From 07fb2c92908a6358b73537188472233bed0a0091 Mon Sep 17 00:00:00 2001
From: Dan Burton <danburton.email@gmail.com>
Date: Tue, 17 Mar 2015 11:20:09 -0700
Subject: [PATCH] Snapshot list pagination now correctly uses row count to
 determine whether the last page has been reached.

---
 Handler/Snapshots.hs           | 36 ++++++++++++++++++++++------------
 templates/snapshots-nav.hamlet | 12 ++++++------
 2 files changed, 29 insertions(+), 19 deletions(-)

diff --git a/Handler/Snapshots.hs b/Handler/Snapshots.hs
index bb9139e..88b9802 100644
--- a/Handler/Snapshots.hs
+++ b/Handler/Snapshots.hs
@@ -24,19 +24,27 @@ getAllSnapshotsR = do
     currentPageMay <- lookupGetParam "page"
     let currentPage :: Int64
         currentPage = fromMaybe 1 (currentPageMay >>= readMay)
-    groups <- fmap (groupBy (on (==) (\(_,_,uploaded,_,_) -> uploaded)) . map (uncrapify now')) $
-        runDB $ E.select $ E.from $ \(stackage `E.InnerJoin` user) -> do
-          E.on (stackage E.^. StackageUser E.==. user E.^. UserId)
-          E.orderBy [E.desc $ stackage E.^. StackageUploaded]
-          E.limit snapshotsPerPage
-          E.offset ((currentPage - 1) * snapshotsPerPage)
-          return
-              ( stackage E.^. StackageSlug
-              , stackage E.^. StackageTitle
-              , stackage E.^. StackageUploaded
-              , user E.^. UserDisplay
-              , user E.^. UserHandle
-              )
+    (totalCount :: Int64, groups) <- fmap (groupUp now') $ runDB $ do
+        c <- E.select $ E.from $ \(stackage `E.InnerJoin` user) -> do
+            E.on (stackage E.^. StackageUser E.==. user E.^. UserId)
+            return E.countRows
+        rs <- E.select $ E.from $ \(stackage `E.InnerJoin` user) -> do
+            E.on (stackage E.^. StackageUser E.==. user E.^. UserId)
+            E.orderBy [E.desc $ stackage E.^. StackageUploaded]
+            E.limit snapshotsPerPage
+            E.offset ((currentPage - 1) * snapshotsPerPage)
+            return
+                ( stackage E.^. StackageSlug
+                , stackage E.^. StackageTitle
+                , stackage E.^. StackageUploaded
+                , user E.^. UserDisplay
+                , user E.^. UserHandle
+                )
+        return (c, rs)
+
+    let isFirstPage = currentPage == 1
+        isLastPage = currentPage * snapshotsPerPage >= totalCount
+
     defaultLayout $ do
         setTitle "Stackage Server"
         let snapshotsNav = $(widgetFile "snapshots-nav")
@@ -44,3 +52,5 @@ getAllSnapshotsR = do
   where uncrapify now' c =
             let (E.Value ident, E.Value title, E.Value uploaded, E.Value display, E.Value handle') = c
             in (ident,title,format (diff True) (diffUTCTime uploaded now'),display,handle')
+        groupUp now' ([E.Value c], rs) = (c, (groupBy (on (==) (\(_,_,uploaded,_,_) -> uploaded)) . map (uncrapify now')) rs)
+        groupUp _ _ = error "Expected countRows to have exactly 1 result."
diff --git a/templates/snapshots-nav.hamlet b/templates/snapshots-nav.hamlet
index 331080e..c887e16 100644
--- a/templates/snapshots-nav.hamlet
+++ b/templates/snapshots-nav.hamlet
@@ -1,12 +1,12 @@
 <div .snapshot-nav>
-  $if currentPage > 1
+  $if isFirstPage
+    at newest --
+  $else
     <a href=@{AllSnapshotsR}?page=#{currentPage - 1}>
       see newer --
-  $else
-    at newest --
   \ Page #{currentPage} #
-  $if length (concat groups) == snapshotsPerPage
+  $if isLastPage
+    ++ at oldest
+  $else
     <a href=@{AllSnapshotsR}?page=#{currentPage + 1}>
       ++ see older
-  $else
-    ++ at oldest