/*
 * 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.tokenize.lang.en;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.regex.Pattern;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import opennlp.tools.tokenize.TokenSample;
import opennlp.tools.util.Span;

/**
 * Class which produces an Iterator&lt;TokenSample&gt; from a file of space delimited token.
 * This class uses a number of English-specific heuristics to un-separate tokens which
 * are typically found together in text.
 */
public class TokenSampleStream implements Iterator<TokenSample> {

  private static final Logger logger = LoggerFactory.getLogger(TokenSampleStream.class);
  private final BufferedReader in;
  private String line;
  private final Pattern alphaNumeric = Pattern.compile("[A-Za-z0-9]");
  private boolean evenq = true;

  public TokenSampleStream(InputStream is) throws IOException {
    this.in = new BufferedReader(new InputStreamReader(is));
    line = in.readLine();
  }

  public boolean hasNext() {
    return line != null;
  }

  public TokenSample next() {
    String[] tokens = line.split("\\s+");
    if (tokens.length == 0) {
      evenq = true;
    }
    StringBuilder sb = new StringBuilder(line.length());
    List<Span> spans = new ArrayList<>();
    int length = 0;
    for (int ti = 0; ti < tokens.length; ti++) {
      String token = tokens[ti];
      String lastToken = ti - 1 >= 0 ? tokens[ti - 1] : "";
      switch (token) {
        case "-LRB-":
          token = "(";
          break;
        case "-LCB-":
          token = "{";
          break;
        case "-RRB-":
          token = ")";
          break;
        case "-RCB-":
          token = "}";
          break;
      }
      if (sb.length() != 0) {
        if (!alphaNumeric.matcher(token).find() || token.startsWith("'") || token.equalsIgnoreCase("n't")) {
          if ((token.equals("``") || token.equals("--") || token.equals("$") ||
              token.equals("(")  || token.equals("&")  || token.equals("#") ||
              (token.equals("\"") && (evenq && ti != tokens.length - 1)))
              && (!lastToken.equals("(") || !lastToken.equals("{"))) {
            length++;
          }
        }
        else {
          if (!lastToken.equals("``") && (!lastToken.equals("\"") || evenq) && !lastToken.equals("(")
              && !lastToken.equals("{") && !lastToken.equals("$") && !lastToken.equals("#")) {
            length++;
          }
        }
      }
      if (token.equals("\"")) {
        evenq = ti == tokens.length - 1 || !evenq;
      }
      if (sb.length() < length) {
        sb.append(" ");
      }
      sb.append(token);
      spans.add(new Span(length, length + token.length()));
      length += token.length();
    }

    try {
      line = in.readLine();
    } catch (IOException e) {
      logger.error(e.getLocalizedMessage(), e);
      line = null;
    }
    return new TokenSample(sb.toString(),spans.toArray(new Span[0]));
  }


  public void remove() {
    throw new UnsupportedOperationException();
  }

  private static void usage() {
    logger.info("TokenSampleStream [-spans] < in");
    logger.info("Where in is a space delimited list of tokens.");
  }
}
