Make NEXRAD radar range a magic number

lib/nexrad/radar.py

@@ -38,6 +38,8 @@ def parse(text: str):
 
     return Coord(sign_lat * lat, sign_lon * lon)
 
+RADAR_RANGE = 230000
+
 class Radar():
     __slots__ = 'wban', 'call', 'name', 'coord', 'site_elevation', 'tower_height',
 

lib/nexrad/s3.py

@@ -0,0 +1,74 @@
+import re
+import datetime
+
+S3_BUCKET = 'noaa-nexrad-level2'
+S3_KEY_RE = re.compile(r'^(\d{4})/(\d{2})/(\d{2})/([A-Z]{4})/([A-Z]{4})(\d{4})(\d{2})(\d{2})_(\d{2})(\d{2})(\d{2})[_\.]')
+
+def key_matches(key: str,
+                   start: datetime.datetime,
+                   end: datetime.datetime):
+    match = S3_KEY_RE.match(key)
+
+    if match is None:
+        return False
+
+    date = datetime.datetime(
+        year   = int(match[6]),
+        month  = int(match[7]),
+        day    = int(match[8]),
+        hour   = int(match[9]),
+        minute = int(match[10]),
+        second = int(match[11]),
+        tzinfo = datetime.UTC
+    )
+
+    return date >= start and date <= end
+
+class S3Bucket():
+    def __init__(self, s3, name: str=S3_BUCKET):
+        self.s3    = s3
+        self.name  = name
+        self.cache = dict()
+
+    def each_key_by_prefix(self, prefix: str):
+        if prefix in self.cache:
+            for key in self.cache[prefix]:
+                yield key
+        else:
+            result = self.s3.list_objects_v2(
+                Bucket = self.name,
+                Prefix = prefix
+            )
+
+            cache = list()
+            self.cache[prefix] = cache
+
+            if result is None or 'Contents' not in result:
+                return
+
+            for item in result['Contents']:
+                key = item['Key']
+
+                cache.append(key)
+
+                yield key
+
+    def each_matching_key(self,
+                    radars: list,
+                    start: datetime.datetime,
+                    end:   datetime.datetime):
+        elapsed = end - start
+
+        for radar in radars:
+            for day in range(0, 1+elapsed.days):
+                date   = start + datetime.timedelta(days=day)
+                prefix = '%04d/%02d/%02d/%s/' % (
+                    date.year,
+                    date.month,
+                    date.day,
+                    radar[1]
+                )
+
+                for key in self.each_key_by_prefix(prefix):
+                    if key_matches(key, start, end):
+                        yield key

lib/nexrad/storm.py

@@ -3,6 +3,7 @@ import csv
 import datetime
 
 from nexrad.coord import Coord, COORD_SYSTEM
+from nexrad.radar import RADAR_RANGE
 
 def time_from_str(time: str):
     size = len(time)
@@ -124,10 +125,10 @@ class StormReport():
             from
                 nexrad_radar
             where
-                distance <= 230000
+                distance <= {range}
             order by
                 distance asc
-        """.format(csr=COORD_SYSTEM)
+        """.format(csr=COORD_SYSTEM, range=RADAR_RANGE)
 
         radars = list()