code: ///////////////////////////////////////////////////////////////////////////////////////////////
  // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
  // Copyright (C) 2001-2023 the original author or authors.
  //
  // This library 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 2.1 of the License, or (at your option) any later version.
  //
  // This library 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 this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle.filters;
  
  import static com.google.common.truth.Truth.assertWithMessage;
  import static com.puppycrawl.tools.checkstyle.checks.naming.AbstractNameCheck.MSG_INVALID_PATTERN;
  import static org.junit.jupiter.api.Assumptions.assumeTrue;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.HttpURLConnection;
  import java.net.URL;
  
  import org.junit.jupiter.api.Test;
  import org.junit.jupiter.api.io.TempDir;
  
  import com.puppycrawl.tools.checkstyle.AbstractModuleTestSupport;
  import com.puppycrawl.tools.checkstyle.DefaultConfiguration;
  import com.puppycrawl.tools.checkstyle.api.AuditEvent;
  import com.puppycrawl.tools.checkstyle.api.CheckstyleException;
  import com.puppycrawl.tools.checkstyle.api.SeverityLevel;
  import com.puppycrawl.tools.checkstyle.api.Violation;
  import com.puppycrawl.tools.checkstyle.checks.naming.ConstantNameCheck;
  import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
  
  public class SuppressionFilterTest extends AbstractModuleTestSupport {
  
      @TempDir
      public File temporaryFolder;
  
      @Override
      protected String getPackageLocation() {
          return "com/puppycrawl/tools/checkstyle/filters/suppressionfilter";
      }
  
      @Test
      public void testAccept() throws Exception {
          final String fileName = getPath("InputSuppressionFilterNone.xml");
          final boolean optional = false;
          final SuppressionFilter filter = createSuppressionFilter(fileName, optional);
  
          final AuditEvent ev = new AuditEvent(this, "ATest.java", null);
  
          assertWithMessage("Audit event should be excepted when there are no suppressions")
                  .that(filter.accept(ev))
                  .isTrue();
      }
  
      @Test
      public void testAcceptFalse() throws Exception {
          final String fileName = getPath("InputSuppressionFilterSuppress.xml");
          final boolean optional = false;
          final SuppressionFilter filter = createSuppressionFilter(fileName, optional);
  
          final Violation message = new Violation(1, 1, null, "msg", null,
                  SeverityLevel.ERROR, null, getClass(), null);
          final AuditEvent ev = new AuditEvent(this, "ATest.java", message);
  
          assertWithMessage("Audit event should be rejected when there is a matching suppression")
                  .that(filter.accept(ev))
                  .isFalse();
      }
  
      @Test
      public void testAcceptOnNullFile() throws CheckstyleException {
          final String fileName = null;
          final boolean optional = false;
          final SuppressionFilter filter = createSuppressionFilter(fileName, optional);
  
          final AuditEvent ev = new AuditEvent(this, "AnyJava.java", null);
          assertWithMessage("Audit event on null file should be excepted, but was not")
                  .that(filter.accept(ev))
                  .isTrue();
      }
  
      @Test
      public void testNonExistentSuppressionFileWithFalseOptional() {
          final String fileName = "non_existent_suppression_file.xml";
          try {
              final boolean optional = false;
              createSuppressionFilter(fileName, optional);
              assertWithMessage("Exception is expected").fail();
          }
          catch (CheckstyleException ex) {
              assertWithMessage("Invalid error message")
                  .that(ex.getMessage())
                  .isEqualTo("Unable to find: " + fileName);
          }
      }
  
      @Test
      public void testExistingInvalidSuppressionFileWithTrueOptional() throws IOException {
          final String fileName = getPath("InputSuppressionFilterInvalidFile.xml");
          try {
              final boolean optional = true;
              createSuppressionFilter(fileName, optional);
              assertWithMessage("Exception is expected").fail();
          }
          catch (CheckstyleException ex) {
              assertWithMessage("Invalid error message")
                  .that(ex.getMessage())
                  .isEqualTo("Unable to parse " + fileName
                          + " - invalid files or checks or message format");
          }
      }
  
      @Test
      public void testExistingSuppressionFileWithTrueOptional() throws Exception {
          final String fileName = getPath("InputSuppressionFilterNone.xml");
          final boolean optional = true;
          final SuppressionFilter filter = createSuppressionFilter(fileName, optional);
  
          final AuditEvent ev = new AuditEvent(this, "AnyFile.java", null);
  
          assertWithMessage("Suppression file with true optional was not accepted")
                  .that(filter.accept(ev))
                  .isTrue();
      }
  
      @Test
      public void testNonExistentSuppressionFileWithTrueOptional() throws Exception {
          final String fileName = "non_existent_suppression_file.xml";
          final boolean optional = true;
          final SuppressionFilter filter = createSuppressionFilter(fileName, optional);
  
          final AuditEvent ev = new AuditEvent(this, "AnyFile.java", null);
  
          assertWithMessage("Should except event when suppression file does not exist")
                  .that(filter.accept(ev))
                  .isTrue();
      }
  
