package org.wikimedia.search.extra.regex.expression;
   
   import java.util.List;
   
   import com.google.common.collect.ImmutableSet;
   
   /**
    * Disjunction.
    */
  public final class Or<T> extends AbstractCompositeExpression<T> {
      public static <T> Expression<T> fromExpressionSources(List<? extends ExpressionSource<T>> sources) {
          switch (sources.size()) {
              case 0:
                  return True.instance();
              case 1:
                  return sources.get(0).expression();
              default:
                  ImmutableSet.Builder<Expression<T>> or = ImmutableSet.builder();
                  for (ExpressionSource<T> source : sources) {
                      or.add(source.expression());
                  }
                  return new Or<>(or.build()).simplify();
          }
      }
  
      @SafeVarargs
      public Or(Expression<T>... components) {
          this(ImmutableSet.copyOf(components));
      }
  
      public Or(ImmutableSet<Expression<T>> components) {
          super(components);
      }
  
      @Override
      protected boolean doesNotAffectOutcome(Expression<T> expression) {
          return expression.alwaysFalse();
      }
  
      @Override
      protected Expression<T> componentForcesOutcome(Expression<T> expression) {
          if (expression.alwaysTrue()) {
              return expression;
          }
          return null;
      }
  
      @Override
      protected AbstractCompositeExpression<T> newFrom(ImmutableSet<Expression<T>> components) {
          return new Or<>(components);
      }
  
      @Override
      protected String toStringJoiner() {
          return " OR ";
      }
  
      @Override
      public <J> J transform(Expression.Transformer<T, J> transformer) {
          return transformer.or(transformComponents(transformer));
      }
  }