/*
    * 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 org.apache.logging.log4j.core.impl;
  
  import java.io.Serializable;
  import java.net.URL;
  import java.security.CodeSource;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.Stack;
  
  import org.apache.logging.log4j.core.util.Loader;
  import org.apache.logging.log4j.status.StatusLogger;
  import org.apache.logging.log4j.util.ReflectionUtil;
  import org.apache.logging.log4j.util.Strings;
  
  /**
   * Wraps a Throwable to add packaging information about each stack trace element.
   * 
   * <p>
   * A proxy is used to represent a throwable that may not exist in a different class loader or JVM. When an application
   * deserializes a ThrowableProxy, the throwable may not be set, but the throwable's information is preserved in other
   * fields of the proxy like the message and stack trace.
   * </p>
   * 
   * <p>
   * TODO: Move this class to org.apache.logging.log4j.core because it is used from LogEvent.
   * </p>
   * <p>
   * TODO: Deserialize: Try to rebuild Throwable if the target exception is in this class loader?
   * </p>
   */
  public class ThrowableProxy implements Serializable {
  
  	private static final String CAUSED_BY_LABEL = "Caused by: ";
  	private static final String SUPPRESSED_LABEL = "Suppressed: ";
      private static final String WRAPPED_BY_LABEL = "Wrapped by: ";
  
  	/**
       * Cached StackTracePackageElement and ClassLoader.
       * <p>
       * Consider this class private.
       * </p>
       */
      static class CacheEntry {
          private final ExtendedClassInfo element;
          private final ClassLoader loader;
  
          public CacheEntry(final ExtendedClassInfo element, final ClassLoader loader) {
              this.element = element;
              this.loader = loader;
          }
      }
  
      private static final ThrowableProxy[] EMPTY_THROWABLE_PROXY_ARRAY = new ThrowableProxy[0];
  
      private static final char EOL = '\n';
  
      private static final long serialVersionUID = -2752771578252251910L;
  
      private final ThrowableProxy causeProxy;
  
      private int commonElementCount;
  
      private final ExtendedStackTraceElement[] extendedStackTrace;
  
      private final String localizedMessage;
  
      private final String message;
  
      private final String name;
  
      private final ThrowableProxy[] suppressedProxies;
  
      private final transient Throwable throwable;
  
      /**
       * For JSON and XML IO via Jackson.
       */
      @SuppressWarnings("unused")
     private ThrowableProxy() {
         this.throwable = null;
         this.name = null;
         this.extendedStackTrace = null;
         this.causeProxy = null;
         this.message = null;
         this.localizedMessage = null;
         this.suppressedProxies = EMPTY_THROWABLE_PROXY_ARRAY;
     }
 
     /**
      * Constructs the wrapper for the Throwable that includes packaging data.
      * 
      * @param throwable
      *        The Throwable to wrap, must not be null.
      */
     public ThrowableProxy(final Throwable throwable) {
         this(throwable, null);
     }
 
     /**
      * Constructs the wrapper for the Throwable that includes packaging data.
      * 
      * @param throwable
      *        The Throwable to wrap, must not be null.
      * @param visited
      *        The set of visited suppressed exceptions.
      */
     private ThrowableProxy(final Throwable throwable, final Set<Throwable> visited) {
         this.throwable = throwable;
         this.name = throwable.getClass().getName();
         this.message = throwable.getMessage();
         this.localizedMessage = throwable.getLocalizedMessage();
         final Map<String, CacheEntry> map = new HashMap<>();
         final Stack<Class<?>> stack = ReflectionUtil.getCurrentStackTrace();
         this.extendedStackTrace = this.toExtendedStackTrace(stack, map, null, throwable.getStackTrace());
         final Throwable throwableCause = throwable.getCause();
         final Set<Throwable> causeVisited = new HashSet<>(1);
         this.causeProxy = throwableCause == null ? null : new ThrowableProxy(throwable, stack, map, throwableCause, visited, causeVisited);
         this.suppressedProxies = this.toSuppressedProxies(throwable, visited);
     }
 
