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/*
 * Copyright 2001-2013 Artima, Inc.
 *
 * Licensed 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.scalatest.enablers

/**
 * Supertrait for Messaging typeclasses.
 *
 * 
 * Trait Messaging is a typeclass trait for objects that can be queried for message.
 * Objects of type T for which an implicit Messaging[T] is available can be used
 * with the should have message syntax.
 * You can enable the have message matcher syntax on your own
 * type U by defining a Messaging[U] for the type and making it available implicitly.
 * 
 *
 * 
 * ScalaTest provides an implicit Messaging instance for java.lang.Throwable and
 * arbitary object with message(), message, getMessage() or getMessage
 * method in the Messaging companion object.
 * 
 *
 * @author Bill Venners
 * @author Chee Seng
 */
trait Messaging[T] {

  /**
   * Returns the message of the passed object.
   *
   * @param obj object whose message to return
   * @return the message of the passed object
   */
  def messageOf(obj: T): String
}

/**
 * Companion object for Messaging that provides implicit implementations for the following types:
 *
 * 
 * java.lang.Throwable
 * arbitary object with a message() method that returns String
 * arbitary object with a parameterless message method that returns String
 * arbitary object with a getMessage() method that returns String
 * arbitary object with a parameterless getMessage method that returns String
 * 
 */
object Messaging {

  /**
   * Enable Messaging implementation for java.lang.Throwable
   *
   * @tparam EX any subtype of java.lang.Throwable
   * @return Messaging[EX] that supports java.lang.Throwable in have message syntax
   */
  implicit def messagingNatureOfThrowable[EX <: Throwable]: Messaging[EX] = 
    new Messaging[EX] {
      def messageOf(exception: EX): String = exception.getMessage
    }

  import scala.language.reflectiveCalls

  /**
   * Provides Messaging implementation for any arbitrary object with a message() method that returns String
   *
   * @tparam T any type that has a message() method that returns String
   * @return Messaging[T] that supports T in have message syntax
   */
  implicit def messagingNatureOfAnyRefWithMessageMethod[T <: AnyRef { def message(): String}]: Messaging[T] = 
    new Messaging[T] {
      def messageOf(obj: T): String = obj.message
    }

  /**
   * Provides Messaging implementation for any arbitrary object with a parameterless message method that returns String
   *
   * @tparam T any type that has a parameterless message method that returns String
   * @return Messaging[T] that supports T in have message syntax
   */
  implicit def messagingNatureOfAnyRefWithParameterlessMessageMethod[T <: AnyRef { def message: String}]: Messaging[T] = 
    new Messaging[T] {
      def messageOf(obj: T): String = obj.message
    }

  /**
   * Provides Messaging implementation for any arbitrary object with a getMessage() method that returns String
   *
   * @tparam T any type that has a getMessage() method that returns String
   * @return Messaging[T] that supports T in have message syntax
   */
  implicit def messagingNatureOfAnyRefWithGetMessageMethod[T <: AnyRef { def getMessage(): String}]: Messaging[T] = 
    new Messaging[T] {
      def messageOf(obj: T): String = obj.getMessage
    }

  /**
   * Provides Messaging implementation for any arbitrary object with a parameterless getMessage method that returns String
   *
   * @tparam T any type that has a parameterless getMessage method that returns String
   * @return Messaging[T] that supports T in have message syntax
   */
  implicit def messagingNatureOfAnyRefWithParameterlessGetMessageMethod[T <: AnyRef { def getMessage: String}]: Messaging[T] = 
    new Messaging[T] {
      def messageOf(obj: T): String = obj.getMessage
    }
}