/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 opennlp.tools.formats;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;

import opennlp.tools.commons.Internal;
import opennlp.tools.namefind.NameSample;
import opennlp.tools.util.InputStreamFactory;
import opennlp.tools.util.InvalidFormatException;
import opennlp.tools.util.ObjectStream;
import opennlp.tools.util.PlainTextByLineStream;
import opennlp.tools.util.Span;
import opennlp.tools.util.StringUtil;

/**
 * Parser for the Dutch and Spanish ner training files of the CONLL 2002 shared task.
 * <p>
 * The Dutch data has a {@link #DOCSTART} tag to mark article boundaries,
 * adaptive data in the feature generators will be cleared before every article.<br>
 * The Spanish data does not contain article boundaries,
 * adaptive data will be cleared for every sentence.
 * <p>
 * The data contains four named entity types: Person, Organization, Location and Misc.<br>
 * <p>
 * Data can be found on this
 * <a href="http://www.cnts.ua.ac.be/conll2002/ner/">web site</a>.
 * <p>
 * <b>Note:</b>
 * Do not use this class, internal use only!
 */
@Internal
public class Conll02NameSampleStream implements ObjectStream<NameSample> {

  public enum LANGUAGE {
    NLD,
    SPA
  }

  public static final int GENERATE_PERSON_ENTITIES = 0x01;
  public static final int GENERATE_ORGANIZATION_ENTITIES = 0x01 << 1;
  public static final int GENERATE_LOCATION_ENTITIES = 0x01 << 2;
  public static final int GENERATE_MISC_ENTITIES = 0x01 << 3;

  public static final String DOCSTART = "-DOCSTART-";

  private final LANGUAGE lang;
  private final ObjectStream<String> lineStream;

  private final int types;

  /**
   * Initializes a {@link Conll02NameSampleStream}.
   *
   * @param lang The language of the CONLL 02 data.
   * @param lineStream An {@link ObjectStream<String>} over the lines
   *                   in the CONLL 02 data file.
   * @param types The entity types to include in the Name Sample object stream.
   */
  public Conll02NameSampleStream(LANGUAGE lang, ObjectStream<String> lineStream, int types) {
    this.lang = lang;
    this.lineStream = lineStream;
    this.types = types;
  }

  /**
   * Initializes a {@link Conll02NameSampleStream}.
   *
   * @param lang The language of the CONLL 02 data.
   * @param in  The {@link InputStreamFactory} for the input file.
   * @param types The entity types to include in the Name Sample object stream.
   *
   * @throws IOException Thrown if IO errors occurred.
   */
  public Conll02NameSampleStream(LANGUAGE lang, InputStreamFactory in, int types) throws IOException {
    this (lang, new PlainTextByLineStream(in, StandardCharsets.UTF_8), types);
  }

  static Span extract(int begin, int end, String beginTag) throws InvalidFormatException {

    String type = beginTag.substring(2);

    switch (type) {
      case "PER":
        type = "person";
        break;
      case "LOC":
        type = "location";
        break;
      case "MISC":
        type = "misc";
        break;
      case "ORG":
        type = "organization";
        break;
      default:
        throw new InvalidFormatException("Unknown type: " + type);
    }

    return new Span(begin, end, type);
  }

  @Override
  public NameSample read() throws IOException {

    List<String> sentence = new ArrayList<>();
    List<String> tags = new ArrayList<>();

    boolean isClearAdaptiveData = false;

    // Empty line indicates end of sentence

    String line;
    while ((line = lineStream.read()) != null && !StringUtil.isEmpty(line)) {

      if (LANGUAGE.NLD.equals(lang) && line.startsWith(DOCSTART)) {
        isClearAdaptiveData = true;
        continue;
      }

      String[] fields = line.split(" ");

      if (fields.length == 3) {
        sentence.add(fields[0]);
        tags.add(fields[2]);
      }
      else {
        throw new IOException("Expected three fields per line in training data, got " +
            fields.length + " for line '" + line + "'!");
      }
    }

    // Always clear adaptive data for spanish
    if (LANGUAGE.SPA.equals(lang))
      isClearAdaptiveData = true;

    if (sentence.size() > 0) {

      // convert name tags into spans
      List<Span> names = new ArrayList<>();

      int beginIndex = -1;
      int endIndex = -1;
      for (int i = 0; i < tags.size(); i++) {

        String tag = tags.get(i);

        if (tag.endsWith("PER") && (types & GENERATE_PERSON_ENTITIES) == 0)
          tag = "O";

        if (tag.endsWith("ORG") && (types & GENERATE_ORGANIZATION_ENTITIES) == 0)
          tag = "O";

        if (tag.endsWith("LOC") && (types & GENERATE_LOCATION_ENTITIES) == 0)
          tag = "O";

        if (tag.endsWith("MISC") && (types & GENERATE_MISC_ENTITIES) == 0)
          tag = "O";

        if (tag.startsWith("B-")) {

          if (beginIndex != -1) {
            names.add(extract(beginIndex, endIndex, tags.get(beginIndex)));
            beginIndex = -1;
            endIndex = -1;
          }

          beginIndex = i;
          endIndex = i + 1;
        }
        else if (tag.startsWith("I-")) {
          endIndex++;
        }
        else if (tag.equals("O")) {
          if (beginIndex != -1) {
            names.add(extract(beginIndex, endIndex, tags.get(beginIndex)));
            beginIndex = -1;
            endIndex = -1;
          }
        }
        else {
          throw new IOException("Invalid tag: " + tag);
        }
      }

      // if one span remains, create it here
      if (beginIndex != -1)
        names.add(extract(beginIndex, endIndex, tags.get(beginIndex)));

      return new NameSample(sentence.toArray(new String[0]),
          names.toArray(new Span[0]), isClearAdaptiveData);
    }
    else if (line != null) {
      // Just filter out empty events, if two lines in a row are empty
      return read();
    }
    else {
      // source stream is not returning anymore lines
      return null;
    }
  }

  @Override
  public void reset() throws IOException, UnsupportedOperationException {
    lineStream.reset();
  }

  @Override
  public void close() throws IOException {
    lineStream.close();
  }
}
