/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package co.aikar.commands.apachecommonslang;

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.List;
import java.util.StringTokenizer;

/**
 * <p>Provides utilities for manipulating and examining
 * <code>Throwable</code> objects.</p>
 *
 * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
 * @author Dmitri Plotnikov
 * @author Stephen Colebourne
 * @author <a href="mailto:ggregory@seagullsw.com">Gary Gregory</a>
 * @author Pete Gieser
 * @since 1.0
 * @version $Id$
 */
public class ApacheCommonsExceptionUtil {
    private static final String LINE_SEPARATOR = System.getProperty("line.separator");

    /**
     * <p>Used when printing stack frames to denote the start of a
     * wrapped exception.</p>
     *
     * <p>Package private for accessibility by test suite.</p>
     */
    static final String WRAPPED_MARKER = " [wrapped] ";

    /**
     * <p>The names of methods commonly used to access a wrapped exception.</p>
     */
    private static String[] CAUSE_METHOD_NAMES = {
            "getCause",
            "getNextException",
            "getTargetException",
            "getException",
            "getSourceException",
            "getRootCause",
            "getCausedByException",
            "getNested",
            "getLinkedException",
            "getNestedException",
            "getLinkedCause",
            "getThrowable",
    };

    /**
     * <p>The Method object for Java 1.4 getCause.</p>
     */
    private static final Method THROWABLE_CAUSE_METHOD;

    /**
     * <p>The Method object for Java 1.4 initCause.</p>
     */
    private static final Method THROWABLE_INITCAUSE_METHOD;

    static {
        Method causeMethod;
        try {
            causeMethod = Throwable.class.getMethod("getCause", null);
        } catch (Exception e) {
            causeMethod = null;
        }
        THROWABLE_CAUSE_METHOD = causeMethod;
        try {
            causeMethod = Throwable.class.getMethod("initCause", Throwable.class);
        } catch (Exception e) {
            causeMethod = null;
        }
        THROWABLE_INITCAUSE_METHOD = causeMethod;
    }

    /**
     * <p>
     * Public constructor allows an instance of <code>ExceptionUtils</code> to be created, although that is not
     * normally necessary.
     * </p>
     */
    public ApacheCommonsExceptionUtil() {
        super();
    }

    //-----------------------------------------------------------------------
    /**
     * <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, <code>null</code>
     *  and empty strings are ignored
     * @since 2.0
     */
    public static void addCauseMethodName(String methodName) {
        if (methodName != null && !methodName.isEmpty() && !isCauseMethodName(methodName)) {
            List list = getCauseMethodNameList();
            if (list.add(methodName)) {
                CAUSE_METHOD_NAMES = toArray(list);
            }
        }
    }

    /**
     * <p>Removes from the list of method names used in the search for <code>Throwable</code>
     * objects.</p>
     *
     * @param methodName  the methodName to remove from the list, <code>null</code>
     *  and empty strings are ignored
     * @since 2.1
     */
    public static void removeCauseMethodName(String methodName) {
        if (methodName != null && !methodName.isEmpty()) {
            List list = getCauseMethodNameList();
            if (list.remove(methodName)) {
                CAUSE_METHOD_NAMES = toArray(list);
            }
        }
    }

    /**
     * <p>Sets the cause of a <code>Throwable</code> using introspection, allowing
     * source code compatibility between pre-1.4 and post-1.4 Java releases.</p>
     *
     * <p>The typical use of this method is inside a constructor as in
     * the following example:</p>
     *
     * <pre>
     * import org.apache.commons.lang.exception.ExceptionUtils;
     *
     * public class MyException extends Exception {
     *
     *    public MyException(String msg) {
     *       super(msg);
     *    }
     *
     *    public MyException(String msg, Throwable cause) {
     *       super(msg);
     *       ExceptionUtils.setCause(this, cause);
     *    }
     * }
     * </pre>
     *
     * @param target  the target <code>Throwable</code>
     * @param cause  the <code>Throwable</code> to set in the target
     * @return a <code>true</code> if the target has been modified
     * @since 2.2
     */
    public static boolean setCause(Throwable target, Throwable cause) {
        if (target == null) {
            throw new IllegalArgumentException("target");
        }
        Object[] causeArgs = new Object[]{cause};
        boolean modifiedTarget = false;
        if (THROWABLE_INITCAUSE_METHOD != null) {
            try {
                THROWABLE_INITCAUSE_METHOD.invoke(target, causeArgs);
                modifiedTarget = true;
            } catch (IllegalAccessException ignored) {
                // Exception ignored.
            } catch (InvocationTargetException ignored) {
                // Exception ignored.
            }
        }
        try {
            Method setCauseMethod = target.getClass().getMethod("setCause", Throwable.class);
            setCauseMethod.invoke(target, causeArgs);
            modifiedTarget = true;
        } catch (NoSuchMethodException ignored) {
            // Exception ignored.
        } catch (IllegalAccessException ignored) {
            // Exception ignored.
        } catch (InvocationTargetException ignored) {
            // Exception ignored.
        }
        return modifiedTarget;
    }

