////////////////////////////////////////////////////////////////////////////////
   // checkstyle: Checks Java source code for adherence to a set of rules.
   // Copyright (C) 2001-2019 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.checks.imports;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.MalformedURLException;
  import java.net.URI;
  import java.util.ArrayDeque;
  import java.util.Deque;
  import java.util.HashMap;
  import java.util.Map;
  
  import javax.xml.parsers.ParserConfigurationException;
  
  import org.xml.sax.Attributes;
  import org.xml.sax.InputSource;
  import org.xml.sax.SAXException;
  
  import com.puppycrawl.tools.checkstyle.XmlLoader;
  import com.puppycrawl.tools.checkstyle.api.CheckstyleException;
  
  /**
   * Responsible for loading the contents of an import control configuration file.
   */
  public final class ImportControlLoader extends XmlLoader {
  
      /** The public ID for the configuration dtd. */
      private static final String DTD_PUBLIC_ID_1_0 =
          "-//Puppy Crawl//DTD Import Control 1.0//EN";
  
      /** The new public ID for version 1_0 of the configuration dtd. */
      private static final String DTD_PUBLIC_CS_ID_1_0 =
          "-//Checkstyle//DTD ImportControl Configuration 1.0//EN";
  
      /** The public ID for the configuration dtd. */
      private static final String DTD_PUBLIC_ID_1_1 =
          "-//Puppy Crawl//DTD Import Control 1.1//EN";
  
      /** The new public ID for version 1_1 of the configuration dtd. */
      private static final String DTD_PUBLIC_CS_ID_1_1 =
          "-//Checkstyle//DTD ImportControl Configuration 1.1//EN";
  
      /** The public ID for the configuration dtd. */
      private static final String DTD_PUBLIC_ID_1_2 =
          "-//Puppy Crawl//DTD Import Control 1.2//EN";
  
      /** The new public ID for version 1_2 of the configuration dtd. */
      private static final String DTD_PUBLIC_CS_ID_1_2 =
          "-//Checkstyle//DTD ImportControl Configuration 1.2//EN";
  
      /** The public ID for the configuration dtd. */
      private static final String DTD_PUBLIC_ID_1_3 =
          "-//Puppy Crawl//DTD Import Control 1.3//EN";
  
      /** The new public ID for version 1_3 of the configuration dtd. */
      private static final String DTD_PUBLIC_CS_ID_1_3 =
          "-//Checkstyle//DTD ImportControl Configuration 1.3//EN";
  
      /** The public ID for the configuration dtd. */
      private static final String DTD_PUBLIC_ID_1_4 =
          "-//Puppy Crawl//DTD Import Control 1.4//EN";
  
      /** The new public ID for version 1_4 of the configuration dtd. */
      private static final String DTD_PUBLIC_CS_ID_1_4 =
          "-//Checkstyle//DTD ImportControl Configuration 1.4//EN";
  
      /** The resource for the configuration dtd. */
      private static final String DTD_RESOURCE_NAME_1_0 =
          "com/puppycrawl/tools/checkstyle/checks/imports/import_control_1_0.dtd";
  
      /** The resource for the configuration dtd. */
      private static final String DTD_RESOURCE_NAME_1_1 =
          "com/puppycrawl/tools/checkstyle/checks/imports/import_control_1_1.dtd";
  
      /** The resource for the configuration dtd. */
      private static final String DTD_RESOURCE_NAME_1_2 =
          "com/puppycrawl/tools/checkstyle/checks/imports/import_control_1_2.dtd";
  
      /** The resource for the configuration dtd. */
      private static final String DTD_RESOURCE_NAME_1_3 =
          "com/puppycrawl/tools/checkstyle/checks/imports/import_control_1_3.dtd";
 
     /** The resource for the configuration dtd. */
     private static final String DTD_RESOURCE_NAME_1_4 =
         "com/puppycrawl/tools/checkstyle/checks/imports/import_control_1_4.dtd";
 
     /** The map to lookup the resource name by the id. */
     private static final Map<String, String> DTD_RESOURCE_BY_ID = new HashMap<>();
 
     /** Name for attribute 'pkg'. */
     private static final String PKG_ATTRIBUTE_NAME = "pkg";
 
     /** Name for attribute 'name'. */
     private static final String NAME_ATTRIBUTE_NAME = "name";
 
     /** Name for attribute 'strategyOnMismatch'. */
     private static final String STRATEGY_ON_MISMATCH_ATTRIBUTE_NAME = "strategyOnMismatch";
 
     /** Value "allowed" for attribute 'strategyOnMismatch'. */
     private static final String STRATEGY_ON_MISMATCH_ALLOWED_VALUE = "allowed";
 
     /** Value "disallowed" for attribute 'strategyOnMismatch'. */
     private static final String STRATEGY_ON_MISMATCH_DISALLOWED_VALUE = "disallowed";
 
