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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.scalautils

/**
 * Defines a custom way to normalize instances of a type.
 *
 * 
 * This trait exists to enforce that Normalization instances can be
 * passed to whenBothAre and whenAllAre, but not decidedBy.
 * 
 * 
 * @tparam A the type whose normalization is being defined
 */
trait Normalization[A] { thisNormalization =>

// TODO: Add an example of Array[String] isInstanceOfA here and in NormalizedEquality
  /**
   * Indicates whether the passed object is an instance of type A.
   *
   * 
   * This method is invoked by the areEqual method of subclass NormalizedEquality to determine whether or not
   * b can be cast to A so that it can be safely passed to normalized.
   * To implement this method, simply call b.isInstanceOf[A] for the actual A type.
   * For example, if you are defining a NormalizedEquality[String], your isInstanceOf
   * method should look like:
   * 
   *
   *    * def isInstanceOfA(b: Any) = b.isInstanceOf[String]
   * 
   *
   * 
   * If you are defining a NormalizedEquality[xml.Node] your isInstanceOf method
   * should look like:
   * 
   *
   *    * def isInstanceOfA(b: Any) = b.isInstanceOf[xml.Node]
   * 
   *
   * @param b the object to inspect to determine whether it is an instance of A
   * @return true if the passed object is an instance of A
   */
  def normalizedIfInstanceOfA(b: Any): Any

  /**
   * Normalizes the passed object.
   *
   * @param a the object to normalize
   * @return the normalized form of the passed object
   */
  def normalized(a: A): A

  final def and(other: Normalization[A]): Normalization[A] =
    new Normalization[A] {
      def normalizedIfInstanceOfA(b: Any): Any = other.normalizedIfInstanceOfA(thisNormalization.normalizedIfInstanceOfA(b))
      // Note in Scaladoc what order, and recommend people don't do side effects anyway.
      // By order, I mean left's normalized gets called first then right's normalized gets called on that result, for "left and right"
      def normalized(a: A): A = other.normalized(thisNormalization.normalized(a))
    }
}