/*-
 * #%L
 * rapidoid-commons
 * %%
 * Copyright (C) 2014 - 2020 <NAME> and contributors
 * %%
 * 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.
 * #L%
 */

package org.rapidoid.datamodel.impl;

import org.rapidoid.RapidoidThing;
import org.rapidoid.annotation.Authors;
import org.rapidoid.annotation.Since;
import org.rapidoid.datamodel.PageableData;

import java.util.Iterator;
import java.util.List;

@Authors("<NAME>")
@Since("5.1.0")
public class PagingIterator<T> extends RapidoidThing implements Iterator<T> {

    private final PageableData<T> data;

    private List<T> page;

    private int offset;
    private int pageLength;

    private int index;

    public PagingIterator(PageableData<T> data) {
        this(data, 100);
    }

    public PagingIterator(PageableData<T> data, int pageLength) {
        this.data = data;
        this.pageLength = pageLength;
    }

    @Override
    public boolean hasNext() {
        if (page == null || index >= page.size()) {
            page = data.getPage(offset, pageLength);
            offset += page.size();
            index = 0;
        }

        return index < page.size();
    }

    @Override
    public T next() {
        return page.get(index++);
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("remove");
    }

}
