[#66] Prepare command and JSON deserialization

src/Headroom/Command/Readers.hs

@@ -19,6 +19,7 @@ module Headroom.Command.Readers
   ( licenseReader
   , licenseTypeReader
   , regexReader
+  , templateRefReader
   , parseLicense
   )
 where
@@ -30,6 +31,10 @@ import           Headroom.Data.Regex                 ( Regex(..)
                                                      , compile
                                                      )
 import           Headroom.FileType.Types             ( FileType(..) )
+import           Headroom.Meta                       ( TemplateType )
+import           Headroom.Template.TemplateRef       ( TemplateRef(..)
+                                                     , mkTemplateRef
+                                                     )
 import           Options.Applicative
 import           RIO
 import qualified RIO.Text                           as T
@@ -69,6 +74,14 @@ regexReader =
   in  eitherReader parse
 
 
+-- | Reader for 'TemplateRef'.
+templateRefReader :: ReadM TemplateRef
+templateRefReader =
+  let parse input = mapLeft displayException
+                            (mkTemplateRef @TemplateType . T.pack $ input)
+  in  eitherReader parse
+
+
 -- | Parses 'LicenseType' and 'FileType' from the input string,
 -- formatted as @licenseType:fileType@.
 --

src/Headroom/Command/Run.hs

@@ -350,7 +350,9 @@ chooseAction info header = do
   justify = T.justifyLeft 30 ' '
 
 
--- | Loads templates using given template references.
+-- | Loads templates using given template references. If multiple sources define
+-- template for the same 'FileType', then the preferred one (based on ordering
+-- of 'TemplateRef' is selected).
 loadTemplateRefs :: forall a env
                   . ( Template a
                     , Has (Network (RIO env)) env

src/Headroom/Template/TemplateRef.hs

@@ -36,12 +36,16 @@ module Headroom.Template.TemplateRef
   )
 where
 
+import           Data.Aeson                          ( FromJSON(..)
+                                                     , Value(String)
+                                                     )
 import           Data.String.Interpolate             ( iii )
 import           Headroom.Data.EnumExtra             ( textToEnum )
 import           Headroom.Data.Regex                 ( match
                                                      , re
                                                      )
 import           Headroom.FileType.Types             ( FileType(..) )
+import           Headroom.Meta                       ( TemplateType )
 import           Headroom.Template                   ( Template(..) )
 import           Headroom.Types                      ( fromHeadroomError
                                                      , toHeadroomError
@@ -63,6 +67,12 @@ data TemplateRef
   deriving (Eq, Ord, Show)
 
 
+instance FromJSON TemplateRef where
+  parseJSON = \case
+    String s -> maybe (error $ T.unpack s) pure (mkTemplateRef @TemplateType s)
+    other    -> error $ "Invalid value for template reference: " <> show other
+
+
 ------------------------------  PUBLIC FUNCTIONS  ------------------------------
 
 -- | Creates a 'TemplateRef' from given text. If the raw text appears to be

test/Headroom/Template/TemplateRefSpec.hs

@@ -10,6 +10,7 @@ module Headroom.Template.TemplateRefSpec
 where
 
 
+import qualified Data.Aeson                         as Aeson
 import           Headroom.Template.Mustache          ( Mustache )
 import           Headroom.Template.TemplateRef
 import           RIO
@@ -57,6 +58,13 @@ spec = do
       renderRef sample `shouldBe` expected
 
 
+  describe "FromJSON instance for TemplateRef" $ do
+    it "deserializes TemplateRef from JSON value" $ do
+      let sample   = "\"http://foo/haskell.mustache\""
+          expected = UriTemplateRef [uri|http://foo/haskell.mustache|]
+      Aeson.decode sample `shouldBe` Just expected
+
+
   describe "Ord instance for TemplateRef" $ do
     it "should properly order records" $ do
       let sample =