/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/* $Id$ */

package org.apache.fop.fonts;

import java.nio.IntBuffer;
import java.util.ArrayList;
import java.util.List;

// CSOFF: LineLengthCheck
// CSOFF: NoWhitespaceAfterCheck

/**
 * The <code>GlyphProcessingState</code> implements a common, base state object used during glyph substitution
 * and positioning processing.
 * @author Glenn Adams
 */

public class GlyphProcessingState {

    /** governing glyph definition table */
    protected GlyphDefinitionTable gdef;
    /** governing script */
    protected String script;
    /** governing language */
    protected String language;
    /** governing feature */
    protected String feature;
    /** current input glyph sequence */
    protected GlyphSequence igs;
    /** current index in input sequence */
    protected int index;
    /** last (maximum) index of input sequence (exclusive) */
    protected int indexLast;
    /** consumed, updated after each successful subtable application */
    protected int consumed;
    /** lookup flags */
    protected int flags;
    /** class match set */
    protected int classMatchSet;
    /** script specific context tester or null */
    protected ScriptContextTester sct;
    /** glyph context tester or null */
    protected GlyphContextTester gct;
    /** ignore base glyph tester */
    protected GlyphTester ignoreBase;
    /** ignore ligature glyph tester */
    protected GlyphTester ignoreLigature;
    /** ignore mark glyph tester */
    protected GlyphTester ignoreMark;
    /** default ignore glyph tester */
    protected GlyphTester ignoreDefault;

    /**
     * Construct glyph processing state.
     * @param gs input glyph sequence
     * @param script script identifier
     * @param language language identifier
     * @param feature feature identifier
     * @param sct script context tester (or null)
     */
    protected GlyphProcessingState ( GlyphSequence gs, String script, String language, String feature, ScriptContextTester sct ) {
        this.script = script;
        this.language = language;
        this.feature = feature;
        this.igs = gs;
        this.indexLast = gs.getGlyphCount();
        this.sct = sct;
        this.gct = ( sct != null ) ? sct.getTester ( feature ) : null;
        this.ignoreBase = new GlyphTester() { public boolean test(int gi) { return isBase(gi); } };
        this.ignoreLigature = new GlyphTester() { public boolean test(int gi) { return isLigature(gi); } };
        this.ignoreMark = new GlyphTester() { public boolean test(int gi) { return isMark(gi); } };
    }

    /**
     * Construct glyph processing state using an existing state object using shallow copy
     * except as follows: input glyph sequence is copied deep except for its characters array.
     * @param s existing processing state to copy from
     */
    protected GlyphProcessingState ( GlyphProcessingState s ) {
        this ( new GlyphSequence ( s.igs ), s.script, s.language, s.feature, s.sct );
        setPosition ( s.index );
    }

    /**
     * Set governing glyph definition table.
     * @param gdef glyph definition table (or null, to unset)
     */
    public void setGDEF ( GlyphDefinitionTable gdef ) {
        if ( this.gdef == null ) {
            this.gdef = gdef;
        } else if ( gdef == null ) {
            this.gdef = null;
        }
    }

    /**
     * Obtain governing glyph definition table.
     * @return glyph definition table (or null, to not set)
     */
    public GlyphDefinitionTable getGDEF() {
        return gdef;
    }

    /**
     * Set governing lookup flags
     * @param flags lookup flags (or zero, to unset)
     */
    public void setFlags ( int flags ) {
        if ( this.flags == 0 ) {
            this.flags = flags;
        } else if ( flags == 0 ) {
            this.flags = 0;
        }
    }

    /**
     * Obtain governing lookup  flags.
     * @return lookup flags (zero may indicate unset or no flags)
     */
    public int getFlags() {
        return flags;
    }

    /**
     * Obtain governing class match set.
     * @param gi glyph index that may be used to determine which match set applies
     * @return class match set (zero may indicate unset or no set)
     */
    public int getClassMatchSet ( int gi ) {
        return 0;
    }

    /**
     * Set default ignore tester.
     * @param ignoreDefault glyph tester (or null, to unset)
     */
    public void setIgnoreDefault ( GlyphTester ignoreDefault ) {
        if ( this.ignoreDefault == null ) {
            this.ignoreDefault = ignoreDefault;
        } else if ( ignoreDefault == null ) {
            this.ignoreDefault = null;
        }
    }

    /**
     * Obtain governing default ignores tester.
     * @return default ignores tester
     */
    public GlyphTester getIgnoreDefault() {
        return ignoreDefault;
    }

