package us.codecraft.webmagic.utils;
   
   import us.codecraft.webmagic.Request;
   
   import java.util.ArrayList;
   import java.util.Collections;
   import java.util.List;
   import java.util.regex.Matcher;
   import java.util.regex.Pattern;
  
  /**
   * @author code4crafter@gmail.com
   *         Date: 2017/6/5
   *         Time: 下午4:58
   */
  public abstract class RequestUtils {
  
      private static Pattern p4Range = Pattern.compile("\\[(\\d+)\\-(\\d+)\\]");
  
      public static List<Request> from(String exp){
          Matcher matcher = p4Range.matcher(exp);
          if (!matcher.find()) {
              return Collections.singletonList(new Request(exp));
          }
          int rangeFrom = Integer.parseInt(matcher.group(1));
          int rangeTo = Integer.parseInt(matcher.group(2));
          if (rangeFrom > rangeTo) {
              return Collections.emptyList();
          }
          List<Request> requests = new ArrayList<Request>(rangeTo - rangeFrom + 1);
          for (int i = rangeFrom; i <= rangeTo; i++) {
              requests.add(new Request(matcher.replaceAll(String.valueOf(i))));
          }
          return requests;
      }
  
  }