Back-office ui: create loan details page about invenio-app-ils HOT 4 CLOSED

• loan record json response in links does not include self
• for pending loans, LoanAvailableItems component
• for running loans, LoanItem component displaying information on loaned item
• address loan actions
• resolve item_pid, pickup_location_pid, transaction_location_pid, transaction_user_pid to their actual objects

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While working on loan details page, I came across an issue which should be addressed.

The story is when fetching the loan it comes with an item_id. In order to present relevant information of the item we have to fetch the actual record. In that step we have two options:

1. we fire a request from the front end to fetch the entity or
2. we create a $ref property in the loan and a json ref resolver to replace it with the actual item record.

The benefit of the second approach apart from the extraneous requests (we might need to resolve more type of records), is that if we resolve it we are also able to index it in elastic search.

The hidden circular dependencies problem was not visible straight away due to the fact that we were calling item.replace_refs() because the item has also $refs and then we were calling loan.replace_refs() which had an item with resolved refs inside it. This was preventing the circulation problem to show up and instead threw a Python copy error for failing to deep copy objects.

The actual problem raises from the fact that the item has a property called circulation_status (which represents a loan) and the loan has an item, so they are point one another.

Proposed solution is to index everything on the item. It might feel a bit "slow" firing extra requests on the front end but like this, we leave circulation isolated without the hassle of overriding methods that resolve records from other services and we keep all our business logic to ils. As it concerns indexing we had a conversation with @zzacharo and we believe that in the worst case we will have to do an extra db query to fetch the record with the id we are looking for.

I might be missing something obvious or not but is there a case that item -> loan reference cannot address and we need loan -> item relation? @ntarocco, @kprzerwa, @ludmilamarian ?

In case you want to test, experiment or whatever the following branches contain the solution with the $ref.

Branches with circular dependencies: invenio-app-ils, invenio-circulation

Update: After a short talk with the team, we will have to explore further and agree on how we will structure our models and their dependencies. Something we tried out with @zzacharo and actually worked, is to manually remove the circulation_status from the item when it gets resolved by a loan. Either way I have a branch with each one of the aforementioned solutions (1 and 2) on top.

I will also tag @ntarocco for his feedback since he loves manual manipulations on models.

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@topless nice writing here, thanks for the detailed explanations!
I agree with the solution!

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