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// * 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                                                                             *
// *                                                                                                                         *
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// * specific language governing permissions and limitations under the License.                                              *
// ***************************************************************************************************************************
package org.apache.juneau.http.exception;

import static org.apache.juneau.internal.StringUtils.*;

import java.lang.reflect.*;
import java.text.*;

/**
 * Exception thrown to trigger an error HTTP status.
 *
 * <p>
 * REST methods on subclasses of <c>RestServlet</c> can throw this exception to trigger an HTTP status other than the
 * automatically-generated <c>404</c>, <c>405</c>, and <c>500</c> statuses.
 */
public class HttpException extends RuntimeException {

   private static final long serialVersionUID = 1L;

   private int status;

   /**
    * Constructor.
    *
    * @param cause The cause of this exception.
    * @param status The HTTP status code.
    * @param msg The status message.
    * @param args Optional {@link MessageFormat}-style arguments.
    */
   public HttpException(Throwable cause, int status, String msg, Object...args) {
      super(message(cause, msg, args), cause);
      this.status = status;
   }

   /**
    * Constructor.
    *
    * @param msg The status message.
    */
   public HttpException(String msg) {
      super(msg, null);
   }

   private static String message(Throwable cause, String msg, Object...args) {
      if (msg == null && cause != null)
         return firstNonEmpty(cause.getLocalizedMessage(), cause.getClass().getName());
      return format(msg, args);
   }

   /**
    * Constructor.
    * @param cause The root exception.
    * @param status The HTTP status code.
    */
   public HttpException(Throwable cause, int status) {
      this(cause, status, null);
   }

   /**
    * Constructor.
    *
    * @param status The HTTP status code.
    * @param msg The status message.
    * @param args Optional {@link MessageFormat}-style arguments.
    */
   public HttpException(int status, String msg, Object...args) {
      this(null, status, msg, args);
   }

   /**
    * Returns the root cause of this exception.
    *
    * <p>
    * The root cause is the first exception in the init-cause parent chain that's not one of the following:
    * <ul>
    *    <li>{@link HttpException}
    *    <li>{@link InvocationTargetException}
    * </ul>
    *
    * @return The root cause of this exception, or <jk>null</jk> if no root cause was found.
    */
   public Throwable getRootCause() {
      Throwable t = this;
      while(t != null) {
         t = t.getCause();
         if (! (t instanceof HttpException || t instanceof InvocationTargetException))
            return t;
      }
      return null;
   }

   /**
    * Returns all error messages from all errors in this stack.
    *
    * <p>
    * Typically useful if you want to render all the error messages in the stack, but don't want to render all the
    * stack traces too.
    *
    * @param scrubForXssVulnerabilities
    *    If <jk>true</jk>, replaces <js>'&lt;'</js>, <js>'&gt;'</js>, and <js>'&amp;'</js> characters with spaces.
    * @return All error messages from all errors in this stack.
    */
   public String getFullStackMessage(boolean scrubForXssVulnerabilities) {
      String msg = getMessage();
      StringBuilder sb = new StringBuilder();
      if (msg != null) {
         if (scrubForXssVulnerabilities)
            msg = msg.replace('<', ' ').replace('>', ' ').replace('&', ' ');
         sb.append(msg);
      }
      Throwable e = getCause();
      while (e != null) {
         msg = e.getMessage();
         if (msg != null && scrubForXssVulnerabilities)
            msg = msg.replace('<', ' ').replace('>', ' ').replace('&', ' ');
         String cls = e.getClass().getSimpleName();
         if (msg == null)
            sb.append(format("\nCaused by ({0})", cls));
         else
            sb.append(format("\nCaused by ({0}): {1}", cls, msg));
         e = e.getCause();
      }
      return sb.toString();
   }

   @Override /* Object */
   public int hashCode() {
      int i = 0;
      Throwable t = this;
      while (t != null) {
         for (StackTraceElement e : t.getStackTrace())
         i ^= e.hashCode();
         t = t.getCause();
      }
      return i;
   }

   /**
    * Set the status code on this exception.
    *
    * @param status The status code.
    * @return This object (for method chaining).
    */
   protected HttpException setStatus(int status) {
      this.status = status;
      return this;
   }

   /**
    * Returns the HTTP status code.
    *
    * @return The HTTP status code.
    */
   public int getStatus() {
      return status;
   }

   // When serialized, just serialize the message itself.
   @Override /* Object */
   public String toString() {
      return emptyIfNull(getLocalizedMessage());
   }
}