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 * 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
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 * 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
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/* $Id$ */

package org.apache.fop.complexscripts.scripts;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.fop.complexscripts.fonts.GlyphDefinitionTable;
import org.apache.fop.complexscripts.fonts.GlyphPositioningTable;
import org.apache.fop.complexscripts.fonts.GlyphSubstitutionTable;
import org.apache.fop.complexscripts.fonts.GlyphTable;
import org.apache.fop.complexscripts.util.CharScript;
import org.apache.fop.complexscripts.util.GlyphSequence;
import org.apache.fop.complexscripts.util.ScriptContextTester;

// CSOFF: LineLengthCheck

Abstract script processor base class for which an implementation of the substitution and positioning methods
must be supplied.
This work was originally authored by Glenn Adams (gadams@apache.org).
/**
 * <p>Abstract script processor base class for which an implementation of the substitution and positioning methods
 * must be supplied.</p>
 *
 * <p>This work was originally authored by Glenn Adams (gadams@apache.org).</p>
 */
public abstract class ScriptProcessor {

    private final String script;

    private final Map<AssembledLookupsKey, GlyphTable.UseSpec[]> assembledLookups;

    
Instantiate a script processor.
Params:
script – a script identifier/**
     * Instantiate a script processor.
     * @param script a script identifier
     */
    protected ScriptProcessor(String script) {
        if ((script == null) || (script.length() == 0)) {
            throw new IllegalArgumentException("script must be non-empty string");
        } else {
            this.script = script;
            this.assembledLookups = new HashMap<AssembledLookupsKey, GlyphTable.UseSpec[]>();
        }
    }

    
Returns:
script identifier/** @return script identifier */
    public final String getScript() {
        return script;
    }

    
Obtain script specific required substitution features.
Returns:
array of suppported substitution features or null/**
     * Obtain script specific required substitution features.
     * @return array of suppported substitution features or null
     */
    public abstract String[] getSubstitutionFeatures();

    
Obtain script specific optional substitution features.
Returns:
array of suppported substitution features or null/**
     * Obtain script specific optional substitution features.
     * @return array of suppported substitution features or null
     */
    public String[] getOptionalSubstitutionFeatures() {
        return new String[0];
    }

    
Obtain script specific substitution context tester.
Returns:
substitution context tester or null/**
     * Obtain script specific substitution context tester.
     * @return substitution context tester or null
     */
    public abstract ScriptContextTester getSubstitutionContextTester();

    
Perform substitution processing using a specific set of lookup tables.
Params:
gsub – the glyph substitution table that applies
gs – an input glyph sequence
script – a script identifier
language – a language identifier
lookups – a mapping from lookup specifications to glyph subtables to use for substitution processing
Returns:
the substituted (output) glyph sequence/**
     * Perform substitution processing using a specific set of lookup tables.
     * @param gsub the glyph substitution table that applies
     * @param gs an input glyph sequence
     * @param script a script identifier
     * @param language a language identifier
     * @param lookups a mapping from lookup specifications to glyph subtables to use for substitution processing
     * @return the substituted (output) glyph sequence
     */
    public final GlyphSequence substitute(GlyphSubstitutionTable gsub, GlyphSequence gs, String script, String language,
                                          Map<GlyphTable.LookupSpec, List<GlyphTable.LookupTable>> lookups) {
        return substitute(gs, script, language, assembleLookups(gsub, getSubstitutionFeatures(), lookups), getSubstitutionContextTester());
    }

    
Perform substitution processing using a specific set of ordered glyph table use specifications.
Params:
gs – an input glyph sequence
script – a script identifier
language – a language identifier
usa – an ordered array of glyph table use specs
sct – a script specific context tester (or null)
Returns:
the substituted (output) glyph sequence/**
     * Perform substitution processing using a specific set of ordered glyph table use specifications.
     * @param gs an input glyph sequence
     * @param script a script identifier
     * @param language a language identifier
     * @param usa an ordered array of glyph table use specs
     * @param sct a script specific context tester (or null)
     * @return the substituted (output) glyph sequence
     */
    public GlyphSequence substitute(GlyphSequence gs, String script, String language, GlyphTable.UseSpec[] usa, ScriptContextTester sct) {
        assert usa != null;
        for (GlyphTable.UseSpec us : usa) {
            gs = us.substitute(gs, script, language, sct);
        }
        return gs;
    }

