Allow users to order anonymous fragments within topics

[tcouch]

Splitting this out from #290 as these requests can be tackled independently.

Description

On the /anonymous/list page, anonymous fragments are currently displayed under topic headings and the order in which they're displayed within those topics is determined by the fragment's order value. Users would like to be able to change the fragment's order within topics by dragging them up and down (or clicking up/down buttons) within the topic list (c.f. /topic/list/ page).

Current functionality

• Anonymous fragments have an order field (OrderableModel) which is a positive integer initially assigned as the last position in the list of anon fragments when the object is first saved; e.g. if there are 100 anon fragments, a new fragment would be given the order value 100 (order starts counting from 0). Order is then used to generate the display name for the fragment, which in this case would be F101 (the get_display_name function adds 1 to the order).
• Anonymous fragments have a many-to-many relationship with Topics (they can belong to many topics, and topics can relate to many fragments). E.g. if an AnonymousFragment is assigned to three topics, they will appear three times in the anonymous section, once under each topic.
• Topics also have an order, which can be changed by users on the /topic/list page.
• Every time an anonymous fragment is added to, or removed from a topic, or the topic order changes, the order values of all anonymous fragments are recalculated. To do this: a reindex_anonymous_fragments function creates a queryset containing all AnonymousFragments ordered by topic order, then by their own order value; duplicates are removed; then order values are updated for each fragment according to its position in the queryset.
• Anonymous fragments which are not assigned to any topic are listed in the “Uncategorised” section and are implicitly treated as belonging to a topic with the highest order value.

Proposed solution

Luckily @peterbispham seems to have anticipated this and added an order field to AnonymousTopicLink which we can use to record the order with respect to Topic for Anonymous Fragments. A quick survey of the database confirms this field is not currently used.

Once we have an order wrt topic for each AnonymousTopicLink, we can change the reindex_anonymous_fragments function to order AnonymousFragments by Topic order, then by AnonymousTopicLink order to determine their overall order.

[tcouch]

Preferred option is to remove pagination on /anonymous/list and just list the topics, clicking on a topic shows all the relevant anonymous fragments in one page (not sure the url /anonymous/list makes sense in that case)

Richard confirms they would not want to move anon fragments across topics

[tcouch]

Testing expected functionality

Models

AnonymousTopicLink

• [x] test_new_link_order_is_last_if_not_apposita

• when a new AnonymousTopicLink is saved, if it is not an apposita, it should be given an order value equal to the number of pre-existing links associated with that topic plus one; e.g. if there are 10 non-apposita AnonymousTopicLinks associated with the topic "Monarchy", a new AnonymousTopicLink associated with "Monarchy" should have order = 11.

• [x] test_new_link_order_is_zero_if_apposita

• whan a new AnonymousTopicLink is saved, and the fragment is an apposita, it should be given an order of zero.

• [x] test_links_reindexed_when_link_removed

• when an AnonymousTopicLink is deleted, anonymous topic links within the affected topic should be reindexed

• [x] test_link_order_change_updates_anon_fragment_order

• when AnonymousTopicLinks are reordered within a topic, anonymous fragments should be reindexed to take this into account; e.g. assert AnonymousFragment.reindex_anonymous_fragments is called when link order changes

• [x] test_apposita_not_in_related_queryset

• apposita (anonymous fragments with links to fragments) should not appear in related_queryset

• [x] test_related_queryset_relates_to_topic

AnonymousFragment

setUpTestData():

• two topics: topic1(name="Monarchy", order=0), topic2 (name="Law", order=1)

• three anonymous fragments: anon1, anon2, anon3

• one fragment: frag1

• one appositum_link: (frag1, anon3)

• add anon1, anon2, and anon3 to topic1 in that order

• add anon2 and anon1 to topic2 in that order

• [x] test_reindex_anonymous_fragments_order_by_topic

• when reindexing anonymous fragments, topic order should take precedence over order within topic. With setUpData:

  • after running reindex_anonymous_fragments, anon1 should have a lower order than anon2
  • if we then swap the order of topic1 and topic2, anon2 should have a lower order than anon1, and both should now have a lower order than anon3

• [x] test_reindex_anonymous_fragments_order_by_topic_link_order

• when reindexing anonymous fragments, their order with respect to topics should be taken into account. Where two fragments both belong to the same two topics and their order relative to each other is different within those topics, their order with respect to the topic with lower order should take precedence. With the setUpData:

  • if the orders of at_link2 and at_link3 are swapped, anon2 should now have a lower order than anon1
  • if at_link4 and at_link5 are then swapped, anon2 should still have a lower order than anon1

Views

MoveAnonymousTopicLinkView

• [ ] test_move_to

• [ ] test_cannot_move_to_zero

• [ ] test_cannot_move_beyond_end

• [ ] test_no_gaps_in_order_after_move