Resolve "Fix move slides on backend"

Closes #161 (closed)

server/app/database/controller/utils.py

@@ -14,8 +14,17 @@ def move_slides(item_competition, from_order, to_order):
     Move slide from from_order to to_order in item_competition.
     """
 
-    # TODO: Please refactor this terrible piece of code
-    # This function is
+    num_slides = len(item_competition.slides)
+    assert 0 <= from_order < num_slides, "Invalid order to move from"
+    assert 0 <= to_order < num_slides, "Invalid order to move to"
+
+    # TODO: Please improve this terrible piece of code
+    # This function is sooo terrible, someone please tell me how to update
+    # multiple values in the database at the same time with unique constraints.
+    # If you update all the values at the same time none of them will collide
+    # but that database doesn't know that so you have to update them to some
+    # other value before and then change every value back to the correct one,
+    # so 2 commits.
 
     slides = item_competition.slides
 
@@ -23,35 +32,29 @@ def move_slides(item_competition, from_order, to_order):
     start_order = min(from_order, to_order)
     end_order = max(from_order, to_order)
 
+    for item_slide in slides:
+        item_slide.order += 100
+
     # Move slides between from and to order either up or down, but minus in front
     for item_slide in slides:
-        if start_order <= item_slide.order <= end_order:
+        if start_order <= item_slide.order - 100 <= end_order:
             item_slide.order = -(item_slide.order + change)
 
     # Find the slide that was to be moved and change it to correct order with minus in front
     for item_slide in slides:
-        if -item_slide.order - change == from_order:
-            item_slide.order = -to_order
-            break
-
-    # -0 = 0 so have to do a special case for it
-    for item_slide in slides:
-        if item_slide.order == 0:
-            item_slide.order = -999
+        if item_slide.order == -(from_order + change + 100):
+            item_slide.order = -(to_order + 100)
             break
 
     db.session.commit()
 
     # Negate all order so that they become correct and positive
     for item_slide in slides:
-        if start_order <= -item_slide.order <= end_order:
+        if start_order <= -(item_slide.order + 100) <= end_order:
             item_slide.order = -(item_slide.order)
 
-    # Change order back
     for item_slide in slides:
-        if item_slide.order == -999:
-            item_slide.order = 0
-            break
+        item_slide.order -= 100
 
     return commit_and_refresh(item_competition)