    /**
     * Update glyph subtable specific state. Each time a
     * different glyph subtable is to be applied, it is used
     * to update this state prior to application, after which
     * this state is to be reset.
     * @param st glyph subtable to use for update
     */
    public void updateSubtableState ( GlyphSubtable st ) {
        setGDEF ( st.getGDEF() );
        setFlags ( st.getFlags() );
        setIgnoreDefault ( getIgnoreTester ( flags ) );
    }

    /**
     * Reset glyph subtable specific state.
     */
    public void resetSubtableState() {
        setGDEF ( null );
        setFlags ( 0 );
        setIgnoreDefault ( null );
    }

    /**
     * Obtain current position index in input glyph sequence.
     * @return current index
     */
    public int getPosition() {
        return index;
    }

    /**
     * Set (seek to) position index in input glyph sequence.
     * @param index to seek to
     * @throws IndexOutOfBoundsException if index is less than zero
     * or exceeds last valid position
     */
    public void setPosition ( int index ) throws IndexOutOfBoundsException {
        if ( ( index >= 0 ) && ( index <= indexLast ) ) {
            this.index =  index;
        } else {
            throw new IndexOutOfBoundsException();
        }
    }

    /**
     * Obtain last valid position index in input glyph sequence.
     * @return current last index
     */
    public int getLastPosition() {
        return indexLast;
    }

    /**
     * Determine if at least one glyph remains in
     * input sequence.
     * @return true if one or more glyph remains
     */
    public boolean hasNext() {
        return hasNext ( 1 );
    }

    /**
     * Determine if at least <code>count</code> glyphs remain in
     * input sequence.
     * @param count of glyphs to test
     * @return true if at least <code>count</code> glyphs are available
     */
    public boolean hasNext ( int count ) {
        return ( index + count ) <= indexLast;
    }

    /**
     * Update the current position index based upon previously consumed
     * glyphs, i.e., add the consuemd count to the current position index.
     * If no glyphs were previously consumed, then forces exactly one
     * glyph to be consumed.
     * @return the new (updated) position index
     */
    public int next() {
        if ( index < indexLast ) {
            // force consumption of at least one input glyph
            if ( consumed == 0 ) {
                consumed = 1;
            }
            index += consumed; consumed = 0;
            if ( index > indexLast ) {
                index = indexLast;
            }
        }
        return index;
    }

    /**
     * Determine if at least one backtrack (previous) glyph is present
     * in input sequence.
     * @return true if one or more glyph remains
     */
    public boolean hasPrev() {
        return hasPrev ( 1 );
    }

    /**
     * Determine if at least <code>count</code> backtrack (previous) glyphs
     * are present in input sequence.
     * @param count of glyphs to test
     * @return true if at least <code>count</code> glyphs are available
     */
    public boolean hasPrev ( int count ) {
        return ( index - count ) >= 0;
    }

    /**
     * Update the current position index based upon previously consumed
     * glyphs, i.e., subtract the consuemd count from the current position index.
     * If no glyphs were previously consumed, then forces exactly one
     * glyph to be consumed. This method is used to traverse an input
     * glyph sequence in reverse order.
     * @return the new (updated) position index
     */
    public int prev() {
        if ( index > 0 ) {
            // force consumption of at least one input glyph
            if ( consumed == 0 ) {
                consumed = 1;
            }
            index -= consumed; consumed = 0;
            if ( index < 0 ) {
                index = 0;
            }
        }
        return index;
    }

    /**
     * Record the consumption of <code>count</code> glyphs such that
     * this consumption never exceeds the number of glyphs in the input glyph
     * sequence.
     * @param count of glyphs to consume
     * @return newly adjusted consumption count
     * @throws IndexOutOfBoundsException if count would cause consumption
     * to exceed count of glyphs in input glyph sequence
     */
    public int consume ( int count ) throws IndexOutOfBoundsException {
        if ( ( consumed + count ) <= indexLast ) {
            consumed += count;
            return consumed;
        } else {
            throw new IndexOutOfBoundsException();
        }
    }

    /**
     * Determine if any consumption has occurred.
     * @return true if consumption count is greater than zero
     */
    public boolean didConsume() {
        return consumed > 0;
    }

    /**
     * Obtain reference to input glyph sequence, which must not be modified.
     * @return input glyph sequence
     */
    public GlyphSequence getInput() {
        return igs;
    }

    /**
     * Obtain glyph at specified offset from current position.
     * @param offset from current position
     * @return glyph at specified offset from current position
     * @throws IndexOutOfBoundsException if no glyph available at offset
     */
    public int getGlyph ( int offset ) throws IndexOutOfBoundsException {
        int i = index + offset;
        if ( ( i >= 0 ) && ( i < indexLast ) ) {
            return igs.getGlyph ( i );
        } else {
            throw new IndexOutOfBoundsException ( "attempting index at " + i );
        }
    }

