[main] Add paginated vocabulary search with 'Show previous/next results' controls in hierarchical browse

[ZahraaChreim-Atmire]

References

• Fixes Hierarchical browse returns only first 20 results when searching/filtering #4500
• 7.x port is available at [dspace-7_x] Add paginated vocabulary search with 'Show previous/next results' controls in hierarchical browse #4504

Description

Added paging state management to the vocabulary treeview service, updating after each query based on whether previous or next pages exist; this state is exposed to the component to conditionally render navigation buttons in the hierarchical vocabulary browse.

Instructions for Reviewers

List of changes in this PR:

• First, added currentPage, totalPages, showNextPageSubject, and showPreviousPageSubject to the vocabulary-treeview.service to manage and expose pagination state.
• Second, created a new method searchByQueryAndPage(query, selectedItems, page) to support page-specific vocabulary search requests. The existing searchByQuery method was updated to call this with page 1 by default.
• Third, updated searchByQueryAndPage to extract pagination info from the search response and update the showNextPageSubject and showPreviousPageSubject based on whether more pages are available.
• Fourth, exposed showNextPage$ and showPreviousPage$ in the component, derived from showNextPageSubject, and showPreviousPageSubject, to reactively control the display of pagination buttons.
• Fifth, added conditional rendering of “Show next results” and “Show previous results” buttons in the template, along with loadNextPage and `loadPreviousPage to trigger paging behavior.

To test this PR:

1. Create a custom vocabulary XML file containing more than 20 nodes. Example: nodes with label="label1" through label="label100" and corresponding values like "value test 1" to "value test 100".
2. Deploy the vocabulary to your backend instance.
3. Navigate to the hierarchical browse interface in the UI (e.g., /browse/srsc).
4. Enter the query label.

Expected behavior after applying this PR:

• Only the first 20 matching entries are displayed initially.
• A “Show next results” button appears below the filtered tree.
• Clicking it displays the next 20 results and replaces the tree content.
• When on subsequent pages, a “Show previous results” button also appears to navigate back.
• On the final page, only the “Show previous results” button should be visible (no “Show next”).
• On the first page, only the “Show next results” button should be visible.

First page:

Intermediate page:

Last page:

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[nwoodward]

Thanks @ZahraaChreim-Atmire. The pagination works very well, except for one small issue. If there are more than 20 nodes and I click "Show next results" and then navigate away from Browsing by Subject Category to any other page of the repository when I come back to Browsing by Subject Category the "Show previous results" button still appears, even though I'm on the first page of subjects. Is there a way to reset the buttons when the user navigates away from this page?

[ZahraaChreim-Atmire]

Thanks @ZahraaChreim-Atmire. The pagination works very well, except for one small issue. If there are more than 20 nodes and I click "Show next results" and then navigate away from Browsing by Subject Category to any other page of the repository when I come back to Browsing by Subject Category the "Show previous results" button still appears, even though I'm on the first page of subjects. Is there a way to reset the buttons when the user navigates away from this page?

Thank you for your feedback! I’ve updated the code to reset the pagination observables on component initialization, ensuring the buttons are hidden when returning to the page.

[nwoodward]

Thanks @ZahraaChreim-Atmire! Now when I navigate away from browsing by subject category the pagination resets. Can you also reset the pagination when the user clicks on the "Reset" button? When I search for "label" in the subject categories and then navigate though the results and then click "Reset" then the bottom of the categories list looks like the screenshot. It's still showing the previous and next buttons, but the search box is empty so it's a bit confusing.

[ZahraaChreim-Atmire]

Thanks @ZahraaChreim-Atmire! Now when I navigate away from browsing by subject category the pagination resets. Can you also reset the pagination when the user clicks on the "Reset" button? When I search for "label" in the subject categories and then navigate though the results and then click "Reset" then the bottom of the categories list looks like the screenshot. It's still showing the previous and next buttons, but the search box is empty so it's a bit confusing.

@nwoodward Fixed! Pagination is also reset when the "Reset" button is clicked.

[nwoodward]

👍 Thanks @ZahraaChreim-Atmire! I tested again this morning, and the pagination works really well in every scenario I could envision.

[github-actions]

Hi @ZahraaChreim-Atmire,
Conflicts have been detected against the base branch.
Please resolve these conflicts as soon as you can. Thanks!

[tdonohue]

Temporarily closing & reopening to get an updated test result. Apologies this has taken long to get back to, but I'd like to see if we can merge this soon.