/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */

package fixture.aws;

import org.elasticsearch.test.ESTestCase;

import java.util.Objects;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Supplier;

/**
 * Lazy supplier for a region name. We cannot use randomness like {@link ESTestCase#randomIdentifier()} when creating the test fixtures in
 * the first place because this happens in static context, so instead we create one of these and defer the creation of the region name
 * itself until the test actually starts running.
 */
public class DynamicRegionSupplier implements Supplier<String> {
    private final AtomicReference<String> generatedRegion = new AtomicReference<>();

    @Override
    public String get() {
        return Objects.requireNonNullElseGet(generatedRegion.get(), this::generateAndGet);
    }

    private String generateAndGet() {
        final var newRegion = "DynamicRegionSupplier-" + ESTestCase.randomIdentifier();
        return Objects.requireNonNullElse(generatedRegion.compareAndExchange(null, newRegion), newRegion);
    }
}