# RulesTracing.java

    /*
    ** Module   : RulesTracing.java
    ** Abstract : Class implementing rules tracing.
    **
    ** Copyright (c) 2016-2017, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ---------------------------------Description----------------------------------
    ** 001 HC  20160907 Created initial version.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program 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 Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
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    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
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    **
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    */
    package com.goldencode.p2j.pattern;

    import com.goldencode.ast.*;

    import java.util.*;

    /**
     * The class implements support for simple tracing of rules processing.
     * <p>
     * When tracing is active all {@link Rule} instances originating from rules xml files are created
     * with additional tracing information - the rules file and line number each rule is defined on.
     * Also all {@link AnnotatedAst} nodes created as the result of processing of the individual
     * rules are annotated with the positional information.
     * <p>
     * To turn tracing ON the Java property "rules.tracing" must be defined (for example with the
     * -D param on the command line when the Java process is started).
     */
    public class RulesTracing
    {
       /**
        * Flag to indicate whether tracing is ON.
        */
       public static final boolean isOn = System.getProperty("rules.tracing") != null;

       /**
        * The stack of rule processing locations.
        **/
       private static ThreadLocal<Stack<Location>> locationStack =
               ThreadLocal.withInitial(() -> new Stack<Location>());

       /**
        * Flag preventing infinite recursion.
        */
       private static ThreadLocal<Boolean> annotating = new ThreadLocal<>();

       /**
        * Annotation key suffix.
        */
       private static final String ANNOTATION_SUFFIX = "ByRule";

       /**
        * Pushes positional information on the stack.
        *
        * @param file File name.
        * @param line Line number.
        */
       public static void pushLocation(String file, int line)
       {
          locationStack.get().push(new Location(file, line));
       }

       /**
        * Pops positional information from the stack.
        *
        * @return The popped location.
        */
       public static Location popLocation()
       {
          return locationStack.get().pop();
       }

       /**
        * Peeks the positional information currently on the top of the stack.
        *
        * @return The location on the top of the stack.
        */
       public static Location peekLocation()
       {
          Stack<Location> stack = locationStack.get();
          return stack.isEmpty() ? null : stack.peek();
       }

       /**
        * Annotates the passed in node instance with positional information currently on the top of
        * the stack.
        *
        * @param ast A valid syntax tree node instance to annotate.
        */
       public static void putCreateLocation(AnnotatedAst ast)
       {
          // prevent recursion on the thread
          if (Boolean.TRUE.equals(annotating.get()))
          {
             return;
          }

          Location loc = peekLocation();
          if (loc == null)
          {
             // no location being recorded, nothing to do
             return;
          }

          try
          {
             annotating.set(Boolean.TRUE);
             ast.putAnnotation(ANNOTATION_SUFFIX, formatLocation(loc));
          }
          finally
          {
             annotating.remove();
          }
       }

       /**
        * Annotates the passed in node instance with positional information currently on the top of
        * the stack. The positional information is subjected to the passed in annotation name.
        *
        * @param ast            A valid syntax tree node instance to annotate.
        * @param annotationName A valid annotation name.
        */
       public static void putCreateLocation(AnnotatedAst ast, String annotationName)
       {
          // prevent recursion on the thread
          if (Boolean.TRUE.equals(annotating.get()))
          {
             return;
          }

          Location loc = peekLocation();
          if (loc == null)
          {
             return;
          }

          try
          {
             annotating.set(Boolean.TRUE);
             ast.putAnnotation(annotationName + "-" + ANNOTATION_SUFFIX, formatLocation(loc));
          }
          finally
          {
             annotating.remove();
          }
       }

       /**
        * Remover the tracing annotation from the passed in node instance.
        *
        * @param ast
        *        A valid syntax tree node instance to annotate.
        * @param annotationName
        *        A valid annotation name.
        */
       public static void removeCreateLocation(AnnotatedAst ast, String annotationName)
       {
          // prevent recursion on the thread
          if (Boolean.TRUE.equals(annotating.get()))
          {
             return;
          }

          try
          {
             annotating.set(Boolean.TRUE);
             ast.removeAnnotation(annotationName + "-" + ANNOTATION_SUFFIX);
          }
          finally
          {
             annotating.remove();
          }
       }

       /**
        * Returns the formatted string of the passed in location.
        *
        * @param loc A valid location.
        * @return See above.
        */
       private static String formatLocation(Location loc)
       {
          return loc.file + ":" + loc.line;
       }

       /**
        * Holds the positional information.
        */
       public static class Location
       {
          /**
           * Ctor.
           *
           * @param file A valid file name.
           * @param line A valid line number.
           */
          public Location(String file, int line)
          {
             this.file = file;
             this.line = line;
          }

          /**
           * File name.
           */
          public String file;

          /**
           * File number.
           */
          public int line;
       }
    }