/*
    * SPDX-FileCopyrightText: Copyright (c) 2011-2026 Yegor Bugayenko
    * SPDX-License-Identifier: MIT
    */
   package com.qulice.checkstyle;
   
   import com.jcabi.log.Logger;
   import com.puppycrawl.tools.checkstyle.Checker;
   import com.puppycrawl.tools.checkstyle.ConfigurationLoader;
  import com.puppycrawl.tools.checkstyle.DefaultConfiguration;
  import com.puppycrawl.tools.checkstyle.PropertiesExpander;
  import com.puppycrawl.tools.checkstyle.api.AuditEvent;
  import com.puppycrawl.tools.checkstyle.api.CheckstyleException;
  import com.puppycrawl.tools.checkstyle.api.Configuration;
  import com.qulice.spi.Environment;
  import com.qulice.spi.Ignored;
  import com.qulice.spi.Relative;
  import com.qulice.spi.ResourceValidator;
  import com.qulice.spi.Violation;
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.Locale;
  import java.util.Properties;
  import java.util.Set;
  import org.xml.sax.InputSource;
  
  /**
   * Validator with Checkstyle.
   *
   * @since 0.3
   */
  public final class CheckstyleValidator implements ResourceValidator {
  
      /**
       * Extensions of files that are passed to Checkstyle. These match the
       * file extensions referenced by checks in {@code checks.xml}. Checkstyle
       * itself filters further based on each module's {@code fileExtensions}.
       */
      private static final Set<String> EXTENSIONS = Set.of(
          "java", "txt", "xml", "xsl", "xsd", "properties", "groovy", "vm",
          "mf", "sh", "sql", "tokens", "g", "spec", "css", "csv", "js", "json",
          "md", "yml", "yaml", "gradle", "dtd", "scss", "html"
      );
  
      /**
       * Checks that suggest fixes relying on Java language features not
       * available under {@code -source 8}/{@code -target 8} (and other
       * pre-14 levels). Such a check must be stripped from the configuration
       * when the project targets an older Java, otherwise it recommends code
       * that fails to compile. {@code UseEnhancedSwitch} suggests arrow-switch
       * syntax, which is a Java 14+ feature (see #1694).
       */
      private static final Set<String> MODERN = Set.of("UseEnhancedSwitch");
  
      /**
       * The minimum Java source level at which the {@link #MODERN} checks are
       * applicable. Below this, they are removed from the configuration.
       */
      private static final int MINIMUM = 14;
  
      /**
       * Checkstyle checker.
       */
      private final Checker checker;
  
      /**
       * Listener of checkstyle messages.
       */
      private final CheckstyleListener listener;
  
      /**
       * Environment to use.
       */
      private final Environment env;
  
      /**
       * Constructor.
       *
       * @param env Environment to use
       */
      public CheckstyleValidator(final Environment env) {
          this.env = env;
          this.checker = new Checker();
          this.listener = new CheckstyleListener(this.env);
      }
  
      @Override
      public Collection<Violation> validate(final Collection<File> files) {
          this.checker.setModuleClassLoader(
              Thread.currentThread().getContextClassLoader()
          );
          try {
              this.checker.configure(this.configuration());
          } catch (final CheckstyleException ex) {
              throw new IllegalStateException("Failed to configure checker", ex);
         }
         this.checker.addListener(this.listener);
         final List<File> sources = this.getNonExcludedFiles(files);
         final Collection<Violation> results = new ArrayList<>(0);
         if (sources.isEmpty()) {
             Logger.debug(
                 this,
                 "No files to check with Checkstyle, all %d are excluded",
                 files.size()
             );
         } else {
             try {
                 Logger.debug(this, "Checkstyle processing %d files", sources.size());
                 this.checker.process(sources);
                 Logger.debug(this, "Checkstyle processed %d files", sources.size());
             } catch (final CheckstyleException ex) {
                 throw new IllegalStateException("Failed to process files", ex);
             }
             for (final AuditEvent event : this.listener.events()) {
                 final String check = event.getSourceName();
                 results.add(
                     new Violation.Default(
                         this.name(),
                         check.substring(check.lastIndexOf('.') + 1),
                         event.getFileName(),
                         String.valueOf(event.getLine()),
                         event.getMessage()
                     )
                 );
             }
             results.addAll(
                 new UnusedSuppressions(this.env).validate(this.listener.processed())
             );
         }
         return results;
     }
 
