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

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;

/**
 * An operation that adds a new element to an array field, only if it wasn't already present.
 */
/** package */ class ParseAddUniqueOperation implements ParseFieldOperation {
  /* package */ final static String OP_NAME = "AddUnique";

  protected final LinkedHashSet<Object> objects = new LinkedHashSet<>();

  public ParseAddUniqueOperation(Collection<?> col) {
    objects.addAll(col);
  }

  @Override
  public JSONObject encode(ParseEncoder objectEncoder) throws JSONException {
    JSONObject output = new JSONObject();
    output.put("__op", OP_NAME);
    output.put("objects", objectEncoder.encode(new ArrayList<>(objects)));
    return output;
  }

  @Override
  public void encode(Parcel dest, ParseParcelEncoder parcelableEncoder) {
    dest.writeString(OP_NAME);
    dest.writeInt(objects.size());
    for (Object object : objects) {
      parcelableEncoder.encode(object, dest);
    }
  }

    @Override
  @SuppressWarnings("unchecked")
  public ParseFieldOperation mergeWithPrevious(ParseFieldOperation previous) {
    if (previous == null) {
      return this;
    } else if (previous instanceof ParseDeleteOperation) {
      return new ParseSetOperation(objects);
    } else if (previous instanceof ParseSetOperation) {
      Object value = ((ParseSetOperation) previous).getValue();
      if (value instanceof JSONArray || value instanceof List) {
        return new ParseSetOperation(this.apply(value, null));
      } else {
        throw new IllegalArgumentException("You can only add an item to a List or JSONArray.");
      }
    } else if (previous instanceof ParseAddUniqueOperation) {
      List<Object> previousResult =
          new ArrayList<>(((ParseAddUniqueOperation) previous).objects);
      return new ParseAddUniqueOperation((List<Object>) this.apply(previousResult, null));
    } else {
      throw new IllegalArgumentException("Operation is invalid after previous operation.");
    }
  }

  @Override
  public Object apply(Object oldValue, String key) {
    if (oldValue == null) {
      return new ArrayList<>(objects);
    } else if (oldValue instanceof JSONArray) {
      ArrayList<Object> old = ParseFieldOperations.jsonArrayAsArrayList((JSONArray) oldValue);
      @SuppressWarnings("unchecked")
      ArrayList<Object> newValue = (ArrayList<Object>) this.apply(old, key);
      return new JSONArray(newValue);
    } else if (oldValue instanceof List) {
      ArrayList<Object> result = new ArrayList<>((List<?>) oldValue);

      // Build up a Map of objectIds of the existing ParseObjects in this field.
      HashMap<String, Integer> existingObjectIds = new HashMap<>();
      for (int i = 0; i < result.size(); i++) {
        if (result.get(i) instanceof ParseObject) {
          existingObjectIds.put(((ParseObject) result.get(i)).getObjectId(), i);
        }
      }

      // Iterate over the objects to add. If it already exists in the field,
      // remove the old one and add the new one. Otherwise, just add normally.
      for (Object obj : objects) {
        if (obj instanceof ParseObject) {
          String objectId = ((ParseObject) obj).getObjectId();
          if (objectId != null && existingObjectIds.containsKey(objectId)) {
            result.set(existingObjectIds.get(objectId), obj);
          } else if (!result.contains(obj)) {
            result.add(obj);
          }
        } else {
          if (!result.contains(obj)) {
            result.add(obj);
          }
        }
      }
      return result;
    } else {
      throw new IllegalArgumentException("Operation is invalid after previous operation.");
    }
  }
}