    /**
     * Returns the given list as a <code>String[]</code>.
     * @param list a list to transform.
     * @return the given list as a <code>String[]</code>.
     */
    private static String[] toArray(List list) {
        return (String[]) list.toArray(new String[list.size()]);
    }

    /**
     * Returns {@link #CAUSE_METHOD_NAMES} as a List.
     *
     * @return {@link #CAUSE_METHOD_NAMES} as a List.
     */
    private static ArrayList getCauseMethodNameList() {
        return new ArrayList(Arrays.asList(CAUSE_METHOD_NAMES));
    }

    /**
     * <p>Tests if the list of method names used in the search for <code>Throwable</code>
     * objects include the given name.</p>
     *
     * @param methodName  the methodName to search in the list.
     * @return if the list of method names used in the search for <code>Throwable</code>
     *  objects include the given name.
     * @since 2.1
     */
    public static boolean isCauseMethodName(String methodName) {
        return ApacheCommonsLangUtil.indexOf(CAUSE_METHOD_NAMES, methodName) >= 0;
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Introspects the <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)}.</p>
     *
     * <p>The default list searched for are:</p>
     * <ul>
     *  <li><code>getCause()</code></li>
     *  <li><code>getNextException()</code></li>
     *  <li><code>getTargetException()</code></li>
     *  <li><code>getException()</code></li>
     *  <li><code>getSourceException()</code></li>
     *  <li><code>getRootCause()</code></li>
     *  <li><code>getCausedByException()</code></li>
     *  <li><code>getNested()</code></li>
     * </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 throwable to introspect for a cause, may be null
     * @return the cause of the <code>Throwable</code>,
     *  <code>null</code> if none found or null throwable input
     * @since 1.0
     */
    public static Throwable getCause(Throwable throwable) {
        return getCause(throwable, CAUSE_METHOD_NAMES);
    }

    /**
     * <p>Introspects the <code>Throwable</code> to obtain the cause.</p>
     *
     * <ol>
     * <li>Try known exception types.</li>
     * <li>Try the supplied array of method names.</li>
     * <li>Try the field 'detail'.</li>
     * </ol>
     *
     * <p>A <code>null</code> set of method names means use the default set.
     * A <code>null</code> in the set of method names will be ignored.</p>
     *
     * @param throwable  the throwable to introspect for a cause, may be null
     * @param methodNames  the method names, null treated as default set
     * @return the cause of the <code>Throwable</code>,
     *  <code>null</code> if none found or null throwable input
     * @since 1.0
     */
    public static Throwable getCause(Throwable throwable, String[] methodNames) {
        if (throwable == null) {
            return null;
        }
        Throwable cause = getCauseUsingWellKnownTypes(throwable);
        if (cause == null) {
            if (methodNames == null) {
                methodNames = CAUSE_METHOD_NAMES;
            }
            for (int i = 0; i < methodNames.length; i++) {
                String methodName = methodNames[i];
                if (methodName != null) {
                    cause = getCauseUsingMethodName(throwable, methodName);
                    if (cause != null) {
                        break;
                    }
                }
            }

            if (cause == null) {
                cause = getCauseUsingFieldName(throwable, "detail");
            }
        }
        return cause;
    }

