From 8eab68a8d30aaab9338b8ed29a5186ed1e90949c Mon Sep 17 00:00:00 2001
From: Fintan Halpenny <rossmanf@tcd.ie>
Date: Thu, 3 Aug 2017 20:48:42 +0100
Subject: [PATCH] Removed now from typeclass and moved it to PostgreSQL.
 Testing for DB clock against machine clock

---
 src/Database/Esqueleto.hs                   |  2 +-
 src/Database/Esqueleto/Internal/Language.hs |  2 --
 src/Database/Esqueleto/Internal/Sql.hs      |  1 -
 src/Database/Esqueleto/PostgreSQL.hs        |  6 +++++-
 test/Test.hs                                | 18 ++++++++++++++----
 5 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/Database/Esqueleto.hs b/src/Database/Esqueleto.hs
index b3f61be..495e1a6 100644
--- a/src/Database/Esqueleto.hs
+++ b/src/Database/Esqueleto.hs
@@ -45,7 +45,7 @@ module Database.Esqueleto
              , countRows, count, countDistinct
              , not_, (==.), (>=.), (>.), (<=.), (<.), (!=.), (&&.), (||.)
              , (+.), (-.), (/.), (*.)
-             , random_, now_, round_, ceiling_, floor_
+             , random_, round_, ceiling_, floor_
              , min_, max_, sum_, avg_, castNum, castNumM
              , coalesce, coalesceDefault
              , lower_, like, ilike, (%), concat_, (++.), castString
diff --git a/src/Database/Esqueleto/Internal/Language.hs b/src/Database/Esqueleto/Internal/Language.hs
index 6536f3e..b3188da 100644
--- a/src/Database/Esqueleto/Internal/Language.hs
+++ b/src/Database/Esqueleto/Internal/Language.hs
@@ -53,7 +53,6 @@ import Text.Blaze.Html (Html)
 import qualified Data.ByteString as B
 import qualified Data.Text as T
 import qualified Data.Text.Lazy as TL
-import Data.Time.Clock (UTCTime)
 
 
 -- | Finally tagless representation of @esqueleto@'s EDSL.
@@ -353,7 +352,6 @@ class (Functor query, Applicative query, Monad query) =>
 
 
   random_  :: (PersistField a, Num a) => expr (Value a)
-  now_     :: (PersistField a, a ~ UTCTime) => expr (Value a)
   round_   :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b)
   ceiling_ :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b)
   floor_   :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b)
diff --git a/src/Database/Esqueleto/Internal/Sql.hs b/src/Database/Esqueleto/Internal/Sql.hs
index b5bd9a3..02861ab 100644
--- a/src/Database/Esqueleto/Internal/Sql.hs
+++ b/src/Database/Esqueleto/Internal/Sql.hs
@@ -504,7 +504,6 @@ instance Esqueleto SqlQuery SqlExpr SqlBackend where
   (*.)  = unsafeSqlBinOp " * "
 
   random_  = unsafeSqlValue "RANDOM()"
-  now_     = unsafeSqlValue "NOW()"
   round_   = unsafeSqlFunction "ROUND"
   ceiling_ = unsafeSqlFunction "CEILING"
   floor_   = unsafeSqlFunction "FLOOR"
diff --git a/src/Database/Esqueleto/PostgreSQL.hs b/src/Database/Esqueleto/PostgreSQL.hs
index 0a31cc2..2e9f8d8 100644
--- a/src/Database/Esqueleto/PostgreSQL.hs
+++ b/src/Database/Esqueleto/PostgreSQL.hs
@@ -7,11 +7,12 @@ module Database.Esqueleto.PostgreSQL
   ( arrayAgg
   , stringAgg
   , chr
+  , now_
   ) where
 
 import Database.Esqueleto.Internal.Language
 import Database.Esqueleto.Internal.Sql
-
+import Data.Time.Clock (UTCTime)
 
 -- | (@array_agg@) Concatenate input values, including @NULL@s,
 -- into an array.
@@ -38,3 +39,6 @@ stringAgg expr delim = unsafeSqlFunction "string_agg" (expr, delim)
 -- /Since: 2.2.11/
 chr :: SqlString s => SqlExpr (Value Int) -> SqlExpr (Value s)
 chr = unsafeSqlFunction "chr"
+
+now_ :: SqlExpr (Value UTCTime)
+now_ = unsafeSqlValue "NOW()"
diff --git a/test/Test.hs b/test/Test.hs
index 5e32d1b..a0c2e93 100644
--- a/test/Test.hs
+++ b/test/Test.hs
@@ -51,7 +51,7 @@ import qualified Data.List as L
 import qualified Data.Set as S
 import qualified Data.Text.Lazy.Builder as TLB
 import qualified Database.Esqueleto.Internal.Sql as EI
-import Data.Time.Clock (UTCTime)
+import Data.Time.Clock (getCurrentTime, diffUTCTime, NominalDiffTime)
 
 
 -- Test schema
@@ -645,10 +645,20 @@ main = do
 #endif
           return ()
 
-      it "works with now_" $
+      it "works with now" $
         run $ do
-          _ <- select $ return (now_ :: SqlExpr (Value UTCTime))
-          return ()
+          nowDb <- select $ return EP.now_
+          nowUtc <- liftIO getCurrentTime
+          let halfSecond = realToFrac 0.5 :: NominalDiffTime
+
+          -- | Check the result is not null
+          liftIO $ nowDb `shouldSatisfy` (not . null)
+
+          -- | Unpack the now value
+          let (Value now: _) = nowDb
+
+          -- | Get the time diff and check it's less than half a second
+          liftIO $ diffUTCTime nowUtc now `shouldSatisfy` (< halfSecond)
 
       it "works with round_" $
         run $ do