fix: parsing of watch replacement number

CHANGELOG.md

@@ -22,6 +22,7 @@ memcache is short circuited.
 
 ### Bug Fixes
 
+- Fix and refactor SPC `saw` parsing of watch replacement number.
 - Pop kwargs `fig` on `MapPlot`.
 - Use less confusing landing page at WPC for ERO.
 - Use `round` instead of `int` to compute zonal stats grid navigation.

data/product_examples/SAW/SAW6.txt

@@ -0,0 +1,18 @@
+392
+WWUS30 KWNS 050955
+SAW6 
+SPC AWW 050955
+WW 596 TORNADO FL GA CW 050955Z - 052000Z
+AXIS..50 STATUTE MILES EAST AND WEST OF LINE..
+50ESE PIE/SAINT PETERSBURG FL/ - 50N SSI/BRUNSWICK GA/
+..AVIATION COORDS.. 45NM E/W /36ENE SRQ - 24SW SAV/
+WIND GUSTS..60 KNOTS.
+MAX TOPS TO 450.MEAN STORM MOTION VECTOR 18035.
+
+REPLACES WW 595..FL GA CW
+
+LAT...LON 27648274 31878230 31878060 27648111
+
+THIS IS AN APPROXIMATION TO THE WATCH AREA.  FOR A
+COMPLETE DEPICTION OF THE WATCH SEE WOUS64 KWNS
+FOR WOU6.

src/pyiem/nws/products/saw.py

@@ -5,6 +5,7 @@
 
 import datetime
 import re
+from typing import Optional
 
 from shapely.geometry import MultiPolygon
 from shapely.geometry import Polygon as ShapelyPolygon
@@ -42,8 +43,16 @@ def __init__(self, text, utcnow=None):
         self.ww_num = self.find_ww_num()
         (self.sts, self.ets) = self.find_time()
         self.ww_type = self.find_ww_type()
+        self.replaces_num = self.find_replaces()
         self.affected_wfos = []
 
+    def find_replaces(self) -> Optional[int]:
+        """Figure out what this watch replaces."""
+        tokens = REPLACES_RE.findall(self.unixtext)
+        if not tokens:
+            return None
+        return int(tokens[0])
+
     def find_action(self):
         """Figure out if this is an issuance or cancells statement
 
@@ -114,12 +123,11 @@ def sql(self, txn):
             )
             txn.execute(sql, args)
             # Is this a replacement?
-            if REPLACES_RE.findall(self.unixtext):
-                rnum = REPLACES_RE.findall(self.unixtext)[0][0]
+            if self.replaces_num is not None:
                 txn.execute(
                     "UPDATE watches SET expired = %s "
                     "WHERE num = %s and extract(year from expired) = %s",
-                    (self.valid, rnum, self.sts.year),
+                    (self.valid, self.replaces_num, self.sts.year),
                 )
         elif self.action == self.CANCELS:
             for table in ("watches", "watches_current"):
@@ -288,12 +296,9 @@ def get_jabbers(self, uri, _uri2=None, **kwargs):
                 f"Watch {self.ww_num}</a> {pds_extra}"
                 f"till {self.ets:%-H:%M} UTC"
             )
-            if REPLACES_RE.findall(self.unixtext):
-                rtext = (
-                    f"WW {REPLACES_RE.findall(self.unixtext)[0][0].strip()} "
-                )
-                plain += ", new watch replaces " + rtext
-                html += ", new watch replaces " + rtext
+            if self.replaces_num is not None:
+                plain += f", new watch replaces WW {self.replaces_num}"
+                html += f", new watch replaces WW {self.replaces_num}"
 
             plain2 = f"{plain} {url}"
             plain2 = " ".join(plain2.split())

tests/nws/products/test_saw.py

@@ -6,6 +6,16 @@
 from pyiem.util import get_test_file, utc
 
 
+def test_240805_bad_time():
+    """Test what we parse this as."""
+    utcnow = utc(2024, 8, 5, 11)
+    prod = parser(get_test_file("SAW/SAW6.txt"), utcnow=utcnow)
+    assert prod.ww_num == 596
+    assert prod.sts == utc(2024, 8, 5, 9, 55)
+    assert prod.ets == utc(2024, 8, 5, 20, 0)
+    assert prod.replaces_num == 595
+
+
 def test_220502_jabber():
     """Test that we can generate fancy messages."""
     utcnow = utc(2021, 7, 29, 0)
@@ -80,14 +90,15 @@ def test_181231_linkisok():
 @pytest.mark.parametrize("database", ["postgis"])
 def test_replacement(dbcursor):
     """Can we do replacements?"""
-    utcnow = utc(2017, 8, 21, 9, 17)
+    utcnow = utc(2017, 4, 21, 9, 17)
     prod = sawparser(get_test_file("SAW/SAW-replaces.txt"), utcnow=utcnow)
+    assert prod.replaces_num == 152
     prod.sql(dbcursor)
     jmsgs = prod.get_jabbers("")
     assert len(jmsgs) == 1
     ans = (
         "SPC issues Severe Thunderstorm Watch"
-        " 153 till 17:00Z, new watch replaces WW 1 "
+        " 153 till 17:00Z, new watch replaces WW 152 "
         "https://www.spc.noaa.gov/products/watch/2017/ww0153.html"
     )
     assert jmsgs[0][0] == ans