package cn.home1.oss.lib.common.crypto;
   
   import static com.google.common.base.Preconditions.checkArgument;
   
   import io.jsonwebtoken.SignatureAlgorithm;
   import io.jsonwebtoken.impl.crypto.MacProvider;
   
   import lombok.Getter;
   
  import cn.home1.oss.lib.common.CodecUtils;
  
  /**
   * Created by zhanghaolun on 16/10/29.
   */
  public class JwtKeyGenerator implements KeyGenerator {
  
    @Getter
    private final String spec;
    @Getter
    private KeyExpression key;
  
    public JwtKeyGenerator(final String spec) {
      this.spec = spec;
    }
  
    @Override
    public KeyExpression generateKey() {
      return JwtKeyGenerator.generateJwtKey(this.spec);
    }
  
    @Override
    public KeyExpression getKey(final String spec) {
      checkArgument(this.spec.equals(spec), "spec " + spec + " not supported.");
      if (this.key == null) {
        this.key = this.generateKey();
      }
      return this.key;
    }
  
    /**
     * generate JWT key
     *
     * @param spec eg: SignatureAlgorithm.HS512.getValue()
     * @return JWT base64EncodedKeyBytes
     */
    public static KeyExpression generateJwtKey(final String spec) {
      final String signatureAlgorithmName = "" + spec;
      final SignatureAlgorithm algorithm = SignatureAlgorithm.forName(signatureAlgorithmName);
      return new KeyExpression( //
        spec, //
        CodecUtils.encodeBase64(MacProvider.generateKey(algorithm).getEncoded()) //
      );
    }
  }