    /**
     * <p>Introspects the <code>Throwable</code> to obtain the root cause.</p>
     *
     * <p>This method walks through the exception chain to the last element,
     * "root" of the tree, using {@link #getCause(Throwable)}, and
     * returns that exception.</p>
     *
     * <p>From version 2.2, this method handles recursive cause structures
     * that might otherwise cause infinite loops. If the throwable parameter
     * has a cause of itself, then null will be returned. If the throwable
     * parameter cause chain loops, the last element in the chain before the
     * loop is returned.</p>
     *
     * @param throwable  the throwable to get the root cause for, may be null
     * @return the root cause of the <code>Throwable</code>,
     *  <code>null</code> if none found or null throwable input
     */
    public static Throwable getRootCause(Throwable throwable) {
        List list = getThrowableList(throwable);
        return (list.size() < 2 ? null : (Throwable)list.get(list.size() - 1));
    }

    /**
     * <p>Finds a <code>Throwable</code> for known types.</p>
     *
     * <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 Nestable) {
            return throwable.getCause();
        } else if (throwable instanceof SQLException) {
            return ((SQLException) throwable).getNextException();
        } else if (throwable instanceof InvocationTargetException) {
            return ((InvocationTargetException) throwable).getTargetException();
        } else {
            return null;
        }
    }

    /**
     * <p>Finds a <code>Throwable</code> 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) {
            // exception ignored
        } catch (SecurityException ignored) {
            // exception ignored
        }

        if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) {
            try {
                return (Throwable) method.invoke(throwable);
            } catch (IllegalAccessException ignored) {
                // exception ignored
            } catch (IllegalArgumentException ignored) {
                // exception ignored
            } catch (InvocationTargetException ignored) {
                // exception ignored
            }
        }
        return null;
    }

    /**
     * <p>Finds a <code>Throwable</code> 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) {
            // exception ignored
        } catch (SecurityException ignored) {
            // exception ignored
        }

        if (field != null && Throwable.class.isAssignableFrom(field.getType())) {
            try {
                return (Throwable) field.get(throwable);
            } catch (IllegalAccessException ignored) {
                // exception ignored
            } catch (IllegalArgumentException ignored) {
                // exception ignored
            }
        }
        return null;
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Checks if the Throwable class has a <code>getCause</code> method.</p>
     *
     * <p>This is true for JDK 1.4 and above.</p>
     *
     * @return true if Throwable is nestable
     * @since 2.0
     */
    public static boolean isThrowableNested() {
        return THROWABLE_CAUSE_METHOD != null;
    }

    /**
     * <p>Checks whether this <code>Throwable</code> class can store a cause.</p>
     *
     * <p>This method does <b>not</b> check whether it actually does store a cause.<p>
     *
     * @param throwable  the <code>Throwable</code> to examine, may be null
     * @return boolean <code>true</code> if nested otherwise <code>false</code>
     * @since 2.0
     */
    public static boolean isNestedThrowable(Throwable throwable) {
        if (throwable == null) {
            return false;
        }

        if (throwable instanceof Nestable) {
            return true;
        } else if (throwable instanceof SQLException) {
            return true;
        } else if (throwable instanceof InvocationTargetException) {
            return true;
        } else if (isThrowableNested()) {
            return true;
        }

        Class cls = throwable.getClass();
        for (int i = 0, isize = CAUSE_METHOD_NAMES.length; i < isize; i++) {
            try {
                Method method = cls.getMethod(CAUSE_METHOD_NAMES[i], null);
                if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) {
                    return true;
                }
            } catch (NoSuchMethodException ignored) {
                // exception ignored
            } catch (SecurityException ignored) {
                // exception ignored
            }
        }

        try {
            Field field = cls.getField("detail");
            if (field != null) {
                return true;
            }
        } catch (NoSuchFieldException ignored) {
            // exception ignored
        } catch (SecurityException ignored) {
            // exception ignored
        }

        return false;
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Counts the number of <code>Throwable</code> objects in the
     * exception chain.</p>
     *
     * <p>A throwable without cause will return <code>1</code>.
     * A throwable with one cause will return <code>2</code> and so on.
     * A <code>null</code> throwable will return <code>0</code>.</p>
     *
     * <p>From version 2.2, this method handles recursive cause structures
     * that might otherwise cause infinite loops. The cause chain is
     * processed until the end is reached, or until the next item in the
     * chain is already in the result set.</p>
     *
     * @param throwable  the throwable to inspect, may be null
     * @return the count of throwables, zero if null input
     */
    public static int getThrowableCount(Throwable throwable) {
        return getThrowableList(throwable).size();
    }