    
Reorder combining marks in glyph sequence so that they precede (within the sequence) the base
character to which they are applied. N.B. In the case of RTL segments, marks are not reordered by this,
method since when the segment is reversed by BIDI processing, marks are automatically reordered to precede
their base glyph.
Params:
gdef – the glyph definition table that applies
gs – an input glyph sequence
unscaledWidths – associated unscaled advance widths (also reordered)
gpa – associated glyph position adjustments (also reordered)
script – a script identifier
language – a language identifier
Returns:
the reordered (output) glyph sequence/**
     * Reorder combining marks in glyph sequence so that they precede (within the sequence) the base
     * character to which they are applied. N.B. In the case of RTL segments, marks are not reordered by this,
     * method since when the segment is reversed by BIDI processing, marks are automatically reordered to precede
     * their base glyph.
     * @param gdef the glyph definition table that applies
     * @param gs an input glyph sequence
     * @param unscaledWidths associated unscaled advance widths (also reordered)
     * @param gpa associated glyph position adjustments (also reordered)
     * @param script a script identifier
     * @param language a language identifier
     * @return the reordered (output) glyph sequence
     */
    public GlyphSequence reorderCombiningMarks(GlyphDefinitionTable gdef, GlyphSequence gs, int[] unscaledWidths, int[][] gpa, String script, String language) {
        return gs;
    }

    
Obtain script specific required positioning features.
Returns:
array of suppported positioning features or null/**
     * Obtain script specific required positioning features.
     * @return array of suppported positioning features or null
     */
    public abstract String[] getPositioningFeatures();

    
Obtain script specific optional positioning features.
Returns:
array of suppported positioning features or null/**
     * Obtain script specific optional positioning features.
     * @return array of suppported positioning features or null
     */
    public String[] getOptionalPositioningFeatures() {
        return new String[0];
    }

    
Obtain script specific positioning context tester.
Returns:
positioning context tester or null/**
     * Obtain script specific positioning context tester.
     * @return positioning context tester or null
     */
    public abstract ScriptContextTester getPositioningContextTester();

    
Perform positioning processing using a specific set of lookup tables.
Params:
gpos – the glyph positioning table that applies
gs – an input glyph sequence
script – a script identifier
language – a language identifier
fontSize – size in device units
lookups – a mapping from lookup specifications to glyph subtables to use for positioning processing
widths – array of default advancements for each glyph
adjustments – accumulated adjustments array (sequence) of 4-tuples of placement [PX,PY] and advance [AX,AY] adjustments, in that order,
with one 4-tuple for each element of glyph sequence
Returns:
true if some adjustment is not zero; otherwise, false/**
     * Perform positioning processing using a specific set of lookup tables.
     * @param gpos the glyph positioning table that applies
     * @param gs an input glyph sequence
     * @param script a script identifier
     * @param language a language identifier
     * @param fontSize size in device units
     * @param lookups a mapping from lookup specifications to glyph subtables to use for positioning processing
     * @param widths array of default advancements for each glyph
     * @param adjustments accumulated adjustments array (sequence) of 4-tuples of placement [PX,PY] and advance [AX,AY] adjustments, in that order,
     * with one 4-tuple for each element of glyph sequence
     * @return true if some adjustment is not zero; otherwise, false
     */
    public final boolean position(GlyphPositioningTable gpos, GlyphSequence gs, String script, String language, int fontSize,
                                  Map<GlyphTable.LookupSpec, List<GlyphTable.LookupTable>> lookups, int[] widths, int[][] adjustments) {
        return position(gs, script, language, fontSize, assembleLookups(gpos, getPositioningFeatures(), lookups), widths, adjustments, getPositioningContextTester());
    }

    
Perform positioning processing using a specific set of ordered glyph table use specifications.
Params:
gs – an input glyph sequence
script – a script identifier
language – a language identifier
fontSize – size in device units
usa – an ordered array of glyph table use specs
widths – array of default advancements for each glyph in font
adjustments – accumulated adjustments array (sequence) of 4-tuples of placement [PX,PY] and advance [AX,AY] adjustments, in that order,
with one 4-tuple for each element of glyph sequence
sct – a script specific context tester (or null)
Returns:
true if some adjustment is not zero; otherwise, false/**
     * Perform positioning processing using a specific set of ordered glyph table use specifications.
     * @param gs an input glyph sequence
     * @param script a script identifier
     * @param language a language identifier
     * @param fontSize size in device units
     * @param usa an ordered array of glyph table use specs
     * @param widths array of default advancements for each glyph in font
     * @param adjustments accumulated adjustments array (sequence) of 4-tuples of placement [PX,PY] and advance [AX,AY] adjustments, in that order,
     * with one 4-tuple for each element of glyph sequence
     * @param sct a script specific context tester (or null)
     * @return true if some adjustment is not zero; otherwise, false
     */
    public boolean position(GlyphSequence gs, String script, String language, int fontSize, GlyphTable.UseSpec[] usa, int[] widths, int[][] adjustments, ScriptContextTester sct) {
        assert usa != null;
        boolean adjusted = false;
        for (GlyphTable.UseSpec us : usa) {
            if (us.position(gs, script, language, fontSize, widths, adjustments, sct)) {
                adjusted = true;
            }
        }
        return adjusted;
    }

