/*
 * 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.namefind.NameSample;
import opennlp.tools.util.InputStreamFactory;
import opennlp.tools.util.ObjectStream;
import opennlp.tools.util.PlainTextByLineStream;
import opennlp.tools.util.Span;
import opennlp.tools.util.StringUtil;

/**
 * An import stream which can parse the CONLL03 data.
 */
public class Conll03NameSampleStream implements ObjectStream<NameSample> {

  public enum LANGUAGE {
    EN,
    DE
  }

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

  private final int types;

  /**
   * Initializes a {@link Conll03NameSampleStream}.
   * 
   * @param lang The language of the CONLL 03 data.
   * @param lineStream An {@link ObjectStream<String>} over the lines
   *                   in the CONLL 03 data file.
   * @param types The entity types to include in the Name Sample object stream.
   */
  public Conll03NameSampleStream(LANGUAGE lang, ObjectStream<String> lineStream, int types) {
    this.lang = lang;
    this.lineStream = lineStream;
    this.types = types;
  }

  /**
   * Initializes a {@link Conll03NameSampleStream}.
   *
   * @param lang The language of the CONLL 03 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 Conll03NameSampleStream(LANGUAGE lang, InputStreamFactory in, int types) throws IOException {
    this(lang, new PlainTextByLineStream(in, StandardCharsets.UTF_8), types);
  }

  @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 (line.startsWith(Conll02NameSampleStream.DOCSTART)) {
        isClearAdaptiveData = true;
        String emptyLine = lineStream.read();

        if (!StringUtil.isEmpty(emptyLine))
          throw new IOException("Empty line after -DOCSTART- not empty: '" + emptyLine + "'!");

        continue;
      }

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

      // For English: WORD  POS-TAG SC-TAG NE-TAG
      if (LANGUAGE.EN.equals(lang) && fields.length == 4) {
        sentence.add(fields[0]);
        tags.add(fields[3]); // 3 is NE-TAG
      }
      // For German: WORD  LEMA-TAG POS-TAG SC-TAG NE-TAG
      else if (LANGUAGE.DE.equals(lang) && fields.length == 5) {
        sentence.add(fields[0]);
        tags.add(fields[4]); // 4 is NE-TAG
      }
      else {
        throw new IOException("Incorrect number of fields per line for language: '" + line + "'!");
      }
    }

    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 & Conll02NameSampleStream.GENERATE_PERSON_ENTITIES) == 0)
          tag = "O";

        if (tag.endsWith("ORG") &&
            (types & Conll02NameSampleStream.GENERATE_ORGANIZATION_ENTITIES) == 0)
          tag = "O";

        if (tag.endsWith("LOC") &&
            (types & Conll02NameSampleStream.GENERATE_LOCATION_ENTITIES) == 0)
          tag = "O";

        if (tag.endsWith("MISC") &&
            (types & Conll02NameSampleStream.GENERATE_MISC_ENTITIES) == 0)
          tag = "O";

        if (tag.equals("O")) {
          // O means we don't have anything this round.
          if (beginIndex != -1) {
            names.add(Conll02NameSampleStream.extract(beginIndex, endIndex, tags.get(beginIndex)));
            beginIndex = -1;
            endIndex = -1;
          }
        }
        else if (tag.startsWith("B-")) {
          // B- prefix means we have two same entities next to each other
          if (beginIndex != -1) {
            names.add(Conll02NameSampleStream.extract(beginIndex, endIndex, tags.get(beginIndex)));
          }
          beginIndex = i;
          endIndex = i + 1;
        }
        else if (tag.startsWith("I-")) {
          // I- starts or continues a current name entity
          if (beginIndex == -1) {
            beginIndex = i;
            endIndex = i + 1;
          }
          else if (!tag.endsWith(tags.get(beginIndex).substring(1))) {
            // we have a new tag type following a tagged word series
            // also may not have the same I- starting the previous!
            names.add(Conll02NameSampleStream.extract(beginIndex, endIndex, tags.get(beginIndex)));
            beginIndex = i;
            endIndex = i + 1;
          }
          else {
            endIndex ++;
          }
        }
        else {
          throw new IOException("Invalid tag: " + tag);
        }
      }

      // if one span remains, create it here
      if (beginIndex != -1)
        names.add(Conll02NameSampleStream.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();
  }

}
