Stub function

hasql.cabal

@@ -106,6 +106,8 @@ library
     Hasql.PTI
     Hasql.Session.Core
     Hasql.Settings
+    Hasql.Statement.Function
+    Hasql.Statement.Function.SqlBuilder
 
   build-depends:
     , aeson >=2 && <3

library/Hasql/Statement.hs

@@ -1,5 +1,6 @@
 module Hasql.Statement
   ( Statement (..),
+    function,
     refineResult,
 
     -- * Recipies
@@ -16,6 +17,7 @@ import qualified Hasql.Decoders as Decoders
 import qualified Hasql.Decoders.All as Decoders
 import qualified Hasql.Encoders as Encoders
 import Hasql.Prelude
+import qualified Hasql.Statement.Function as Function
 
 -- |
 -- Specification of a strictly single-statement query, which can be parameterized and prepared.
@@ -117,3 +119,24 @@ refineResult refiner (Statement template encoder decoder preparable) =
 --
 -- For details see
 -- <https://www.postgresql.org/docs/9.6/static/functions-comparisons.html#AEN20944 the Postgresql docs>.
+
+-- |
+-- Utility for execution of stored procedures and functions, which automates the SQL generation.
+--
+-- Produces SQL like the following:
+--
+-- > SELECT function_name($1, $2, ..)
+--
+-- with the amount of parameter placeholders derived from the encoder.
+function ::
+  -- | Function name.
+  --
+  -- Will get automatically escaped for injection-safety.
+  Text ->
+  Encoders.Params a ->
+  Decoders.Result b ->
+  -- | Whether the statement should be prepared.
+  Bool ->
+  Statement a b
+function functionName encoders =
+  Statement (Function.sql functionName encoders) encoders

library/Hasql/Statement/Function.hs

@@ -0,0 +1,12 @@
+module Hasql.Statement.Function where
+
+import qualified ByteString.StrictBuilder as Builder
+import qualified Hasql.Encoders.All as Encoders
+import Hasql.Prelude
+import qualified Hasql.Statement.Function.SqlBuilder as SqlBuilder
+
+sql :: Text -> Encoders.Params a -> ByteString
+sql name encoders =
+  Builder.builderBytes
+    $ SqlBuilder.sql name
+    $ error "TODO: Get size" encoders

library/Hasql/Statement/Function/SqlBuilder.hs

@@ -0,0 +1,25 @@
+module Hasql.Statement.Function.SqlBuilder where
+
+import ByteString.StrictBuilder
+import qualified Data.Text as Text
+import qualified Data.Text.Encoding as Text
+import Hasql.Prelude
+
+sql :: Text -> Int -> Builder
+sql name size =
+  "select " <> functionName name <> "(" <> arguments size <> ")"
+
+functionName :: Text -> Builder
+functionName =
+  bytes . Text.encodeUtf8 . Text.replace "\"" ""
+
+arguments :: Int -> Builder
+arguments size =
+  [1 .. size]
+    & fmap argument
+    & intersperse ", "
+    & mconcat
+
+argument :: Int -> Builder
+argument num =
+  "$" <> asciiIntegral num