Fix OpenCellID integration: CID=0 handling, API key check, tab parsing

- /lookup_cell and /detect_rogue rejected CID=0 towers because
  `all([..., cid])` is falsy when cid=0; use `is not None` checks
- can_use_api() now returns False when GSM_OPENCELLID_API_KEY is empty,
  preventing the geocoding worker from wasting daily quota on doomed calls
- /lookup_cell returns 503 with clear message when API key not configured
- parse_tshark_output uses rstrip('\n\r') instead of strip() to preserve
  leading empty tab-separated fields (strip() ate leading tabs, shifting
  all columns when the first field was empty)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

routes/gsm_spy.py

@@ -89,6 +89,8 @@ def increment_api_usage():
 
 def can_use_api():
     """Check if we can make an API call within daily limit."""
+    if not config.GSM_OPENCELLID_API_KEY:
+        return False
     current_usage = get_api_usage_today()
     return current_usage < config.GSM_API_DAILY_LIMIT
 
@@ -800,7 +802,7 @@ def lookup_cell():
     lac = data.get('lac')
     cid = data.get('cid')
 
-    if not all([mcc, mnc, lac, cid]):
+    if any(v is None for v in [mcc, mnc, lac, cid]):
         return jsonify({'error': 'MCC, MNC, LAC, and CID required'}), 400
 
     try:
@@ -823,7 +825,9 @@ def lookup_cell():
                     'radio': result['radio']
                 })
 
-            # Check API usage limit
+            # Check API key and usage limit
+            if not config.GSM_OPENCELLID_API_KEY:
+                return jsonify({'error': 'OpenCellID API key not configured'}), 503
             if not can_use_api():
                 current_usage = get_api_usage_today()
                 return jsonify({
@@ -905,7 +909,7 @@ def detect_rogue():
         lac = tower_info.get('lac')
         cid = tower_info.get('cid')
 
-        if all([mcc, mnc, lac, cid]):
+        if all(v is not None for v in [mcc, mnc, lac, cid]):
             with get_db() as conn:
                 result = conn.execute('''
                     SELECT id FROM gsm_cells
@@ -1384,7 +1388,7 @@ def parse_tshark_output(line: str, field_order: list[str] | None = None) -> dict
         field_order = ['ta', 'tmsi', 'imsi', 'lac', 'cid']
 
     try:
-        parts = line.strip().split('\t')
+        parts = line.rstrip('\n\r').split('\t')
 
         if len(parts) < len(field_order):
             return None

tests/test_gsm_spy.py

@@ -120,25 +120,38 @@ class TestParseTsharkOutput:
         assert 'timestamp' in result
 
     def test_missing_optional_fields(self):
-        """Test parsing with missing optional fields (empty tabs)."""
+        """Test parsing with missing optional fields (empty tabs).
+
+        A packet with TA but no TMSI/IMSI is discarded since there's
+        no device identifier to track.
+        """
         line = "3\t\t\t1234\t31245"
         result = parse_tshark_output(line)
+        assert result is None
+
+    def test_missing_optional_fields_with_tmsi(self):
+        """Test parsing with TMSI but missing TA, IMSI, CID."""
+        line = "\t0xABCD\t\t1234\t"
+        result = parse_tshark_output(line)
 
         assert result is not None
-        assert result['ta_value'] == 3
-        assert result['tmsi'] is None
+        assert result['ta_value'] is None
+        assert result['tmsi'] == '0xABCD'
         assert result['imsi'] is None
         assert result['lac'] == 1234
-        assert result['cid'] == 31245
+        assert result['cid'] is None
 
     def test_no_ta_value(self):
-        """Test parsing without TA value (empty field)."""
-        # When TA is empty, int('') will fail, so the parse returns None
-        # This is the current behavior - the function expects valid integers or valid empty handling
+        """Test parsing without TA value (empty first field)."""
         line = "\t0xABCD1234\t123456789012345\t1234\t31245"
         result = parse_tshark_output(line)
-        # Current implementation will fail to parse this due to int('') failing
-        assert result is None
+
+        assert result is not None
+        assert result['ta_value'] is None
+        assert result['tmsi'] == '0xABCD1234'
+        assert result['imsi'] == '123456789012345'
+        assert result['lac'] == 1234
+        assert result['cid'] == 31245
 
     def test_invalid_line(self):
         """Test handling of invalid tshark output."""