fix: NWS Product Signature logic

closes #865

CHANGELOG.md

@@ -15,6 +15,9 @@ web services to get the raw text. (#857)
 
 ### Bug Fixes
 
+- Improve NWS Text Product signature logic so to more generally match what
+looks like a signature (#865).
+
 ## **1.19.0** (4 Mar 2024)
 
 ### API Changes

src/pyiem/nws/product.py

@@ -799,10 +799,18 @@ def get_jabbers(self, uri, _uri2=None):
         return [(plain, html, xtra)]
 
     def get_signature(self):
-        """Find the signature at the bottom of the page"""
-        return " ".join(
-            self.segments[-1].unixtext.replace("\n", " ").strip().split()
-        )
+        """Return a signature that matches basic constraints (1 word)."""
+        lines = [x.strip() for x in self.unixtext.split("\n") if x.strip()]
+        res = None
+        for line in lines[::-1][:3]:
+            if line in ["$$", "&&", "$", "&"]:
+                continue
+            if line.find(" ") > -1 or line.find(".") > -1:
+                break
+            if 0 < len(line) < 25:
+                res = line
+                break
+        return res
 
     def parse_segments(self):
         """Split the product by its $$"""

src/pyiem/nws/products/_vtec_util.py

@@ -370,10 +370,6 @@ def _do_sql_vtec_new(prod, txn, warning_table, segment, vtec):
     if vtec.endts is None:
         ets = bts + DEFAULT_EXPIRE_DELTA
 
-    fcster = prod.get_signature()
-    if fcster is not None:
-        fcster = fcster[:24]
-
     # For each UGC code in this segment, we create a database entry
     for ugc in segment.ugcs:
         # Check to see if we have entries already for this UGC
@@ -438,7 +434,7 @@ def _do_sql_vtec_new(prod, txn, warning_table, segment, vtec):
                 vtec.office,
                 vtec.etn,
                 vtec.action,
-                fcster,
+                prod.get_signature(),
                 str(ugc),
                 vtec.phenomena,
                 vtec.significance,

tests/nws/test_product.py

@@ -14,6 +14,22 @@
 from pyiem.wmo import WMO_RE
 
 
+def test_gh865_fcster_none():
+    """Test that we don't use the generic signature on this product."""
+    data = get_test_file("NPW/NPWDMX.txt")
+    prod = productparser(data)
+    assert prod.get_signature() is None
+
+
+def test_gh865_fcster_scenarios():
+    """Test that we handle all kinds of things."""
+    data = get_test_file("TORILX.txt")
+    prod = productparser(data)
+    assert prod.get_signature() == "MILLER"
+    prod = productparser(data.replace("MILLER", ""))
+    assert prod.get_signature() is None
+
+
 def test_ahdnwc():
     """Test the jabber result we get from this product."""
     data = get_test_file("AHD/AHDNWC.txt")