/*
 * Copyright (c) 2010-2016. Axon Framework
 * 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 org.axonframework.eventsourcing.eventstore;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;

import java.io.Serializable;
import java.util.Objects;

/**
 * Tracking token based on the global sequence number of an event.
 *
 * @author Rene de Waele
 */
public class GlobalSequenceTrackingToken implements TrackingToken, Comparable<GlobalSequenceTrackingToken>,
                                                    Serializable {

    private final long globalIndex;

    /**
     * Initializes a {@link GlobalSequenceTrackingToken} from the given {@code globalIndex} of the event.
     *
     * @param globalIndex the global sequence number of the event
     */
    @JsonCreator
    public GlobalSequenceTrackingToken(@JsonProperty("globalIndex") long globalIndex) {
        this.globalIndex = globalIndex;
    }

    /**
     * Get the global sequence number of the event
     *
     * @return the global sequence number of the event
     */
    public long getGlobalIndex() {
        return globalIndex;
    }

    /**
     * Returns a new {@link GlobalSequenceTrackingToken} instance that is the sum of this token's sequence number and
     * the given {@code offset}.
     *
     * @param offset the offset between this token's sequence number of that of the returned instance
     * @return a new tracking token with global sequence increased with the given offset
     */
    public GlobalSequenceTrackingToken offsetBy(int offset) {
        return new GlobalSequenceTrackingToken(globalIndex + offset);
    }

    /**
     * Returns a new {@link GlobalSequenceTrackingToken} instance with sequence number incremented by 1.
     *
     * @return a new tracking token with sequence number incremented by 1
     */
    public GlobalSequenceTrackingToken next() {
        return offsetBy(1);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        GlobalSequenceTrackingToken that = (GlobalSequenceTrackingToken) o;
        return globalIndex == that.globalIndex;
    }

    @Override
    public int hashCode() {
        return Objects.hash(globalIndex);
    }

    @Override
    public String toString() {
        return "IndexTrackingToken{" + "globalIndex=" + globalIndex + '}';
    }

    @Override
    public int compareTo(GlobalSequenceTrackingToken o) {
        return Long.compare(globalIndex, o.globalIndex);
    }
}