com.spotify.helios.client.EndpointIterator.java Source code

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Here is the source code for com.spotify.helios.client.EndpointIterator.java

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/*
 * Copyright (c) 2015 Spotify AB.
 *
 * 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 com.spotify.helios.client;

import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;

import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Random;

import javax.annotation.Nullable;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * An {@link Iterator} of {@link Endpoint} that restarts when it reaches the end.
 *
 * The iterator will loop continuously around the provided elements, unless there are no elements
 * in the collection to begin with.
 */
class EndpointIterator implements Iterator<Endpoint> {

    private final List<Endpoint> endpoints;
    private final int size;
    private int cursor;

    private EndpointIterator(final List<Endpoint> endpoints) {
        this.endpoints = ImmutableList.copyOf(checkNotNull(endpoints));
        size = this.endpoints.size();
        // Set the cursor to a random location within the backing list.
        // TODO (dxia) It'd be nice to enforce the backing list to not be empty.
        // But this breaks an existing test.
        cursor = size == 0 ? 0 : new Random().nextInt(size);
    }

    static EndpointIterator of(final List<Endpoint> endpoints) {
        return new EndpointIterator(endpoints);
    }

    @Override
    public boolean hasNext() {
        return size > 0;
    }

    @Override
    public Endpoint next() {
        if (size == 0) {
            throw new NoSuchElementException();
        }

        return cursor < size ? endpoints.get(cursor++) : endpoints.get(cursor = 0);
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }

    /**
     * @return true if any endpoints' scheme is HTTPS
     */
    boolean hasHttps() {
        return Iterables.any(endpoints, new Predicate<Endpoint>() {
            @Override
            public boolean apply(@Nullable Endpoint endpoint) {
                return endpoint != null && endpoint.getUri() != null && endpoint.getUri().getScheme() != null
                        && endpoint.getUri().getScheme().equalsIgnoreCase("https");
            }
        });
    }
}