Refactored add_appointment and get_appointment to avoid block nesting

apps/cli/pisa_cli.py

@@ -92,7 +92,10 @@ def add_appointment(args):
     appointment_data = None
     use_help = "Use 'help add_appointment' for help of how to use the command."
 
-    if args:
+    if not args:
+        logger.error("No appointment data provided. " + use_help)
+        return False
+
     arg_opt = args.pop(0)
 
     try:
@@ -100,24 +103,34 @@ def add_appointment(args):
             sys.exit(help_add_appointment())
 
         if arg_opt in ['-f', '--file']:
-                if args:
             fin = args.pop(0)
-                    if os.path.isfile(fin):
-                        appointment_data = json.load(open(fin))
-                    else:
+            if not os.path.isfile(fin):
                 logger.error("Can't find file " + fin)
-                else:
-                    logger.error("No file provided as appointment. " + use_help)
+                return False
+
+            try:
+                with open(fin) as f:
+                    appointment_data = json.load(open(fin))
+            except IOError as e:
+                logger.error("I/O error({}): {}".format(e.errno, e.strerror))
+                return False
         else:
             appointment_data = json.loads(arg_opt)
 
     except json.JSONDecodeError:
         logger.error("Non-JSON encoded data provided as appointment. " + use_help)
+        return False
+
+    if not appointment_data:
+        logger.error("The provided JSON is empty.")
+        return False
 
-        if appointment_data:
     valid_locator = check_txid_format(appointment_data.get('tx_id'))
 
-            if valid_locator:
+    if not valid_locator:
+        logger.error("The provided locator is not valid.")
+        return False
+
     add_appointment_endpoint = "http://{}:{}".format(pisa_api_server, pisa_api_port)
     appointment = build_appointment(appointment_data.get('tx'), appointment_data.get('tx_id'),
                                     appointment_data.get('start_time'), appointment_data.get('end_time'),
@@ -143,10 +156,20 @@ def add_appointment(args):
         logger.error("Can't connect to pisa API. Server cannot be reached.")
         return False
 
-                if r.status_code == HTTP_OK:
+    if r.status_code != HTTP_OK:
+        if 'error' not in response_json:
+            logger.error("The server returned status code {}, but no error description."
+                         .format(r.status_code))
+        else:
+            error = response_json['error']
+            logger.error("The server returned status code {}, and the following error: {}."
+                         .format(r.status_code, error))
+        return False
+
     if 'signature' not in response_json:
         logger.error("The response does not contain the signature of the appointment.")
-                    else:
+        return False
+
     signature = response_json['signature']
     # verify that the returned signature is valid
     try:
@@ -162,36 +185,26 @@ def add_appointment(args):
         logger.error("I/O error({}): {}".format(e.errno, e.strerror))
         return False
 
-                        if is_sig_valid:
+    if not is_sig_valid:
+        logger.error("The returned appointment's signature is invalid.")
+        return False
+
     logger.info("Appointment accepted and signed by Pisa.")
     # all good, store appointment and signature
     try:
         save_signed_appointment(appointment, signature)
-                                return True
     except OSError as e:
         logger.error("There was an error while saving the appointment: {}".format(e))
-                        else:
-                            logger.error("The returned appointment's signature is invalid.")
+        return False
 
-                else:
-                    if 'error' not in response_json:
-                        logger.error("The server returned status code {}, but no error description."
-                                     .format(r.status_code))
-                    else:
-                        error = r.json()['error']
-                        logger.error("The server returned status code {}, and the following error: {}."
-                                     .format(r.status_code, error))
-
-            else:
-                logger.error("The provided locator is not valid.")
-    else:
-        logger.error("No appointment data provided. " + use_help)
-
-    return False  # return False for any path that returned an error message
+    return True
 
 
 def get_appointment(args):
-    if args:
+    if not args:
+        logger.error("No arguments were given.")
+        return False
+
     arg_opt = args.pop(0)
 
     if arg_opt in ['-h', '--help']:
@@ -200,27 +213,25 @@ def get_appointment(args):
         locator = arg_opt
         valid_locator = check_txid_format(locator)
 
-        if valid_locator:
+    if not valid_locator:
+        logger.error("The provided locator is not valid: {}".format(locator))
+        return False
+
     get_appointment_endpoint = "http://{}:{}/get_appointment".format(pisa_api_server, pisa_api_port)
     parameters = "?locator={}".format(locator)
     try:
         r = requests.get(url=get_appointment_endpoint + parameters, timeout=5)
 
         print(json.dumps(r.json(), indent=4, sort_keys=True))
-                return True
     except ConnectTimeout:
         logger.error("Can't connect to pisa API. Connection timeout.")
+        return False
 
     except ConnectionError:
         logger.error("Can't connect to pisa API. Server cannot be reached.")
+        return False
 
-        else:
-            logger.error("The provided locator is not valid.")
-
-    else:
-        logger.error("The provided locator is not valid.")
-
-    return False  # return False for any path that returned an error message
+    return True
 
 
 def build_appointment(tx, tx_id, start_time, end_time, dispute_delta):