     /**
      * Constructs the wrapper for a Throwable that is referenced as the cause by another Throwable.
      * 
      * @param parent
      *        The Throwable referencing this Throwable.
      * @param stack
      *        The Class stack.
      * @param map
      *        The cache containing the packaging data.
      * @param cause
      *        The Throwable to wrap.
      * @param suppressedVisited TODO
      * @param causeVisited TODO
      */
     private ThrowableProxy(final Throwable parent, final Stack<Class<?>> stack, final Map<String, CacheEntry> map,
             final Throwable cause, final Set<Throwable> suppressedVisited, final Set<Throwable> causeVisited) {
         causeVisited.add(cause);
         this.throwable = cause;
         this.name = cause.getClass().getName();
         this.message = this.throwable.getMessage();
         this.localizedMessage = this.throwable.getLocalizedMessage();
         this.extendedStackTrace = this.toExtendedStackTrace(stack, map, parent.getStackTrace(), cause.getStackTrace());
         final Throwable causeCause = cause.getCause();
         this.causeProxy = causeCause == null || causeVisited.contains(causeCause) ? null : new ThrowableProxy(parent,
                 stack, map, causeCause, suppressedVisited, causeVisited);
         this.suppressedProxies = this.toSuppressedProxies(cause, suppressedVisited);
     }
 
     @Override
     public boolean equals(final Object obj) {
         if (this == obj) {
             return true;
         }
         if (obj == null) {
             return false;
         }
         if (this.getClass() != obj.getClass()) {
             return false;
         }
         final ThrowableProxy other = (ThrowableProxy) obj;
         if (this.causeProxy == null) {
             if (other.causeProxy != null) {
                 return false;
             }
         } else if (!this.causeProxy.equals(other.causeProxy)) {
             return false;
         }
         if (this.commonElementCount != other.commonElementCount) {
             return false;
         }
         if (this.name == null) {
             if (other.name != null) {
                 return false;
             }
         } else if (!this.name.equals(other.name)) {
             return false;
         }
         if (!Arrays.equals(this.extendedStackTrace, other.extendedStackTrace)) {
             return false;
         }
         if (!Arrays.equals(this.suppressedProxies, other.suppressedProxies)) {
             return false;
         }
         return true;
     }
 
 	private void formatCause(final StringBuilder sb, final String prefix, final ThrowableProxy cause, final List<String> ignorePackages) {
 		formatThrowableProxy(sb, prefix, CAUSED_BY_LABEL, cause, ignorePackages);
 	}
 
 	private void formatThrowableProxy(final StringBuilder sb, final String prefix, final String causeLabel,
 			final ThrowableProxy throwableProxy, final List<String> ignorePackages) {
 		if (throwableProxy == null) {
 			return;
 		}
 		sb.append(prefix).append(causeLabel).append(throwableProxy).append(EOL);
 		this.formatElements(sb, prefix, throwableProxy.commonElementCount,
 				throwableProxy.getStackTrace(), throwableProxy.extendedStackTrace, ignorePackages);
 		this.formatSuppressed(sb, prefix + "\t", throwableProxy.suppressedProxies, ignorePackages);
 		this.formatCause(sb, prefix, throwableProxy.causeProxy, ignorePackages);
 	}
 
 	private void formatSuppressed(final StringBuilder sb, final String prefix, final ThrowableProxy[] suppressedProxies,
 			final List<String> ignorePackages) {
 		if (suppressedProxies == null) {
 			return;
 		}
 		for (final ThrowableProxy suppressedProxy : suppressedProxies) {
 			final ThrowableProxy cause = suppressedProxy;
 			formatThrowableProxy(sb, prefix, SUPPRESSED_LABEL, cause, ignorePackages);
 		}
 	}
 
 	private void formatElements(final StringBuilder sb, final String prefix, final int commonCount,
 			final StackTraceElement[] causedTrace, final ExtendedStackTraceElement[] extStackTrace,
 			final List<String> ignorePackages) {
 		if (ignorePackages == null || ignorePackages.isEmpty()) {
 			for (final ExtendedStackTraceElement element : extStackTrace) {
 				this.formatEntry(element, sb, prefix);
 			}
 		} else {
 			int count = 0;
 			for (int i = 0; i < extStackTrace.length; ++i) {
 				if (!this.ignoreElement(causedTrace[i], ignorePackages)) {
 					if (count > 0) {
 						appendSuppressedCount(sb, prefix, count);
 						count = 0;
 					}
 					this.formatEntry(extStackTrace[i], sb, prefix);
 				} else {
 					++count;
 				}
 			}
 			if (count > 0) {
 				appendSuppressedCount(sb, prefix, count);
 			}
 		}
 		if (commonCount != 0) {
 			sb.append(prefix).append("\t... ").append(commonCount).append(" more").append(EOL);
 		}
 	}
 
     private void appendSuppressedCount(final StringBuilder sb, final String prefix, final int count) {
     	sb.append(prefix);
         if (count == 1) {
             sb.append("\t....").append(EOL);
         } else {
             sb.append("\t... suppressed ").append(count).append(" lines").append(EOL);
         }
     }
 
     private void formatEntry(final ExtendedStackTraceElement extStackTraceElement, final StringBuilder sb, final String prefix) {
         sb.append(prefix);
         sb.append("\tat ");
         sb.append(extStackTraceElement);
         sb.append(EOL);
     }
 
