aitf.ancil.GFS needs custom get_cachefilesets

example/aitf/ancil.py

@@ -5,6 +5,7 @@ import sys
 import datetime as dt
 sys.path.append(os.path.abspath('..'))
 import csppfetch
+import csppfetch.daterange
 from csppfetch.roundtozero import roundtozero
 
 ################################################################################
@@ -104,6 +105,34 @@ class GFSDownloader(csppfetch.Downloader):
         local = self._expand(self.local, time, hours_str)
         return {url:local}
 
+    def get_cache_filesets(self, start = None, end = None):
+
+        # A copy of Downloader's implementation, but we don't use
+        # self._daterange; we call daterange.daterange directly so we can pass
+        # in a step of self.forecast_step instead of self.period. We do this
+        # because although our period is only every 6 hours, we change which
+        # files someone might want every _3_. That is to process 5Z data, we'd
+        # use the 0Z GFS data's 3 and 6 hour forecasts, but for 7Z data, we'd
+        # use the 0Z GFS data's 6 and 9 hour forecasts.
+        #
+        # Perhaps the ablity to override the period here should be in the
+        # parent class? Or maybe this case is too specialized to bother.
+
+        if self.oldest_cache < dt.timedelta(days=0):
+            raise ValueError(f"oldest_cache should be positive; it is {self.oldest_cache}")
+
+        if end is None: end = dt.datetime.now()
+        if start is None: start = end - self.oldest_cache
+
+        if start > end:
+            raise ValueError(f"start ({start}) should be before end ({end})")
+
+        fileset_list_list = []
+        for time in csppfetch.daterange.daterange(end, start, -self.forecast_step, inclusive=True):
+            fileset_list = self.get_filesets_for_time(time)
+            fileset_list_list.append(fileset_list)
+        return fileset_list_list
+
     def get_filesets_for_time(self, scan_time):
         generated_time = self._nearest_preceeding_time(scan_time)
         time_since_gen = scan_time - generated_time