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/*
 * Copyright © 2015-2019 Cask Data, Inc.
 *
 * 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.cdap.plugin.common;

import com.google.common.base.Splitter;
import io.cdap.cdap.api.dataset.lib.KeyValue;

import java.util.Iterator;
import java.util.regex.Pattern;

/**
 * Parses a list of key value pairs.
 */
public class KeyValueListParser {
  private final Pattern pairDelimiter;
  private final Pattern keyValDelimiter;
  public static final KeyValueListParser DEFAULT = new KeyValueListParser(",", ":");

  /**
   * Create a parser that uses the given regexes to parse a list of key value pairs.
   *
   * @param pairDelimiterRegex the delimiter between key value pairs.
   * @param keyValDelimiterRegex the delimiter between a key and value.
   */
  public KeyValueListParser(String pairDelimiterRegex, String keyValDelimiterRegex) {
    pairDelimiter = Pattern.compile(pairDelimiterRegex);
    keyValDelimiter = Pattern.compile(keyValDelimiterRegex);
  }

  /**
   * Parses the given list of key value pairs.
   *
   * @param kvList the string to parse
   * @return an iterable of key values
   */
  public Iterable> parse(String kvList) {
    return new KeyValueIterable(kvList);
  }

  private class KeyValueIterable implements Iterable> {
    private final String kvList;

    private KeyValueIterable(String kvList) {
      this.kvList = kvList;
    }

    @Override
    public Iterator> iterator() {
      return new KeyValueIterator(kvList);
    }
  }

  private class KeyValueIterator implements Iterator> {
    private final Iterator pairIter;

    private KeyValueIterator(String kvList) {
      pairIter = Splitter.on(pairDelimiter).trimResults().split(kvList).iterator();
    }

    @Override
    public boolean hasNext() {
      return pairIter.hasNext();
    }

    @Override
    public KeyValue next() {
      String pair = pairIter.next();
      Iterator keyValIter = Splitter.on(keyValDelimiter).trimResults().split(pair).iterator();
      String key = keyValIter.next();
      if (!keyValIter.hasNext()) {
        throw new IllegalArgumentException(String.format("Invalid syntax for key-value pair in list: %s. " +
                                                           "It is expected to be a string separated " +
                                                           "by exactly one %s", pair, keyValDelimiter));
      }
      String val = keyValIter.next();
      if (keyValIter.hasNext()) {
        throw new IllegalArgumentException(String.format("Invalid syntax for key-value pair in list: %s. " +
                                                           "It is expected to be a string separated " +
                                                           "by exactly one %s", pair, keyValDelimiter));
      }
      return new KeyValue<>(key, val);
    }

    @Override
    public void remove() {
      //no-op
    }
  }
}