     /**
      * Formats the specified Throwable.
      * 
      * @param sb
      *        StringBuilder to contain the formatted Throwable.
      * @param cause
      *        The Throwable to format.
      */
     public void formatWrapper(final StringBuilder sb, final ThrowableProxy cause) {
         this.formatWrapper(sb, cause, null);
     }
 
     /**
      * Formats the specified Throwable.
      * 
      * @param sb
      *        StringBuilder to contain the formatted Throwable.
      * @param cause
      *        The Throwable to format.
      * @param packages
      *        The List of packages to be suppressed from the trace.
      */
     @SuppressWarnings("ThrowableResultOfMethodCallIgnored")
     public void formatWrapper(final StringBuilder sb, final ThrowableProxy cause, final List<String> packages) {
         final Throwable caused = cause.getCauseProxy() != null ? cause.getCauseProxy().getThrowable() : null;
         if (caused != null) {
             this.formatWrapper(sb, cause.causeProxy);
             sb.append(WRAPPED_BY_LABEL);
         }
         sb.append(cause).append(EOL);
         this.formatElements(sb, "", cause.commonElementCount,
                 cause.getThrowable().getStackTrace(), cause.extendedStackTrace, packages);
     }
 
     public ThrowableProxy getCauseProxy() {
         return this.causeProxy;
     }
 
     /**
      * Format the Throwable that is the cause of this Throwable.
      * 
      * @return The formatted Throwable that caused this Throwable.
      */
     public String getCauseStackTraceAsString() {
         return this.getCauseStackTraceAsString(null);
     }
 
     /**
      * Format the Throwable that is the cause of this Throwable.
      * 
      * @param packages
      *        The List of packages to be suppressed from the trace.
      * @return The formatted Throwable that caused this Throwable.
      */
     public String getCauseStackTraceAsString(final List<String> packages) {
         final StringBuilder sb = new StringBuilder();
         if (this.causeProxy != null) {
             this.formatWrapper(sb, this.causeProxy);
             sb.append(WRAPPED_BY_LABEL);
         }
         sb.append(this.toString());
         sb.append(EOL);
         this.formatElements(sb, "", 0, this.throwable.getStackTrace(), this.extendedStackTrace, packages);
         return sb.toString();
     }
 
     /**
      * Return the number of elements that are being omitted because they are common with the parent Throwable's stack
      * trace.
      * 
      * @return The number of elements omitted from the stack trace.
      */
     public int getCommonElementCount() {
         return this.commonElementCount;
     }
 
     /**
      * Gets the stack trace including packaging information.
      * 
      * @return The stack trace including packaging information.
      */
     public ExtendedStackTraceElement[] getExtendedStackTrace() {
         return this.extendedStackTrace;
     }
 
     /**
      * Format the stack trace including packaging information.
      * 
      * @return The formatted stack trace including packaging information.
      */
     public String getExtendedStackTraceAsString() {
         return this.getExtendedStackTraceAsString(null);
     }
 
     /**
      * Format the stack trace including packaging information.
      * 
      * @param ignorePackages
      *        List of packages to be ignored in the trace.
      * @return The formatted stack trace including packaging information.
      */
     public String getExtendedStackTraceAsString(final List<String> ignorePackages) {
         final StringBuilder sb = new StringBuilder(this.name);
         final String msg = this.message;
         if (msg != null) {
             sb.append(": ").append(msg);
         }
         sb.append(EOL);
         final StackTraceElement[] causedTrace = this.throwable != null ? this.throwable.getStackTrace() : null;
         this.formatElements(sb, "", 0, causedTrace, this.extendedStackTrace, ignorePackages);
         this.formatSuppressed(sb, "\t", this.suppressedProxies, ignorePackages);
         this.formatCause(sb, "", this.causeProxy, ignorePackages);
         return sb.toString();
     }
 
     public String getLocalizedMessage() {
         return this.localizedMessage;
     }
 
     public String getMessage() {
         return this.message;
     }
 
     /**
      * Return the FQCN of the Throwable.
      * 
      * @return The FQCN of the Throwable.
      */
     public String getName() {
         return this.name;
     }
 
     public StackTraceElement[] getStackTrace() {
         return this.throwable == null ? null : this.throwable.getStackTrace();
     }
 
