Add "alternate for" column in Catapult export, based on like codes

this is more of an FYI column, user must do with it what they will

rattail_corepos/corepos/importing/db/exporters/catapult_inventory.py

@@ -125,6 +125,9 @@ class InventoryItemImporter(FromCore, catapult_importing.model.InventoryItemImpo
     # we want to add a "duplicate" column at the end
     include_duplicate_column = True
 
+    # we want to add an "alternate for" column at the end
+    include_alt_for_column = True
+
     type2_upc_pattern = re.compile(r'^2(\d{5})00000\d')
 
     def setup(self):
@@ -212,6 +215,10 @@ class InventoryItemImporter(FromCore, catapult_importing.model.InventoryItemImpo
         # tax_component_ids_1 = (1,)
         # tax_component_ids_2 = (2,)
 
+        self.cache_bottle_deposits()
+        self.cache_like_codes()
+
+    def cache_bottle_deposits(self):
         self.deposits = {}
         deposits = self.host_session.query(corepos.Product.deposit.distinct())\
                                     .all()
@@ -235,6 +242,19 @@ class InventoryItemImporter(FromCore, catapult_importing.model.InventoryItemImpo
         self.progress_loop(cache, deposits,
                            message="Caching product deposits data")
 
+    def cache_like_codes(self):
+        self.like_codes = {}
+        mappings = self.host_session.query(corepos.ProductLikeCode)\
+                                    .order_by(corepos.ProductLikeCode.like_code_id,
+                                              corepos.ProductLikeCode.upc)\
+                                    .all()
+
+        def cache(mapping, i):
+            self.like_codes.setdefault(mapping.like_code_id, []).append(mapping)
+
+        self.progress_loop(cache, mappings,
+                           message="Caching like codes data")
+
     def query(self):
         query = self.host_session.query(corepos.Product)\
                                  .order_by(corepos.Product.upc)\
@@ -245,7 +265,8 @@ class InventoryItemImporter(FromCore, catapult_importing.model.InventoryItemImpo
                                  .options(orm.joinedload(corepos.Product.default_vendor))\
                                  .options(orm.joinedload(corepos.Product.scale_item))\
                                  .options(orm.joinedload(corepos.Product.user_info))\
-                                 .options(orm.joinedload(corepos.Product.tax_rate))
+                                 .options(orm.joinedload(corepos.Product.tax_rate))\
+                                 .options(orm.joinedload(corepos.Product._like_code))
         if self.floor_sections_exist:
             query = query.options(orm.joinedload(corepos.Product.physical_location)\
                                   .joinedload(corepos.ProductPhysicalLocation.floor_section))
@@ -289,6 +310,33 @@ class InventoryItemImporter(FromCore, catapult_importing.model.InventoryItemImpo
 
         self.progress_loop(inspect, list(items.values()),
                            message="Marking any duplicate Item IDs")
+
+        # finally, we must inspect the like codes and figure out which
+        # product(s) should potentially be considered "alternate for" another.
+        # first step here will be to create mapping of item_id values for each
+        # CORE product in our result set
+        item_ids = {}
+
+        def mapp(row, i):
+            product = row['__product__']
+            item_ids[product.upc] = row['item_id']
+
+        self.progress_loop(mapp, normalized,
+                           message="Mapping item_id for CORE products")
+
+        # next step here is to check each product and mark "alt for" as needed
+        def inspect(row, i):
+            product = row['__product__']
+            if product.like_code:
+                others = self.like_codes.get(product.like_code.id)
+                if others:
+                    first = others[0]
+                    if first.upc != product.upc:
+                        row['__alternate_for__'] = item_ids[first.upc]
+
+        self.progress_loop(inspect, normalized,
+                           message="Marking any \"alternate for\" items")
+
         return normalized
 
     def normalize_host_object(self, product):
@@ -545,6 +593,7 @@ class InventoryItemImporter(FromCore, catapult_importing.model.InventoryItemImpo
                 scale_ingredient_text = scale_ingredient_text.replace("\n", " ")
 
         return {
+            '__product__': product,
             'uuid': get_uuid(),
             'item_id': item_id,
             'dept_id': department.number if department else None,