/**

* Copyright 2014 Netflix, Inc.

*

* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in

* compliance with the License. You may obtain a copy of the License at

*

* http://www.apache.org/licenses/LICENSE-2.0

*

* Unless required by applicable law or agreed to in writing, software distributed under the License is

* distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See

* the License for the specific language governing permissions and limitations under the License.

*/

package rx.internal.util;

import rx.functions.Func0;

import rx.functions.Func1;

import rx.functions.Func2;

import rx.functions.Func3;

import rx.functions.Func4;

import rx.functions.Func5;

import rx.functions.Func6;

import rx.functions.Func7;

import rx.functions.Func8;

import rx.functions.Func9;

import rx.functions.FuncN;

/**

* Utility functions for internal use that we don't want part of the public API.

*/

public final class UtilityFunctions {

/**

* Returns a function that always returns {@code true}.

*

* @return a {@link Func1} that accepts an Object and returns the Boolean {@code true}

*/

public static <T> Func1<? super T, Boolean> alwaysTrue() {

return AlwaysTrue.INSTANCE;

}

/**

* Returns a function that always returns {@code false}.

*

* @return a {@link Func1} that accepts an Object and returns the Boolean {@code false}

*/

public static <T> Func1<? super T, Boolean> alwaysFalse() {

return AlwaysFalse.INSTANCE;

}

/**

* Returns a function that always returns the Object it is passed.

*

* @return a {@link Func1} that accepts an Object and returns the same Object

*/

public static <T> Func1<T, T> identity() {

return new Func1<T, T>() {

@Override

public T call(T o) {

return o;

}

};

}

private enum AlwaysTrue implements Func1<Object, Boolean> {

INSTANCE;

@Override

public Boolean call(Object o) {

return true;

}

}

private enum AlwaysFalse implements Func1<Object, Boolean> {

INSTANCE;

@Override

public Boolean call(Object o) {

return false;

}

}

/**

* Returns a function that merely returns {@code null}, without side effects.

*

* @return a function that returns {@code null}

*/

@SuppressWarnings("unchecked")

public static <T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, R> NullFunction<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, R> returnNull() {

return NULL_FUNCTION;

}

@SuppressWarnings("rawtypes")

private static final NullFunction NULL_FUNCTION = new NullFunction();

private static final class NullFunction<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, R> implements

Func0<R>,

Func1<T0, R>,

Func2<T0, T1, R>,

Func3<T0, T1, T2, R>,

Func4<T0, T1, T2, T3, R>,

Func5<T0, T1, T2, T3, T4, R>,

Func6<T0, T1, T2, T3, T4, T5, R>,

Func7<T0, T1, T2, T3, T4, T5, T6, R>,

Func8<T0, T1, T2, T3, T4, T5, T6, T7, R>,

Func9<T0, T1, T2, T3, T4, T5, T6, T7, T8, R>,

FuncN<R> {

@Override

public R call() {

return null;

}

@Override

public R call(T0 t1) {

return null;

}

@Override

public R call(T0 t1, T1 t2) {

return null;

}

@Override

public R call(T0 t1, T1 t2, T2 t3) {

return null;

}

@Override

public R call(T0 t1, T1 t2, T2 t3, T3 t4) {

return null;

}

@Override

public R call(T0 t1, T1 t2, T2 t3, T3 t4, T4 t5) {

return null;

}

@Override

public R call(T0 t1, T1 t2, T2 t3, T3 t4, T4 t5, T5 t6) {

return null;

}

@Override

public R call(T0 t1, T1 t2, T2 t3, T3 t4, T4 t5, T5 t6, T6 t7) {

return null;

}

@Override

public R call(T0 t1, T1 t2, T2 t3, T3 t4, T4 t5, T5 t6, T6 t7, T7 t8) {

return null;

}

@Override

public R call(T0 t1, T1 t2, T2 t3, T3 t4, T4 t5, T5 t6, T6 t7, T7 t8, T8 t9) {

return null;

}

@Override

public R call(Object... args) {

return null;

}

}

}