    /**
     * Obtain glyph at current position.
     * @return glyph at current position
     * @throws IndexOutOfBoundsException if no glyph available
     */
    public int getGlyph() throws IndexOutOfBoundsException {
        return getGlyph ( 0 );
    }

    /**
     * Set (replace) glyph at specified offset from current position.
     * @param offset from current position
     * @param glyph to set at specified offset from current position
     * @throws IndexOutOfBoundsException if specified offset is not valid position
     */
    public void setGlyph ( int offset, int glyph ) throws IndexOutOfBoundsException {
        int i = index + offset;
        if ( ( i >= 0 ) && ( i < indexLast ) ) {
            igs.setGlyph ( i, glyph );
        } else {
            throw new IndexOutOfBoundsException ( "attempting index at " + i );
        }
    }

    /**
     * Obtain character association of glyph at specified offset from current position.
     * @param offset from current position
     * @return character association of glyph at current position
     * @throws IndexOutOfBoundsException if offset results in an invalid index into input glyph sequence
     */
    public GlyphSequence.CharAssociation getAssociation ( int offset ) throws IndexOutOfBoundsException {
        int i = index + offset;
        if ( ( i >= 0 ) && ( i < indexLast ) ) {
            return igs.getAssociation ( i );
        } else {
            throw new IndexOutOfBoundsException ( "attempting index at " + i );
        }
    }

    /**
     * Obtain character association of glyph at current position.
     * @return character association of glyph at current position
     * @throws IndexOutOfBoundsException if no glyph available
     */
    public GlyphSequence.CharAssociation getAssociation() throws IndexOutOfBoundsException {
        return getAssociation ( 0 );
    }

    /**
     * Obtain <code>count</code> glyphs starting at specified offset from current position. If
     * <code>reverseOrder</code> is true, then glyphs are returned in reverse order starting at specified offset
     * and going in reverse towards beginning of input glyph sequence.
     * @param offset from current position
     * @param count number of glyphs to obtain
     * @param reverseOrder true if to obtain in reverse order
     * @param ignoreTester glyph tester to use to determine which glyphs are ignored (or null, in which case none are ignored)
     * @param glyphs array to use to fetch glyphs
     * @param counts int[2] array to receive fetched glyph counts, where counts[0] will
     * receive the number of glyphs obtained, and counts[1] will receive the number of glyphs
     * ignored
     * @return array of glyphs
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public int[] getGlyphs ( int offset, int count, boolean reverseOrder, GlyphTester ignoreTester, int[] glyphs, int[] counts ) throws IndexOutOfBoundsException {
        if ( count < 0 ) {
            count = getGlyphsAvailable ( offset, reverseOrder, ignoreTester ) [ 0 ];
        }
        int start = index + offset;
        if ( start < 0 ) {
            throw new IndexOutOfBoundsException ( "will attempt index at " + start );
        } else if ( ! reverseOrder && ( ( start + count ) > indexLast ) ) {
            throw new IndexOutOfBoundsException ( "will attempt index at " + ( start + count ) );
        } else if ( reverseOrder && ( ( start + 1 ) < count ) ) {
            throw new IndexOutOfBoundsException ( "will attempt index at " + ( start - count ) );
        }
        if ( glyphs == null ) {
            glyphs = new int [ count ];
        } else if ( glyphs.length != count ) {
            throw new IllegalArgumentException ( "glyphs array is non-null, but its length (" + glyphs.length + "), is not equal to count (" + count + ")" );
        }
        if ( ! reverseOrder ) {
            return getGlyphsForward ( start, count, ignoreTester, glyphs, counts );
        } else {
            return getGlyphsReverse ( start, count, ignoreTester, glyphs, counts );
        }
    }

    private int[] getGlyphsForward ( int start, int count, GlyphTester ignoreTester, int[] glyphs, int[] counts ) throws IndexOutOfBoundsException {
        int counted = 0;
        int ignored = 0;
        for ( int i = start, n = indexLast, k = 0; i < n; i++ ) {
            int gi = getGlyph ( i - index );
            if ( gi == 65535 ) {
                ignored++;
            } else {
                if ( ( ignoreTester == null ) || ! ignoreTester.test ( gi ) ) {
                    if ( k < count ) {
                        glyphs [ k++ ] = gi; counted++;
                    } else {
                        break;
                    }
                } else {
                    ignored++;
                }
            }
        }
        if ( ( counts != null ) && ( counts.length > 1 ) ) {
            counts[0] = counted;
            counts[1] = ignored;
        }
        return glyphs;
    }

    private int[] getGlyphsReverse ( int start, int count, GlyphTester ignoreTester, int[] glyphs, int[] counts ) throws IndexOutOfBoundsException {
        int counted = 0;
        int ignored = 0;
        for ( int i = start, k = 0; i >= 0; i-- ) {
            int gi = getGlyph ( i - index );
            if ( gi == 65535 ) {
                ignored++;
            } else {
                if ( ( ignoreTester == null ) || ! ignoreTester.test ( gi ) ) {
                    if ( k < count ) {
                        glyphs [ k++ ] = gi; counted++;
                    } else {
                        break;
                    }
                } else {
                    ignored++;
                }
            }
        }
        if ( ( counts != null ) && ( counts.length > 1 ) ) {
            counts[0] = counted;
            counts[1] = ignored;
        }
        return glyphs;
    }