      @Test
      public void testNonExistentSuppressionUrlWithTrueOptional() throws Exception {
          final String fileName =
                  "https://checkstyle.org/non_existent_suppression.xml";
          final boolean optional = true;
          final SuppressionFilter filter = createSuppressionFilter(fileName, optional);
  
          final AuditEvent ev = new AuditEvent(this, "AnyFile.java", null);
  
          assertWithMessage("Should except event when suppression file url does not exist")
                  .that(filter.accept(ev))
                  .isTrue();
      }
  
      @Test
      public void testUseCacheLocalFileExternalResourceContentDoesNotChange() throws Exception {
          final DefaultConfiguration filterConfig = createModuleConfig(SuppressionFilter.class);
          filterConfig.addProperty("file", getPath("InputSuppressionFilterNone.xml"));
  
          final DefaultConfiguration checkerConfig = createRootConfig(filterConfig);
          final File cacheFile = File.createTempFile("junit", null, temporaryFolder);
          checkerConfig.addProperty("cacheFile", cacheFile.getPath());
  
          final String filePath = File.createTempFile("file", ".java", temporaryFolder).getPath();
  
          execute(checkerConfig, filePath);
          // One more time to use cache.
          execute(checkerConfig, filePath);
      }
  
      @Test
      public void testUseCacheRemoteFileExternalResourceContentDoesNotChange() throws Exception {
          final String[] urlCandidates = {
              "https://checkstyle.org/files/suppressions_none.xml",
              "https://raw.githubusercontent.com/checkstyle/checkstyle/master/src/site/resources/"
                  + "files/suppressions_none.xml",
          };
  
          String urlForTest = null;
          for (String url : urlCandidates) {
              if (isConnectionAvailableAndStable(url)) {
                  urlForTest = url;
                  break;
              }
          }
  
          assumeTrue(urlForTest != null, "No Internet connection.");
          final DefaultConfiguration firstFilterConfig = createModuleConfig(SuppressionFilter.class);
          // -@cs[CheckstyleTestMakeup] need to test dynamic property
          firstFilterConfig.addProperty("file", urlForTest);
  
          final DefaultConfiguration firstCheckerConfig = createRootConfig(firstFilterConfig);
          final File cacheFile = File.createTempFile("junit", null, temporaryFolder);
          firstCheckerConfig.addProperty("cacheFile", cacheFile.getPath());
  
          final String pathToEmptyFile =
                  File.createTempFile("file", ".java", temporaryFolder).getPath();
  
          execute(firstCheckerConfig, pathToEmptyFile);
  
          // One more time to use cache.
          final DefaultConfiguration secondFilterConfig =
              createModuleConfig(SuppressionFilter.class);
          // -@cs[CheckstyleTestMakeup] need to test dynamic property
          secondFilterConfig.addProperty("file", urlForTest);
  
          final DefaultConfiguration secondCheckerConfig = createRootConfig(secondFilterConfig);
          secondCheckerConfig.addProperty("cacheFile", cacheFile.getPath());
  
          execute(secondCheckerConfig, pathToEmptyFile);
      }
  
      private static boolean isConnectionAvailableAndStable(String url) throws Exception {
          boolean available = false;
  
          if (isUrlReachable(url)) {
              final int attemptLimit = 5;
              int attemptCount = 0;
  
              while (attemptCount <= attemptLimit) {
                  try (InputStream stream = new URL(url).openStream()) {
                      // Attempt to read a byte in order to check whether file content is available
                      available = stream.read() != -1;
                      break;
                  }
                  catch (IOException ex) {
                      // for some reason Travis CI failed sometimes (unstable) on reading the file
                      if (attemptCount < attemptLimit && ex.getMessage().contains("Unable to read")) {
                          attemptCount++;
                          available = false;
                          // wait for bad / disconnection time to pass
                          Thread.sleep(1000);
                      }
                      else {
                          throw ex;
                      }
                  }
              }
          }
          return available;
      }
  
      private static boolean isUrlReachable(String url) {
          boolean result = true;
          try {
              final URL verifiableUrl = new URL(url);
              final HttpURLConnection urlConnect = (HttpURLConnection) verifiableUrl.openConnection();
              urlConnect.getContent();
          }
          catch (IOException ignored) {
              result = false;
          }
          return result;
      }
  
      private static SuppressionFilter createSuppressionFilter(String fileName, boolean optional)
              throws CheckstyleException {
          final SuppressionFilter suppressionFilter = new SuppressionFilter();
          suppressionFilter.setFile(fileName);
          suppressionFilter.setOptional(optional);
          suppressionFilter.finishLocalSetup();
          return suppressionFilter;
      }
  
      @Test
      public void testXpathSuppression() throws Exception {
          for (int test = 1; test <= 6; test++) {
              final String pattern = "^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$";
              final String[] expected = {
                  "19:29: " + getCheckMessage(ConstantNameCheck.class, MSG_INVALID_PATTERN,
                          "different_name_than_suppression", pattern),
              };
              final String[] suppressed = CommonUtil.EMPTY_STRING_ARRAY;
              final String path = "InputSuppressionFilter" + test + ".java";
              verifyFilterWithInlineConfigParser(getPath(path),
                      expected, suppressed);
          }
      }
  }
  