first pass of supprot functions to allow query/entry_list to drive pagination, and do not go back to the server to calc next/prev page

internal/js/files_support.js

@@ -316,3 +316,90 @@ function NoSel() {
     else
         return true
 }
+
+function handlePageOfData()
+{
+    // FIXME: this should get back a json'd array of entries, and I can/should
+    // use this to redraw the figures dynamically on the page
+}
+
+
+// Function to get the 'page' of entry ids out of entryList
+function getPage(pageNumber) 
+{
+    const startIndex = (pageNumber - 1) * howMany;
+    const endIndex = startIndex + howMany;
+    pageList = entryList.slice(startIndex, endIndex);
+    // FIXME: should POST here to get the data for new pl
+    return
+}
+
+// Quick Function to check if we are on the first page
+function isFirstPage(pageNumber) 
+{
+    return pageNumber <= 1;
+}
+
+// Function to check if we are on the last page
+function isLastPage(pageNumber) 
+{
+    const totalPages = Math.ceil(entryList.length / howMany);
+    return pageNumber >= totalPages;
+}
+
+// given an id in the list, return which page we are on (page 1 is first page)
+function getPageNumberForId(id) {
+    const idx = entryList.indexOf(id);
+    // should be impossible but jic
+    if (idx === -1) {
+        return -1; // or null, if you prefer
+    }
+    return Math.floor(idx / howMany) + 1;
+}
+
+// if we are on first page, disable prev, it not ensure next is enabled
+// if we are on last page, disable next, it not ensure prev is enabled
+function resetNextPrevButtons()
+{
+    if ( isFirstPage( getPageNumberForId(pageList[0]) ) )
+        $('.prev').prop('disabled', true).addClass('disabled');
+    else
+        $('.prev').prop('disabled', false).removeClass('disabled');
+
+    if ( isLastPage( getPageNumberForId(pageList[0]) ) )
+        $('.next').prop('disabled', true).addClass('disabled');
+    else
+        $('.next').prop('disabled', false).removeClass('disabled');
+}
+
+// get list of eids for the next page, also make sure next/prev buttons make sense for page we are on
+function nextPage()
+{
+    // pageList[0] is the first entry on this page
+    const currentPage=getPageNumberForId( pageList[0] )
+    // should never happen / just return pageList unchanged
+    if ( currentPage === -1 || isLastPage( currentPage ) )
+    {
+        console.log( "WARNING: seems first on pg=" + firstEntryOnPage + " of how many=" + howMany + " gives currentPage=" + currentPage + " and we cant go next page?" )
+        return
+    }
+    getPage( currentPage+1 )
+    resetNextPrevButtons()
+    return
+}
+
+// get list of eids for the prev page, also make sure next/prev buttons make sense for page we are on
+function prevPage()
+{
+    // pageList[0] is the first entry on this page
+    const currentPage=getPageNumberForId( pageList[0] )
+    // should never happen / just return pageList unchanged
+    if (currentPage === 1 || currentPage === -1 )
+    {
+        console.log( "WARNING: seems first on pg=" + firstEntryOnPage + " of how many=" + howMany + " gives currentPage=" + currentPage + " and we cant go prev page?" )
+        return
+    }
+    getPage( currentPage-1 )
+    resetNextPrevButtons()
+    return
+}