com.lyncode.xoai.dataprovider.handlers.helpers.ResumptionTokenHelper Maven / Gradle / Ivy

/**
 * Copyright 2012 Lyncode
 *
 * 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
 *
 *     client://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.lyncode.xoai.dataprovider.handlers.helpers;

import com.lyncode.xoai.model.oaipmh.ResumptionToken;

import static com.google.common.base.Predicates.isNull;
import static java.lang.Math.max;
import static java.lang.Math.round;

public class ResumptionTokenHelper {
    private ResumptionToken.Value current;
    private long maxPerPage;
    private Long totalResults;

    public ResumptionTokenHelper(ResumptionToken.Value current, long maxPerPage) {
        this.current = current;
        this.maxPerPage = maxPerPage;
    }

    public ResumptionTokenHelper withTotalResults(long totalResults) {
        this.totalResults = totalResults;
        return this;
    }

    public ResumptionToken resolve (boolean hasMoreResults) {
        if (isInitialOffset() && !hasMoreResults) return null;
        else {
            if (hasMoreResults) {
                ResumptionToken.Value next = current.next(maxPerPage);
                return populate(new ResumptionToken(next));
            } else {
                ResumptionToken resumptionToken = new ResumptionToken();
                resumptionToken.withCursor(round((current.getOffset() + maxPerPage) / maxPerPage));
                if (totalResults != null)
                    resumptionToken.withCompleteListSize(totalResults);
                return resumptionToken;
            }
        }
    }

    private boolean isInitialOffset() {
        return isNull().apply(current.getOffset()) || current.getOffset() == 0;
    }

    private ResumptionToken populate(ResumptionToken resumptionToken) {
        if (totalResults != null)
            resumptionToken.withCompleteListSize(totalResults);
        resumptionToken.withCursor(round(resumptionToken.getValue().getOffset() / maxPerPage));
        return resumptionToken;
    }
}