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/*
 * Copyright © 2017 camunda services GmbH ([email protected])
 *
 * 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 io.zeebe.msgpack.mapping;

import io.zeebe.msgpack.spec.MsgPackFormat;
import io.zeebe.msgpack.spec.MsgPackType;
import io.zeebe.util.EnsureUtil;
import org.agrona.DirectBuffer;
import org.agrona.concurrent.UnsafeBuffer;

public class MsgPackMergeTool {

  /** The maximum JSON key length. */
  public static final int MAX_JSON_KEY_LEN = 256;

  /**
   * The message for the exception, which is thrown if the resulting document is not a map (json
   * object).
   */
  public static final String EXCEPTION_MSG_RESULTING_DOCUMENT_IS_NOT_OF_TYPE_MAP =
      "Processing failed, since mapping will result in a non map object (json object).";

  /** The message for the exception which is thrown if the mapping is either null or empty. */
  public static final String EXCEPTION_MSG_MAPPING_NULL_NOR_EMPTY =
      "Mapping must be neither null nor empty!";

  private final MsgPackDocumentIndexer documentIndexer;
  private final MsgPackDocumentExtractor documentExtractor;
  private final MsgPackDocumentTreeWriter treeWriter;

  private final MsgPackTree currentTree = new MsgPackTree();
  private final UnsafeBuffer resultBuffer = new UnsafeBuffer(0, 0);

  public MsgPackMergeTool(int initialDocumentSize) {
    this.documentIndexer = new MsgPackDocumentIndexer();
    this.documentExtractor = new MsgPackDocumentExtractor();
    this.treeWriter = new MsgPackDocumentTreeWriter(initialDocumentSize);

    reset();
  }

  public void reset() {
    currentTree.clear();
  }

  /**
   * Throws no mapping exceptions. Assumes default values in case a mapping has ambiguous results.
   */
  public void mergeDocument(DirectBuffer document, Mapping... mappings) {
    mergeDocument(document, false, mappings);
  }

  /**
   * Throws exceptions on ambiguous mapping results
   *
   * @throws MappingException in case a mapping has ambiguous results
   */
  public void mergeDocumentStrictly(DirectBuffer document, Mapping... mappings) {
    mergeDocument(document, true, mappings);
  }

  private void mergeDocument(DirectBuffer document, boolean strictMode, Mapping... mappings) {
    EnsureUtil.ensureNotNull("document", document);

    if (mappings != null && mappings.length > 0) {
      final MsgPackDiff diff = documentExtractor.extract(document, strictMode, mappings);
      diff.mergeInto(currentTree);
    } else {
      final MsgPackDiff diff = documentIndexer.index(document);

      diff.mergeInto(currentTree);
    }
  }

  public DirectBuffer writeResultToBuffer() {
    final int resultLen = treeWriter.write(currentTree);
    resultBuffer.wrap(treeWriter.getResult(), 0, resultLen);

    // would be nicer to do this in the merge methods, but not easily doable with
    // current MsgPackTree implementation
    ensureDocumentIsAMsgPackMap(resultBuffer, EXCEPTION_MSG_RESULTING_DOCUMENT_IS_NOT_OF_TYPE_MAP);

    return resultBuffer;
  }

  private void ensureDocumentIsAMsgPackMap(DirectBuffer document, String exceptionMsg) {
    final byte b = document.getByte(0);
    final MsgPackFormat format = MsgPackFormat.valueOf(b);
    if (format.getType() != MsgPackType.MAP && format.getType() != MsgPackType.NIL) {
      throw new MappingException(exceptionMsg);
    }
  }
}