[vtec] add check for UGC uniqueness

closes #540

CHANGELOG.md

@@ -3,6 +3,16 @@
 
 All notable changes to this library are documented in this file.
 
+## Unreleased Version
+
+### API Changes
+
+### New Features
+
+- Added VTEC product check for uniqueness of UGCs (#540).
+
+### Bug Fixes
+
 ## **1.11.0** (25 Feb 2022)
 
 ### API Changes

src/pyiem/nws/products/_vtec_util.py

@@ -108,6 +108,35 @@ def which_year(txn, prod, segment, vtec):
     return prod.valid.year
 
 
+def _check_unique_ugc(prod) -> bool:
+    """Quality Control check that a given product uniquely uses UGCS.
+
+    Discussions with AWIPS developer expressed interesting in knowing that
+    this was being enforced.  It adds a warning message and returns a bool
+    on if this was a problem.
+
+    Args:
+        prod: Product object to check.
+
+    Returns:
+        True if UGCS are unique, False if not.
+    """
+    domain = []
+    for seg in prod.segments:
+        # HVTEC products are an exception to this rule.
+        if seg.hvtec:
+            continue
+        domain.extend([str(u) for u in seg.ugcs])
+    ugcs = pd.Series(domain, dtype=str)
+    if ugcs.duplicated().any():
+        vals = ugcs[ugcs.duplicated()].values
+        prod.warnings.append(
+            f"Duplicated UGCs Found (10.1701 3.9.1): {','.join(vals)}"
+        )
+        return False
+    return True
+
+
 def _associate_vtec_year(prod, txn):
     """Figure out to which year each VTEC in the product belongs.
 

src/pyiem/nws/products/vtec.py

@@ -7,6 +7,7 @@
 from pyiem.reference import TWEET_CHARS
 from pyiem.nws.products._vtec_util import (
     _associate_vtec_year,
+    _check_unique_ugc,
     _resent_match,
     _do_sql_vtec_new,
     _do_sql_vtec_cor,
@@ -49,6 +50,8 @@ def __init__(
             and self.unixtext.find("$$") == -1
         ):
             raise ValueError("Aborting processing of TSU without $$")
+        # Arb checks
+        _check_unique_ugc(self)
 
     def sql(self, txn):
         """Persist to the database