////////////////////////////////////////////////////////////////////////////////
   // 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.design;
  
  import com.puppycrawl.tools.checkstyle.StatelessCheck;
  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  
  /**
   * <p>
   * Restricts throws statements to a specified count (default = 4).
   * Methods with "Override" or "java.lang.Override" annotation are skipped
   * from validation as current class cannot change signature of these methods.
   * </p>
   * <p>
   * Rationale:
   * Exceptions form part of a methods interface. Declaring
   * a method to throw too many differently rooted
   * exceptions makes exception handling onerous and leads
   * to poor programming practices such as catch
   * (Exception). 4 is the empirical value which is based
   * on reports that we had for the ThrowsCountCheck over big projects
   * such as OpenJDK. This check also forces developers to put exceptions
   * into a hierarchy such that in the simplest
   * case, only one type of exception need be checked for by
   * a caller but allows any sub-classes to be caught
   * specifically if necessary. For more information on rules
   * for the exceptions and their issues, see Effective Java:
   * Programming Language Guide Second Edition
   * by Joshua Bloch pages 264-273.
   * </p>
   * <p>
   * <b>ignorePrivateMethods</b> - allows to skip private methods as they do
   * not cause problems for other classes.
   * </p>
   */
  @StatelessCheck
  public final class ThrowsCountCheck extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "throws.count";
  
      /** Default value of max property. */
      private static final int DEFAULT_MAX = 4;
  
      /** Whether private methods must be ignored. **/
      private boolean ignorePrivateMethods = true;
  
      /** Maximum allowed throws statements. */
      private int max;
  
      /** Creates new instance of the check. */
      public ThrowsCountCheck() {
          max = DEFAULT_MAX;
      }
  
      @Override
      public int[] getDefaultTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return new int[] {
              TokenTypes.LITERAL_THROWS,
          };
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return getRequiredTokens();
      }
  
      /**
       * Sets whether private methods must be ignored.
       * @param ignorePrivateMethods whether private methods must be ignored.
       */
      public void setIgnorePrivateMethods(boolean ignorePrivateMethods) {
         this.ignorePrivateMethods = ignorePrivateMethods;
     }
 
     /**
      * Setter for max property.
      * @param max maximum allowed throws statements.
      */
     public void setMax(int max) {
         this.max = max;
     }
 
     @Override
     public void visitToken(DetailAST ast) {
         if (ast.getType() == TokenTypes.LITERAL_THROWS) {
             visitLiteralThrows(ast);
         }
         else {
             throw new IllegalStateException(ast.toString());
         }
     }
 
     /**
      * Checks number of throws statements.
      * @param ast throws for check.
      */
     private void visitLiteralThrows(DetailAST ast) {
         if ((!ignorePrivateMethods || !isInPrivateMethod(ast))
                 && !isOverriding(ast)) {
             // Account for all the commas!
             final int count = (ast.getChildCount() + 1) / 2;
             if (count > max) {
                 log(ast, MSG_KEY, count, max);
             }
         }
     }
 
     /**
      * Check if a method has annotation @Override.
      * @param ast throws, which is being checked.
      * @return true, if a method has annotation @Override.
      */
     private static boolean isOverriding(DetailAST ast) {
         final DetailAST modifiers = ast.getParent().findFirstToken(TokenTypes.MODIFIERS);
         boolean isOverriding = false;
         DetailAST child = modifiers.getFirstChild();
         while (child != null) {
             if (child.getType() == TokenTypes.ANNOTATION
                     && "Override".equals(getAnnotationName(child))) {
                 isOverriding = true;
                 break;
             }
             child = child.getNextSibling();
         }
         return isOverriding;
     }
 
     /**
      * Gets name of an annotation.
      * @param annotation to get name of.
      * @return name of an annotation.
      */
     private static String getAnnotationName(DetailAST annotation) {
         final DetailAST dotAst = annotation.findFirstToken(TokenTypes.DOT);
         final String name;
         if (dotAst == null) {
             name = annotation.findFirstToken(TokenTypes.IDENT).getText();
         }
         else {
             name = dotAst.findFirstToken(TokenTypes.IDENT).getText();
         }
         return name;
     }
 
     /**
      * Checks if method, which throws an exception is private.
      * @param ast throws, which is being checked.
      * @return true, if method, which throws an exception is private.
      */
     private static boolean isInPrivateMethod(DetailAST ast) {
         final DetailAST methodModifiers = ast.getParent().findFirstToken(TokenTypes.MODIFIERS);
         return methodModifiers.findFirstToken(TokenTypes.LITERAL_PRIVATE) != null;
     }
 
 }