    
Assemble ordered array of lookup table use specifications according to the specified features and candidate lookups,
where the order of the array is in accordance to the order of the applicable lookup list.
Params:
table – the governing glyph table
features – array of feature identifiers to apply
lookups – a mapping from lookup specifications to lists of look tables from which to select lookup tables according to the specified features
Returns:
ordered array of assembled lookup table use specifications/**
     * Assemble ordered array of lookup table use specifications according to the specified features and candidate lookups,
     * where the order of the array is in accordance to the order of the applicable lookup list.
     * @param table the governing glyph table
     * @param features array of feature identifiers to apply
     * @param lookups a mapping from lookup specifications to lists of look tables from which to select lookup tables according to the specified features
     * @return ordered array of assembled lookup table use specifications
     */
    public final GlyphTable.UseSpec[] assembleLookups(GlyphTable table, String[] features,
                                                      Map<GlyphTable.LookupSpec, List<GlyphTable.LookupTable>> lookups) {
        AssembledLookupsKey key = new AssembledLookupsKey(table, features, lookups);
        GlyphTable.UseSpec[] usa;
        if ((usa = assembledLookupsGet(key)) != null) {
            return usa;
        } else {
            return assembledLookupsPut(key, table.assembleLookups(features, lookups));
        }
    }

    private GlyphTable.UseSpec[] assembledLookupsGet(AssembledLookupsKey key) {
        return assembledLookups.get(key);
    }

    private GlyphTable.UseSpec[]  assembledLookupsPut(AssembledLookupsKey key, GlyphTable.UseSpec[] usa) {
        assembledLookups.put(key, usa);
        return usa;
    }

    
Obtain script processor instance associated with specified script.
Params:
script – a script identifier
Returns:
a script processor instance or null if none found/**
     * Obtain script processor instance associated with specified script.
     * @param script a script identifier
     * @return a script processor instance or null if none found
     */
    public static synchronized ScriptProcessor getInstance(String script, Map<String, ScriptProcessor> processors) {
        ScriptProcessor sp = null;
        assert processors != null;
        if ((sp = processors.get(script)) == null) {
            processors.put(script, sp = createProcessor(script));
        }
        return sp;
    }

    // [TBD] - rework to provide more configurable binding between script name and script processor constructor
    private static ScriptProcessor createProcessor(String script) {
        ScriptProcessor sp = null;
        int sc = CharScript.scriptCodeFromTag(script);
        if (sc == CharScript.SCRIPT_ARABIC) {
            sp = new ArabicScriptProcessor(script);
        } else if (CharScript.isIndicScript(sc)) {
            sp = IndicScriptProcessor.makeProcessor(script);
        } else {
            sp = new DefaultScriptProcessor(script);
        }
        return sp;
    }

    private static class AssembledLookupsKey {

        private final GlyphTable table;
        private final String[] features;
        private final Map<GlyphTable.LookupSpec, List<GlyphTable.LookupTable>> lookups;

        AssembledLookupsKey(GlyphTable table, String[] features, Map<GlyphTable.LookupSpec, List<GlyphTable.LookupTable>> lookups) {
            this.table = table;
            this.features = features;
            this.lookups = lookups;
        }

        
{@inheritDoc} /** {@inheritDoc} */
        public int hashCode() {
            int hc = 0;
            hc =  7 * hc + (hc ^ table.hashCode());
            hc = 11 * hc + (hc ^ Arrays.hashCode(features));
            hc = 17 * hc + (hc ^ lookups.hashCode());
            return hc;
        }

        
{@inheritDoc} /** {@inheritDoc} */
        public boolean equals(Object o) {
            if (o instanceof AssembledLookupsKey) {
                AssembledLookupsKey k = (AssembledLookupsKey) o;
                if (!table.equals(k.table)) {
                    return false;
                } else if (!Arrays.equals(features, k.features)) {
                    return false;
                } else {
                    return lookups.equals(k.lookups);
                }
            } else {
                return false;
            }
        }

    }

}