package org.wikimedia.search.extra.regex.expression;
   
   import static com.google.common.base.Preconditions.checkNotNull;
   
   import com.google.common.collect.ImmutableSet;
   
   import lombok.EqualsAndHashCode;
   
   /**
   * A leaf expression.
   */
  @EqualsAndHashCode
  public final class Leaf<T> implements Expression<T> {
      @SafeVarargs
      public static <T> ImmutableSet<Expression<T>> leaves(T... ts) {
          ImmutableSet.Builder<Expression<T>> builder = ImmutableSet.builder();
          for (T t : ts) {
              builder.add(new Leaf<>(t));
          }
          return builder.build();
      }
  
      private final T t;
  
      public Leaf(T t) {
          this.t = checkNotNull(t);
      }
  
      public String toString() {
          return t.toString();
      }
  
      @Override
      public Expression<T> simplify() {
          return this;
      }
  
      @Override
      public boolean alwaysTrue() {
          return false;
      }
  
      @Override
      public boolean alwaysFalse() {
          return false;
      }
  
      @Override
      public boolean isComposite() {
          return false;
      }
  
      @Override
      public <J> J transform(Expression.Transformer<T, J> transformer) {
          return transformer.leaf(t);
      }
  
      @Override
      public int countClauses() {
          return 0;
      }
  }