     /** Qualified name for element 'subpackage'. */
     private static final String SUBPACKAGE_ELEMENT_NAME = "subpackage";
 
     /** Qualified name for element 'file'. */
     private static final String FILE_ELEMENT_NAME = "file";
 
     /** Qualified name for element 'allow'. */
     private static final String ALLOW_ELEMENT_NAME = "allow";
 
     /** Used to hold the {@link AbstractImportControl} objects. */
     private final Deque<AbstractImportControl> stack = new ArrayDeque<>();
 
     static {
         DTD_RESOURCE_BY_ID.put(DTD_PUBLIC_ID_1_0, DTD_RESOURCE_NAME_1_0);
         DTD_RESOURCE_BY_ID.put(DTD_PUBLIC_ID_1_1, DTD_RESOURCE_NAME_1_1);
         DTD_RESOURCE_BY_ID.put(DTD_PUBLIC_ID_1_2, DTD_RESOURCE_NAME_1_2);
         DTD_RESOURCE_BY_ID.put(DTD_PUBLIC_ID_1_3, DTD_RESOURCE_NAME_1_3);
         DTD_RESOURCE_BY_ID.put(DTD_PUBLIC_ID_1_4, DTD_RESOURCE_NAME_1_4);
         DTD_RESOURCE_BY_ID.put(DTD_PUBLIC_CS_ID_1_0, DTD_RESOURCE_NAME_1_0);
         DTD_RESOURCE_BY_ID.put(DTD_PUBLIC_CS_ID_1_1, DTD_RESOURCE_NAME_1_1);
         DTD_RESOURCE_BY_ID.put(DTD_PUBLIC_CS_ID_1_2, DTD_RESOURCE_NAME_1_2);
         DTD_RESOURCE_BY_ID.put(DTD_PUBLIC_CS_ID_1_3, DTD_RESOURCE_NAME_1_3);
         DTD_RESOURCE_BY_ID.put(DTD_PUBLIC_CS_ID_1_4, DTD_RESOURCE_NAME_1_4);
     }
 
     /**
      * Constructs an instance.
      * @throws ParserConfigurationException if an error occurs.
      * @throws SAXException if an error occurs.
      */
     private ImportControlLoader() throws ParserConfigurationException,
             SAXException {
         super(DTD_RESOURCE_BY_ID);
     }
 
     @Override
     public void startElement(String namespaceUri,
                              String localName,
                              String qName,
                              Attributes attributes)
             throws SAXException {
         if ("import-control".equals(qName)) {
             final String pkg = safeGet(attributes, PKG_ATTRIBUTE_NAME);
             final MismatchStrategy strategyOnMismatch = getStrategyForImportControl(attributes);
             final boolean regex = containsRegexAttribute(attributes);
             stack.push(new PkgImportControl(pkg, regex, strategyOnMismatch));
         }
         else if (SUBPACKAGE_ELEMENT_NAME.equals(qName)) {
             final String name = safeGet(attributes, NAME_ATTRIBUTE_NAME);
             final MismatchStrategy strategyOnMismatch = getStrategyForSubpackage(attributes);
             final boolean regex = containsRegexAttribute(attributes);
             final PkgImportControl parentImportControl = (PkgImportControl) stack.peek();
             final AbstractImportControl importControl = new PkgImportControl(parentImportControl,
                     name, regex, strategyOnMismatch);
             parentImportControl.addChild(importControl);
             stack.push(importControl);
         }
         else if (FILE_ELEMENT_NAME.equals(qName)) {
             final String name = safeGet(attributes, NAME_ATTRIBUTE_NAME);
             final boolean regex = containsRegexAttribute(attributes);
             final PkgImportControl parentImportControl = (PkgImportControl) stack.peek();
             final AbstractImportControl importControl = new FileImportControl(parentImportControl,
                     name, regex);
             parentImportControl.addChild(importControl);
             stack.push(importControl);
         }
         else if (ALLOW_ELEMENT_NAME.equals(qName) || "disallow".equals(qName)) {
             final AbstractImportRule rule = createImportRule(qName, attributes);
             stack.peek().addImportRule(rule);
         }
     }
 
     /**
      * Constructs an instance of an import rule based on the given {@code name} and
      * {@code attributes}.
      * @param qName The qualified name.
      * @param attributes The attributes attached to the element.
      * @return The created import rule.
      * @throws SAXException if an error occurs.
      */
     private static AbstractImportRule createImportRule(String qName, Attributes attributes)
             throws SAXException {
         // Need to handle either "pkg" or "class" attribute.
         // May have "exact-match" for "pkg"
         // May have "local-only"
         final boolean isAllow = ALLOW_ELEMENT_NAME.equals(qName);
         final boolean isLocalOnly = attributes.getValue("local-only") != null;
         final String pkg = attributes.getValue(PKG_ATTRIBUTE_NAME);
         final boolean regex = containsRegexAttribute(attributes);
         final AbstractImportRule rule;
         if (pkg == null) {
             // handle class names which can be normal class names or regular
             // expressions
             final String clazz = safeGet(attributes, "class");
             rule = new ClassImportRule(isAllow, isLocalOnly, clazz, regex);
         }
         else {
             final boolean exactMatch =
                     attributes.getValue("exact-match") != null;
             rule = new PkgImportRule(isAllow, isLocalOnly, pkg, exactMatch, regex);
         }
         return rule;
     }
 
