package org.codehaus.plexus.util;
   
   /* ====================================================================
    * The Apache Software License, Version 1.1
    *
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    * reserved.
    *
    * Redistribution and use in source and binary forms, with or without
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   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
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   *    any, must include the following acknowledgement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.codehaus.org/)."
   *    Alternately, this acknowledgement may appear in the software itself,
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  import java.io.PrintStream;
  import java.io.PrintWriter;
  import java.io.StringWriter;
  import java.lang.reflect.Field;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.sql.SQLException;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.StringTokenizer;
  
  /**
   * <p>
   * <code>ExceptionUtils</code> provides utilities for manipulating <code>Throwable</code> objects.
   * </p>
   *
   * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
   * @author Dmitri Plotnikov
   * @author Stephen Colebourne
   * @since 1.0
   *
   */
  public class ExceptionUtils {
      /**
       * Used when printing stack frames to denote the start of a wrapped exception. Package private for accessibility by
       * test suite.
       */
      static final String WRAPPED_MARKER = " [wrapped] ";
  
      /**
       * The names of methods commonly used to access a wrapped exception.
       */
      protected static String[] CAUSE_METHOD_NAMES = {
          "getCause",
          "getNextException",
          "getTargetException",
          "getException",
          "getSourceException",
          "getRootCause",
          "getCausedByException",
          "getNested"
     };
 
     /**
      * Constructs a new <code>ExceptionUtils</code>. Protected to discourage instantiation.
      */
     protected ExceptionUtils() {}
 
     /**
      * <p>
      * Adds to the list of method names used in the search for <code>Throwable</code> objects.
      * </p>
      *
      * @param methodName the methodName to add to the list, null and empty strings are ignored
      */
     public static void addCauseMethodName(String methodName) {
         if (methodName != null && methodName.length() > 0) {
             List<String> list = new ArrayList<String>(Arrays.asList(CAUSE_METHOD_NAMES));
             list.add(methodName);
             CAUSE_METHOD_NAMES = list.toArray(new String[0]);
         }
     }
 
     /**
      * <p>
      * Introspects the specified <code>Throwable</code> to obtain the cause.
      * </p>
      * <p>
      * The method searches for methods with specific names that return a <code>Throwable</code> object. This will pick
      * up most wrapping exceptions, including those from JDK 1.4, and The method names can be added to using
      * {@link #addCauseMethodName(String)}. The default list searched for are:
      * </p>
      * <ul>
      * <li><code>getCause()</code>
      * <li><code>getNextException()</code>
      * <li><code>getTargetException()</code>
      * <li><code>getException()</code>
      * <li><code>getSourceException()</code>
      * <li><code>getRootCause()</code>
      * <li><code>getCausedByException()</code>
      * <li><code>getNested()</code>
      * </ul>
      * <p>
      * In the absence of any such method, the object is inspected for a <code>detail</code> field assignable to a
      * <code>Throwable</code>.
      * </p>
      * <p>
      * If none of the above is found, returns <code>null</code>.
      * </p>
      *
      * @param throwable The exception to introspect for a cause.
      * @return The cause of the <code>Throwable</code>.
      * @throws NullPointerException if the throwable is null
      */
     public static Throwable getCause(Throwable throwable) {
         return getCause(throwable, CAUSE_METHOD_NAMES);
     }
 
     /**
      * <p>
      * Introspects the specified <code>Throwable</code> to obtain the cause using a supplied array of method names.
      * </p>
      *
      * @param throwable The exception to introspect for a cause.
      * @param methodNames the methods names to match
      * @return The cause of the <code>Throwable</code>.
      * @throws NullPointerException if the method names array is null or contains null
      * @throws NullPointerException if the throwable is null
      */
     public static Throwable getCause(Throwable throwable, String[] methodNames) {
         Throwable cause = getCauseUsingWellKnownTypes(throwable);
         if (cause == null) {
             for (String methodName : methodNames) {
                 cause = getCauseUsingMethodName(throwable, methodName);
                 if (cause != null) {
                     break;
                 }
             }
 
             if (cause == null) {
                 cause = getCauseUsingFieldName(throwable, "detail");
             }
         }
         return cause;
     }
 
