/*
 * Copyright 2023 Code Intelligence GmbH
 *
 * 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 com.code_intelligence.jazzer.mutation.api;

/**
 * Knows how to initialize and mutate (parts of) an existing object of type {@code T} in place and
 * how to incorporate (cross over) parts of another object of the same type.
 *
 * <p>Certain types, such as immutable and primitive types, can not be mutated in place. For
 * example, {@link java.util.List} can be mutated in place whereas {@link String} and {@code int}
 * can't. In such cases, use {@link ValueMutator} instead.
 *
 * <p>Implementations
 * <ul>
 *   <li>MAY weakly associate mutable state with the identity (not equality class) of objects they
 *   have been passed as arguments or returned from initialization functions;
 *   <li>MAY assume that they are only passed arguments that they have initialized or mutated;</li>
 *   <li>SHOULD use {@link com.code_intelligence.jazzer.mutation.support.WeakIdentityHashMap} for
 *   this purpose;
 *   <li>MUST otherwise be deeply immutable;
 *   <li>SHOULD override {@link Object#toString()} to return {@code
 * Debuggable.getDebugString(this)}.
 * </ul>
 *
 * @param <T> the reference type this mutator operates on
 */
public interface InPlaceMutator<T> extends Debuggable {
  /**
   * Implementations
   * <ul>
   *   <li>MUST accept any mutable instance of {@code T}, not just those it creates itself.
   *   <li>SHOULD, when called repeatedly, initialize the object in ways that are likely to be
   *   distinct.
   * </ul>
   */
  void initInPlace(T reference, PseudoRandom prng);

  /**
   * Implementations
   * <ul>
   *   <li>MUST ensure that {@code reference} does not {@link Object#equals(Object)} the state it
   * had prior to the call (if possible);
   *   <li>MUST accept any mutable instance of {@code T}, not just those it creates itself.
   *   <li>SHOULD, when called repeatedly, be able to eventually reach any valid state of the part
   * of {@code T} governed by this mutator;
   * </ul>
   */
  void mutateInPlace(T reference, PseudoRandom prng);

  /**
   * Implementations
   * <ul>
   *   <li>MUST ensure that {@code reference} does not {@link Object#equals(Object)} the state it
   * had prior to the call (if possible);
   *   <li>MUST accept any mutable instance of {@code T}, not just those it creates itself.
   *   <li>MUST NOT mutate {@code otherReference}</li>
   * </ul>
   */
  void crossOverInPlace(T reference, T otherReference, PseudoRandom prng);
}