    /**
     * Obtain <code>count</code> glyphs starting at specified offset from current position. If
     * offset is negative, then glyphs are returned in reverse order starting at specified offset
     * and going in reverse towards beginning of input glyph sequence.
     * @param offset from current position
     * @param count number of glyphs to obtain
     * @param glyphs array to use to fetch glyphs
     * @param counts int[2] array to receive fetched glyph counts, where counts[0] will
     * receive the number of glyphs obtained, and counts[1] will receive the number of glyphs
     * ignored
     * @return array of glyphs
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public int[] getGlyphs ( int offset, int count, int[] glyphs, int[] counts ) throws IndexOutOfBoundsException {
        return getGlyphs ( offset, count, offset < 0, ignoreDefault, glyphs, counts );
    }

    /**
     * Obtain all glyphs starting from current position to end of input glyph sequence.
     * @return array of available glyphs
     * @throws IndexOutOfBoundsException if no glyph available
     */
    public int[] getGlyphs() throws IndexOutOfBoundsException {
        return getGlyphs ( 0, indexLast - index, false, null, null, null );
    }

    /**
     * Obtain <code>count</code> ignored glyphs starting at specified offset from current position. If
     * <code>reverseOrder</code> is true, then glyphs are returned in reverse order starting at specified offset
     * and going in reverse towards beginning of input glyph sequence.
     * @param offset from current position
     * @param count number of glyphs to obtain
     * @param reverseOrder true if to obtain in reverse order
     * @param ignoreTester glyph tester to use to determine which glyphs are ignored (or null, in which case none are ignored)
     * @param glyphs array to use to fetch glyphs
     * @param counts int[2] array to receive fetched glyph counts, where counts[0] will
     * receive the number of glyphs obtained, and counts[1] will receive the number of glyphs
     * ignored
     * @return array of glyphs
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public int[] getIgnoredGlyphs ( int offset, int count, boolean reverseOrder, GlyphTester ignoreTester, int[] glyphs, int[] counts ) throws IndexOutOfBoundsException {
        return getGlyphs ( offset, count, reverseOrder, new NotGlyphTester ( ignoreTester ), glyphs, counts );
    }

    /**
     * Obtain <code>count</code> ignored glyphs starting at specified offset from current position. If <code>offset</code> is
     * negative, then fetch in reverse order.
     * @param offset from current position
     * @param count number of glyphs to obtain
     * @return array of glyphs
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public int[] getIgnoredGlyphs ( int offset, int count ) throws IndexOutOfBoundsException {
        return getIgnoredGlyphs ( offset, count, offset < 0, ignoreDefault, null, null );
    }

    /**
     * Determine number of glyphs available starting at specified offset from current position. If
     * <code>reverseOrder</code> is true, then search backwards in input glyph sequence.
     * @param offset from current position
     * @param reverseOrder true if to obtain in reverse order
     * @param ignoreTester glyph tester to use to determine which glyphs to count (or null, in which case none are ignored)
     * @return an int[2] array where counts[0] is the number of glyphs available, and counts[1] is the number of glyphs ignored
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public int[] getGlyphsAvailable ( int offset, boolean reverseOrder, GlyphTester ignoreTester ) throws IndexOutOfBoundsException {
        int start = index + offset;
        if ( ( start < 0 ) || ( start > indexLast ) ) {
            return new int[] { 0, 0 };
        } else if ( ! reverseOrder ) {
            return getGlyphsAvailableForward ( start, ignoreTester );
        } else {
            return getGlyphsAvailableReverse ( start, ignoreTester );
        }
    }

    private int[] getGlyphsAvailableForward ( int start, GlyphTester ignoreTester ) throws IndexOutOfBoundsException {
        int counted = 0;
        int ignored = 0;
        if ( ignoreTester == null ) {
            counted = indexLast - start;
        } else {
            for ( int i = start, n = indexLast; i < n; i++ ) {
                int gi = getGlyph ( i - index );
                if ( gi == 65535 ) {
                    ignored++;
                } else {
                    if ( ignoreTester.test ( gi ) ) {
                        ignored++;
                    } else {
                        counted++;
                    }
                }
            }
        }
        return new int[] { counted, ignored };
    }

