/*
* Copyright 2010-2013 Ning, Inc.
*
* Ning licenses this file to you 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.killbill.billing.util.entity;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import javax.annotation.Nullable;
import com.google.common.collect.ImmutableList;
// Assumes the original offset starts at zero.
public class DefaultPagination<T> implements Pagination<T> {
private final Long currentOffset;
private final Long limit;
private final Long totalNbRecords;
private final Long maxNbRecords;
private final Iterator<T> delegateIterator;
// Builders when the streaming API can't be used (should only be used for tests)
// Notes: elements should be the entire records set (regardless of filtering) otherwise maxNbRecords won't be accurate
public static <T> Pagination<T> build(final Long offset, final Long limit, final Collection<T> elements) {
return build(offset, limit, elements.size(), elements);
}
public static <T> Pagination<T> build(final Long offset, final Long limit, final Integer maxNbRecords, final Collection<T> elements) {
final List<T> allResults = ImmutableList.<T>copyOf(elements);
final List<T> results;
if (offset >= allResults.size()) {
results = ImmutableList.<T>of();
} else if (offset + limit > allResults.size()) {
results = allResults.subList(offset.intValue(), allResults.size());
} else {
results = allResults.subList(offset.intValue(), offset.intValue() + limit.intValue());
}
return new DefaultPagination<T>(offset, limit, (long) results.size(), (long) maxNbRecords, results.iterator());
}
// Constructor for DAO -> API bridge
public DefaultPagination(final Pagination original, final Long limit, final Iterator<T> delegate) {
this(original.getCurrentOffset(), limit, original.getTotalNbRecords(), original.getMaxNbRecords(), delegate);
}
// Constructor for DAO getAll calls
public DefaultPagination(final Long maxNbRecords, final Iterator<T> results) {
this(0L, Long.MAX_VALUE, maxNbRecords, maxNbRecords, results);
}
public DefaultPagination(final Long currentOffset, final Long limit,
@Nullable final Long totalNbRecords, @Nullable final Long maxNbRecords,
final Iterator<T> delegateIterator) {
this.currentOffset = currentOffset;
// See DefaultPaginationSqlDaoHelper
this.limit = Math.abs(limit);
this.totalNbRecords = totalNbRecords;
this.maxNbRecords = maxNbRecords;
this.delegateIterator = delegateIterator;
}
@Override
public Iterator<T> iterator() {
return delegateIterator;
}
@Override
public Long getCurrentOffset() {
return currentOffset;
}
@Override
public Long getNextOffset() {
final long candidate = currentOffset + limit;
if (totalNbRecords != null && candidate >= totalNbRecords) {
// No more results
return null;
} else {
// When we don't know the total number of records, the next offset
// returned here won't make sense once the last result is returned.
// It is the responsibility of the client to handle the pagination stop condition
// in that case (i.e. check if there is no more results).
return candidate;
}
}
@Override
public Long getMaxNbRecords() {
return maxNbRecords;
}
@Override
public Long getTotalNbRecords() {
return totalNbRecords;
}
@Override
public String toString() {
final StringBuilder sb = new StringBuilder("DefaultPagination{");
sb.append("currentOffset=").append(currentOffset);
sb.append(", nextOffset=").append(getNextOffset());
sb.append(", totalNbRecords=").append(totalNbRecords);
sb.append(", maxNbRecords=").append(maxNbRecords);
sb.append('}');
return sb.toString();
}
// Expensive! Will compare the content of the iterator
@Override
public boolean equals(final Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
final DefaultPagination that = (DefaultPagination) o;
if (totalNbRecords != null ? !totalNbRecords.equals(that.totalNbRecords) : that.totalNbRecords != null) {
return false;
}
if (maxNbRecords != null ? !maxNbRecords.equals(that.maxNbRecords) : that.maxNbRecords != null) {
return false;
}
if (currentOffset != null ? !currentOffset.equals(that.currentOffset) : that.currentOffset != null) {
return false;
}
if (delegateIterator != null ? !ImmutableList.<T>copyOf(delegateIterator).equals(ImmutableList.<T>copyOf(that.delegateIterator)) : that.delegateIterator != null) {
return false;
}
return true;
}
@Override
public int hashCode() {
int result = currentOffset != null ? currentOffset.hashCode() : 0;
result = 31 * result + (totalNbRecords != null ? totalNbRecords.hashCode() : 0);
result = 31 * result + (maxNbRecords != null ? maxNbRecords.hashCode() : 0);
result = 31 * result + (delegateIterator != null ? delegateIterator.hashCode() : 0);
return result;
}
}