class SawtoothService:
    def __init__(self, rest_api_url):
        context = create_context('secp256k1')
        private_key = context.new_random_private_key()
        signer = CryptoFactory(context).new_signer(private_key)

        self._signer = signer
        self._rest_api_url = rest_api_url

    def SingleTransaction(self, family, payload):
        txn = self.BuildTransaction(
            family,
            '1.0',
            payload,
            self.BuildAddress(family, payload['Session'])
        )

        batchlist = self.BuildBatchList([txn])

        responseContent = WebRequest.Post(
            self._rest_api_url + '/batches',
            batchlist.SerializeToString(),
            'application/octet-stream'
        )
        return responseContent

    def BuildTransaction(self, family_name, family_version, payload, address):

        payload_bytes = cbor.dumps(payload)

        txn_header_bytes = TransactionHeader(
            family_name=family_name,
            family_version=family_version,
            inputs=[address],
            outputs=[address],
            signer_public_key=self._signer.get_public_key().as_hex(),
            batcher_public_key=self._signer.get_public_key().as_hex(),
            dependencies=[],
            payload_sha512=sha512(payload_bytes).hexdigest()
        ).SerializeToString()

        signature = self._signer.sign(txn_header_bytes)

        return Transaction(
            header=txn_header_bytes,
            header_signature=signature,
            payload=payload_bytes,
        )

    def BuildBatchList(self, txns):
        batch_header_bytes = BatchHeader(
            signer_public_key=self._signer.get_public_key().as_hex(),
            transaction_ids=[txn.header_signature for txn in txns],
        ).SerializeToString()

        signature = self._signer.sign(batch_header_bytes)

        batch = Batch(
            header=batch_header_bytes,
            header_signature=signature,
            transactions=txns,
            trace=True
        )

        return BatchList(batches=[batch])

    def BuildAddress(self, prefix, name):
        return sha512(prefix.encode('utf-8')).hexdigest()[0:6] + sha512(name.encode('utf-8')).hexdigest()[-64:]