org.itsallcode.matcher.MismatchReporter Maven / Gradle / Ivy

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package org.itsallcode.matcher;

import org.hamcrest.Description;
import org.hamcrest.Matcher;

/**
 * This class allows reporting mismatches during comparison of two objects in a
 * matcher. It takes care of the overall matching state, i.e. when one attribute
 * does not match, the overall state is 'not matching'. Additionally it builds a
 * description of the mismatch.
 */
public class MismatchReporter {
    private final Description mismatchDescription;
    private boolean firstMismatch = true;
    private boolean matches = true;

    private MismatchReporter(final Description mismatchDescription) {
        this.mismatchDescription = mismatchDescription;
    }

    static MismatchReporter start(final Description mismatchDescription) {
        mismatchDescription.appendText("{");
        return new MismatchReporter(mismatchDescription);
    }

    boolean finishAndCheckMatching() {
        this.mismatchDescription.appendText("}");
        return this.matches;
    }

    /**
     * Check if the actual object matches using the given {@link Matcher} and record
     * a message if it does not match.
     * 
     * @param message the message to output in case of a failed match
     * @param matcher the {@link Matcher} used for checking the actual value
     * @param actual  the actual value that will be compared using the
     *                {@link Matcher}.
     * @param      the type of the matcher.
     * @return this {@link MismatchReporter} allowing a fluent programming style.
     */
    public  MismatchReporter checkMismatch(final String message, final Matcher matcher, final T actual) {
        if (!matcher.matches(actual)) {
            reportMismatch(message, matcher, actual);
            this.matches = false;
        }
        return this;
    }

    private void reportMismatch(final String name, final Matcher matcher, final Object actual) {
        appendComma();
        this.mismatchDescription //
                .appendText(name) //
                .appendText(" ");
        matcher.describeMismatch(actual, this.mismatchDescription);
    }

    private void appendComma() {
        if (!this.firstMismatch) {
            this.mismatchDescription.appendText(", ");
        }
        this.firstMismatch = false;
    }
}