function moved

bookwyrm/views/search.py

@@ -24,6 +24,8 @@ class Search(View):
     def get(self, request):
         """that search bar up top"""
         query = request.GET.get("q")
+        # check if query is isbn
+        query =  isbn_check(query)
         min_confidence = request.GET.get("min_confidence", 0)
         search_type = request.GET.get("type")
         search_remote = (
@@ -123,3 +125,29 @@ def list_search(query, viewer, *_):
         )
         .order_by("-similarity")
     ), None
+
+
+def isbn_check(query):
+    n = query.replace('-','').replace(' ', '')
+    if len(n) == 13:
+        # Multiply every other digit by  3
+        # Add these numbers and the other digits
+        product = (sum(int(ch) for ch in n[::2]) 
+                + sum(int(ch) * 3 for ch in n[1::2]))
+        if product % 10 == 0:
+            return n
+    elif len(n) == 10:
+        if n[0:8].isdigit() and (n[9].isdigit() or n[9].lower() == "x"):
+            product = 0
+            # Iterate through code_string
+            for i in range(9):
+                # for each character, multiply by a different decreasing number: 10 - x
+                product = product + int(n[i]) * (10 - i)
+            # Handle last character
+            if n[9].lower() == "x":
+                product += 10
+            else:
+                product += int(n[9])
+            if product % 11 == 0:
+                return n
+    return query