package com.github.davidmoten.rx2;
   
   import com.github.davidmoten.rx2.exceptions.ThrowingException;
   
   import io.reactivex.functions.Function;
   
   public final class Functions {
   
       private Functions() {
          // prevent instantiation
      }
  
      public static <T> Function<Object, T> constant(final T value) {
          return new Function<Object, T>() {
  
              @Override
              public T apply(Object t) throws Exception {
                  return value;
              }
          };
      }
  
      @SuppressWarnings("unchecked")
      public static <T> Function<T, T> identity() {
          return (Function<T, T>) IdentityHolder.INSTANCE;
      }
  
      private static final class IdentityHolder {
          static final Function<Object, Object> INSTANCE = new Function<Object, Object>() {
  
              @Override
              public Object apply(Object t) throws Exception {
                  return t;
              }
          };
      }
  
      public static <T, R> Function<T, R> throwing() {
          // TODO make holder
          return new Function<T, R>() {
  
              @Override
              public R apply(T t) {
                  throw new ThrowingException();
              }
          };
      }
      
      public static <T> Function<T, String> toStringFunction() {
          // TODO make holder
          return new Function<T,String> () {
  
              @Override
              public String apply(T t) throws Exception {
                  return String.valueOf(t);
              }
          };
      }
  
  }