     /**
      * <p>
      * Walks through the exception chain to the last element -- the "root" of the tree -- using
      * {@link #getCause(Throwable)}, and returns that exception.
      * </p>
      *
      * @param throwable the throwable to get the root cause for
      * @return The root cause of the <code>Throwable</code>.
      */
     public static Throwable getRootCause(Throwable throwable) {
         Throwable cause = getCause(throwable);
         if (cause != null) {
             throwable = cause;
             while ((throwable = getCause(throwable)) != null) {
                 cause = throwable;
             }
         }
         return cause;
     }
 
     /**
      * <p>
      * Uses <code>instanceof</code> checks to examine the exception, looking for well known types which could contain
      * chained or wrapped exceptions.
      * </p>
      *
      * @param throwable the exception to examine
      * @return The wrapped exception, or <code>null</code> if not found.
      */
     private static Throwable getCauseUsingWellKnownTypes(Throwable throwable) {
         if (throwable instanceof SQLException) {
             return ((SQLException) throwable).getNextException();
         } else if (throwable instanceof InvocationTargetException) {
             return ((InvocationTargetException) throwable).getTargetException();
         } else {
             return null;
         }
     }
 
     /**
      * <p>
      * Find a throwable by method name.
      * </p>
      *
      * @param throwable the exception to examine
      * @param methodName the name of the method to find and invoke
      * @return The wrapped exception, or <code>null</code> if not found.
      */
     private static Throwable getCauseUsingMethodName(Throwable throwable, String methodName) {
         Method method = null;
         try {
             method = throwable.getClass().getMethod(methodName, null);
         } catch (NoSuchMethodException ignored) {
         } catch (SecurityException ignored) {
         }
 
         if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) {
             try {
                 return (Throwable) method.invoke(throwable, new Object[0]);
             } catch (IllegalAccessException ignored) {
             } catch (IllegalArgumentException ignored) {
             } catch (InvocationTargetException ignored) {
             }
         }
         return null;
     }
 
     /**
      * <p>
      * Find a throwable by field name.
      * </p>
      *
      * @param throwable the exception to examine
      * @param fieldName the name of the attribute to examine
      * @return The wrapped exception, or <code>null</code> if not found.
      */
     private static Throwable getCauseUsingFieldName(Throwable throwable, String fieldName) {
         Field field = null;
         try {
             field = throwable.getClass().getField(fieldName);
         } catch (NoSuchFieldException ignored) {
         } catch (SecurityException ignored) {
         }
 
         if (field != null && Throwable.class.isAssignableFrom(field.getType())) {
             try {
                 return (Throwable) field.get(throwable);
             } catch (IllegalAccessException ignored) {
             } catch (IllegalArgumentException ignored) {
             }
         }
         return null;
     }
 
     /**
      * <p>
      * Returns the number of <code>Throwable</code> objects in the exception chain.
      * </p>
      *
      * @param throwable the exception to inspect
      * @return The throwable count.
      */
     public static int getThrowableCount(Throwable throwable) {
         // Count the number of throwables
         int count = 0;
         while (throwable != null) {
             count++;
             throwable = ExceptionUtils.getCause(throwable);
         }
         return count;
     }
 
     /**
      * <p>
      * Returns the list of <code>Throwable</code> objects in the exception chain.
      * </p>
      *
      * @param throwable the exception to inspect
      * @return The list of <code>Throwable</code> objects.
      */
     public static Throwable[] getThrowables(Throwable throwable) {
         List<Throwable> list = new ArrayList<>();
         while (throwable != null) {
             list.add(throwable);
             throwable = getCause(throwable);
         }
         return list.toArray(new Throwable[0]);
     }
 
     /**
      * <p>
      * Delegates to {@link #indexOfThrowable(Throwable, Class, int)}, starting the search at the beginning of the
      * exception chain.
      * </p>
      * @param throwable the exception to inspect
      * @param type <code>Class</code> to look for
      * @return index of the stack matching the type
      * @see #indexOfThrowable(Throwable, Class, int)
      */
     public static int indexOfThrowable(Throwable throwable, Class type) {
         return indexOfThrowable(throwable, type, 0);
     }
 