    /**
     * <p>Returns the list of <code>Throwable</code> objects in the
     * exception chain.</p>
     *
     * <p>A throwable without cause will return an array containing
     * one element - the input throwable.
     * A throwable with one cause will return an array containing
     * two elements. - the input throwable and the cause throwable.
     * A <code>null</code> throwable will return an array of size zero.</p>
     *
     * <p>From version 2.2, this method handles recursive cause structures
     * that might otherwise cause infinite loops. The cause chain is
     * processed until the end is reached, or until the next item in the
     * chain is already in the result set.</p>
     *
     * @see #getThrowableList(Throwable)
     * @param throwable  the throwable to inspect, may be null
     * @return the array of throwables, never null
     */
    public static Throwable[] getThrowables(Throwable throwable) {
        List list = getThrowableList(throwable);
        return (Throwable[]) list.toArray(new Throwable[list.size()]);
    }

    /**
     * <p>Returns the list of <code>Throwable</code> objects in the
     * exception chain.</p>
     *
     * <p>A throwable without cause will return a list containing
     * one element - the input throwable.
     * A throwable with one cause will return a list containing
     * two elements. - the input throwable and the cause throwable.
     * A <code>null</code> throwable will return a list of size zero.</p>
     *
     * <p>This method handles recursive cause structures that might
     * otherwise cause infinite loops. The cause chain is processed until
     * the end is reached, or until the next item in the chain is already
     * in the result set.</p>
     *
     * @param throwable  the throwable to inspect, may be null
     * @return the list of throwables, never null
     * @since Commons Lang 2.2
     */
    public static List getThrowableList(Throwable throwable) {
        List list = new ArrayList();
        while (throwable != null && list.contains(throwable) == false) {
            list.add(throwable);
            throwable = getCause(throwable);
        }
        return list;
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Returns the (zero based) index of the first <code>Throwable</code>
     * that matches the specified class (exactly) in the exception chain.
     * Subclasses of the specified class do not match - see
     * {@link #indexOfType(Throwable, Class)} for the opposite.</p>
     *
     * <p>A <code>null</code> throwable returns <code>-1</code>.
     * A <code>null</code> type returns <code>-1</code>.
     * No match in the chain returns <code>-1</code>.</p>
     *
     * @param throwable  the throwable to inspect, may be null
     * @param clazz  the class to search for, subclasses do not match, null returns -1
     * @return the index into the throwable chain, -1 if no match or null input
     */
    public static int indexOfThrowable(Throwable throwable, Class clazz) {
        return indexOf(throwable, clazz, 0, false);
    }

    /**
     * <p>Returns the (zero based) index of the first <code>Throwable</code>
     * that matches the specified type in the exception chain from
     * a specified index.
     * Subclasses of the specified class do not match - see
     * {@link #indexOfType(Throwable, Class, int)} for the opposite.</p>
     *
     * <p>A <code>null</code> throwable returns <code>-1</code>.
     * A <code>null</code> type returns <code>-1</code>.
     * No match in the chain returns <code>-1</code>.
     * A negative start index is treated as zero.
     * A start index greater than the number of throwables returns <code>-1</code>.</p>
     *
     * @param throwable  the throwable to inspect, may be null
     * @param clazz  the class to search for, subclasses do not match, null returns -1
     * @param fromIndex  the (zero based) index of the starting position,
     *  negative treated as zero, larger than chain size returns -1
     * @return the index into the throwable chain, -1 if no match or null input
     */
    public static int indexOfThrowable(Throwable throwable, Class clazz, int fromIndex) {
        return indexOf(throwable, clazz, fromIndex, false);
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Returns the (zero based) index of the first <code>Throwable</code>
     * that matches the specified class or subclass in the exception chain.
     * Subclasses of the specified class do match - see
     * {@link #indexOfThrowable(Throwable, Class)} for the opposite.</p>
     *
     * <p>A <code>null</code> throwable returns <code>-1</code>.
     * A <code>null</code> type returns <code>-1</code>.
     * No match in the chain returns <code>-1</code>.</p>
     *
     * @param throwable  the throwable to inspect, may be null
     * @param type  the type to search for, subclasses match, null returns -1
     * @return the index into the throwable chain, -1 if no match or null input
     * @since 2.1
     */
    public static int indexOfType(Throwable throwable, Class type) {
        return indexOf(throwable, type, 0, true);
    }

