Rework Pagination about feedjack HOT 4 CLOSED

• Address of the current page: from xxxx-xx-xx_xx:xx to yyyy-yy-yy_yy-yy
• Address of the next / previous page: Allow Steps 1 hour / day / ... or based on post volume (calculate the date range of the next 20 posts) and "everything after start date"
• Allow loading more items with ajax on the current page
• Maybe use history API and scroll position to update the url to page / #item_id links. Avoid cluttering the browser history with too many entries.

Alternatives for previous page:

• count 20 items backwards, take date of this item and store it in normal since/PREVIOUS_DATE/ascending format
• store date of the first item of the current page + direction backwards like before/CURRENT_DATE/ascending/ and calculate the minus 20 before the date on access.

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• Display 20 Items
• Text "123 older posts" (link: previous)
• Text "456 newer posts" (link: next)

Link next: since (last post on page)
Link previous: filter(date__lt=first_post.date).order_by("-id)[:20].order_by("id") (order backward, get 20 posts, order forward)

Alternative: Use calculated permalinks ?from=date1&to=date2&order=asc, which may change the number of posts in between. Integrate with endless scroll, which loads this via ajax on scrolling.

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Forward pagination with (or without) ajax works after commit 6cfeff3.

TODO:

• Add "X later items" 1e4b062 acfd6d4
• Add "previous" (needs to calculate items backwards and use the appropriate since= parameter)
  • reverse ordering, then count posts_per_page items forward and use the date there as since= parameter. Leave asc= as it is.
• Add a "until" parameter 06c7250

The until= parameter will be needed in the pagination for pages with less then posts_per_page items.

When having 5 Items per page and these pages (previous, current, next) are:

``[1, 2] [3, 4, 5, 6, 7] [8,9]``

the previous page with respect to ordering (either 1 or 3) should only contain 2 items. so a since= alone would for example produce

``[1, 2, 3, 4, 5]``

which contains 3 entries from the current page on the "previous page".

For forward pagination not having an until-parameter means that a page can get new items on reload, if it was incomplete before, which probably is okay.

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Completed with commit bf943e6.

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