package io.github.reggert.reb4j.charclass;
   
   import io.github.reggert.reb4j.Literal;
   
   import fj.F2;
   import fj.data.LazyString;
   import fj.data.Set;
   
   /**
   * Character class consisting of multiple characters.
   */
  public final class MultiChar extends CharClass
  {
  	private static final long serialVersionUID = 1L;
  	public final Set<Character> characters;
  	
  	public MultiChar(final Set<Character> characters)
  	{
  		if (characters == null) throw new NullPointerException("characters");
  		this.characters = characters;
  	}
  
  	@Override
  	public Negated<MultiChar> negated()
  	{
  		return new Negated<MultiChar>(this);
  	}
  
  	@Override
  	public LazyString unitableForm()
  	{
  		return characters.toStream().foldLeft(
  				new F2<LazyString, Character, LazyString>()
  				{
  					@Override
  					public LazyString f(final LazyString a, final Character b)
  					{return a.append(Literal.escapeChar(b));}
  				},
  				LazyString.empty
  			);
  	}
  
  	@Override
  	public LazyString independentForm()
  	{
  		return LazyString.str("[").append(unitableForm()).append("]");
  	}
  	
  	/**
  	 * Overloaded version of {@link CharClass#union(CharClass)} for arguments 
  	 * of type {@link MultiChar} that simply merges the two objects into
  	 * a single instance of {@link MultiChar}.
  	 * 
  	 * @param right another instance of {@link MultiChar}; must not be <code>null</code>.
  	 * @return a new instance of {@link MultiChar}.
  	 * @throws NullPointerException
  	 * 	if the argument is <code>null</code>.
  	 */
  	public MultiChar union(final MultiChar right)
  	{
  		if (right == null) throw new NullPointerException("right == null");
  		return new MultiChar(characters.union(right.characters));
  	}
  	
  	/**
  	 * Overloaded version of {@link CharClass#union(CharClass)} for arguments 
  	 * of type {@link SingleChar} that simply merges the two objects into
  	 * a single instance of {@link MultiChar}.
  	 * 
  	 * @param right another instance of {@link MultiChar}; must not be <code>null</code>.
  	 * @return a new instance of {@link MultiChar}.
  	 * @throws NullPointerException
  	 * 	if the argument is <code>null</code>.
  	 */
  	public MultiChar union(final SingleChar right)
  	{
  		if (right == null) throw new NullPointerException("right == null");
  		return new MultiChar(characters.insert(right.character));
  	}
  
  }