/*
 * Copyright (c) 2015-present, Parse, LLC.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */
package com.parse;

import android.os.Parcel;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

/**
 * A ParseFieldOperation represents a modification to a value in a ParseObject. For example,
 * setting, deleting, or incrementing a value are all different kinds of ParseFieldOperations.
 * ParseFieldOperations themselves can be considered to be immutable.
 */
/** package */ interface ParseFieldOperation {
  /**
   * Converts the ParseFieldOperation to a data structure (typically a JSONObject) that can be
   * converted to JSON and sent to Parse as part of a save operation.
   * 
   * @param objectEncoder
   *          An object responsible for serializing ParseObjects.
   * @return An object to be jsonified.
   */
  Object encode(ParseEncoder objectEncoder) throws JSONException;

  /**
   * Writes the ParseFieldOperation to the given Parcel using the given encoder.
   *
   * @param dest
   *          The destination Parcel.
   * @param parcelableEncoder
   *          A ParseParcelableEncoder.
   */
  void encode(Parcel dest, ParseParcelEncoder parcelableEncoder);

  /**
   * Returns a field operation that is composed of a previous operation followed by this operation.
   * This will not mutate either operation. However, it may return self if the current operation is
   * not affected by previous changes. For example:
   * 
   * <pre>
   * {increment by 2}.mergeWithPrevious({set to 5}) -> {set to 7}
   * {set to 5}.mergeWithPrevious({increment by 2}) -> {set to 5}
   * {add "foo"}.mergeWithPrevious({delete}) -> {set to ["foo"]}
   * {delete}.mergeWithPrevious({add "foo"}) -> {delete}
   * </pre>
   * 
   * @param previous
   *          The most recent operation on the field, or null if none.
   * @return A new ParseFieldOperation or this.
   */
  ParseFieldOperation mergeWithPrevious(ParseFieldOperation previous);

  /**
   * Returns a new estimated value based on a previous value and this operation. This value is not
   * intended to be sent to Parse, but it used locally on the client to inspect the most likely
   * current value for a field. The key and object are used solely for ParseRelation to be able to
   * construct objects that refer back to its parent.
   * 
   * @param oldValue
   *          The previous value for the field.
   * @param key
   *          The key that this value is for.
   * @return The new value for the field.
   */
  Object apply(Object oldValue, String key);
}