001package org.hamcrest;
002
003/**
004 * A Condition implements part of a multi-step match. We sometimes need to write matchers
005 * that have a sequence of steps, where each step depends on the result of the previous
006 * step and we can stop processing as soon as a step fails. These classes provide
007 * infrastructure for writing such a sequence.
008 *
009 * Based on https://github.com/npryce/maybe-java
010 * @author Steve Freeman 2012 http://www.hamcrest.com
011 */
012
013public abstract class Condition<T> {
014    public static final NotMatched<Object> NOT_MATCHED = new NotMatched<Object>();
015
016    public interface Step<I, O> {
017        Condition<O> apply(I value, Description mismatch);
018    }
019
020    private Condition() { }
021
022    public abstract boolean matching(Matcher<T> match, String message);
023    public abstract <U> Condition<U> and(Step<? super T, U> mapping);
024
025    public final boolean matching(Matcher<T> match) { return matching(match, ""); }
026    public final <U> Condition<U> then(Step<? super T, U> mapping) { return and(mapping); }
027
028    @SuppressWarnings("unchecked")
029    public static <T> Condition<T> notMatched() {
030        return (Condition<T>) NOT_MATCHED;
031    }
032
033    public static <T> Condition<T> matched(final T theValue, final Description mismatch) {
034        return new Matched<T>(theValue, mismatch);
035    }
036
037    private static final class Matched<T> extends Condition<T> {
038        private final T theValue;
039        private final Description mismatch;
040
041        private Matched(T theValue, Description mismatch) {
042            this.theValue = theValue;
043            this.mismatch = mismatch;
044        }
045
046        @Override
047        public boolean matching(Matcher<T> matcher, String message) {
048            if (matcher.matches(theValue)) {
049                return true;
050            }
051            mismatch.appendText(message);
052            matcher.describeMismatch(theValue, mismatch);
053            return false;
054        }
055
056        @Override
057        public <U> Condition<U> and(Step<? super T, U> next) {
058            return next.apply(theValue, mismatch);
059        }
060    }
061
062    private static final class NotMatched<T> extends Condition<T> {
063        @Override public boolean matching(Matcher<T> match, String message) { return false; }
064
065        @Override public <U> Condition<U> and(Step<? super T, U> mapping) {
066            return notMatched();
067        }
068    }
069}