     @Override public String name() {
         return "Checkstyle";
     }
 
     @Override
     public int rules() {
         return CheckstyleValidator.count(this.configuration());
     }
 
     /**
      * Filters out excluded files from further validation.
      *
      * @param files Files to validate
      * @return List of relevant files
      */
     public List<File> getNonExcludedFiles(final Collection<File> files) {
         final List<File> relevant = new ArrayList<>(files.size());
         for (final File file : files) {
             final String name = new Relative(this.env.basedir(), file).path();
             if (this.env.exclude("checkstyle", name)) {
                 continue;
             }
             if (new Ignored(name).yes()) {
                 continue;
             }
             final int dot = name.lastIndexOf('.');
             if (dot < 0) {
                 continue;
             }
             final String ext = name.substring(dot + 1).toLowerCase(Locale.ROOT);
             if (!CheckstyleValidator.EXTENSIONS.contains(ext)) {
                 continue;
             }
             relevant.add(file);
         }
         return relevant;
     }
 
     private Configuration configuration() {
         final File cache =
             new File(this.env.tempdir(), "checkstyle/checkstyle.cache");
         final File parent = cache.getParentFile();
         if (!parent.exists() && !parent.mkdirs()) {
             throw new IllegalStateException(
                 String.format(
                     "Unable to create directories needed for %s",
                     cache.getPath()
                 )
             );
         }
         if (!parent.canWrite()) {
             throw new IllegalStateException(
                 String.format(
                     "Cannot write to %s, check filesystem permissions",
                     parent.getAbsolutePath()
                 )
             );
         }
         final Properties props = new Properties();
         props.setProperty("cache.file", cache.getPath());
         final Configuration config;
         try (InputStream stream = this.getClass().getResourceAsStream("checks.xml")) {
             if (stream == null) {
                 throw new IllegalStateException(
                     "Checkstyle configuration file 'checks.xml' not found in classpath."
                 );
             }
             config = ConfigurationLoader.loadConfiguration(
                 new InputSource(stream),
                 new PropertiesExpander(props),
                 ConfigurationLoader.IgnoredModulesOptions.OMIT
             );
         } catch (final CheckstyleException | IOException ex) {
             throw new IllegalStateException("Failed to load config", ex);
         }
         if (this.level() < CheckstyleValidator.MINIMUM) {
             CheckstyleValidator.strip(config, CheckstyleValidator.MODERN);
         }
         return config;
     }
 
     private int level() {
         int level = CheckstyleValidator.parse(
             this.env.param("maven.compiler.release", "")
         );
         if (level < 0) {
             level = CheckstyleValidator.parse(
                 this.env.param("maven.compiler.source", "")
             );
         }
         final int result;
         if (level < 0) {
             result = CheckstyleValidator.MINIMUM - 1;
         } else {
             result = level;
         }
         return result;
     }
 
     private static int parse(final String value) {
         int result = -1;
         if (value != null) {
             String txt = value.trim();
             if (txt.startsWith("1.")) {
                 txt = txt.substring(2);
             }
             try {
                 result = Integer.parseInt(txt);
             } catch (final NumberFormatException ex) {
                 result = -1;
             }
         }
         return result;
     }
 
     private static int count(final Configuration config) {
         int total = 0;
         for (final Configuration child : config.getChildren()) {
             final String name = child.getName();
             if (child.getChildren().length > 0) {
                 total += CheckstyleValidator.count(child);
             } else if (!name.endsWith("Filter") && !name.endsWith("Holder")) {
                 total += 1;
             }
         }
         return total;
     }
 
     private static void strip(final Configuration config,
         final Set<String> names) {
         for (final Configuration child : config.getChildren()) {
             final String name = child.getName();
             final String simple = name.substring(name.lastIndexOf('.') + 1);
             if (names.contains(simple)) {
                 ((DefaultConfiguration) config).removeChild(child);
             } else {
                 CheckstyleValidator.strip(child, names);
             }
         }
     }
 }