     /**
      * <p>
      * Returns the (zero based) index, of the first <code>Throwable</code> that matches the specified type in the
      * exception chain of <code>Throwable</code> objects with an index greater than or equal to the specified index, or
      * <code>-1</code> if the type is not found.
      * </p>
      *
      * @param throwable the exception to inspect
      * @param type <code>Class</code> to look for
      * @param fromIndex the (zero based) index of the starting position in the chain to be searched
      * @return the first occurrence of the type in the chain, or <code>-1</code> if the type is not found
      * @throws IndexOutOfBoundsException If the <code>fromIndex</code> argument is negative or not less than the count
      *             of <code>Throwable</code>s in the chain.
      */
     public static int indexOfThrowable(Throwable throwable, Class type, int fromIndex) {
         if (fromIndex < 0) {
             throw new IndexOutOfBoundsException("Throwable index out of range: " + fromIndex);
         }
         Throwable[] throwables = ExceptionUtils.getThrowables(throwable);
         if (fromIndex >= throwables.length) {
             throw new IndexOutOfBoundsException("Throwable index out of range: " + fromIndex);
         }
         for (int i = fromIndex; i < throwables.length; i++) {
             if (throwables[i].getClass().equals(type)) {
                 return i;
             }
         }
         return -1;
     }
 
     /**
      * Prints a compact stack trace for the root cause of a throwable. The compact stack trace starts with the root
      * cause and prints stack frames up to the place where it was caught and wrapped. Then it prints the wrapped
      * exception and continues with stack frames until the wrapper exception is caught and wrapped again, etc.
      * <p>
      * The method is equivalent to t.printStackTrace() for throwables that don't have nested causes.
      * @param t the exception
      * @param stream the stream
      */
     public static void printRootCauseStackTrace(Throwable t, PrintStream stream) {
         String trace[] = getRootCauseStackTrace(t);
         for (String aTrace : trace) {
             stream.println(aTrace);
         }
         stream.flush();
     }
 
     /**
      * Equivalent to printRootCauseStackTrace(t, System.err)
      * @param t the exception
      */
     public static void printRootCauseStackTrace(Throwable t) {
         printRootCauseStackTrace(t, System.err);
     }
 
     /**
      * Same as printRootCauseStackTrace(t, stream), except it takes a PrintWriter as an argument.
      * @param t the cause
      * @param writer the writer
      */
     public static void printRootCauseStackTrace(Throwable t, PrintWriter writer) {
         String trace[] = getRootCauseStackTrace(t);
         for (String aTrace : trace) {
             writer.println(aTrace);
         }
         writer.flush();
     }
 
     /**
      * Creates a compact stack trace for the root cause of the supplied throwable. See
      * <code>printRootCauseStackTrace(Throwable t, PrintStream s)</code>
      * @param t the cause
      * @return the Stack
      */
     public static String[] getRootCauseStackTrace(Throwable t) {
         Throwable[] throwables = getThrowables(t);
         int count = throwables.length;
         ArrayList<String> frames = new ArrayList<>();
         List<String> nextTrace = getStackFrameList(throwables[count - 1]);
         for (int i = count; --i >= 0; ) {
             List<String> trace = nextTrace;
             if (i != 0) {
                 nextTrace = getStackFrameList(throwables[i - 1]);
                 removeCommonFrames(trace, nextTrace);
             }
             if (i == (count - 1)) {
                 frames.add(throwables[i].toString());
             } else {
                 frames.add(WRAPPED_MARKER + throwables[i].toString());
             }
             for (String aTrace : trace) {
                 frames.add(aTrace);
             }
         }
         return frames.toArray(new String[0]);
     }
 
