From 022dce886cdbb495b75e1a8767af5f19a02cefe3 Mon Sep 17 00:00:00 2001
From: Dmitrii Polovnev <dmitrii_polovnev@epam.com>
Date: Wed, 5 Jun 2024 18:13:35 +0300
Subject: [PATCH] #4607 - Bugfix (monomers.ts): Correct `isValidNucleoside(1)`,
 `isValidNucleotide(1)`

---
 .../src/domain/helpers/monomers.ts            | 36 +++++++++++++------
 1 file changed, 26 insertions(+), 10 deletions(-)

diff --git a/packages/ketcher-core/src/domain/helpers/monomers.ts b/packages/ketcher-core/src/domain/helpers/monomers.ts
index 9400fc0315..a99a435986 100644
--- a/packages/ketcher-core/src/domain/helpers/monomers.ts
+++ b/packages/ketcher-core/src/domain/helpers/monomers.ts
@@ -86,22 +86,38 @@ export function isMonomerBeginningOfChain(
   );
 }
 
-export function isValidNucleotide(sugar: Sugar) {
+export function isValidNucleotide(sugar: Sugar): boolean {
+  if (!getRnaBaseFromSugar(sugar)) {
+    return false;
+  }
+
   const phosphate = getPhosphateFromSugar(sugar);
+  if (!phosphate) {
+    return false;
+  }
+
   const nextMonomerAfterPhosphate = getNextMonomerInChain(phosphate);
+  if (!(nextMonomerAfterPhosphate instanceof Sugar)) {
+    return false;
+  }
 
-  return Boolean(
-    getRnaBaseFromSugar(sugar) &&
-      getPhosphateFromSugar(sugar) &&
-      nextMonomerAfterPhosphate,
-  );
+  return !!getRnaBaseFromSugar(nextMonomerAfterPhosphate);
 }
 
-export function isValidNucleoside(sugar: Sugar) {
+export function isValidNucleoside(sugar: Sugar): boolean {
+  if (!getRnaBaseFromSugar(sugar)) {
+    return false;
+  }
+
   const phosphate = getPhosphateFromSugar(sugar);
+  if (!phosphate) {
+    return true;
+  }
+
   const nextMonomerAfterPhosphate = getNextMonomerInChain(phosphate);
+  if (!(nextMonomerAfterPhosphate instanceof Sugar)) {
+    return true;
+  }
 
-  return (
-    getRnaBaseFromSugar(sugar) && (!phosphate || !nextMonomerAfterPhosphate)
-  );
+  return !getRnaBaseFromSugar(nextMonomerAfterPhosphate);
 }