package io.github.reggert.reb4j.charclass;
   
   import fj.F2;
   import fj.data.LazyString;
   import fj.data.List;
   
   /**
    * Character class composed of the union of two other character classes.
    */
  public final class Union extends CharClass
  {
  	private static final long serialVersionUID = 1L;
  	public final List<CharClass> subsets;
  	
  	Union(final List<CharClass> subsets)
  	{
  		if (subsets == null) throw new NullPointerException("subsets");
  		this.subsets = subsets;
  	}
  
  	@Override
  	public Negated<Union> negated()
  	{
  		return new Negated<Union>(this);
  	}
  
  	@Override
  	public LazyString unitableForm()
  	{
  		return subsets.foldLeft(
  				new F2<LazyString, CharClass, LazyString>()
  				{
  					@Override
  					public LazyString f(final LazyString a, final CharClass b)
  					{return a.append(b.unitableForm());}
  				},
  				LazyString.empty
  			);
  	}
  
  	@Override
  	public LazyString independentForm()
  	{
  		return LazyString.str("[").append(unitableForm()).append("]");
  	}
  
  	@Override
  	public Union union(final Union right)
  	{
  		return new Union(subsets.append(right.subsets));
  	}
  
  	@Override
  	public Union union(final CharClass right)
  	{
  		return new Union(subsets.append(List.single(right)));
  	}
  	
  	static Union union(final CharClass left, final Union right)
  	{
  		return new Union(right.subsets.cons(left));
  	}
  	
  	static Union union(final CharClass left, final CharClass right)
  	{
  		return new Union(List.list(left, right));
  	}
  
  	@Override
  	public int hashCode()
  	{
  		final int prime = 31;
  		int result = 1;
  		result = prime * result + subsets.hashCode();
  		return result;
  	}
  
  	@Override
  	public boolean equals(final Object obj)
  	{
  		if (this == obj)
  			return true;
  		if (obj == null)
  			return false;
  		if (getClass() != obj.getClass())
  			return false;
  		final Union other = (Union) obj;
  		return subsets.equals(other.subsets);
  	}
  	
  }