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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

import Aggregating.tryEquality
import org.scalactic.Equality
import org.scalatest.FailureMessages
import scala.annotation.tailrec
import scala.collection.GenTraversable

/**
 * Supertrait for typeclasses that enable be empty matcher syntax.
 *
 * 
 * An Emptiness[T] provides access to the "emptiness" of type T in such
 * a way that be empty matcher syntax can be used with type T. A T
 * can be any type that in some way can be empty. ScalaTest provides implicit implementations for several types. 
 * You can enable the be empty matcher syntax on your own type U by defining an Emptiness[U]
 * for the type and making it available implicitly.
 * 
 * 

 * ScalaTest provides implicit Emptiness instances for scala.collection.GenTraversable,
 * java.util.Collection, java.util.Map, String, Array, 
 * and scala.Option in the Emptiness companion object.
 * 
 */
trait Emptiness[-T] {

  /**
   * Determines whether the passed thing is readable, i.e., the passed file is readable.
   *
   * @param thing the thing to check for emptiness
   * @return true if passed thing is empty, false otherwise
   */
  def isEmpty(thing: T): Boolean
}

/**
 * Companion object for Emptiness that provides implicit implementations for the following types:
 *
 * 
 * scala.collection.GenTraversable
 * String
 * Array
 * scala.Option
 * java.util.Collection
 * java.util.Map
 * arbitary object with a isEmpty() method that returns Boolean
 * arbitary object with a parameterless isEmpty method that returns Boolean
 * 
 */
object Emptiness {

  import scala.language.higherKinds
import scala.reflect.Selectable.reflectiveSelectable

  /**
   * Enable Emptiness implementation for scala.collection.GenTraversable
   *
   * @tparam E the type of the element in the scala.collection.GenTraversable
   * @tparam TRAV any subtype of scala.collection.GenTraversable
   * @return Emptiness[TRAV[E]] that supports scala.collection.GenTraversable in be empty syntax
   */
  implicit def emptinessOfGenTraversable[E, TRAV[e] <: scala.collection.GenTraversable[e]]: Emptiness[TRAV[E]] =
    new Emptiness[TRAV[E]] {
      def isEmpty(trav: TRAV[E]): Boolean = trav.isEmpty
    }
  
  /**
   * Enable Emptiness implementation for Array
   *
   * @tparam E the type of the element in the Array
   * @return Emptiness[Array[E]] that supports Array in be empty syntax
   */
  implicit def emptinessOfArray[E]: Emptiness[Array[E]] =
    new Emptiness[Array[E]] {
      def isEmpty(arr: Array[E]): Boolean = arr.length == 0
    }
  
  /**
   * Enable Emptiness implementation for String
   *
   * @return Emptiness[String] that supports String in be empty syntax
   */
  implicit def emptinessOfString: Emptiness[String] =
    new Emptiness[String] {
      def isEmpty(str: String): Boolean = str.isEmpty
    }
  
  /**
   * Enable Emptiness implementation for scala.Option
   *
   * @tparam E the type of the element in the scala.Option
   * @tparam OPT any subtype of scala.Option
   * @return Emptiness[OPT[E]] that supports scala.Option in be empty syntax
   */
  implicit def emptinessOfOption[E, OPT[e] <: Option[e]]: Emptiness[OPT[E]] =
    new Emptiness[OPT[E]] {
      def isEmpty(opt: OPT[E]): Boolean = opt.isEmpty
    }
  
  /**
   * Enable Emptiness implementation for java.util.Collection
   *
   * @tparam E the type of the element in the java.util.Collection
   * @tparam JCOL any subtype of java.util.Collection
   * @return Emptiness[JCOL[E]] that supports java.util.Collection in be empty syntax
   */
  implicit def emptinessOfJavaCollection[E, JCOL[e] <: java.util.Collection[e]]: Emptiness[JCOL[E]] =
    new Emptiness[JCOL[E]] {
      def isEmpty(jcol: JCOL[E]): Boolean = jcol.isEmpty
    }

  /**
   * Enable Emptiness implementation for java.util.Map
   *
   * @tparam K the type of the key in the java.util.Map
   * @tparam V the type of the value in the java.util.Map
   * @tparam JMAP any subtype of java.util.Map
   * @return Emptiness[JMAP[K, V]] that supports java.util.Map in be empty syntax
   */
  implicit def emptinessOfJavaMap[K, V, JMAP[k, v] <: java.util.Map[k, v]]: Emptiness[JMAP[K, V]] =
    new Emptiness[JMAP[K, V]] {
      def isEmpty(jmap: JMAP[K, V]): Boolean = jmap.isEmpty
    }

  import scala.language.reflectiveCalls
  
  /**
   * Enable Emptiness implementation for any arbitrary object with a isEmpty() method that returns Boolean
   *
   * @tparam T any type that has a isEmpty() method that returns Boolean
   * @return Emptiness[T] that supports T in be empty syntax
   */
  implicit def emptinessOfAnyRefWithIsEmptyMethod[T <: AnyRef { def isEmpty(): Boolean}]: Emptiness[T] = 
    new Emptiness[T] {
      def isEmpty(obj: T): Boolean = obj.isEmpty()
    }
  
  /**
   * Enable Emptiness implementation for any arbitrary object with a isEmpty method that returns Boolean
   *
   * @tparam T any type that has a parameterless isEmpty method that returns Boolean
   * @return Emptiness[T] that supports T in be empty syntax
   */
  implicit def emptinessOfAnyRefWithParameterlessIsEmptyMethod[T <: AnyRef { def isEmpty: Boolean}]: Emptiness[T] = 
    new Emptiness[T] {
      def isEmpty(obj: T): Boolean = obj.isEmpty
    }
}