    private int[] getGlyphsAvailableReverse ( int start, GlyphTester ignoreTester ) throws IndexOutOfBoundsException {
        int counted = 0;
        int ignored = 0;
        if ( ignoreTester == null ) {
            counted = start + 1;
        } else {
            for ( int i = start; i >= 0; i-- ) {
                int gi = getGlyph ( i - index );
                if ( gi == 65535 ) {
                    ignored++;
                } else {
                    if ( ignoreTester.test ( gi ) ) {
                        ignored++;
                    } else {
                        counted++;
                    }
                }
            }
        }
        return new int[] { counted, ignored };
    }

    /**
     * Determine number of glyphs available starting at specified offset from current position. If
     * <code>reverseOrder</code> is true, then search backwards in input glyph sequence. Uses the
     * default ignores tester.
     * @param offset from current position
     * @param reverseOrder true if to obtain in reverse order
     * @return an int[2] array where counts[0] is the number of glyphs available, and counts[1] is the number of glyphs ignored
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public int[] getGlyphsAvailable ( int offset, boolean reverseOrder ) throws IndexOutOfBoundsException {
        return getGlyphsAvailable ( offset, reverseOrder, ignoreDefault );
    }

    /**
     * Determine number of glyphs available starting at specified offset from current position. If
     * offset is negative, then search backwards in input glyph sequence. Uses the
     * default ignores tester.
     * @param offset from current position
     * @return an int[2] array where counts[0] is the number of glyphs available, and counts[1] is the number of glyphs ignored
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public int[] getGlyphsAvailable ( int offset ) throws IndexOutOfBoundsException {
        return getGlyphsAvailable ( offset, offset < 0 );
    }

    /**
     * Obtain <code>count</code> character associations of glyphs starting at specified offset from current position. If
     * <code>reverseOrder</code> is true, then associations are returned in reverse order starting at specified offset
     * and going in reverse towards beginning of input glyph sequence.
     * @param offset from current position
     * @param count number of associations to obtain
     * @param reverseOrder true if to obtain in reverse order
     * @param ignoreTester glyph tester to use to determine which glyphs are ignored (or null, in which case none are ignored)
     * @param associations array to use to fetch associations
     * @param counts int[2] array to receive fetched association counts, where counts[0] will
     * receive the number of associations obtained, and counts[1] will receive the number of glyphs whose
     * associations were ignored
     * @return array of associations
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public GlyphSequence.CharAssociation[] getAssociations ( int offset, int count, boolean reverseOrder, GlyphTester ignoreTester, GlyphSequence.CharAssociation[] associations, int[] counts )
        throws IndexOutOfBoundsException {
        if ( count < 0 ) {
            count = getGlyphsAvailable ( offset, reverseOrder, ignoreTester ) [ 0 ];
        }
        int start = index + offset;
        if ( start < 0 ) {
            throw new IndexOutOfBoundsException ( "will attempt index at " + start );
        } else if ( ! reverseOrder && ( ( start + count ) > indexLast ) ) {
            throw new IndexOutOfBoundsException ( "will attempt index at " + ( start + count ) );
        } else if ( reverseOrder && ( ( start + 1 ) < count ) ) {
            throw new IndexOutOfBoundsException ( "will attempt index at " + ( start - count ) );
        }
        if ( associations == null ) {
            associations = new GlyphSequence.CharAssociation [ count ];
        } else if ( associations.length != count ) {
            throw new IllegalArgumentException ( "associations array is non-null, but its length (" + associations.length + "), is not equal to count (" + count + ")" );
        }
        if ( ! reverseOrder ) {
            return getAssociationsForward ( start, count, ignoreTester, associations, counts );
        } else {
            return getAssociationsReverse ( start, count, ignoreTester, associations, counts );
        }
    }

    private GlyphSequence.CharAssociation[] getAssociationsForward ( int start, int count, GlyphTester ignoreTester, GlyphSequence.CharAssociation[] associations, int[] counts )
        throws IndexOutOfBoundsException {
        int counted = 0;
        int ignored = 0;
        for ( int i = start, n = indexLast, k = 0; i < n; i++ ) {
            int gi = getGlyph ( i - index );
            if ( gi == 65535 ) {
                ignored++;
            } else {
                if ( ( ignoreTester == null ) || ! ignoreTester.test ( gi ) ) {
                    if ( k < count ) {
                        associations [ k++ ] = getAssociation ( i - index ); counted++;
                    } else {
                        break;
                    }
                } else {
                    ignored++;
                }
            }
        }
        if ( ( counts != null ) && ( counts.length > 1 ) ) {
            counts[0] = counted;
            counts[1] = ignored;
        }
        return associations;
    }

