/*
 * Copyright (C) 2022  Alessandro Iezzi <aiezzi AT alessandroiezzi PERIOD it>
 *
 * This file is part of commons-page.
 *
 * commons-page is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * commons-page is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with commons-page.  If not, see <https://www.gnu.org/licenses/>.
 */

package it.alessandroiezzi.util;
import java.util.*;

public class PagedList<T> extends ArrayList<T> implements Page<T> {
    private final int pageSize;
    private int pageNumber;
    private boolean pageChanged = false;
    private Page<T> currentPage;

    public PagedList(Collection<T> elements, int pageSize) {
        addAll(elements);
        this.pageSize = pageSize;
        this.pageNumber = 0;
    }

    public PagedList(Collection<T> elements) {
        this(elements, 15);
    }

    public Page<T> firstPage() {
        return toPage(0);
    }

    public Page<T> lastPage() {
        return toPage(getTotalPages() - 1);
    }

    public Page<T> previousPage() {
        return toPage(pageNumber - 1);
    }

    public Page<T> nextPage() {
        return toPage(pageNumber + 1);
    }

    public Page<T> toPage(int page) {
        if (page < 0) {
            page = 0;
        } else if (page >= getTotalPages()) {
            page = getTotalPages() - 1;
        }

        int totalElements = getNumberOfElements();
        int startIndex = page * pageSize;
        if (startIndex > totalElements) {
            startIndex = totalElements;
        }

        int count = startIndex + pageSize;
        if (count > totalElements) {
            count = totalElements;
        }

        pageChanged = page != pageNumber;
        pageNumber = page;
        List<T> subElements = subList(startIndex, count);
        currentPage = Page.of(subElements, pageSize);

        return currentPage;
    }

    public Page<T> getCurrentPage() {
        return currentPage;
    }

    public int getCurrentPageNumber() {
        return pageNumber;
    }

    public boolean isPageChanged() {
        return pageChanged;
    }

    public int firstRowNumber() {
        return (pageNumber * pageSize) + 1;
    }

    public int lastRowNumber() {
        int currentSize = getContent().size();
        return currentSize < pageSize ? getNumberOfElements() : (pageNumber + 1) * currentSize;
    }

    public List<T> getContent() {
        return getCurrentPage().getContent();
    }

    public int getPageSize() {
        return pageSize;
    }

    public int getNumberOfElements() {
        return size();
    }

    public int getTotalPages() {
        double pages = (double) getNumberOfElements() / (double) getPageSize();
        int pagesInt = (int) pages;

        if (pages > pagesInt)
            pagesInt++;

        return pagesInt;
    }
}