Add 'cas_wrapper.py'

Add cas wrapper

cas_wrapper.py

@@ -0,0 +1,66 @@
+import json
+
+from plumbum import local, ProcessExecutionError
+
+
+class CasWrapper:
+    """
+    The python wrapper around binary `cas`
+    from Codenotary Community Attestation Service
+    """
+
+    binary_name = 'cas'
+
+    def __init__(
+            self,
+            cas_api_key: str,
+            cas_signer_id: str,
+    ):
+        if self.binary_name not in local:
+            raise FileNotFoundError(
+                'Binary CAS is not found in PATH on the machine',
+            )
+        self._cas_api_key = cas_api_key
+        self._cas_signer_id = cas_signer_id
+        with local.env(
+                CAS_API_KEY=self._cas_api_key,
+                SIGNER_ID=self._cas_signer_id
+        ):
+            self._cas = local['cas']
+            self._cas('login')
+
+    def notarize(self, local_git_repo_path: str) -> str:
+        """
+        Wrapper around `cas notarize`
+        :param local_git_repo_path: path to a local Git repo
+        :return: hash of notarized commit
+        :rtype: str
+        """
+        command = self._cas[
+            'notarize',
+            f'git://{local_git_repo_path}',
+            '-o',
+            'json',
+        ]
+        result_of_execution = command()
+        return json.loads(result_of_execution)['hash']
+
+    def authenticate(self, local_git_repo_path: str) -> bool:
+        """
+        Wrapper around `cas authenticate`
+        :param local_git_repo_path: path to a local Git repo
+        :return: true if a commit is trusted, vice versa - false
+        :rtype: bool
+        """
+        command = self._cas[
+            'authenticate',
+            f'git://{local_git_repo_path}',
+            '-o',
+            'json',
+        ]
+        try:
+            result_of_execution = command()
+        except ProcessExecutionError:
+            # in case if commit is untrusted
+            result_of_execution = command(retcode=1)
+        return not bool(json.loads(result_of_execution)['status'])