    private GlyphSequence.CharAssociation[] getAssociationsReverse ( int start, int count, GlyphTester ignoreTester, GlyphSequence.CharAssociation[] associations, int[] counts )
        throws IndexOutOfBoundsException {
        int counted = 0;
        int ignored = 0;
        for ( int i = start, k = 0; i >= 0; i-- ) {
            int gi = getGlyph ( i - index );
            if ( gi == 65535 ) {
                ignored++;
            } else {
                if ( ( ignoreTester == null ) || ! ignoreTester.test ( gi ) ) {
                    if ( k < count ) {
                        associations [ k++ ] = getAssociation ( i - index ); counted++;
                    } else {
                        break;
                    }
                } else {
                    ignored++;
                }
            }
        }
        if ( ( counts != null ) && ( counts.length > 1 ) ) {
            counts[0] = counted;
            counts[1] = ignored;
        }
        return associations;
    }

    /**
     * Obtain <code>count</code> character associations of glyphs starting at specified offset from current position. If
     * offset is negative, then search backwards in input glyph sequence. Uses the
     * default ignores tester.
     * @param offset from current position
     * @param count number of associations to obtain
     * @return array of associations
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public GlyphSequence.CharAssociation[] getAssociations ( int offset, int count ) throws IndexOutOfBoundsException {
        return getAssociations ( offset, count, offset < 0, ignoreDefault, null, null );
    }

    /**
     * Obtain <code>count</code> character associations of ignored glyphs starting at specified offset from current position. If
     * <code>reverseOrder</code> is true, then glyphs are returned in reverse order starting at specified offset
     * and going in reverse towards beginning of input glyph sequence.
     * @param offset from current position
     * @param count number of character associations to obtain
     * @param reverseOrder true if to obtain in reverse order
     * @param ignoreTester glyph tester to use to determine which glyphs are ignored (or null, in which case none are ignored)
     * @param associations array to use to fetch associations
     * @param counts int[2] array to receive fetched association counts, where counts[0] will
     * receive the number of associations obtained, and counts[1] will receive the number of glyphs whose
     * associations were ignored
     * @return array of associations
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public GlyphSequence.CharAssociation[] getIgnoredAssociations ( int offset, int count, boolean reverseOrder, GlyphTester ignoreTester, GlyphSequence.CharAssociation[] associations, int[] counts )
        throws IndexOutOfBoundsException {
        return getAssociations ( offset, count, reverseOrder, new NotGlyphTester ( ignoreTester ), associations, counts );
    }

    /**
     * Obtain <code>count</code> character associations of ignored glyphs starting at specified offset from current position. If
     * offset is negative, then search backwards in input glyph sequence. Uses the
     * default ignores tester.
     * @param offset from current position
     * @param count number of character associations to obtain
     * @return array of associations
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public GlyphSequence.CharAssociation[] getIgnoredAssociations ( int offset, int count ) throws IndexOutOfBoundsException {
        return getIgnoredAssociations ( offset, count, offset < 0, ignoreDefault, null, null );
    }

    /**
     * Replace subsequence of input glyph sequence starting at specified offset from current position and of
     * length <code>count</code> glyphs with a subsequence of the sequence <code>gs</code> starting from the specified
     * offset <code>gsOffset</code> of length <code>gsCount</code> glyphs.
     * @param offset from current position
     * @param count number of glyphs to replace, which, if negative means all glyphs from offset to end of input sequence
     * @param gs glyph sequence from which to obtain replacement glyphs
     * @param gsOffset offset of first glyph in replacement sequence
     * @param gsCount count of glyphs in replacement sequence starting at <code>gsOffset</code>
     * @return true if replacement occurred, or false if replacement would result in no change to input glyph sequence
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public boolean replaceInput ( int offset, int count, GlyphSequence gs, int gsOffset, int gsCount ) throws IndexOutOfBoundsException {
        int nig = ( igs != null ) ? igs.getGlyphCount() : 0;
        int position = getPosition() + offset;
        if ( position < 0 ) {
            position = 0;
        } else if ( position > nig ) {
            position = nig;
        }
        if ( ( count < 0 ) || ( ( position + count ) > nig ) ) {
            count = nig - position;
        }
        int nrg = ( gs != null ) ? gs.getGlyphCount() : 0;
        if ( gsOffset < 0 ) {
            gsOffset = 0;
        } else if ( gsOffset > nrg ) {
            gsOffset = nrg;
        }
        if ( ( gsCount < 0 ) || ( ( gsOffset + gsCount ) > nrg ) ) {
            gsCount = nrg - gsOffset;
        }
        int ng = nig + gsCount - count;
        IntBuffer gb = IntBuffer.allocate ( ng );
        List al = new ArrayList ( ng );
        for ( int i = 0, n = position; i < n; i++ ) {
            gb.put ( igs.getGlyph ( i ) );
            al.add ( igs.getAssociation ( i ) );
        }
        for ( int i = gsOffset, n = gsOffset + gsCount; i < n; i++ ) {
            gb.put ( gs.getGlyph ( i ) );
            al.add ( gs.getAssociation ( i ) );
        }
        for ( int i = position + count, n = nig; i < n; i++ ) {
            gb.put ( igs.getGlyph ( i ) );
            al.add ( igs.getAssociation ( i ) );
        }
        gb.flip();
        if ( igs.compareGlyphs ( gb ) != 0 ) {
            this.igs = new GlyphSequence ( igs.getCharacters(), gb, al );
            this.indexLast = gb.limit();
            return true;
        } else {
            return false;
        }
    }

