/**
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * 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 io.reactivex;

import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;

/**
 * Test rule to retry flaky tests.
 * <a href="http://stackoverflow.com/a/8301639/61158">From Stackoverflow</a>.
 */
public class Retry implements TestRule {

    final int retryCount;

    final int sleep;

    final boolean backoff;

    public Retry(int retryCount, int sleep, boolean backoff) {
        this.retryCount = retryCount;
        this.sleep = sleep;
        this.backoff = backoff;
    }

    @Override
    public Statement apply(Statement base, Description description) {
        return statement(base, description);
    }

    private Statement statement(final Statement base, final Description description) {
        return new Statement() {
            @Override
            public void evaluate() throws Throwable {
                Throwable caughtThrowable = null;

                for (int i = 0; i < retryCount; i++) {
                    try {
                        base.evaluate();
                        return;
                    } catch (Throwable t) {
                        caughtThrowable = t;
                        System.err.println(description.getDisplayName() + ": run " + (i + 1) + " failed");
                        int n = sleep;
                        if (backoff && i != 0) {
                            n = n * (2 << i);
                        }
                        Thread.sleep(n);
                    }
                }
                System.err.println(description.getDisplayName() + ": giving up after " + retryCount + " failures");
                throw caughtThrowable;
            }
        };
    }
}