Determine output file name automatically

intercal/main.py

@@ -83,20 +83,26 @@ def unix_time(t):
 
     return (t - datetime(1970, 1, 1)).total_seconds()
 
+def output_file_name(args):
+
+    earlier_time = min(args.metop_time, args.npp_time)
+    return 'sno_{}_npp_{}_{}.h5'.format(args.iasi_platform.lower(), args.sensor.lower(),
+                                        earlier_time.strftime('%Y-%m-%dT%H-%M'))
+
 def main():
 
     args = _parse_args()
     granule = _create_granule(args.sensor, args.files)
     scan_idx, for_idx, fov_idx = (
         _filter_by_proximity(granule, args.latitude, args.longitude, args.max_distance))
-    with h5py.File(args.output_file, 'w') as output_file:
+    with h5py.File(output_file_name(args), 'w') as output_file:
         _process_spectra(granule, granule.radiance, scan_idx, for_idx, fov_idx,
                          output_file)
         if granule.has_imaginary_radiance:
             _process_spectra(
                 granule, granule.imaginary_radiance, scan_idx, for_idx, fov_idx,
                 output_file, 'Imaginary')
-        output_file.create_dataset('Metop-{}_Time'.format(arg.iasi_platform[-1].upper()),
+        output_file.create_dataset('Metop-{}_Time'.format(args.iasi_platform[-1].upper()),
                                    data=unix_time(args.metop_time))
         output_file.create_dataset('NPP_Time', data=unix_time(args.npp_time))
         output_file.create_dataset('SNO_Latitude', data=args.latitude)