package us.codecraft.webmagic.selector;
   
   import org.apache.commons.lang3.StringUtils;
   
   import java.util.ArrayList;
   import java.util.List;
   import java.util.regex.Matcher;
   import java.util.regex.Pattern;
   import java.util.regex.PatternSyntaxException;
  
  /**
   * Selector in regex.<br>
   *
   * @author code4crafter@gmail.com <br>
   * @since 0.1.0
   */
  public class RegexSelector implements Selector {
  
      private String regexStr;
  
      private Pattern regex;
  
      private int group = 1;
  
      public RegexSelector(String regexStr, int group) {
          this.compileRegex(regexStr);
          this.group = group;
      }
  
      private void compileRegex(String regexStr) {
          if (StringUtils.isBlank(regexStr)) {
              throw new IllegalArgumentException("regex must not be empty");
          }
          try {
              this.regex = Pattern.compile(regexStr, Pattern.DOTALL | Pattern.CASE_INSENSITIVE);
              this.regexStr = regexStr;
          } catch (PatternSyntaxException e) {
              throw new IllegalArgumentException("invalid regex "+regexStr, e);
          }
      }
  
      /**
       * Create a RegexSelector. When there is no capture group, the value is set to 0 else set to 1.
       * @param regexStr the regular expression.
       */
      public RegexSelector(String regexStr) {
          this.compileRegex(regexStr);
          if (regex.matcher("").groupCount() == 0) {
              this.group = 0;
          } else {
              this.group = 1;
          }
      }
  
      @Override
      public String select(String text) {
          return selectGroup(text).get(group);
      }
  
      @Override
      public List<String> selectList(String text) {
          List<String> strings = new ArrayList<String>();
          List<RegexResult> results = selectGroupList(text);
          for (RegexResult result : results) {
              strings.add(result.get(group));
          }
          return strings;
      }
  
      public RegexResult selectGroup(String text) {
          Matcher matcher = regex.matcher(text);
          if (matcher.find()) {
              String[] groups = new String[matcher.groupCount() + 1];
              for (int i = 0; i < groups.length; i++) {
                  groups[i] = matcher.group(i);
              }
              return new RegexResult(groups);
          }
          return RegexResult.EMPTY_RESULT;
      }
  
      public List<RegexResult> selectGroupList(String text) {
          Matcher matcher = regex.matcher(text);
          List<RegexResult> resultList = new ArrayList<RegexResult>();
          while (matcher.find()) {
              String[] groups = new String[matcher.groupCount() + 1];
              for (int i = 0; i < groups.length; i++) {
                  groups[i] = matcher.group(i);
              }
              resultList.add(new RegexResult(groups));
          }
          return resultList;
      }
  
      @Override
      public String toString() {
          return regexStr;
      }
  
 }