     /**
      * Given two stack traces, removes common frames from the cause trace.
      *
      * @param causeFrames stack trace of a cause throwable
      * @param wrapperFrames stack trace of a wrapper throwable
      */
     private static void removeCommonFrames(List<String> causeFrames, List<String> wrapperFrames) {
         int causeFrameIndex = causeFrames.size() - 1;
         int wrapperFrameIndex = wrapperFrames.size() - 1;
         while (causeFrameIndex >= 0 && wrapperFrameIndex >= 0) {
             // Remove the frame from the cause trace if it is the same
             // as in the wrapper trace
             String causeFrame = causeFrames.get(causeFrameIndex);
             String wrapperFrame = wrapperFrames.get(wrapperFrameIndex);
             if (causeFrame.equals(wrapperFrame)) {
                 causeFrames.remove(causeFrameIndex);
             }
             causeFrameIndex--;
             wrapperFrameIndex--;
         }
     }
 
     /**
      * A convenient way of extracting the stack trace from an exception.
      *
      * @param t The <code>Throwable</code>.
      * @return The stack trace as generated by the exception's <code>printStackTrace(PrintWriter)</code> method.
      */
     public static String getStackTrace(Throwable t) {
         StringWriter sw = new StringWriter();
         PrintWriter pw = new PrintWriter(sw, true);
         t.printStackTrace(pw);
         return sw.getBuffer().toString();
     }
 
     /**
      * A way to get the entire nested stack-trace of an throwable.
      *
      * @param t The <code>Throwable</code>.
      * @return The nested stack trace, with the root cause first.
      */
     public static String getFullStackTrace(Throwable t) {
         StringWriter sw = new StringWriter();
         PrintWriter pw = new PrintWriter(sw, true);
         Throwable[] ts = getThrowables(t);
         for (Throwable t1 : ts) {
             t1.printStackTrace(pw);
             if (isNestedThrowable(t1)) {
                 break;
             }
         }
         return sw.getBuffer().toString();
     }
 
     /**
      * Whether an Throwable is considered nested or not.
      *
      * @param throwable The <code>Throwable</code>.
      * @return boolean true/false
      */
     public static boolean isNestedThrowable(Throwable throwable) {
         if (throwable == null) {
             return false;
         }
 
         if (throwable instanceof SQLException) {
             return true;
         } else if (throwable instanceof InvocationTargetException) {
             return true;
         }
 
         for (String CAUSE_METHOD_NAME : CAUSE_METHOD_NAMES) {
             try {
                 Method method = throwable.getClass().getMethod(CAUSE_METHOD_NAME, null);
                 if (method != null) {
                     return true;
                 }
             } catch (NoSuchMethodException ignored) {
             } catch (SecurityException ignored) {
             }
         }
 
         try {
             Field field = throwable.getClass().getField("detail");
             if (field != null) {
                 return true;
             }
         } catch (NoSuchFieldException ignored) {
         } catch (SecurityException ignored) {
         }
 
         return false;
     }
 
     /**
      * Captures the stack trace associated with the specified <code>Throwable</code> object, decomposing it into a list
      * of stack frames.
      *
      * @param t The <code>Throwable</code>.
      * @return An array of strings describing each stack frame.
      */
     public static String[] getStackFrames(Throwable t) {
         return getStackFrames(getStackTrace(t));
     }
 
     /**
      * Functionality shared between the <code>getStackFrames(Throwable)</code> methods of this and the classes.
      */
     static String[] getStackFrames(String stackTrace) {
         String linebreak = System.getProperty("line.separator");
         StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
         List<String> list = new LinkedList<String>();
         while (frames.hasMoreTokens()) {
             list.add(frames.nextToken());
         }
         return list.toArray(new String[0]);
     }
 
     /**
      * Produces a List of stack frames - the message is not included. This works in most cases - it will only fail if
      * the exception message contains a line that starts with: " at".
      *
      * @param t is any throwable
      * @return List of stack frames
      */
     static List<String> getStackFrameList(Throwable t) {
         String stackTrace = getStackTrace(t);
         String linebreak = System.getProperty("line.separator");
         StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
         List<String> list = new LinkedList<String>();
         boolean traceStarted = false;
         while (frames.hasMoreTokens()) {
             String token = frames.nextToken();
             // Determine if the line starts with <whitespace>at
             int at = token.indexOf("at");
             if (at != -1 && token.substring(0, at).trim().length() == 0) {
                 traceStarted = true;
                 list.add(token);
             } else if (traceStarted) {
                 break;
             }
         }
         return list;
     }
 }