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/*
 * Copyright 2019 Netflix, Inc.
 *
 * 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.mantisrx.common.network;

import io.mantisrx.common.metrics.Gauge;
import io.mantisrx.common.metrics.Metrics;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


public class RoundRobinRouter {

    private Map> endpoints = new HashMap<>();
    private List idList = new ArrayList();
    private int currentListSize;
    private int count;
    private Metrics metrics;
    private Gauge activeConnections;

    public RoundRobinRouter() {
        metrics = new Metrics.Builder()
                .name("RoundRobin")
                .addGauge("activeConnections")
                .build();

        activeConnections = metrics.getGauge("activeConnections");
    }

    public Metrics getMetrics() {
        return metrics;
    }

    public synchronized boolean add(WritableEndpoint endpoint) {
        String id = Endpoint.uniqueHost(endpoint.getHost(),
                endpoint.getPort(), endpoint.getSlotId());
        boolean added = false;
        if (!endpoints.containsKey(id)) {
            endpoints.put(id, endpoint);
            idList.add(id);
            currentListSize++;
            added = true;
        }
        activeConnections.set(endpoints.size());
        return added;
    }

    public synchronized boolean remove(WritableEndpoint endpoint) {
        String id = Endpoint.uniqueHost(endpoint.getHost(),
                endpoint.getPort(), endpoint.getSlotId());
        boolean removed = false;
        if (endpoints.containsKey(id)) {
            endpoints.remove(id);
            idList.remove(id);
            currentListSize--;
            removed = true;
        }
        activeConnections.set(endpoints.size());
        return removed;
    }

    public synchronized WritableEndpoint nextSlot() {
        return endpoints.get(idList.get((count++ & Integer.MAX_VALUE) % currentListSize));
    }

    // TODO should completeAll and errorAll de-register?
    public synchronized void completeAllEndpoints() {
        for (WritableEndpoint endpoint : endpoints.values()) {
            endpoint.complete();
        }
    }

    public synchronized boolean isEmpty() {
        return endpoints.isEmpty();
    }

    public synchronized void errorAllEndpoints(Throwable e) {
        for (WritableEndpoint endpoint : endpoints.values()) {
            endpoint.error(e);
        }
    }
}