src/java/org/apache/fop/complexscripts/bidi/BidiResolver.java

/*
 * 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.complexscripts.bidi;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Stack;
import java.util.Vector;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.apache.fop.area.LineArea;
import org.apache.fop.area.inline.InlineArea;
import org.apache.fop.fo.pagination.PageSequence;

// CSOFF: EmptyForIteratorPadCheck
// CSOFF: InnerAssignmentCheck
// CSOFF: LineLengthCheck
// CSOFF: NoWhitespaceAfterCheck
// CSOFF: SimplifyBooleanReturnCheck

/**
 * <p>A utility class for performing bidirectional resolution processing.</p>
 *
 * <p>This work was originally authored by Glenn Adams (gadams@apache.org).</p>
 */
public final class BidiResolver {

    /**
     * logging instance
     */
    private static final Log log = LogFactory.getLog(BidiResolver.class);                                                   // CSOK: ConstantNameCheck

    private BidiResolver() {
    }

    /**
     * Resolve inline directionality.
     * @param ps a page sequence FO instance
     */
    public static void resolveInlineDirectionality ( PageSequence ps ) {
        if (log.isDebugEnabled()) {
            log.debug ( "BD: RESOLVE: " + ps );
        }
        List ranges = pruneEmptyRanges ( ps.collectDelimitedTextRanges ( new Stack() ) );
        resolveInlineDirectionality ( ranges );
    }

    /**
     * Reorder line area.
     * @param la a line area instance
     */
    public static void reorder ( LineArea la ) {

        // 1. collect inline levels
        List runs = collectRuns ( la.getInlineAreas(), new Vector() );
        if (log.isDebugEnabled()) {
            dumpRuns ( "BD: REORDER: INPUT:", runs );
        }

        // 2. split heterogeneous inlines
        runs = splitRuns ( runs );
        if (log.isDebugEnabled()) {
            dumpRuns ( "BD: REORDER: SPLIT INLINES:", runs );
        }

        // 3. determine minimum and maximum levels
        int[] mm = computeMinMaxLevel ( runs, null );
        if (log.isDebugEnabled()) {
            log.debug( "BD: REORDER: { min = " + mm[0] + ", max = " + mm[1] + "}" );
        }

        // 4. reorder from maximum level to minimum odd level
        int mn = mm[0];
        int mx = mm[1];
        if ( mx > 0 ) {
            for ( int l1 = mx, l2 = ( ( mn & 1 ) == 0 ) ? ( mn + 1 ) : mn; l1 >= l2; l1-- ) {
                runs = reorderRuns ( runs, l1 );
            }
        }
        if (log.isDebugEnabled()) {
            dumpRuns ( "BD: REORDER: REORDERED RUNS:", runs );
        }

        // 5. reverse word consituents (characters and glyphs) while mirroring
        boolean mirror = true;
        reverseWords ( runs, mirror );
        if (log.isDebugEnabled()) {
            dumpRuns ( "BD: REORDER: REORDERED WORDS:", runs );
        }

        // 6. replace line area's inline areas with reordered runs' inline areas
        replaceInlines ( la, replicateSplitWords ( runs ) );
    }

    private static void resolveInlineDirectionality ( List ranges ) {
        for ( Iterator it = ranges.iterator(); it.hasNext(); ) {
            DelimitedTextRange r = (DelimitedTextRange) it.next();
            r.resolve();
            if (log.isDebugEnabled()) {
                log.debug ( r );
            }
        }
    }

    private static List collectRuns ( List inlines, List runs ) {
        for ( Iterator it = inlines.iterator(); it.hasNext(); ) {
            InlineArea ia = (InlineArea) it.next();
            runs = ia.collectInlineRuns ( runs );
        }
        return runs;
    }

    private static List splitRuns ( List runs ) {
        List runsNew = new Vector();
        for ( Iterator it = runs.iterator(); it.hasNext(); ) {
            InlineRun ir = (InlineRun) it.next();
            if ( ir.isHomogenous() ) {
                runsNew.add ( ir );
            } else {
                runsNew.addAll ( ir.split() );
            }
        }
        if ( ! runsNew.equals ( runs ) ) {
            runs = runsNew;
        }
        return runs;
    }

    private static int[] computeMinMaxLevel ( List runs, int[] mm ) {
        if ( mm == null ) {
            mm = new int[] {Integer.MAX_VALUE, Integer.MIN_VALUE};
        }
        for ( Iterator it = runs.iterator(); it.hasNext(); ) {
            InlineRun ir = (InlineRun) it.next();
            ir.updateMinMax ( mm );
        }
        return mm;
    }
    private static List reorderRuns ( List runs, int level ) {
        assert level >= 0;
        List runsNew = new Vector();
        for ( int i = 0, n = runs.size(); i < n; i++ ) {
            InlineRun iri = (InlineRun) runs.get(i);
            if ( iri.getMinLevel() < level ) {
                runsNew.add ( iri );
            } else {
                int s = i;
                int e = s;
                while ( e < n ) {
                    InlineRun ire = (InlineRun) runs.get(e);
                    if ( ire.getMinLevel() < level ) {
                        break;
                    } else {
                        e++;
                    }
                }
                if ( s < e ) {
                    runsNew.addAll ( reverseRuns ( runs, s, e ) );
                }
                i = e - 1;
            }
        }
        if ( ! runsNew.equals ( runs ) ) {
            runs = runsNew;
        }
        return runs;
    }
    private static List reverseRuns ( List runs, int s, int e ) {
        int n = e - s;
        Vector runsNew = new Vector ( n );
        if ( n > 0 ) {
            for ( int i = 0; i < n; i++ ) {
                int k = ( n - i - 1 );
                InlineRun ir = (InlineRun) runs.get(s + k);
                ir.reverse();
                runsNew.add ( ir );
            }
        }
        return runsNew;
    }
    private static void reverseWords ( List runs, boolean mirror ) {
        for ( Iterator it = runs.iterator(); it.hasNext(); ) {
            InlineRun ir = (InlineRun) it.next();
            ir.maybeReverseWord ( mirror );
        }
    }
    private static List replicateSplitWords ( List runs ) {
        // [TBD] for each run which inline word area appears multiple times in
        // runs, replicate that word
        return runs;
    }
    private static void replaceInlines ( LineArea la, List runs ) {
        List<InlineArea> inlines = new ArrayList<InlineArea>();
        for ( Iterator it = runs.iterator(); it.hasNext(); ) {
            InlineRun ir = (InlineRun) it.next();
            inlines.add ( ir.getInline() );
        }
        la.setInlineAreas ( unflattenInlines ( inlines ) );
    }
    private static List unflattenInlines ( List<InlineArea> inlines ) {
        return new UnflattenProcessor ( inlines ) .unflatten();
    }
    private static void dumpRuns ( String header, List runs ) {
        log.debug ( header );
        for ( Iterator it = runs.iterator(); it.hasNext(); ) {
            InlineRun ir = (InlineRun) it.next();
            log.debug ( ir );
        }
    }

    private static List pruneEmptyRanges ( Stack ranges ) {
        Vector rv = new Vector();
        for ( Iterator it = ranges.iterator(); it.hasNext(); ) {
            DelimitedTextRange r = (DelimitedTextRange) it.next();
            if ( ! r.isEmpty() ) {
                rv.add ( r );
            }
        }
        return rv;
    }

}