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Platform for Functional Reactive Programming with Java 8
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package com.oath.cyclops.matching;

import static cyclops.control.Option.none;

import cyclops.control.Option;
import cyclops.data.tuple.Tuple1;
import cyclops.data.tuple.Tuple2;
import cyclops.data.tuple.Tuple3;
import cyclops.data.tuple.Tuple4;
import cyclops.data.tuple.Tuple5;
import lombok.AllArgsConstructor;
import lombok.NonNull;

import java.util.Optional;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;

/**
 * Pattern matching use case contract.
 *
 * @param  the type that is being tested.
 * @param  the return that the use case will return, it may or note return null.
 */
@FunctionalInterface
public interface Case {

    /**
     * Test the use case and return in case the test is true.
     *
     * @param value the value to be tested.
     * @return the return, implementations may or not return null to determine success.
     */
    Option test(T value);

    /**
     * Return the test for this user case or for the other. there is no guarantee
     * one successful result will be produced.
     *
     * @param orCase the case bo be tested in case this one fail.
     * @return a composite case to perform a XOR operation.
     */
    default Case or(Case orCase) {
        return (t) -> {
            Option val = test(t);
            return val.isPresent() ? val : orCase.test(t);
        };
    }

    @AllArgsConstructor
    final class CaseFn implements Case {


        final Function fn;

        @Override
        public Option test(T value) {
            return Option.some(fn.apply(value));
        }

    }

    @AllArgsConstructor
    final class Case0 implements Case {

        final Predicate predicate;
        final Function supplier;

        @Override
        public Option test(T value) {
            return predicate.test(value) ? Option.some(supplier.apply(value)) : none();
        }

    }

    @AllArgsConstructor
    final class Case1 implements Case, R> {

        final Predicate predicate;
        final Function, R> supplier;

        @Override
        public Option test(Tuple1 value) {
            return predicate.test(value._1()) ? Option.of(supplier.apply(value)) : none();
        }

    }

    @AllArgsConstructor
    final class Case2 implements Case, R> {

        final Predicate predicate1;
        final Predicate predicate2;
        final Function, ? extends R> supplier;

        @Override
        public Option test(Tuple2 value) {
            return predicate1.test(value._1()) && predicate2.test(value._2()) ? Option.some(supplier.apply(value)) : none();
        }

    }

    @AllArgsConstructor
    final class Case3 implements Case, R> {

        final Predicate predicate1;
        final Predicate predicate2;
        final Predicate predicate3;

        final Function, R> supplier;

        @Override
        public Option test(Tuple3 value) {
            return predicate1.test(value._1()) && predicate2.test(value._2()) && predicate3.test(value._3()) ? Option.some(supplier.apply(value)) : none();
        }

    }

    @AllArgsConstructor
    final class Case4 implements Case, R> {

        final Predicate predicate1;
        final Predicate predicate2;
        final Predicate predicate3;
        final Predicate predicate4;

        final Function, R> supplier;

        @Override
        public Option test(Tuple4 value) {
            return predicate1.test(value._1()) && predicate2.test(value._2()) && predicate3.test(value._3()) && predicate4.test(value._4()) ? Option.some(supplier.apply(value)) : none();
        }

    }

    @AllArgsConstructor
    final class Case5 implements Case, R> {

        final Predicate predicate1;
        final Predicate predicate2;
        final Predicate predicate3;
        final Predicate predicate4;
        final Predicate predicate5;

        final Function, R> supplier;

        @Override
        public Option test(Tuple5 value) {
            return predicate1.test(value._1()) && predicate2.test(value._2()) && predicate3.test(value._3()) && predicate4.test(value._4()) && predicate5.test(value._5()) ? Option.some(supplier.apply(value)) : none();
        }

    }

    @AllArgsConstructor
    final class CaseOptional implements Case, R> {
        @NonNull
        final Supplier supplier0;
        @NonNull
        final Supplier supplier1;

        @Override
        public Option test(Optional optional) {
            return Option.some(optional.isPresent() ? supplier0.get() : supplier1.get());
        }

    }

    /**
     * Marker interface to build a Default Case when no pattern matches.
     *
     * @param  return type.
     * @see cyclops.matching.Api#Any(Function)
     * @see cyclops.matching.Api#Any(Supplier)
     **/
    interface Any extends Function {

    }

}