Paging implementation of API response

To implement pagination of API responses use the following procedure as implemented in the Ardor wallet.

All API calls which support paging accept the parameters firstIndex and lastIndex.

These parameters are 0 based and inclusive. Internally they are translated into an SQL OFFSET and LIMIT clauses as follows:

   OFFSET = firstIndex 
   LIMIT = lastIndex - firstIndex + 1

To implement paging with page size P, always fetch (P + 1) rows, set the firstIndex parameter to the first row of the page, 0 based, and the lastIndex parameter to (firstIndex + P).

If the returned number of rows is smaller than (P + 1) stop paging. Otherwise remove the last row and continue paging from the next page.

See an example in the NRS.pages.transactions function in Javascript source file nrs.transactions.js under the <Root>/html/www/js folder. The wallet implementation is using two state variables:

   NRS.pageNumber - representing the current page number, 1 based.
   NRS.itemsPerPage - representing the number of rows per table page.

In our example the parameters for the getBlockchainTransactions API call are set as follows:

   "firstIndex": NRS.pageNumber * NRS.itemsPerPage - NRS.itemsPerPage,
   "lastIndex": NRS.pageNumber * NRS.itemsPerPage

To check if we have more pages to load we are setting the NRS.hasMorePages variable like this:

   NRS.hasMorePages = false;
   if (response.transactions.length > NRS.itemsPerPage) {
       NRS.hasMorePages = true;
       response.transactions.pop(); // remove last row in the response array
   }