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Java 8 Functional interface extentions, collection decorators, I/O interfaces, and assertions
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/*
 * Copyright (C) 2015 fuwjax.org ([email protected])
 *
 * 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 org.fuwjax.oss.util.assertion;

import org.fuwjax.oss.util.collection.ReflectList;

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

public interface Assertion {
    static Supplier toExpected(Object expected){
        return () -> {
            if (expected == null) {
                return "null";
            }
            if (expected instanceof Class) {
                return ((Class) expected).getCanonicalName();
            }
            if (expected.getClass().isArray()) {
                return ReflectList.asList(expected).toString();
            }
            if (expected instanceof Throwable) {
                String message = ((Throwable) expected).getMessage();
                return toExpected(expected.getClass()).get() + "(" + (message == null ? "null" : '"' + message + '"') + ", " + toExpected(((Throwable) expected).getCause()).get() + ")";
            }
            return expected.toString();
        };
    }

    default AssertionError fail(T actual) {
        return new AssertionError(String.format("expected:<%s> but was:<%s>", expected().get(), toExpected(actual).get()));
    }

    Supplier expected();

    default void expects(T value) throws AssertionError{
        if(!test(value)){
            throw fail(value);
        }
    }

    boolean test(T value);

    default  Assertion of(Function function) {
        return of(expected(), function);
    }

    default  Assertion of(Supplier expected, Function function) {
        return new Assertion(){

            @Override
            public Supplier expected() {
                return expected;
            }

            @Override
            public void expects(U value) throws AssertionError {
                Assertion.this.expects(function.apply(value));
            }

            @Override
            public boolean test(U value) {
                return Assertion.this.test(function.apply(value));
            }
        };
    }

    default Assertion and(Assertion assertion) {
        return and(() -> expected().get() + " and " + assertion.expected().get(), assertion);
    }

    default Assertion and(Supplier expected, Assertion assertion){
        return new Assertion(){
            @Override
            public Supplier expected() {
                return expected;
            }

            @Override
            public void expects(T value) throws AssertionError {
                Assertion.this.expects(value);
                assertion.expects(value);
            }

            @Override
            public boolean test(T value) {
                return Assertion.this.test(value) && assertion.test(value);
            }
        };
    }

    default Assertion or(Assertion assertion) {
        return or(() -> expected().get() + " or " + assertion.expected().get(), assertion);
    }

    default Assertion or(Supplier expected, Assertion assertion){
        return new Assertion(){
            @Override
            public Supplier expected() {
                return expected;
            }

            @Override
            public boolean test(T value) {
                return Assertion.this.test(value) || assertion.test(value);
            }
        };
    }

    default Assertion negate() {
        return negate(() -> "not " + expected().get());
    }

    default Assertion negate(Supplier expected){
        return new Assertion(){
            @Override
            public Supplier expected() {
                return expected;
            }

            @Override
            public boolean test(T value) {
                return !Assertion.this.test(value);
            }
        };
    }
}