    /**
     * <p>Returns the (zero based) index of the first <code>Throwable</code>
     * that matches the specified type in the exception chain from
     * a specified index.
     * Subclasses of the specified class do match - see
     * {@link #indexOfThrowable(Throwable, Class)} for the opposite.</p>
     *
     * <p>A <code>null</code> throwable returns <code>-1</code>.
     * A <code>null</code> type returns <code>-1</code>.
     * No match in the chain returns <code>-1</code>.
     * A negative start index is treated as zero.
     * A start index greater than the number of throwables returns <code>-1</code>.</p>
     *
     * @param throwable  the throwable to inspect, may be null
     * @param type  the type to search for, subclasses match, null returns -1
     * @param fromIndex  the (zero based) index of the starting position,
     *  negative treated as zero, larger than chain size returns -1
     * @return the index into the throwable chain, -1 if no match or null input
     * @since 2.1
     */
    public static int indexOfType(Throwable throwable, Class type, int fromIndex) {
        return indexOf(throwable, type, fromIndex, true);
    }

    /**
     * <p>Worker method for the <code>indexOfType</code> methods.</p>
     *
     * @param throwable  the throwable to inspect, may be null
     * @param type  the type to search for, subclasses match, null returns -1
     * @param fromIndex  the (zero based) index of the starting position,
     *  negative treated as zero, larger than chain size returns -1
     * @param subclass if <code>true</code>, compares with {@link Class#isAssignableFrom(Class)}, otherwise compares
     * using references
     * @return index of the <code>type</code> within throwables nested withing the specified <code>throwable</code>
     */
    private static int indexOf(Throwable throwable, Class type, int fromIndex, boolean subclass) {
        if (throwable == null || type == null) {
            return -1;
        }
        if (fromIndex < 0) {
            fromIndex = 0;
        }
        Throwable[] throwables = getThrowables(throwable);
        if (fromIndex >= throwables.length) {
            return -1;
        }
        if (subclass) {
            for (int i = fromIndex; i < throwables.length; i++) {
                if (type.isAssignableFrom(throwables[i].getClass())) {
                    return i;
                }
            }
        } else {
            for (int i = fromIndex; i < throwables.length; i++) {
                if (type.equals(throwables[i].getClass())) {
                    return i;
                }
            }
        }
        return -1;
    }

    /**
     * <p>Removes common frames from the cause trace given the two stack traces.</p>
     *
     * @param causeFrames  stack trace of a cause throwable
     * @param wrapperFrames  stack trace of a wrapper throwable
     * @throws IllegalArgumentException if either argument is null
     * @since 2.0
     */
    public static void removeCommonFrames(List causeFrames, List wrapperFrames) {
        if (causeFrames == null || wrapperFrames == null) {
            throw new IllegalArgumentException("The List must not be null");
        }
        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 = (String) causeFrames.get(causeFrameIndex);
            String wrapperFrame = (String) wrapperFrames.get(wrapperFrameIndex);
            if (causeFrame.equals(wrapperFrame)) {
                causeFrames.remove(causeFrameIndex);
            }
            causeFrameIndex--;
            wrapperFrameIndex--;
        }
    }

    //-----------------------------------------------------------------------
    /**
     * <p>A way to get the entire nested stack-trace of an throwable.</p>
     *
     * <p>The result of this method is highly dependent on the JDK version
     * and whether the exceptions override printStackTrace or not.</p>
     *
     * @param throwable  the <code>Throwable</code> to be examined
     * @return the nested stack trace, with the root cause first
     * @since 2.0
     */
    public static String getFullStackTrace(Throwable throwable) {
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw, true);
        Throwable[] ts = getThrowables(throwable);
        for (int i = 0; i < ts.length; i++) {
            ts[i].printStackTrace(pw);
            if (isNestedThrowable(ts[i])) {
                break;
            }
        }
        return sw.getBuffer().toString();
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Gets the stack trace from a Throwable as a String.</p>
     *
     * <p>The result of this method vary by JDK version as this method
     * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}.
     * On JDK1.3 and earlier, the cause exception will not be shown
     * unless the specified throwable alters printStackTrace.</p>
     *
     * @param throwable  the <code>Throwable</code> to be examined
     * @return the stack trace as generated by the exception's
     *  <code>printStackTrace(PrintWriter)</code> method
     */
    public static String getStackTrace(Throwable throwable) {
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw, true);
        throwable.printStackTrace(pw);
        return sw.getBuffer().toString();
    }

