        }

        this.font = font;

        this.text = text;

        this.start = start;

        this.limit = limit;

        this.mapper = (CompositeGlyphMapper)font.getMapper();

        this.slot = -1;

        this.pos = start;

    }

    public PhysicalFont getFont() {

        return slot == -1 ? null : font.getSlotFont(slot);

    }

    public int getGlyphMask() {

        return slot << 24;

    }

    public int getPos() {

        return pos;

    }

    /*

     * characters that are in the 'common' script become part of the

     * surrounding script run.  we want to fetch these from the same font

     * used to get surrounding characters, where possible.  but we don't

     * want to force non-common characters to come from other than their

     * standard font.

     *

     * what we really want to do is this:

     * 1) fetch a code point from the text.

     * 2) get its 'native' script code

     * 3) determine its 'resolved' script code

     * 4) if its native script is COMMON, and its resolved script is the same as the previous

     *    code point's, then see if the previous font supports this code point.  if so, use it.

     * 5) otherwise resolve the font as usual

     * 6) break the run when either the physical font or the resolved script changes.

     *

     * problems: we optimize latin-1 and cjk text assuming a fixed

     * width for each character.  since latin-1 digits and punctuation

     * are common, following this algorithm they will change to match

     * the fonts used for the preceding text, and potentially change metrics.

     *

     * this also seems to have the potential for changing arbitrary runs of text, e.g.

     * any number of digits and spaces can change depending on the preceding (or following!)

     * non-COMMON character's font assignment.  this is not good.

     *

     * since the goal is to enable layout to be performed using as few physical fonts as

     * possible, and the primary cause of switching fonts is to handle spaces, perhaps

     * we should just special-case spaces and assign them from the current font, whatever

     * it may be.

     *

     * One could also argue that the job of the composite font is to assign physical fonts

     * to text runs, however it wishes.  we don't necessarily have to provide script info

     * to let it do this.  it can determine based on whatever.  so having a special 'next'

     * function that takes script (and limit) is redundant.  It can fetch the script again

     * if need be.

     *

     * both this and the script iterator are turning char sequences into code point

     * sequences.  maybe it would be better to feed a single code point into each iterator-- push

     * the data instead of pull it?

     */

    public boolean next(int script, int lim) {

        if (pos == lim) {

            return false;

        }

        int ch = nextCodePoint(lim);

        int sl = mapper.charToGlyph(ch) & CompositeGlyphMapper.SLOTMASK;

        slot = sl >>> 24;

        while ((ch = nextCodePoint(lim)) != DONE && (mapper.charToGlyph(ch) & CompositeGlyphMapper.SLOTMASK) == sl);

        pushback(ch);

        return true;

    }

    public boolean next() {

        return next(Script.COMMON, limit);

    }

    static final int SURROGATE_START = 0x10000;

    static final int LEAD_START = 0xd800;

    static final int LEAD_LIMIT = 0xdc00;

    static final int TAIL_START = 0xdc00;

    static final int TAIL_LIMIT = 0xe000;

    static final int LEAD_SURROGATE_SHIFT = 10;

    static final int SURROGATE_OFFSET = SURROGATE_START - (LEAD_START << LEAD_SURROGATE_SHIFT) - TAIL_START;

    static final int DONE = -1;

    int nextCodePoint() {

        return nextCodePoint(limit);

    }

    int nextCodePoint(int lim) {

        if (pos >= lim) {

            return DONE;

        }

        int ch = text[pos++];

        if (ch >= LEAD_START && ch < LEAD_LIMIT && pos < lim) {

            int nch = text[pos];

            if (nch >= TAIL_START && nch < TAIL_LIMIT) {

                ++pos;

                ch = (ch << LEAD_SURROGATE_SHIFT) + nch + SURROGATE_OFFSET;

            }

        }

        return ch;

    }

    void pushback(int ch) {

        if (ch >= 0) {

            if (ch >= 0x10000) {

                pos -= 2;

            } else {

                pos -= 1;

            }

        }

    }

}