package com.github.davidmoten.rx2;
   
   import com.github.davidmoten.rx2.exceptions.ThrowingException;
   
   import io.reactivex.functions.BiFunction;
   
   public final class BiFunctions {
   
       private BiFunctions() {
          // prevent instantiation
      }
  
      @SuppressWarnings("unchecked")
      public static <A, B, C> BiFunction<A, B, C> throwing() {
          return (BiFunction<A, B, C>) ThrowingHolder.INSTANCE;
      }
  
      private static final class ThrowingHolder {
          static BiFunction<Object, Object, Object> INSTANCE = new BiFunction<Object, Object, Object>() {
  
              @Override
              public Object apply(Object t1, Object t2) throws Exception {
                  throw new ThrowingException();
              }
          };
      }
  
      public static <T extends Number> BiFunction<Statistics, T, Statistics> collectStats() {
          return new BiFunction<Statistics, T, Statistics>() {
  
              @Override
              public Statistics apply(Statistics s, T t) {
                  return s.add(t);
              }
          };
      }
  
      public static <T, R, S> BiFunction<T, R, S> constant(final S value) {
          // TODO make holder
          return new BiFunction<T, R, S>() {
  
              @Override
              public S apply(T t1, R t2) throws Exception {
                  return value;
              }
          };
      }
  
      public static <T, R, S> BiFunction<T, R, S> toNull() {
          // TODO make holder
          return new BiFunction<T, R, S>() {
  
              @Override
              public S apply(T t1, R t2) throws Exception {
                  return null;
              }
          };
  
      }
  
  }