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Objectos Way allows you to build full-stack web applications using only Java.

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/*
 * Copyright (C) 2023-2024 Objectos Software LTDA.
 *
 * 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 objectos.way;

final record WebPaginator(Http.RequestTarget request, Sql.Page page, int firstItem, int lastItem, int totalCount, int previousPage, int nextPage) implements Web.Paginator {

  public static WebPaginator of(Http.RequestTarget request, String pageAttrName, int pageSize, int totalCount) {
    int pageNumber;
    pageNumber = request.queryParamAsInt(pageAttrName, 1);

    int previousPage;
    previousPage = pageNumber - 1;

    int nextPage;
    nextPage = pageNumber > 0 ? pageNumber + 1 : 2;

    int firstItem;
    firstItem = 1;

    int lastItem;
    lastItem = pageSize;

    if (pageNumber > 0) {
      int zeroBasedNumber;
      zeroBasedNumber = pageNumber - 1;

      firstItem = zeroBasedNumber * pageSize + 1;

      lastItem = firstItem + pageSize - 1;
    }

    if (lastItem >= totalCount) {
      lastItem = totalCount;

      nextPage = 0;
    }

    Sql.Page page;
    page = Sql.createPage(pageNumber, pageSize);

    return new WebPaginator(request, page, firstItem, lastItem, totalCount, previousPage, nextPage);
  }

  @Override
  public final boolean hasPrevious() {
    return previousPage > 0;
  }

  @Override
  public final boolean hasNext() {
    return nextPage > 0;
  }

  @Override
  public final String previousHref() {
    return hasPrevious() ? pageHref(previousPage) : "#";
  }

  @Override
  public final String nextHref() {
    return hasNext() ? pageHref(nextPage) : "#";
  }

  private String pageHref(int page) {
    String value;
    value = Integer.toString(page);

    if (request instanceof HttpExchange line) {
      return line.rawValue("page", value);
    } else {
      throw new UnsupportedOperationException("Implement me");
    }
  }

}