////////////////////////////////////////////////////////////////////////////////
   // 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.coding;
  
  import java.util.Arrays;
  import java.util.HashSet;
  import java.util.Set;
  import java.util.stream.Collectors;
  
  import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.FullIdent;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
  
  /**
   * <p>
   * Checks for illegal instantiations where a factory method is preferred.
   * </p>
   * <p>
   * Rationale: Depending on the project, for some classes it might be
   * preferable to create instances through factory methods rather than
   * calling the constructor.
   * </p>
   * <p>
   * A simple example is the {@code java.lang.Boolean} class.
   * For performance reasons, it is preferable to use the predefined constants
   * {@code TRUE} and {@code FALSE}.
   * Constructor invocations should be replaced by calls to {@code Boolean.valueOf()}.
   * </p>
   * <p>
   * Some extremely performance sensitive projects may require the use of factory
   * methods for other classes as well, to enforce the usage of number caches or
   * object pools.
   * </p>
   * <p>
   * There is a limitation that it is currently not possible to specify array classes.
   * </p>
   * <ul>
   * <li>
   * Property {@code classes} - Specify fully qualified class names that should not be instantiated.
   * Default value is {@code {}}.
   * </li>
   * <li>
   * Property {@code tokens} - tokens to check
   * Default value is:
   * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#CLASS_DEF">
   * CLASS_DEF</a>.
   * </li>
   * </ul>
   * <p>
   * To configure the check to find instantiations of {@code java.lang.Boolean}:
   * </p>
   * <pre>
   * &lt;module name=&quot;IllegalInstantiation&quot;&gt;
   *   &lt;property name=&quot;classes&quot; value=&quot;java.lang.Boolean&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   *
   * @since 3.0
   */
  @FileStatefulCheck
  public class IllegalInstantiationCheck
      extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "instantiation.avoid";
  
      /** {@link java.lang} package as string. */
      private static final String JAVA_LANG = "java.lang.";
  
      /** The imports for the file. */
      private final Set<FullIdent> imports = new HashSet<>();
  
      /** The class names defined in the file. */
      private final Set<String> classNames = new HashSet<>();
  
      /** The instantiations in the file. */
     private final Set<DetailAST> instantiations = new HashSet<>();
 
     /** Specify fully qualified class names that should not be instantiated. */
     private Set<String> classes = new HashSet<>();
 
     /** Name of the package. */
     private String pkgName;
 
     @Override
     public int[] getDefaultTokens() {
         return getAcceptableTokens();
     }
 
     @Override
     public int[] getAcceptableTokens() {
         return new int[] {
             TokenTypes.IMPORT,
             TokenTypes.LITERAL_NEW,
             TokenTypes.PACKAGE_DEF,
             TokenTypes.CLASS_DEF,
         };
     }
 
     @Override
     public int[] getRequiredTokens() {
         return new int[] {
             TokenTypes.IMPORT,
             TokenTypes.LITERAL_NEW,
             TokenTypes.PACKAGE_DEF,
         };
     }
 
     @Override
     public void beginTree(DetailAST rootAST) {
         pkgName = null;
         imports.clear();
         instantiations.clear();
         classNames.clear();
     }
 
     @Override
     public void visitToken(DetailAST ast) {
         switch (ast.getType()) {
             case TokenTypes.LITERAL_NEW:
                 processLiteralNew(ast);
                 break;
             case TokenTypes.PACKAGE_DEF:
                 processPackageDef(ast);
                 break;
             case TokenTypes.IMPORT:
                 processImport(ast);
                 break;
             case TokenTypes.CLASS_DEF:
                 processClassDef(ast);
                 break;
             default:
                 throw new IllegalArgumentException("Unknown type " + ast);
         }
     }
 
     @Override
     public void finishTree(DetailAST rootAST) {
         instantiations.forEach(this::postProcessLiteralNew);
     }
 
     /**
      * Collects classes defined in the source file. Required
      * to avoid false alarms for local vs. java.lang classes.
      *
      * @param ast the class def token.
      */
     private void processClassDef(DetailAST ast) {
         final DetailAST identToken = ast.findFirstToken(TokenTypes.IDENT);
         final String className = identToken.getText();
         classNames.add(className);
     }
 
     /**
      * Perform processing for an import token.
      * @param ast the import token
      */
     private void processImport(DetailAST ast) {
         final FullIdent name = FullIdent.createFullIdentBelow(ast);
         // Note: different from UnusedImportsCheck.processImport(),
         // '.*' imports are also added here
         imports.add(name);
     }
 
