1 files changed, 133 insertions, 2 deletions
diff --git a/src/Xanthous/Orphans.hs b/src/Xanthous/Orphans.hs
index 232eabf4efb1..d2e378cd2817 100644
--- a/src/Xanthous/Orphans.hs
+++ b/src/Xanthous/Orphans.hs
@@ -1,10 +1,23 @@
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE ViewPatterns #-}
 {-# LANGUAGE UndecidableInstances, PatternSynonyms #-}
 {-# OPTIONS_GHC -Wno-orphans #-}
 -- |
 
-module Xanthous.Orphans () where
+module Xanthous.Orphans
+  ( ppTemplate
+  ) where
 
-import Xanthous.Prelude
+import Xanthous.Prelude hiding (elements)
+import Text.Mustache
+import Test.QuickCheck
+import Data.Text.Arbitrary ()
+import Text.Megaparsec (errorBundlePretty)
+import Text.Megaparsec.Pos
+import Text.Mustache.Type ( showKey )
+import Data.List.NonEmpty (NonEmpty(..))
+import qualified Data.List.NonEmpty as NonEmpty
+import Data.Aeson
 
 instance forall s a.
   ( Cons s s a a
@@ -21,3 +34,121 @@ instance forall s a.
       yon ns = case ns ^? _Cons of
         Nothing -> Left ns
         Just (a, ns') -> Right (a, ns')
+
+instance Arbitrary PName where
+  arbitrary = PName . pack <$> listOf1 (elements ['a'..'z'])
+
+instance Arbitrary Key where
+  arbitrary = Key <$> listOf1 arbSafeText
+    where arbSafeText = pack <$> listOf1 (elements ['a'..'z'])
+  shrink (Key []) = error "unreachable"
+  shrink k@(Key [_]) = pure k
+  shrink (Key (p:ps)) = Key . (p :) <$> shrink ps
+
+instance Arbitrary Pos where
+  arbitrary = mkPos . succ . abs <$> arbitrary
+  shrink (unPos -> 1) = []
+  shrink (unPos -> x) = mkPos <$> [x..1]
+
+instance Arbitrary Node where
+  arbitrary = sized node
+    where
+      node n | n > 0 = oneof $ leaves ++ branches (n `div` 2)
+      node _ = oneof leaves
+      branches n =
+        [ Section <$> arbitrary <*> subnodes n
+        , InvertedSection <$> arbitrary <*> subnodes n
+        ]
+      subnodes = fmap concatTextBlocks . listOf . node
+      leaves =
+        [ TextBlock . pack <$> listOf1 (elements ['a'..'z'])
+        , EscapedVar <$> arbitrary
+        , UnescapedVar <$> arbitrary
+        -- TODO fix pretty-printing of mustache partials
+        -- , Partial <$> arbitrary <*> arbitrary
+        ]
+  shrink = genericShrink
+
+concatTextBlocks :: [Node] -> [Node]
+concatTextBlocks [] = []
+concatTextBlocks [x] = [x]
+concatTextBlocks (TextBlock txt₁ : TextBlock txt₂ : xs)
+  = concatTextBlocks $ TextBlock (txt₁ <> txt₂) : concatTextBlocks xs
+concatTextBlocks (x : xs) = x : concatTextBlocks xs
+
+instance Arbitrary Template where
+  arbitrary = do
+    template <- concatTextBlocks <$> arbitrary
+    templateName <- arbitrary
+    rest <- arbitrary
+    pure $ Template
+      { templateActual = templateName
+      , templateCache = rest & at templateName ?~ template
+      }
+  shrink (Template actual cache) =
+    let Just tpl = cache ^. at actual
+    in do
+      cache' <- shrink cache
+      tpl' <- shrink tpl
+      actual' <- shrink actual
+      pure $ Template
+        { templateActual = actual'
+        , templateCache = cache' & at actual' ?~ tpl'
+        }
+
+instance CoArbitrary Template where
+  coarbitrary = coarbitrary . ppTemplate
+
+instance Function Template where
+  function = functionMap ppTemplate parseTemplatePartial
+    where
+      parseTemplatePartial txt
+        = compileMustacheText "template" txt ^?! _Right
+
+instance Arbitrary a => Arbitrary (NonEmpty a) where
+  arbitrary = do
+    x <- arbitrary
+    xs <- arbitrary
+    pure $ x :| xs
+
+instance CoArbitrary a => CoArbitrary (NonEmpty a) where
+  coarbitrary = coarbitrary . toList
+
+instance Function a => Function (NonEmpty a) where
+  function = functionMap toList NonEmpty.fromList
+
+ppNode :: Map PName [Node] -> Node -> Text
+ppNode _ (TextBlock txt) = txt
+ppNode _ (EscapedVar k) = "{{" <> showKey k <> "}}"
+ppNode ctx (Section k body) =
+  let sk = showKey k
+  in "{{#" <> sk <> "}}" <> foldMap (ppNode ctx) body <> "{{/" <> sk <> "}}"
+ppNode _ (UnescapedVar k) = "{{{" <> showKey k <> "}}}"
+ppNode ctx (InvertedSection k body) =
+  let sk = showKey k
+  in "{{^" <> sk <> "}}" <> foldMap (ppNode ctx) body <> "{{/" <> sk <> "}}"
+ppNode _ (Partial n _) = "{{> " <> unPName n <> "}}"
+
+ppTemplate :: Template -> Text
+ppTemplate (Template actual cache) =
+  case cache ^. at actual of
+    Nothing -> error "Template not found?"
+    Just nodes -> foldMap (ppNode cache) nodes
+
+instance ToJSON Template where
+  toJSON = String . ppTemplate
+
+instance FromJSON Template where
+  parseJSON
+    = withText "Template"
+    $ either (fail . errorBundlePretty) pure
+    . compileMustacheText "template"
+
+instance CoArbitrary Text where
+  coarbitrary = coarbitrary . unpack
+
+instance Function Text where
+  function = functionMap unpack pack
+
+deriving anyclass instance NFData Node
+deriving anyclass instance NFData Template