UnpagedPageImpl.java

/*
 * Copyright © 2018 spring-data-dynamodb (https://github.com/prasanna0586/spring-data-dynamodb)
 *
 * 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.socialsignin.spring.data.dynamodb.domain;

import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.lang.NonNull;
import org.springframework.util.Assert;

import java.util.Iterator;
import java.util.List;
import java.util.function.Function;
import java.util.stream.Collectors;

/**
 * {@link Page} implementation that uses only the methods from the {@link Iterable} interface thus the lazy list from
 * the AWS SDK used as result set can be properly used
 * @param <T>
 *            The type of the list's elements
 */
public class UnpagedPageImpl<T> implements Page<T> {

    @NonNull
    private final List<T> content;
    @NonNull
    private final Pageable pageable;
    private final long total;

    /**
     * Creates a new unpaged page instance.
     * @param content the content of this page, must not be null
     * @param total the total number of elements available
     */
    public UnpagedPageImpl(@NonNull List<T> content, long total) {

        Assert.notNull(content, "content must not be null!");

        this.pageable = Pageable.unpaged();
        this.content = content;
        this.total = total;
    }

    @Override
    public int getNumber() {
        return 0;
    }

    @Override
    public int getSize() {
        return getNumberOfElements();
    }

    @Override
    public int getNumberOfElements() {
        if (total > Integer.MAX_VALUE) {
            return Integer.MAX_VALUE;
        } else {
            return (int) total;
        }
    }

    @NonNull
    @Override
    public Sort getSort() {
        return pageable.getSort();
    }

    @Override
    public boolean isFirst() {
        return true;
    }

    @Override
    public boolean isLast() {
        return true;
    }

    @Override
    public boolean hasNext() {
        return false;
    }

    @Override
    public boolean hasPrevious() {
        return false;
    }

    @NonNull
    @Override
    public Pageable nextPageable() {
        return Pageable.unpaged();
    }

    @NonNull
    @Override
    public Pageable previousPageable() {
        return Pageable.unpaged();
    }

    @NonNull
    @Override
    public Iterator<T> iterator() {
        return this.content.iterator();
    }

    @Override
    public int getTotalPages() {
        return 1;
    }

    @Override
    public long getTotalElements() {
        return this.total;
    }

    @NonNull
    @Override
    public <U> UnpagedPageImpl<U> map(@NonNull Function<? super T, ? extends U> converter) {
        List<U> convertedContent = this.content.stream().map(converter).collect(Collectors.toList());

        return new UnpagedPageImpl<>(convertedContent, this.total);
    }

    @NonNull
    @Override
    public List<T> getContent() {
        return content;
    }

    @Override
    public boolean hasContent() {
        return total > 0;
    }

    /*
     * (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @NonNull
    @Override
    public String toString() {

        String contentType = "UNKNOWN";

        if (this.total > 0) {
            contentType = iterator().getClass().getName();
        }

        return String.format("Page %s of %d containing %s instances", getNumber() + 1, getTotalPages(), contentType);
    }

    /*
     * (non-Javadoc)
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(/* @Nullable */ Object obj) {

        if (this == obj) {
            return true;
        }

        if (!(obj instanceof UnpagedPageImpl<?> that)) {
            return false;
        }

        return this.total == that.total && this.pageable.equals(that.pageable) && this.content.equals(that.content);
    }

    /*
     * (non-Javadoc)
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode() {

        int result = 17;

        result += 31 * Long.hashCode(total);
        result += 31 * pageable.hashCode();
        result += 31 * content.hashCode();

        return result;
    }
}