     /**
      * Check if the given attributes contain the regex attribute.
      * @param attributes the attributes.
      * @return if the regex attribute is contained.
      */
     private static boolean containsRegexAttribute(Attributes attributes) {
         return attributes.getValue("regex") != null;
     }
 
     @Override
     public void endElement(String namespaceUri, String localName,
         String qName) {
         if (SUBPACKAGE_ELEMENT_NAME.equals(qName) || FILE_ELEMENT_NAME.equals(qName)) {
             stack.pop();
         }
     }
 
     /**
      * Loads the import control file from a file.
      * @param uri the uri of the file to load.
      * @return the root {@link PkgImportControl} object.
      * @throws CheckstyleException if an error occurs.
      */
     public static PkgImportControl load(URI uri) throws CheckstyleException {
         try (InputStream inputStream = uri.toURL().openStream()) {
             final InputSource source = new InputSource(inputStream);
             return load(source, uri);
         }
         catch (MalformedURLException ex) {
             throw new CheckstyleException("syntax error in url " + uri, ex);
         }
         catch (IOException ex) {
             throw new CheckstyleException("unable to find " + uri, ex);
         }
     }
 
     /**
      * Loads the import control file from a {@link InputSource}.
      * @param source the source to load from.
      * @param uri uri of the source being loaded.
      * @return the root {@link PkgImportControl} object.
      * @throws CheckstyleException if an error occurs.
      */
     private static PkgImportControl load(InputSource source,
         URI uri) throws CheckstyleException {
         try {
             final ImportControlLoader loader = new ImportControlLoader();
             loader.parseInputSource(source);
             return loader.getRoot();
         }
         catch (ParserConfigurationException | SAXException ex) {
             throw new CheckstyleException("unable to parse " + uri
                     + " - " + ex.getMessage(), ex);
         }
         catch (IOException ex) {
             throw new CheckstyleException("unable to read " + uri, ex);
         }
     }
 
     /**
      * Returns root PkgImportControl.
      * @return the root {@link PkgImportControl} object loaded.
      */
     private PkgImportControl getRoot() {
         return (PkgImportControl) stack.peek();
     }
 
     /**
      * Utility to get a strategyOnMismatch property for "import-control" tag.
      * @param attributes collect to get attribute from.
      * @return the value of the attribute.
      */
     private static MismatchStrategy getStrategyForImportControl(Attributes attributes) {
         final String returnValue = attributes.getValue(STRATEGY_ON_MISMATCH_ATTRIBUTE_NAME);
         MismatchStrategy strategyOnMismatch = MismatchStrategy.DISALLOWED;
         if (STRATEGY_ON_MISMATCH_ALLOWED_VALUE.equals(returnValue)) {
             strategyOnMismatch = MismatchStrategy.ALLOWED;
         }
         return strategyOnMismatch;
     }
 
     /**
      * Utility to get a strategyOnMismatch property for "subpackage" tag.
      * @param attributes collect to get attribute from.
      * @return the value of the attribute.
      */
     private static MismatchStrategy getStrategyForSubpackage(Attributes attributes) {
         final String returnValue = attributes.getValue(STRATEGY_ON_MISMATCH_ATTRIBUTE_NAME);
         MismatchStrategy strategyOnMismatch = MismatchStrategy.DELEGATE_TO_PARENT;
         if (STRATEGY_ON_MISMATCH_ALLOWED_VALUE.equals(returnValue)) {
             strategyOnMismatch = MismatchStrategy.ALLOWED;
         }
         else if (STRATEGY_ON_MISMATCH_DISALLOWED_VALUE.equals(returnValue)) {
             strategyOnMismatch = MismatchStrategy.DISALLOWED;
         }
         return strategyOnMismatch;
     }
 
     /**
      * Utility to safely get an attribute. If it does not exist an exception
      * is thrown.
      * @param attributes collect to get attribute from.
      * @param name name of the attribute to get.
      * @return the value of the attribute.
      * @throws SAXException if the attribute does not exist.
      */
     private static String safeGet(Attributes attributes, String name)
             throws SAXException {
         final String returnValue = attributes.getValue(name);
         if (returnValue == null) {
             // -@cs[IllegalInstantiation] SAXException is in the overridden method signature
             // of the only method which calls the current one
             throw new SAXException("missing attribute " + name);
         }
         return returnValue;
     }
 
 }