Almost complete, missing error checking

Nice to have: use autocomplete to suggest names

hyperdia.py

@@ -1,5 +1,6 @@
 #!/usr/bin/env python3
 
+import argparse
 from dataclasses import dataclass
 from datetime import datetime
 from itertools import zip_longest
@@ -52,6 +53,17 @@ HEADERS = {
 }
 
 
+def required_length(nmin, nmax):
+    class RequiredLength(argparse.Action):
+        def __call__(self, parser, args, values, option_string=None):
+            if not nmin <= len(values) <= nmax:
+                msg='argument "{f}" requires between {nmin} and {nmax} arguments'.format(
+                    f=self.dest,nmin=nmin,nmax=nmax)
+                raise argparse.ArgumentTypeError(msg)
+            setattr(args, self.dest, values)
+    return RequiredLength
+
+
 @dataclass
 class HyperdiaStep:
 
@@ -298,6 +310,7 @@ def hyperdia_search(start_station: str, end_station: str, hour: int,
                     year: int = 2020, max_route: int = 5,
                     via: List[str] = None) -> List[str]:
 
+    # TODO: Error checking
     raw_result = get_hyperdia_data(start_station, end_station,
                                    hour, minute, day, month, year, max_route,
                                    via)
@@ -306,3 +319,36 @@ def hyperdia_search(start_station: str, end_station: str, hour: int,
 
     for trip in results:
         print(trip_summary(trip))
+
+
+def main():
+
+    parser = argparse.argumentParser()
+    parser.add_argument("-t", "--time", help="Hour of travel",
+                        type=lambda d: datetime.strptime(d, '%H.%M').time())
+    parser.add_argument("-d", "--date", help="Date of travel",
+                        type=lambda d: datetime.strptime(d, "%Y-%m-%d").date())
+    parser.add_arguments("--max-routes", help="Maximum number of routes",
+                         type=int)
+    parser.add_argument("--via", nargs='+', action=required_length(1, 3),
+                        help="Stations to force route through (min 1, max 3)")
+    parser.add_argument("start_station", help="Start station")
+    parser.add_argument("end_station", help="End station")
+
+    options = parser.parse_args()
+
+    hour, minute = options.time.hour, options.time.minute
+    day, month, year = options.date.day, options.date.month, options.date.year
+
+    if month > 9:
+        # Add "0" in front of single-digit months
+        month = str(month).zfill(2)
+    else:
+        month = str(month)
+
+    hyperdia_search(options.start_station, options.end_station, hour, minute,
+                    day, month, year, options.max_routes, via=options.via)
+
+
+if __name__ == "__main__":
+    main()