Added flag for different number of mods and unit tests for the function

spectrum_fundamentals/mod_string.py

@@ -351,22 +351,29 @@ def get_all_tokens(sequences: List[str]) -> Set[str]:
     return tokens
 
 
-def add_permutations(modified_sequence: str, unimod_id: int, residues: List[str]):
+def add_permutations(modified_sequence: str, unimod_id: int, residues: List[str], allow_one_less_modification: bool = False):
     """
     Generate different peptide sequences with moving the modification to all possible residues.
 
     :param modified_sequence: Peptide sequence
     :param unimod_id: modification unimod id to be used for generating different permutations.
     :param residues: possible amino acids where this mod can exist
+    :param allow_one_less_modification: Flag to indicate if permutations with one less modification should be generated to check 
+                                whether the modification mass was mistakenly picked as the monoisotopic peak. Mainly used for Citrullination.
     :return: list of possible sequence permutations
     """
-    sequence = modified_sequence.replace("[UNIMOD:" + str(unimod_id) + "]", "")
-    modifications = len(re.findall("UNIMOD:" + str(unimod_id), modified_sequence))
+    sequence = modified_sequence.replace("[unimod:" + str(unimod_id) + "]", "")
+    modifications = len(re.findall("unimod:" + str(unimod_id), modified_sequence))
     if modifications == 0:
-        return modified_sequence
+        return [modified_sequence]
     possible_positions = [i for i, ltr in enumerate(sequence) if ltr in residues]
     possible_positions.sort(reverse=True)
     all_combinations = [list(each_permutation) for each_permutation in combinations(possible_positions, modifications)]
+
+    if allow_one_less_modification:
+        all_combinations_1 = [list(each_permutation) for each_permutation in combinations(possible_positions, modifications-1)]
+        all_combinations = all_combinations + all_combinations_1
+
     modified_sequences_comb = []
     for comb in all_combinations:
         modified_sequence = sequence

tests/unit_tests/test_mod_string.py

@@ -331,3 +331,57 @@ def test_custom_to_internal_custom_mods(self):
         custom_mod = {"M[35]": "[UNIMOD:35]"}
         mods = {**fixed_mods, **custom_mod}
         self.assertEqual(mod.custom_to_internal(["ABCDEFGHM[35]"], mods), ["ABC[UNIMOD:4]DEFGHM[UNIMOD:35]"])
+
+class TestAddPermutations(unittest.TestCase):
+    """Class to test add permutations."""
+    def test_no_modifications(self):
+        """Test case where no modifications are present in the sequence"""
+        modified_sequence = "PEPTIDE"
+        unimod_id = 123
+        residues = ['P', 'E']
+        result = mod.add_permutations(modified_sequence, unimod_id, residues)
+        self.assertEqual(result, ["PEPTIDE"])
+
+    def test_single_modification(self):
+        """Test case with a single modification"""
+        modified_sequence = "P[unimod:123]EPTIDE"
+        unimod_id = 123
+        residues = ['P', 'E']
+        result = mod.add_permutations(modified_sequence, unimod_id, residues)
+        expected_result = ['PEPTIDE[unimod:123]',
+                           'PEP[unimod:123]TIDE',
+                           'PE[unimod:123]PTIDE',
+                           'P[unimod:123]EPTIDE']
+        self.assertEqual(result, expected_result)
+
+    def test_multiple_modifications(self):
+        """Test case with multiple modifications"""
+        modified_sequence = "PEP[unimod:123]TIDE[unimod:123]"
+        unimod_id = 123
+        residues = ['P', 'E']
+        result = mod.add_permutations(modified_sequence, unimod_id, residues)
+        expected_result = ['PEP[unimod:123]TIDE[unimod:123]',
+                           'PE[unimod:123]PTIDE[unimod:123]',
+                           'P[unimod:123]EPTIDE[unimod:123]',
+                           'PE[unimod:123]P[unimod:123]TIDE',
+                           'P[unimod:123]EP[unimod:123]TIDE',
+                           'P[unimod:123]E[unimod:123]PTIDE']
+        self.assertEqual(result, expected_result)
+
+    def test_check_monoisotopic_peak_enabled(self):
+        """Test case with check_monoisotopic_peak flag enabled"""
+        modified_sequence = "PEP[unimod:123]TID[unimod:123]E"
+        unimod_id = 123
+        residues = ['P', 'E']
+        result = mod.add_permutations(modified_sequence, unimod_id, residues, check_monoisotopic_peak=True)
+        expected_result = ['PEP[unimod:123]TIDE[unimod:123]',
+                           'PE[unimod:123]PTIDE[unimod:123]',
+                           'P[unimod:123]EPTIDE[unimod:123]',
+                           'PE[unimod:123]P[unimod:123]TIDE',
+                           'P[unimod:123]EP[unimod:123]TIDE',
+                           'P[unimod:123]E[unimod:123]PTIDE',
+                           'PEPTIDE[unimod:123]',
+                           'PEP[unimod:123]TIDE',
+                           'PE[unimod:123]PTIDE',
+                           'P[unimod:123]EPTIDE']
+        self.assertEqual(result, expected_result)