     /**
      * Gets proxies for suppressed exceptions.
      * 
      * @return proxies for suppressed exceptions.
      */
     public ThrowableProxy[] getSuppressedProxies() {
         return this.suppressedProxies;
     }
 
     /**
      * Format the suppressed Throwables.
      * 
      * @return The formatted suppressed Throwables.
      */
     public String getSuppressedStackTrace() {
         final ThrowableProxy[] suppressed = this.getSuppressedProxies();
         if (suppressed == null || suppressed.length == 0) {
             return Strings.EMPTY;
         }
         final StringBuilder sb = new StringBuilder("Suppressed Stack Trace Elements:").append(EOL);
         for (final ThrowableProxy proxy : suppressed) {
             sb.append(proxy.getExtendedStackTraceAsString());
         }
         return sb.toString();
     }
 
     /**
      * The throwable or null if this object is deserialized from XML or JSON.
      * 
      * @return The throwable or null if this object is deserialized from XML or JSON.
      */
     public Throwable getThrowable() {
         return this.throwable;
     }
 
     @Override
     public int hashCode() {
         final int prime = 31;
         int result = 1;
         result = prime * result + (this.causeProxy == null ? 0 : this.causeProxy.hashCode());
         result = prime * result + this.commonElementCount;
         result = prime * result + (this.extendedStackTrace == null ? 0 : Arrays.hashCode(this.extendedStackTrace));
         result = prime * result + (this.suppressedProxies == null ? 0 : Arrays.hashCode(this.suppressedProxies));
         result = prime * result + (this.name == null ? 0 : this.name.hashCode());
         return result;
     }
 
     private boolean ignoreElement(final StackTraceElement element, final List<String> ignorePackages) {
         final String className = element.getClassName();
         for (final String pkg : ignorePackages) {
             if (className.startsWith(pkg)) {
                 return true;
             }
         }
         return false;
     }
 
     /**
      * Loads classes not located via Reflection.getCallerClass.
      * 
      * @param lastLoader
      *        The ClassLoader that loaded the Class that called this Class.
      * @param className
      *        The name of the Class.
      * @return The Class object for the Class or null if it could not be located.
      */
     private Class<?> loadClass(final ClassLoader lastLoader, final String className) {
         // XXX: this is overly complicated
         Class<?> clazz;
         if (lastLoader != null) {
             try {
                 clazz = Loader.initializeClass(className, lastLoader);
                 if (clazz != null) {
                     return clazz;
                 }
             } catch (final Throwable ignore) {
                 // Ignore exception.
             }
         }
         try {
             clazz = Loader.loadClass(className);
         } catch (final ClassNotFoundException ignored) {
             return initializeClass(className);
         } catch (final NoClassDefFoundError ignored) {
             return initializeClass(className);
         }
         return clazz;
     }
 
     private Class<?> initializeClass(final String className) {
         try {
             return Loader.initializeClass(className, this.getClass().getClassLoader());
         } catch (final ClassNotFoundException ignore) {
             return null;
         } catch (final NoClassDefFoundError ignore) {
             return null;
         }
     }
 
     /**
      * Construct the CacheEntry from the Class's information.
      * 
      * @param stackTraceElement
      *        The stack trace element
      * @param callerClass
      *        The Class.
      * @param exact
      *        True if the class was obtained via Reflection.getCallerClass.
      * 
      * @return The CacheEntry.
      */
     private CacheEntry toCacheEntry(final StackTraceElement stackTraceElement, final Class<?> callerClass,
             final boolean exact) {
         String location = "?";
         String version = "?";
         ClassLoader lastLoader = null;
         if (callerClass != null) {
             try {
                 final CodeSource source = callerClass.getProtectionDomain().getCodeSource();
                 if (source != null) {
                     final URL locationURL = source.getLocation();
                     if (locationURL != null) {
                         final String str = locationURL.toString().replace('\\', '/');
                         int index = str.lastIndexOf("/");
                         if (index >= 0 && index == str.length() - 1) {
                             index = str.lastIndexOf("/", index - 1);
                             location = str.substring(index + 1);
                         } else {
                             location = str.substring(index + 1);
                         }
                     }
                 }
             } catch (final Exception ex) {
                 // Ignore the exception.
             }
             final Package pkg = callerClass.getPackage();
             if (pkg != null) {
                 final String ver = pkg.getImplementationVersion();
                 if (ver != null) {
                     version = ver;
                 }
             }
             lastLoader = callerClass.getClassLoader();
         }
         return new CacheEntry(new ExtendedClassInfo(exact, location, version), lastLoader);
     }
 
