package com.atlassian.asap.core.keys;
   
   import java.io.UnsupportedEncodingException;
   import java.net.URLDecoder;
   import java.nio.charset.StandardCharsets;
   import java.util.Base64;
   import java.util.regex.Matcher;
   import java.util.regex.Pattern;
   
  public class DataUriUtil {
      /**
       * A regular expression pattern to match a data uri in the following format:
       * <pre>
       *  data:{key-mediatype};kid={key-identifier};base64,{encoded-key-data}
       * </pre>
       * The value of the kid parameter must be url encoded, in conformance to RFC2397.
       *
       * @see <a href="https://tools.ietf.org/html/rfc2397">RFC 2397 The "data" uri scheme</a>
       */
      private static Pattern DATA_URI_PATTERN = Pattern.compile("data:(?<mimeType>[\\w\\-]+/[\\w\\-]+);kid=(?<keyId>[\\w.\\-\\+%]*);base64," +
              "(?<encodedData>[A-Za-z0-9+/=]+)");
  
      /**
       * Extract the key data from the given data uri. The key data must be base64 encoded.
       *
       * @param dataUri the data uri to extract the key data from
       * @return the decoded key data
       */
      public static byte[] getKeyData(String dataUri) {
          String rawKeyData = getParameterFromDataUri(dataUri, "encodedData");
          return Base64.getDecoder().decode(rawKeyData);
      }
  
      /**
       * Extract the key identifier from the given data uri. The key identifier must be url encoded.
       *
       * @param dataUri the data uri to extract the key id from
       * @return the decoded key identifier
       */
      public static String getKeyId(String dataUri) {
          String rawKeyId = getParameterFromDataUri(dataUri, "keyId");
          try {
              return URLDecoder.decode(rawKeyId, StandardCharsets.US_ASCII.name());
          } catch (UnsupportedEncodingException e) {
              throw new IllegalArgumentException("Could not decode key id parameter in data uri. Key id must be url encoded.", e);
          }
      }
  
      private static String getParameterFromDataUri(String dataUri, String parameter) {
          Matcher dataUriMatcher = DATA_URI_PATTERN.matcher(dataUri);
          if (!dataUriMatcher.matches() || dataUriMatcher.groupCount() != 3) {
              throw new IllegalArgumentException("Unable to parse data uri parameter: " + parameter);
          }
          return dataUriMatcher.group(parameter);
      }
  
  }