    /**
     * Replace subsequence of input glyph sequence starting at specified offset from current position and of
     * length <code>count</code> glyphs with all glyphs in the replacement sequence <code>gs</code>.
     * @param offset from current position
     * @param count number of glyphs to replace, which, if negative means all glyphs from offset to end of input sequence
     * @param gs glyph sequence from which to obtain replacement glyphs
     * @return true if replacement occurred, or false if replacement would result in no change to input glyph sequence
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public boolean replaceInput ( int offset, int count, GlyphSequence gs ) throws IndexOutOfBoundsException {
        return replaceInput ( offset, count, gs, 0, gs.getGlyphCount() );
    }

    /**
     * Erase glyphs in input glyph sequence starting at specified offset from current position, where each glyph
     * in the specified <code>glyphs</code> array is matched, one at a time, and when a (forward searching) match is found
     * in the input glyph sequence, the matching glyph is replaced with the glyph index 65535.
     * @param offset from current position
     * @param glyphs array of glyphs to erase
     * @return the number of glyphs erased, which may be less than the number of specified glyphs
     * @throws IndexOutOfBoundsException if offset or count results in an
     * invalid index into input glyph sequence
     */
    public int erase ( int offset, int[] glyphs ) throws IndexOutOfBoundsException {
        int start = index + offset;
        if ( ( start < 0 ) || ( start > indexLast ) ) {
            throw new IndexOutOfBoundsException ( "will attempt index at " + start );
        } else {
            int erased = 0;
            for ( int i = start - index, n = indexLast - start; i < n; i++ ) {
                int gi = getGlyph ( i );
                if ( gi == glyphs [ erased ] ) {
                    setGlyph ( i, 65535 );
                    erased++;
                }
            }
            return erased;
        }
    }

    /**
     * Determine if is possible that the current input sequence satisfies a script specific
     * context testing predicate. If no predicate applies, then application is always possible.
     * @return true if no script specific context tester applies or if a specified tester returns
     * true for the current input sequence context
     */
    public boolean maybeApplicable() {
        if ( gct == null ) {
            return true;
        } else {
            return gct.test ( script, language, feature, igs, index );
        }
    }

    /**
     * Apply default application semantices; namely, consume one glyph.
     */
    public void applyDefault() {
        consumed += 1;
    }

    /**
     * Determine if specified glyph is a base glyph according to the governing
     * glyph definition table.
     * @param gi glyph index to test
     * @return true if glyph definition table records glyph as a base glyph; otherwise, false
     */
    public boolean isBase ( int gi ) {
        if ( gdef != null ) {
            return gdef.isGlyphClass ( gi, GlyphDefinitionTable.GLYPH_CLASS_BASE );
        } else {
            return false;
        }
    }

    /**
     * Determine if specified glyph is a ligature glyph according to the governing
     * glyph definition table.
     * @param gi glyph index to test
     * @return true if glyph definition table records glyph as a ligature glyph; otherwise, false
     */
    public boolean isLigature ( int gi ) {
        if ( gdef != null ) {
            return gdef.isGlyphClass ( gi, GlyphDefinitionTable.GLYPH_CLASS_LIGATURE );
        } else {
            return false;
        }
    }

    /**
     * Determine if specified glyph is a mark glyph according to the governing
     * glyph definition table.
     * @param gi glyph index to test
     * @return true if glyph definition table records glyph as a mark glyph; otherwise, false
     */
    public boolean isMark ( int gi ) {
        if ( gdef != null ) {
            return gdef.isGlyphClass ( gi, GlyphDefinitionTable.GLYPH_CLASS_MARK );
        } else {
            return false;
        }
    }