    /**
     * <p>Captures the stack trace associated with the specified
     * <code>Throwable</code> object, decomposing it into a list of
     * stack frames.</p>
     *
     * <p>The result of this method vary by JDK version as this method
     * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}.
     * On JDK1.3 and earlier, the cause exception will not be shown
     * unless the specified throwable alters printStackTrace.</p>
     *
     * @param throwable  the <code>Throwable</code> to examine, may be null
     * @return an array of strings describing each stack frame, never null
     */
//    public static String[] getStackFrames(Throwable throwable) {
//        if (throwable == null) {
//            return ArrayUtils.EMPTY_STRING_ARRAY;
//        }
//        return getStackFrames(getStackTrace(throwable));
//    }

    //-----------------------------------------------------------------------
    /**
     * <p>Returns an array where each element is a line from the argument.</p>
     *
     * <p>The end of line is determined by the value of {@link SystemUtils#LINE_SEPARATOR}.</p>
     *
     * <p>Functionality shared between the
     * <code>getStackFrames(Throwable)</code> methods of this and the
     * {@link org.apache.commons.lang.exception.NestableDelegate} classes.</p>
     *
     * @param stackTrace  a stack trace String
     * @return an array where each element is a line from the argument
     */
//    static String[] getStackFrames(String stackTrace) {
//        String linebreak = SystemUtils.LINE_SEPARATOR;
//        StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
//        List list = new ArrayList();
//        while (frames.hasMoreTokens()) {
//            list.add(frames.nextToken());
//        }
//        return toArray(list);
//    }

    /**
     * <p>Produces a <code>List</code> of stack frames - the message
     * is not included. Only the trace of the specified exception is
     * returned, any caused by trace is stripped.</p>
     *
     * <p>This works in most cases - it will only fail if the exception
     * message contains a line that starts with:
     * <code>&quot;&nbsp;&nbsp;&nbsp;at&quot;.</code></p>
     *
     * @param t is any throwable
     * @return List of stack frames
     */
    static List getStackFrameList(Throwable t) {
        String stackTrace = getStackTrace(t);
        String linebreak = LINE_SEPARATOR;
        StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
        List list = new ArrayList();
        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;
    }

    //-----------------------------------------------------------------------
    /**
     * Gets a short message summarising the exception.
     * <p>
     * The message returned is of the form
     * {ClassNameWithoutPackage}: {ThrowableMessage}
     *
     * @param th  the throwable to get a message for, null returns empty string
     * @return the message, non-null
     * @since Commons Lang 2.2
     */
//    public static String getMessage(Throwable th) {
//        if (th == null) {
//            return "";
//        }
//        String clsName = ClassUtils.getShortClassName(th, null);
//        String msg = th.getMessage();
//        return clsName + ": " + StringUtils.defaultString(msg);
//    }

    //-----------------------------------------------------------------------
    /**
     * Gets a short message summarising the root cause exception.
     * <p>
     * The message returned is of the form
     * {ClassNameWithoutPackage}: {ThrowableMessage}
     *
     * @param th  the throwable to get a message for, null returns empty string
     * @return the message, non-null
     * @since Commons Lang 2.2
     */
//    public static String getRootCauseMessage(Throwable th) {
//        Throwable root = ExceptionUtils.getRootCause(th);
//        root = (root == null ? th : root);
//        return getMessage(root);
//    }

    /**
     * An interface to be implemented by {@link java.lang.Throwable}
     * extensions which would like to be able to nest root exceptions
     * inside themselves.
     *
     * @author <a href="mailto:dlr@collab.net">Daniel Rall</a>
     * @author <a href="mailto:knielsen@apache.org">Kasper Nielsen</a>
     * @author <a href="mailto:steven@caswell.name">Steven Caswell</a>
     * @author Pete Gieser
     * @since 1.0
     * @version $Id$
     */
    public interface Nestable {

        /**
         * Returns the reference to the exception or error that caused the
         * exception implementing the <code>Nestable</code> to be thrown.
         *
         * @return throwable that caused the original exception
         */
        Throwable getCause();

