add get_signature function for old signatures that are already in the database for all tables

src/database.py

@@ -63,12 +63,29 @@ class Database:
             # print(f"Error: Unknown signature type '{table}'. Please use 'ma', 'mb', or 'mc'.")
             return self.insert_ma(old_signature)
 
+    def get_signature(self, old_signature: str, table: str) -> str | None:
+        """Get the new signature for the given old signature from the specified table."""
+        cursor = self.connection.cursor()
+        cursor.execute(
+            f"SELECT new_signature FROM {table} WHERE old_signature = ?",
+            (old_signature,),
+        )
+        result = cursor.fetchone()
+        if result:
+            return result[0]
+        else:
+            print(
+                f"Error: The old_signature '{old_signature}' does not exist in the {table} table."
+            )
+            return None
+
     def insert_ma(self, old_signature: str) -> str|None:
         """Insert an old signature into the ma table and return the new signature.
         New Signatures is generated by using 01 / as prefix, then incrementing the number by 1 for each new entry."""
         if self.signature_exists(old_signature, "ma"):
             print(f"Error: The old_signature '{old_signature}' already exists in the ma table.")
-            return None
+            signature = self.get_signature(old_signature, "ma")
+            return signature
         new_signature = self.create_new_signature("ma")
         try:
             cursor = self.connection.cursor()
@@ -84,6 +101,12 @@ class Database:
         """Insert an old signature into the mb table and return the new signature.
         New Signatures is generated by using 02 / as prefix, then incrementing the number by 1 for each new entry."""
         new_signature = self.create_new_signature("mb")
+        if self.signature_exists(old_signature, "mb"):
+            print(
+                f"Error: The old_signature '{old_signature}' already exists in the mb table."
+            )
+            signature = self.get_signature(old_signature, "mb")
+            return signature
         try:
             cursor = self.connection.cursor()
             cursor.execute("INSERT INTO mb (old_signature, new_signature) VALUES (?, ?)", (old_signature, new_signature))
@@ -97,6 +120,12 @@ class Database:
         """Insert an old signature into the mc table and return the new signature.
         New Signatures is generated by using 03 / as prefix, then incrementing the number by 1 for each new entry."""
         new_signature = self.create_new_signature("mc")
+        if self.signature_exists(old_signature, "mc"):
+            print(
+                f"Error: The old_signature '{old_signature}' already exists in the mc table."
+            )
+            signature = self.get_signature(old_signature, "mc")
+            return signature
         try:
             cursor = self.connection.cursor()
             cursor.execute("INSERT INTO mc (old_signature, new_signature) VALUES (?, ?)", (old_signature, new_signature))