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package org.specs2
package control

import java.io. { StringWriter, PrintWriter }
import text.NotNullStrings._

/**
 * This trait allows to add some utility methods to `Throwable` objects.
 */
private [specs2]
trait Throwablex {
  /**
   * Implicit method to add additional methods to Throwable objects
   */
  implicit def extend[T <: Throwable](t: T) = new ExtendedThrowable(t)  
  /**
   * See the ExtendedExceptions object description
   */
  class ExtendedThrowable[T <: Throwable](t: T) {
    private val topTrace = TraceLocation(if (t.getStackTrace().isEmpty) stackTraceElement("specs2") else t.getStackTrace()(0))
    /** @return the file name and the line number where the Throwable was created */
    def location = topTrace.location
    /** @return the class name and the line number where the Throwable was created */
    def classLocation = topTrace.classLocation
    /** @return the class name, file Name and the line number where the Throwable was created */
    def fullLocation= topTrace.fullLocation
    /** @return the ith stacktrace element */
    def apply(i: Int) = t.getStackTrace()(i)
    /** @return the first stacktrace element as an option */
    def headOption = t.getStackTrace().toList.headOption
    /** 
     * Select all traces of this exception matching a given pattern
     */
    def filter(pattern: String) = {
      setStackTrace(t.getStackTrace.toList.filter(patternMatches(pattern)))
    }
    /**
     * Select all traces of this exception according to filtering function
     * WARNING: this mutates the exception to be able to retain its type!
     */
    def filter(f: Seq[StackTraceElement] => Seq[StackTraceElement]): T = {
      chainedExceptions.foreach(_.filter(f))
      setStackTrace(f(t.getStackTrace.toList))
    }

    /** match a stacktrace element with a pattern */
    private def patternMatches(p: String) = (_:StackTraceElement).toString matches (".*"+p+".*")
    /**
     * Select all traces of this exception not matching a given pattern
     */
    def filterNot(pattern: String) = {
      setStackTrace(t.getStackTrace.toList.filterNot(patternMatches(pattern)))
    }
    /** @return true if the pattern exists in one of the traces */
    def exists(pattern: String) = {
      t.getStackTrace.toList.exists(patternMatches(pattern))
    }
    /** @return the list of chained exceptions */
    def chainedExceptions: List[Throwable] = {
      if (t.getCause == null) List() 
      else t.getCause :: t.getCause.chainedExceptions
    }
    /** @return the list of all stacktrace elements */
    def getFullStackTrace: List[java.lang.StackTraceElement] = (t :: chainedExceptions).flatMap(_.getStackTrace)
    /**
     * @return the full stack trace as a string
     */
    def getFullStackTraceAsString: String = {
       val stringWriter = new java.io.StringWriter
       val pr = new PrintWriter(stringWriter)
       try { t.printStackTrace(pr) } finally { pr.close }
       stringWriter.toString
    } 

    /** print all the stacktrace for t, including the traces from its causes */
    def printFullStackTrace() = t.getFullStackTrace.foreach(println(_))

    /** set a new stacktrace */
    private def setStackTrace(st: Seq[StackTraceElement]) = {
      t.setStackTrace(st.toArray)
      t
    }

    /** @return the exception message and its cause if any */
    def messageAndCause = t.getMessage.notNull + (if (t.getCause != null) ". Cause: "+t.getCause.getMessage.notNull else "")
  }
  /** utility method to create a default stacktrace element */
  def stackTraceElement(m: String, className: String = "internals", fileName: String = "file", lineNumber: Int = 1) = 
     new StackTraceElement(m, className, fileName, lineNumber)
  /** @return an exception with the given message and stacktrace */
  def exception(m: String, st: Seq[StackTraceElement], cause: Throwable = null): Exception = {
    val exception = new Exception(m, cause)
    exception.setStackTrace(st.toArray)
    exception
  }
  /** @return an exception with the given stacktrace */
  def exception(st: Seq[StackTraceElement]): Exception = exception("", st)
  /** location information from a stackTrace element */
}

private[specs2]
case class TraceLocation(path: String, fileName: String, className: String, lineNumber: Int) {
  lazy val location: String = fileName + ":" + lineNumber
  /** the class name and the line number where the Throwable was created */
  lazy val classLocation: String = className + ":" + lineNumber
  /** the class name, file Name and the line number where the Throwable was created */
  lazy val fullLocation: String = className + " (" + location + ")"
}

private[specs2]
object TraceLocation {
  def apply(t: StackTraceElement): TraceLocation = {
    /** path corresponding to the class name. This is an approximation corresponding to the
     *  simple case of a top-level class in a file having the same name */
    lazy val path = className.split("\\.").dropRight(1).mkString("", "/", "/"+fileName)
    lazy val fileName = t.getFileName
    lazy val className = t.getClassName.split('$')(0)
    lazy val lineNumber = t.getLineNumber
    TraceLocation(path, fileName, className, lineNumber)
  }
}

private [specs2]
object Throwablex extends Throwablex




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