graphql.annotations.connection.NaivePaginatedData Maven / Gradle / Ivy

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/**
 * Copyright 2016 Yurii Rashkovskii
 *
 * 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
 */
package graphql.annotations.connection;

import java.nio.charset.StandardCharsets;
import java.util.Iterator;

import static java.util.Base64.getEncoder;

public class NaivePaginatedData extends AbstractPaginatedData {
    private static final String DUMMY_CURSOR_PREFIX = "simple-cursor";
    private final String prefix;

    public NaivePaginatedData(boolean hasPreviousPage, boolean hasNextPage, Iterable data) {
        this(hasPreviousPage, hasNextPage, data, DUMMY_CURSOR_PREFIX);
    }

    public NaivePaginatedData(boolean hasPreviousPage, boolean hasNextPage, Iterable data, String prefix) {
        super(hasPreviousPage, hasNextPage, data);
        this.prefix = prefix;
    }

    /**
     * creates the cursor by offset (i.e first entity has cursor 0, the second has 1 and so on)
     * NOTE: to make it consistent, please make the data ordered
     *
     * @param entity the entity
     * @return the cursor of the entity (i.e the offset)
     */
    @Override
    public String getCursor(T entity) {
        Iterator iterator = data.iterator();
        long offset = 0;
        for (; iterator.hasNext(); ) {
            T next = iterator.next();
            if (entity.equals(next)) {
                break;
            }
            offset++;
        }
        return createCursor(offset);
    }

    private String createCursor(long offset) {
        byte[] bytes = (prefix + Long.toString(offset)).getBytes(StandardCharsets.UTF_8);
        return getEncoder().encodeToString(bytes);
    }
}