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Java API for modeling web page content and relationships in a Servlet environment.
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/*
 * semanticcms-core-servlet - Java API for modeling web page content and relationships in a Servlet environment.
 * Copyright (C) 2016, 2017, 2019, 2020, 2021, 2022  AO Industries, Inc.
 *     [email protected]
 *     7262 Bull Pen Cir
 *     Mobile, AL 36695
 *
 * This file is part of semanticcms-core-servlet.
 *
 * semanticcms-core-servlet is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * semanticcms-core-servlet 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with semanticcms-core-servlet.  If not, see .
 */

package com.semanticcms.core.servlet;

import com.aoapps.net.URIDecoder;
import com.aoapps.servlet.http.HttpServletUtil;
import com.semanticcms.core.model.Book;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;

/**
 * Utilities for working with books.
 */
public final class BookUtils {

  /** Make no instances. */
  private BookUtils() {
    throw new AssertionError();
  }

  private static final Logger logger = Logger.getLogger(BookUtils.class.getName());

  /**
   * Optional initialization parameter providing the canonical base URL.
   */
  private static final String CANONICAL_BASE_WARNED_ATTRIBUTE = BookUtils.class.getName() + ".getCanonicalBase.autoWarned.";

  /**
   * Gets the canonical base URL, not including any trailing slash, such as
   * https://example.com
   * This is configured in the book via the "canonicalBase" setting.
   * 
   * TODO: Create central per-request warnings list that could be reported during development mode, include this warning on requests.
   * TODO: Also could use that for broken link detection instead of throwing exceptions.
   * 
   */
  public static String getCanonicalBase(ServletContext servletContext, HttpServletRequest request, Book book) {
    String canonicalBase = book.getCanonicalBase();
    if (canonicalBase == null) {
      String autoCanonical = URIDecoder.decodeURI(HttpServletUtil.getAbsoluteURL(request, book.getPathPrefix()));
      if (
          // Logger checked first, so if warnings enabled mid-run, will get first warning still
          logger.isLoggable(Level.WARNING)
      ) {
        String bookName = book.getName();
        String warningAttribute = CANONICAL_BASE_WARNED_ATTRIBUTE + bookName;
        // Acceptable race condition: logging multiple times would not cause any harm
        if (servletContext.getAttribute(warningAttribute) == null) {
          servletContext.setAttribute(warningAttribute, true);
          logger.warning("Using generated canonical base URL, please configure the \"canonicalBase\" setting in the \"" + bookName + "\" book: " + autoCanonical);
        }
      }
      return autoCanonical;
    } else {
      return canonicalBase;
    }
  }
}