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The AWS SDK for Java with support for OSGi. The AWS SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2014-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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.amazonaws.services.dynamodbv2.document.internal;
import static com.amazonaws.services.dynamodbv2.document.internal.InternalUtils.toItemList;

import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.document.Item;
import com.amazonaws.services.dynamodbv2.document.Page;
import com.amazonaws.services.dynamodbv2.document.ScanOutcome;
import com.amazonaws.services.dynamodbv2.document.spec.ScanSpec;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.dynamodbv2.model.ScanRequest;
import com.amazonaws.services.dynamodbv2.model.ScanResult;

class ScanPage extends Page {

    private final AmazonDynamoDB client;
    private final ScanSpec spec;
    private final ScanRequest request;
    private final int index;
    private final Map lastEvaluatedKey;

    public ScanPage(
            AmazonDynamoDB client,
            ScanSpec spec,
            ScanRequest request,
            int index,
            ScanOutcome outcome) {
        super(Collections.unmodifiableList(
                toItemList(outcome.getScanResult().getItems())),
            outcome);
        this.client = client;
        this.spec = spec;
        this.request = request;
        this.index = index;

        final Integer max = spec.getMaxResultSize();
        final ScanResult result = outcome.getScanResult();
        final List ilist = result.getItems();
        final int size = ilist == null ? 0 : ilist.size();
        if (max != null && (index + size) > max) {
            this.lastEvaluatedKey = null;
        } else {
            this.lastEvaluatedKey = result.getLastEvaluatedKey();
        }
    }

    @Override
    public boolean hasNextPage() {
        if (lastEvaluatedKey == null)
            return false;
        Integer max = spec.getMaxResultSize();
        if (max == null)
            return true;
        return nextRequestLimit(max.intValue()) > 0;
    }

    private int nextRequestLimit(int max) {
        int nextIndex = index + this.size();
        return InternalUtils.minimum(
                max - nextIndex,
                spec.getMaxPageSize());
    }

    @Override
    public Page nextPage() {
        if (lastEvaluatedKey == null) {
            throw new NoSuchElementException("No more pages");
        }
        final Integer max = spec.getMaxResultSize();
        if (max != null) {
            int nextLimit = nextRequestLimit(max.intValue());
            if (nextLimit == 0)
                throw new NoSuchElementException("No more pages");
            request.setLimit(nextLimit);
        }
        request.setExclusiveStartKey(lastEvaluatedKey);
        // fire off request to the server side
        ScanResult result = client.scan(request);
        final int nextIndex = index + this.size();
        return new ScanPage(client, spec, request, nextIndex, 
                new ScanOutcome(result));
    }
}