Hyphenate ISBN numbers and add copy button

bookwyrm/isbn/isbn.py

@@ -0,0 +1,71 @@
+import os
+import requests
+
+from xml.etree import ElementTree
+from bookwyrm import settings
+
+
+class IsbnHyphenator:
+    __range_message_url = "https://www.isbn-international.org/export_rangemessage.xml"
+    __range_file_path = os.path.join(
+        settings.BASE_DIR, "bookwyrm", "isbn", "RangeMessage.xml"
+    )
+    __element_tree = None
+
+    def update_range_message(self):
+        response = requests.get(self.__range_message_url)
+        with open(self.__range_file_path, "w", encoding="utf-8") as file:
+            file.write(response.text)
+        self.__element_tree = None
+
+    def hyphenate(self, isbn_13):
+        if self.__element_tree is None:
+            self.__element_tree = ElementTree.parse(self.__range_file_path)
+        gs1_prefix = isbn_13[:3]
+        reg_group = self.__find_reg_group(isbn_13, gs1_prefix)
+        if reg_group is None:
+            return isbn_13  # failed to hyphenate
+        registrant = self.__find_registrant(isbn_13, gs1_prefix, reg_group)
+        if registrant is None:
+            return isbn_13  # failed to hyphenate
+        publication = isbn_13[len(gs1_prefix) + len(reg_group) + len(registrant) : -1]
+        check_digit = isbn_13[-1:]
+        return "-".join((gs1_prefix, reg_group, registrant, publication, check_digit))
+
+    def __find_reg_group(self, isbn_13, gs1_prefix):
+        for ean_ucc_el in self.__element_tree.find("EAN.UCCPrefixes").findall(
+            "EAN.UCC"
+        ):
+            if ean_ucc_el.find("Prefix").text == gs1_prefix:
+                for rule_el in ean_ucc_el.find("Rules").findall("Rule"):
+                    length = int(rule_el.find("Length").text)
+                    if length == 0:
+                        continue
+                    range = [
+                        int(x[:length]) for x in rule_el.find("Range").text.split("-")
+                    ]
+                    reg_group = isbn_13[len(gs1_prefix) : len(gs1_prefix) + length]
+                    if range[0] <= int(reg_group) <= range[1]:
+                        return reg_group
+                return None
+        return None
+
+    def __find_registrant(self, isbn_13, gs1_prefix, reg_group):
+        from_ind = len(gs1_prefix) + len(reg_group)
+        for group_el in self.__element_tree.find("RegistrationGroups").findall("Group"):
+            if group_el.find("Prefix").text == "-".join((gs1_prefix, reg_group)):
+                for rule_el in group_el.find("Rules").findall("Rule"):
+                    length = int(rule_el.find("Length").text)
+                    if length == 0:
+                        continue
+                    range = [
+                        int(x[:length]) for x in rule_el.find("Range").text.split("-")
+                    ]
+                    registrant = isbn_13[from_ind : from_ind + length]
+                    if range[0] <= int(registrant) <= range[1]:
+                        return registrant
+                return None
+        return None
+
+
+hyphenator_singleton = IsbnHyphenator()