     /**
      * Resolve all the stack entries in this stack trace that are not common with the parent.
      * 
      * @param stack
      *        The callers Class stack.
      * @param map
      *        The cache of CacheEntry objects.
      * @param rootTrace
      *        The first stack trace resolve or null.
      * @param stackTrace
      *        The stack trace being resolved.
      * @return The StackTracePackageElement array.
      */
     ExtendedStackTraceElement[] toExtendedStackTrace(final Stack<Class<?>> stack, final Map<String, CacheEntry> map,
             final StackTraceElement[] rootTrace, final StackTraceElement[] stackTrace) {
         int stackLength;
         if (rootTrace != null) {
             int rootIndex = rootTrace.length - 1;
             int stackIndex = stackTrace.length - 1;
             while (rootIndex >= 0 && stackIndex >= 0 && rootTrace[rootIndex].equals(stackTrace[stackIndex])) {
                 --rootIndex;
                 --stackIndex;
             }
             this.commonElementCount = stackTrace.length - 1 - stackIndex;
             stackLength = stackIndex + 1;
         } else {
             this.commonElementCount = 0;
             stackLength = stackTrace.length;
         }
         final ExtendedStackTraceElement[] extStackTrace = new ExtendedStackTraceElement[stackLength];
         Class<?> clazz = stack.isEmpty() ? null : stack.peek();
         ClassLoader lastLoader = null;
         for (int i = stackLength - 1; i >= 0; --i) {
             final StackTraceElement stackTraceElement = stackTrace[i];
             final String className = stackTraceElement.getClassName();
             // The stack returned from getCurrentStack may be missing entries for java.lang.reflect.Method.invoke()
             // and its implementation. The Throwable might also contain stack entries that are no longer
             // present as those methods have returned.
             ExtendedClassInfo extClassInfo;
             if (clazz != null && className.equals(clazz.getName())) {
                 final CacheEntry entry = this.toCacheEntry(stackTraceElement, clazz, true);
                 extClassInfo = entry.element;
                 lastLoader = entry.loader;
                 stack.pop();
                 clazz = stack.isEmpty() ? null : stack.peek();
             } else {
                 final CacheEntry cacheEntry = map.get(className);
                 if (cacheEntry != null) {
                     final CacheEntry entry = cacheEntry;
                     extClassInfo = entry.element;
                     if (entry.loader != null) {
                         lastLoader = entry.loader;
                     }
                 } else {
                     final CacheEntry entry = this.toCacheEntry(stackTraceElement,
                             this.loadClass(lastLoader, className), false);
                     extClassInfo = entry.element;
                     map.put(stackTraceElement.toString(), entry);
                     if (entry.loader != null) {
                         lastLoader = entry.loader;
                     }
                 }
             }
             extStackTrace[i] = new ExtendedStackTraceElement(stackTraceElement, extClassInfo);
         }
         return extStackTrace;
     }
 
     @Override
     public String toString() {
         final String msg = this.message;
         return msg != null ? this.name + ": " + msg : this.name;
     }
 
     private ThrowableProxy[] toSuppressedProxies(final Throwable thrown, Set<Throwable> suppressedVisited) {
         try {
             final Throwable[] suppressed = thrown.getSuppressed();
             if (suppressed == null) {
                 return EMPTY_THROWABLE_PROXY_ARRAY;
             }
             final List<ThrowableProxy> proxies = new ArrayList<>(suppressed.length);
             if (suppressedVisited == null) {
                 suppressedVisited = new HashSet<>(proxies.size());
             }
             for (int i = 0; i < suppressed.length; i++) {
                 final Throwable candidate = suppressed[i];
                 if (!suppressedVisited.contains(candidate)) {
                     suppressedVisited.add(candidate);
                     proxies.add(new ThrowableProxy(candidate, suppressedVisited));
                 }
             }
             return proxies.toArray(new ThrowableProxy[proxies.size()]);
         } catch (final Exception e) {
             StatusLogger.getLogger().error(e);
         }
         return null;
     }
 }