BlockDelimiter.java

/*
 * Copyright (C) 2011 Laurent Caillette
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation, either
 * version 3 of the License, or (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.novelang.parser.antlr.delimited;

import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;

/**
 * This enum represents blocks (subset of a paragraph-like piece of source document) which
 * have a start and end delimiter and which must be paired.
 * This is more or less a duplicate of what's defined in ANTLR grammar but there is no (simple?)
 * mean to extract literal corresponding to start and end tokens, so we hope that all unit tests
 * will detect any desynchronization.
 *
 * <p>
 * Definition : <em>twin delimiters</em> are start and end delimiters for a kind of block, and
 * those two delimiters are the same.
 * <p>
 * Definition : <em>paired delimiters</em> are start and end delimiters for a kind of block, and
 * those two delimiters are different. It's possible to deduce one delimiter from the other.
 * <p>
 * Unluckily, the {@link #TWO_HYPHENS} is treated as an hybrid case.
 *
 *
 * @see DefaultBlockDelimitersBoundary
 *
 * @author Laurent Caillette
 */
public enum BlockDelimiter {

  PARENTHESIS( false, "(", ")" ),
  SQUARE_BRACKETS( false, "[", "]" ),
  DOUBLE_QUOTES( true, "\"", "\"" ),
  SOLIDUS_PAIRS( true, "//", "//" ),
  ASTERISK_PAIRS( true, "**", "**" ),
  TWO_HYPHENS( true, "--", "--", "-_" ),
  ;

  private final boolean twin ;
  private final String start ;
  private final String[] end ;

  private BlockDelimiter( final boolean twin, final String start, final String... end ) {
    this.twin = twin ;
    this.start = start ;
    this.end = end.clone() ;
  }

  public String getStart() {
    return start ;
  }

  public String[] getEnd() {
    return end.clone() ;
  }

  public boolean isTwin() {
    return twin ;
  }

  private static final Predicate< BlockDelimiter > IS_TWIN = new Predicate<BlockDelimiter>() {
    @Override
    public boolean apply( final BlockDelimiter blockDelimiter ) {
      return blockDelimiter.isTwin() ;
    }
  } ;
  private static final Predicate< BlockDelimiter > IS_PAIRED = Predicates.not( IS_TWIN ) ;

  public static Iterable< BlockDelimiter > getTwinDelimiters() {
    return Iterables.filter( ImmutableList.of( values() ), IS_TWIN ) ;
  }

  public static Iterable< BlockDelimiter > getPairedDelimiters() {
    return Iterables.filter( ImmutableList.of( values() ), IS_PAIRED ) ;
  }
}