    /**
     * Obtain an ignored glyph tester that corresponds to the specified lookup flags.
     * @param flags lookup flags
     * @return a glyph tester
     */
    public GlyphTester getIgnoreTester ( int flags ) {
        if ( ( flags & GlyphSubtable.LF_IGNORE_BASE ) != 0 ) {
            if ( ( flags & (GlyphSubtable.LF_IGNORE_LIGATURE | GlyphSubtable.LF_IGNORE_MARK) ) == 0 ) {
                return ignoreBase;
            } else {
                return getCombinedIgnoreTester ( flags );
            }
        }
        if ( ( flags & GlyphSubtable.LF_IGNORE_LIGATURE ) != 0 ) {
            if ( ( flags & (GlyphSubtable.LF_IGNORE_BASE | GlyphSubtable.LF_IGNORE_MARK) ) == 0 ) {
                return ignoreLigature;
            } else {
                return getCombinedIgnoreTester ( flags );
            }
        }
        if ( ( flags & GlyphSubtable.LF_IGNORE_MARK ) != 0 ) {
            if ( ( flags & (GlyphSubtable.LF_IGNORE_BASE | GlyphSubtable.LF_IGNORE_LIGATURE) ) == 0 ) {
                return ignoreMark;
            } else {
                return getCombinedIgnoreTester ( flags );
            }
        }
        return null;
    }

    /**
     * Obtain an ignored glyph tester that corresponds to the specified multiple (combined) lookup flags.
     * @param flags lookup flags
     * @return a glyph tester
     */
    public GlyphTester getCombinedIgnoreTester ( int flags ) {
        GlyphTester[] gta = new GlyphTester [ 3 ];
        int ngt = 0;
        if ( ( flags & GlyphSubtable.LF_IGNORE_BASE ) != 0 ) {
            gta [ ngt++ ] = ignoreBase;
        }
        if ( ( flags & GlyphSubtable.LF_IGNORE_LIGATURE ) != 0 ) {
            gta [ ngt++ ] = ignoreLigature;
        }
        if ( ( flags & GlyphSubtable.LF_IGNORE_MARK ) != 0 ) {
            gta [ ngt++ ] = ignoreMark;
        }
        return getCombinedOrTester ( gta, ngt );
    }

    /**
     * Obtain an combined OR glyph tester.
     * @param gta an array of glyph testers
     * @param ngt number of glyph testers present in specified array
     * @return a combined OR glyph tester
     */
    public GlyphTester getCombinedOrTester ( GlyphTester[] gta, int ngt ) {
        if ( ngt > 0 ) {
            return new CombinedOrGlyphTester ( gta, ngt );
        } else {
            return null;
        }
    }

    /**
     * Obtain an combined AND glyph tester.
     * @param gta an array of glyph testers
     * @param ngt number of glyph testers present in specified array
     * @return a combined AND glyph tester
     */
    public GlyphTester getCombinedAndTester ( GlyphTester[] gta, int ngt ) {
        if ( ngt > 0 ) {
            return new CombinedAndGlyphTester ( gta, ngt );
        } else {
            return null;
        }
    }

    /** combined OR glyph tester */
    private static class CombinedOrGlyphTester implements GlyphTester {
        private GlyphTester[] gta;
        private int ngt;
        CombinedOrGlyphTester ( GlyphTester[] gta, int ngt ) {
            this.gta = gta;
            this.ngt = ngt;
        }
        /** {@inheritDoc} */
        public boolean test ( int gi ) {
            for ( int i = 0, n = ngt; i < n; i++ ) {
                GlyphTester gt = gta [ i ];
                if ( gt != null ) {
                    if ( gt.test ( gi ) ) {
                        return true;
                    }
                }
            }
            return false;
        }
    }

    /** combined AND glyph tester */
    private static class CombinedAndGlyphTester implements GlyphTester {
        private GlyphTester[] gta;
        private int ngt;
        CombinedAndGlyphTester ( GlyphTester[] gta, int ngt ) {
            this.gta = gta;
            this.ngt = ngt;
        }
        /** {@inheritDoc} */
        public boolean test ( int gi ) {
            for ( int i = 0, n = ngt; i < n; i++ ) {
                GlyphTester gt = gta [ i ];
                if ( gt != null ) {
                    if ( ! gt.test ( gi ) ) {
                        return false;
                    }
                }
            }
            return true;
        }
    }

    /** NOT glyph tester */
    private static class NotGlyphTester implements GlyphTester {
        private GlyphTester gt;
        NotGlyphTester ( GlyphTester gt ) {
            this.gt = gt;
        }
        /** {@inheritDoc} */
        public boolean test ( int gi ) {
            if ( gt != null ) {
                if ( gt.test ( gi ) ) {
                    return false;
                }
            }
            return true;
        }
    }

}