/*
 * Copyright (C) 2000 - 2026 Silverpeas
 *
 * This program 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.
 *
 * As a special exception to the terms and conditions of version 3.0 of
 * the GPL, you may redistribute this Program in connection with Free/Libre
 * Open Source Software ("FLOSS") applications as described in Silverpeas's
 * FLOSS exception.  You should have received a copy of the text describing
 * the FLOSS exception, and it is also available here:
 * "https://www.silverpeas.org/legal/floss_exception.html"
 *
 * This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package org.silverpeas.looks.aurora.matomo;

import org.silverpeas.core.web.look.LookHelper;
import org.silverpeas.kernel.bundle.ResourceLocator;
import org.silverpeas.kernel.bundle.SettingBundle;

import javax.inject.Inject;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

/**
 * Servlet {@link Filter} responsible for injecting the Matomo tracking script into generated JSP
 * pages.
 * <p>
 * The script is dynamically built using a Silverpeas template and enriched with contextual
 * information such as the current user, space and component identifiers.
 * </p>
 * <p>
 * The injection is performed just before the closing {@code </body>} tag of the HTML response.
 * </p>
 */
public class MatomoInjectionFilter implements Filter {

  @Inject
  private TrackableContentProvider contentProvider;

  // Configuration settings related to Matomo integration.
  private SettingBundle settings;

  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
    Filter.super.init(filterConfig);
    this.settings =
        ResourceLocator.getSettingBundle("org.silverpeas.statistics.settings.matomo");
  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {

    // If Matomo tracking is disabled, continue without wrapping the response.
    if (!settings.getBoolean("matomo.enable")) {
      chain.doFilter(request, response);
      return;
    }

    HttpServletRequest httpReq = (HttpServletRequest) request;
    String path = httpReq.getRequestURI();
    String bodyPartJSP = settings.getString("bodypart.jsp");

    // Only process JSP pages and ignore specific technical pages.
    TrackableContent content = contentProvider.get(httpReq);
    boolean isBodyPart = path.contains(bodyPartJSP);
    boolean isTrackableContent = content.isContent();

    if (!isBodyPart && !isTrackableContent) {
      chain.doFilter(request, response);
      return;
    }

    // Wrap the response to capture the generated HTML content.
    ContentResponseWrapper responseWrapper =
        new ContentResponseWrapper((HttpServletResponse) response);
    chain.doFilter(request, responseWrapper);

    // Inject the Matomo script just before the closing </body> tag if present.
    String originalContent = responseWrapper.toString();
    if (originalContent.contains(MatomoInjectionPoints.END_TAG_SCRIPT)) {
      String matomoScript = MatomoScriptBuilder.build((HttpServletRequest) request, content,
          getCurrentUserId((HttpServletRequest) request), settings.getString("matomo.url"),
          settings.getString("matomo.siteId"));
      originalContent = originalContent.replace(MatomoInjectionPoints.END_TAG_SCRIPT,
          MatomoInjectionPoints.END_TAG_SCRIPT + matomoScript);
    }

    // Write the modified content back to the original response output stream.
    byte[] bytes = originalContent.getBytes(response.getCharacterEncoding());
    response.setContentLength(bytes.length);
    response.getOutputStream().write(bytes);
  }

  public String getCurrentUserId(HttpServletRequest request) {
    String userId = "";
    LookHelper helper = getLookHelper(request);
    if (helper != null) userId = helper.getUserId();
    return userId;
  }

  private LookHelper getLookHelper(HttpServletRequest request) {
    if (request == null) return null;
    HttpSession session = request.getSession(false);
    if (session == null) return null;
    Object attr = session.getAttribute("Silverpeas_LookHelper");
    if (attr == null) return null;
    return (LookHelper) attr;
  }

}