        /**
         * Returns the error message of this and any nested
         * <code>Throwable</code>.
         *
         * @return the error message
         */
        String getMessage();

        /**
         * Returns the error message of the <code>Throwable</code> in the chain
         * of <code>Throwable</code>s at the specified index, numbered from 0.
         *
         * @param index the index of the <code>Throwable</code> in the chain of
         * <code>Throwable</code>s
         * @return the error message, or null if the <code>Throwable</code> at the
         * specified index in the chain does not contain a message
         * @throws IndexOutOfBoundsException if the <code>index</code> argument is
         * negative or not less than the count of <code>Throwable</code>s in the
         * chain
         */
        String getMessage(int index);

        /**
         * Returns the error message of this and any nested <code>Throwable</code>s
         * in an array of Strings, one element for each message. Any
         * <code>Throwable</code> not containing a message is represented in the
         * array by a null. This has the effect of cause the length of the returned
         * array to be equal to the result of the {@link #getThrowableCount()}
         * operation.
         *
         * @return the error messages
         */
        String[] getMessages();

        /**
         * Returns the <code>Throwable</code> in the chain of
         * <code>Throwable</code>s at the specified index, numbered from 0.
         *
         * @param index the index, numbered from 0, of the <code>Throwable</code> in
         * the chain of <code>Throwable</code>s
         * @return the <code>Throwable</code>
         * @throws IndexOutOfBoundsException if the <code>index</code> argument is
         * negative or not less than the count of <code>Throwable</code>s in the
         * chain
         */
        Throwable getThrowable(int index);

        /**
         * Returns the number of nested <code>Throwable</code>s represented by
         * this <code>Nestable</code>, including this <code>Nestable</code>.
         *
         * @return the throwable count
         */
        int getThrowableCount();

        /**
         * Returns this <code>Nestable</code> and any nested <code>Throwable</code>s
         * in an array of <code>Throwable</code>s, one element for each
         * <code>Throwable</code>.
         *
         * @return the <code>Throwable</code>s
         */
        Throwable[] getThrowables();

        /**
         * Returns the index, numbered from 0, of the first occurrence of the
         * specified type, or a subclass, in the chain of <code>Throwable</code>s.
         * The method returns -1 if the specified type is not found in the chain.
         * <p>
         * NOTE: From v2.1, we have clarified the <code>Nestable</code> interface
         * such that this method matches subclasses.
         * If you want to NOT match subclasses, please use
         * (which is avaiable in all versions of lang).
         *
         * @param type  the type to find, subclasses match, null returns -1
         * @return index of the first occurrence of the type in the chain, or -1 if
         * the type is not found
         */
        int indexOfThrowable(Class type);

        /**
         * Returns the index, numbered from 0, of the first <code>Throwable</code>
         * that matches the specified type, or a subclass, in the chain of <code>Throwable</code>s
         * with an index greater than or equal to the specified index.
         * The method returns -1 if the specified type is not found in the chain.
         * <p>
         * NOTE: From v2.1, we have clarified the <code>Nestable</code> interface
         * such that this method matches subclasses.
         * If you want to NOT match subclasses, please use
         * (which is avaiable in all versions of lang).
         *
         * @param type  the type to find, subclasses match, null returns -1
         * @param fromIndex the index, numbered from 0, of the starting position in
         * the chain to be searched
         * @return index of the first occurrence of the type in the chain, or -1 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
         */
        int indexOfThrowable(Class type, int fromIndex);

        /**
         * Prints the stack trace of this exception to the specified print
         * writer.  Includes information from the exception, if any,
         * which caused this exception.
         *
         * @param out <code>PrintWriter</code> to use for output.
         */
        void printStackTrace(PrintWriter out);

        /**
         * Prints the stack trace of this exception to the specified print
         * stream.  Includes information from the exception, if any,
         * which caused this exception.
         *
         * @param out <code>PrintStream</code> to use for output.
         */
        void printStackTrace(PrintStream out);

        /**
         * Prints the stack trace for this exception only--root cause not
         * included--using the provided writer.  Used by
         * individual stack traces to a buffer.  The implementation of
         * this method should call
         * <code>super.printStackTrace(out);</code> in most cases.
         *
         * @param out The writer to use.
         */
        void printPartialStackTrace(PrintWriter out);

    }
}
