Nicer use of argparse types

touchdown/aws/logs/tail.py

@@ -18,7 +18,7 @@
 import time
 
 from touchdown.core import plan
-from touchdown.core.datetime import parse_datetime_as_seconds
+from touchdown.core.datetime import as_seconds
 from touchdown.aws import common
 from touchdown.aws.logs import LogGroup
 
@@ -34,9 +34,9 @@ def tail(self, start, end, follow):
             'logGroupName': self.resource.name,
         }
         if start:
-            kwargs['startTime'] = parse_datetime_as_seconds(start)
+            kwargs['startTime'] = as_seconds(start)
         if end:
-            kwargs['endTime'] = parse_datetime_as_seconds(end)
+            kwargs['endTime'] = as_seconds(end)
 
         def pull(kwargs, previous_events):
             seen = set()

touchdown/core/datetime.py

@@ -89,6 +89,5 @@ def parse_datetime(value):
     )
 
 
-def parse_datetime_as_seconds(value):
-    date = parse_datetime(value)
-    return int(date.strftime("%s")) * 1000
+def as_seconds(value):
+    return int(value.strftime("%s")) * 1000

touchdown/goals/tail.py

@@ -13,9 +13,20 @@
 # limitations under the License.
 
 from touchdown.core import errors
+from touchdown.core.datetime import parse_datetime
 from touchdown.core.goals import Goal, register
 
 
+def datetime(value):
+    try:
+        return parse_datetime(value)
+    except errors.Error:
+        import argparse
+        raise argparse.ArgumentTypeError(
+            "{} is not a valid date/time".format(value),
+        )
+
+
 class Tail(Goal):
 
     """ Inspect (and stream) your logs """
@@ -30,10 +41,35 @@ def get_plan_class(self, resource):
 
     @classmethod
     def setup_argparse(cls, parser):
-        parser.add_argument("stream", metavar="STREAM", type=str, help="The logstream to tail")
-        parser.add_argument("-f", "--follow", default=False, action="store_true", help="Don't exit and continue to print new events in the stream")
-        parser.add_argument("-s", "--start", default="5m ago", action="store", help="The earliest event to retrieve")
-        parser.add_argument("-e", "--end", default=None, action="store", help="The latest event to retrieve")
+        parser.add_argument(
+            "stream",
+            metavar="STREAM",
+            type=str,
+            help="The logstream to tail"
+        )
+        parser.add_argument(
+            "-f",
+            "--follow",
+            default=False,
+            action="store_true",
+            help="Don't exit and continue to print new events in the stream"
+        )
+        parser.add_argument(
+            "-s",
+            "--start",
+            default="5m ago",
+            action="store",
+            type=datetime,
+            help="The earliest event to retrieve"
+        )
+        parser.add_argument(
+            "-e",
+            "--end",
+            default=None,
+            action="store",
+            type=datetime,
+            help="The latest event to retrieve"
+        )
 
     def execute(self, stream, start="5m ago", end=None, follow=False):
         tailers = {}