     /**
      * Perform processing for an package token.
      * @param ast the package token
      */
     private void processPackageDef(DetailAST ast) {
         final DetailAST packageNameAST = ast.getLastChild()
                 .getPreviousSibling();
         final FullIdent packageIdent =
                 FullIdent.createFullIdent(packageNameAST);
         pkgName = packageIdent.getText();
     }
 
     /**
      * Collects a "new" token.
      * @param ast the "new" token
      */
     private void processLiteralNew(DetailAST ast) {
         if (ast.getParent().getType() != TokenTypes.METHOD_REF) {
             instantiations.add(ast);
         }
     }
 
     /**
      * Processes one of the collected "new" tokens when walking tree
      * has finished.
      * @param newTokenAst the "new" token.
      */
     private void postProcessLiteralNew(DetailAST newTokenAst) {
         final DetailAST typeNameAst = newTokenAst.getFirstChild();
         final DetailAST nameSibling = typeNameAst.getNextSibling();
         if (nameSibling.getType() != TokenTypes.ARRAY_DECLARATOR) {
             // ast != "new Boolean[]"
             final FullIdent typeIdent = FullIdent.createFullIdent(typeNameAst);
             final String typeName = typeIdent.getText();
             final String fqClassName = getIllegalInstantiation(typeName);
             if (fqClassName != null) {
                 log(newTokenAst, MSG_KEY, fqClassName);
             }
         }
     }
 
     /**
      * Checks illegal instantiations.
      * @param className instantiated class, may or may not be qualified
      * @return the fully qualified class name of className
      *     or null if instantiation of className is OK
      */
     private String getIllegalInstantiation(String className) {
         String fullClassName = null;
 
         if (classes.contains(className)) {
             fullClassName = className;
         }
         else {
             final int pkgNameLen;
 
             if (pkgName == null) {
                 pkgNameLen = 0;
             }
             else {
                 pkgNameLen = pkgName.length();
             }
 
             for (String illegal : classes) {
                 if (isSamePackage(className, pkgNameLen, illegal)
                         || isStandardClass(className, illegal)) {
                     fullClassName = illegal;
                 }
                 else {
                     fullClassName = checkImportStatements(className);
                 }
 
                 if (fullClassName != null) {
                     break;
                 }
             }
         }
         return fullClassName;
     }
 
     /**
      * Check import statements.
      * @param className name of the class
      * @return value of illegal instantiated type
      */
     private String checkImportStatements(String className) {
         String illegalType = null;
         // import statements
         for (FullIdent importLineText : imports) {
             String importArg = importLineText.getText();
             if (importArg.endsWith(".*")) {
                 importArg = importArg.substring(0, importArg.length() - 1)
                         + className;
             }
             if (CommonUtil.baseClassName(importArg).equals(className)
                     && classes.contains(importArg)) {
                 illegalType = importArg;
                 break;
             }
         }
         return illegalType;
     }
 
     /**
      * Check that type is of the same package.
      * @param className class name
      * @param pkgNameLen package name
      * @param illegal illegal value
      * @return true if type of the same package
      */
     private boolean isSamePackage(String className, int pkgNameLen, String illegal) {
         // class from same package
 
         // the top level package (pkgName == null) is covered by the
         // "illegalInstances.contains(className)" check above
 
         // the test is the "no garbage" version of
         // illegal.equals(pkgName + "." + className)
         return pkgName != null
                 && className.length() == illegal.length() - pkgNameLen - 1
                 && illegal.charAt(pkgNameLen) == '.'
                 && illegal.endsWith(className)
                 && illegal.startsWith(pkgName);
     }
 
     /**
      * Is Standard Class.
      * @param className class name
      * @param illegal illegal value
      * @return true if type is standard
      */
     private boolean isStandardClass(String className, String illegal) {
         boolean isStandardClass = false;
         // class from java.lang
         if (illegal.length() - JAVA_LANG.length() == className.length()
             && illegal.endsWith(className)
             && illegal.startsWith(JAVA_LANG)) {
             // java.lang needs no import, but a class without import might
             // also come from the same file or be in the same package.
             // E.g. if a class defines an inner class "Boolean",
             // the expression "new Boolean()" refers to that class,
             // not to java.lang.Boolean
 
             final boolean isSameFile = classNames.contains(className);
 
             if (!isSameFile) {
                 isStandardClass = true;
             }
         }
         return isStandardClass;
     }
 
     /**
      * Setter to specify fully qualified class names that should not be instantiated.
      * @param names a comma separate list of class names
      */
     public void setClasses(String... names) {
         classes = Arrays.stream(names).collect(Collectors.toSet());
     }
 
 }