import java.security.SignatureException
import javax.crypto.Mac
import javax.crypto.spec.SecretKeySpec

def flowFile = session.get()
if (!flowFile) return

def static hmac(String data, String key) throws java.security.SignatureException
{
  String result
  try {
    // get an hmac_sha1 key from the raw key bytes
    SecretKeySpec signingKey = new SecretKeySpec(key.getBytes(), "HmacSHA1");
    // get an hmac_sha1 Mac instance and initialize with the signing key
    Mac mac = Mac.getInstance("HmacSHA1");
    mac.init(signingKey);
    // compute the hmac on input data bytes
    byte[] rawHmac = mac.doFinal(data.getBytes());
    result= rawHmac.encodeBase64()
  } catch (Exception e) {
    throw new SignatureException("Failed to generate HMAC : " + e.getMessage());
  }
  return result
}

def attributes = flowFile.getAttributes()

// retrieve arguments of the target and split arguments
def arguments = attributes.arguments.tokenize('&')
def method = attributes.method
def base_url = attributes.base_url
def consumerSecret = attributes.oauth_consumer_secret
def tokenSecret = attributes.oauth_token_secret

TreeMap map = [:]

for (String item : arguments) {
  def (key, value) = item.tokenize('=')
  map.put(key, value)
}

map.put("oauth_consumer_key", attributes.oauth_consumer_key)
map.put("oauth_nonce", attributes.oauth_nonce)
map.put("oauth_signature_method", attributes.oauth_signature_method)
map.put("oauth_timestamp", attributes.oauth_timestamp)
map.put("oauth_token", attributes.oauth_token)
map.put("oauth_version", attributes.oauth_version)

String.metaClass.encode = {
  java.net.URLEncoder.encode(delegate, "UTF-8").replace("+", "%20").replace("*", "%2A").replace("%7E", "~");
}

String parameterString = map.collect { String key, String value ->
  "${key.encode()}=${value.encode()}"
}.join("&")

String signatureBaseString = ""

signatureBaseString += method.toUpperCase()
signatureBaseString += '&'
signatureBaseString += base_url.encode()
signatureBaseString += '&'
signatureBaseString += parameterString.encode()

String signingKey = consumerSecret.encode() + '&' + tokenSecret.encode()

String oauthSignature = hmac(signatureBaseString, signingKey)

flowFile = session.putAttribute(flowFile, 'oauth_signature', oauthSignature)

String oauth = 'OAuth '
oauth += 'oauth_consumer_key="'
oauth += attributes.oauth_consumer_key.encode()
oauth += '", '
oauth += 'oauth_nonce="'
oauth += attributes.oauth_nonce.encode()
oauth += '", '
oauth += 'oauth_signature="'
oauth += oauthSignature.encode()
oauth += '", '
oauth += 'oauth_signature_method="'
oauth += attributes.oauth_signature_method.encode()
oauth += '", '
oauth += 'oauth_timestamp="'
oauth += attributes.oauth_timestamp.encode()
oauth += '", '
oauth += 'oauth_token="'
oauth += attributes.oauth_token.encode()
oauth += '", '
oauth += 'oauth_version="'
oauth += attributes.oauth_version.encode()
oauth += '"'

flowFile = session.putAttribute(flowFile, 'oauth_header', oauth)

session.transfer(flowFile, REL_SUCCESS)