cwality-maps: add mustache templating

not going to be my faviourite templating language, but it seems to work
pretty well for this.

6 files changed, 120 insertions, 62 deletions

diff --git a/cwality-maps/Main.hs b/cwality-maps/Main.hs
index 8dde445..be2b0a6 100644
--- a/cwality-maps/Main.hs
+++ b/cwality-maps/Main.hs
@@ -6,6 +6,7 @@
 {-# LANGUAGE OverloadedStrings    #-}
 {-# LANGUAGE RankNTypes           #-}
 {-# LANGUAGE ScopedTypeVariables  #-}
+{-# LANGUAGE TupleSections        #-}
 {-# LANGUAGE TypeApplications     #-}
 {-# LANGUAGE TypeFamilies         #-}
 {-# LANGUAGE TypeOperators        #-}
@@ -24,12 +25,7 @@ import qualified Data.Aeson                           as A
 import qualified Data.Map.Strict                      as M
 import qualified Data.Text                            as T
 import           Data.Text.Encoding.Base64.URL        (decodeBase64Unpadded)
-import           Data.Tiled                           (GlobalId, LocalId,
-                                                       Tiledmap)
-import           GHC.Generics                         (Generic (Rep, from, to),
-                                                       K1 (K1), M1 (M1), U1,
-                                                       type (:*:) ((:*:)),
-                                                       type (:+:) (..))
+import           Data.Tiled                           (Tiledmap)
 import           Network.Wai.Handler.Warp             (defaultSettings,
                                                        runSettings, setPort)
 import           Network.Wai.Middleware.Gzip          (def)
@@ -40,12 +36,13 @@ import           Servant                              (Application, Capture,
                                                        CaptureAll,
                                                        FromHttpApiData (parseUrlPiece),
                                                        Get, Handler, JSON, Raw,
-                                                       Server, err400,
-                                                       err404, serve,
-                                                       throwError,
+                                                       Server, err400, err404,
+                                                       serve, throwError,
                                                        type (:<|>) (..),
                                                        type (:>))
 import           Servant.Server.StaticFiles           (serveDirectoryWebApp)
+import           Substitute                           (Substitutable (substitute),
+                                                       SubstitutionError)
 
 -- | a map's filename ending in .json
 -- (a newtype to differentiate between maps and assets in a route)
@@ -88,59 +85,8 @@ type Routes =
 
 
 
-class Substitutable s where
-  substitute :: s -> Map Text Text -> s
 
-instance Substitutable Text where
-  substitute orig subst = "meow" -- TODO: write a simple lexer to replace @vars@ or sth
-
-instance {-# OVERLAPS #-} Substitutable String where
-  substitute orig substs = toString (substitute (toText orig) substs)
-
-instance {-# OVERLAPPING #-} (Functor a, Substitutable b) => Substitutable (a b) where
-  substitute orig subst = map (`substitute` subst) orig
-
-instance {-# OVERLAPS #-} Substitutable A.Value where
-  substitute = const
-
-instance Substitutable Int where
-  substitute = const
-
-instance Substitutable GlobalId where
-  substitute = const
-
-instance Substitutable LocalId where
-  substitute = const
-
-instance Substitutable Double where
-  substitute = const
-
-instance Substitutable Float where
-  substitute = const
-
-class GSubstitutable i where
-  gsubstitute :: i p -> Map Text Text -> i p
-
-instance Substitutable c => GSubstitutable (K1 i c) where
-  gsubstitute (K1 text) = K1 . substitute text
-
-instance (GSubstitutable a, GSubstitutable b) => GSubstitutable (a :*: b) where
-  gsubstitute (a :*: b) substs = gsubstitute a substs :*: gsubstitute b substs
-
-instance (GSubstitutable a, GSubstitutable b) => GSubstitutable (a :+: b) where
-  gsubstitute (L1 a) = L1 . gsubstitute a
-  gsubstitute (R1 a) = R1 . gsubstitute a
-
-instance (GSubstitutable a) => GSubstitutable (M1 x y a) where
-  gsubstitute (M1 a) = M1 . gsubstitute a
-
-instance GSubstitutable U1 where
-  gsubstitute = const
-
-instance {-# OVERLAPPABLE #-} (GSubstitutable (Rep a), Generic a) => Substitutable a where
-  substitute a substs = to (gsubstitute (from a) substs)
-
-mkMap :: Config True -> Tiledmap -> MapParams -> Tiledmap
+mkMap :: Config True -> Tiledmap -> MapParams -> ([SubstitutionError], Tiledmap)
 mkMap _config basemap params =
   substitute basemap (substs params)
 
@@ -148,7 +94,10 @@ mkMap _config basemap params =
 mapHandler :: Config True -> JsonFilename -> MapParams -> Handler Tiledmap
 mapHandler config (JsonFilename mapname) params =
   case M.lookup mapname (snd $ view template config) of
-    Just basemap -> pure $ mkMap config basemap params
+    Just basemap -> do
+      let (errors, map) = mkMap config basemap params
+      print errors
+      pure map
     Nothing      -> throwError err404
 
 -- | Complete set of routes: API + HTML sites
diff --git a/cwality-maps/Substitute.hs b/cwality-maps/Substitute.hs
new file mode 100644
index 0000000..65e8fc3
--- /dev/null
+++ b/cwality-maps/Substitute.hs
@@ -0,0 +1,95 @@
+{-# LANGUAGE FlexibleContexts     #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE OverloadedStrings    #-}
+{-# LANGUAGE RankNTypes           #-}
+{-# LANGUAGE ScopedTypeVariables  #-}
+{-# LANGUAGE TupleSections        #-}
+{-# LANGUAGE TypeFamilies         #-}
+{-# LANGUAGE TypeOperators        #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+-- | Typeclasses for (generic) substitution on all strings contained in an ADT,
+-- failsafe, but with error reporting
+module Substitute (SubstitutionError, Substitutable(..)) where
+
+import           Universum
+
+import qualified Data.Aeson           as A
+import qualified Data.Foldable        as Fold
+import           Data.Tiled           (GlobalId, LocalId)
+import           GHC.Generics         (Generic (Rep, from, to), K1 (K1),
+                                       M1 (M1), U1, type (:*:) ((:*:)),
+                                       type (:+:) (..))
+import qualified Text.Mustache        as MU
+import qualified Text.Mustache.Render as MU
+import           Text.Parsec.Error    (ParseError)
+
+-- | errors that might be encountered. SubstitutionErrors occur during substitution
+-- and a generally non-fatal (but might result e.g. in empty strings being inserted
+-- instead of variables), while CompileErrors may indicate that (invalid) template
+-- syntax got leaked into the output
+data SubstitutionError = CompileError ParseError  | Mustache MU.SubstitutionError
+  deriving Show
+
+
+class Substitutable s where
+  substitute :: s -> Map Text Text -> ([SubstitutionError], s)
+
+instance Substitutable Text where
+  substitute orig substs = case MU.compileTemplate "" orig of
+    Right template -> first (map Mustache) $ MU.checkedSubstitute template substs
+    Left err -> ([CompileError err], orig) -- just ignore syntactic errors (TODO: add a log message?)
+
+
+instance {-# OVERLAPS #-} Substitutable String where
+  substitute orig substs = second toString (substitute (toText orig) substs)
+
+instance {-# OVERLAPPING #-} (Functor a, Substitutable b, Foldable a) => Substitutable (a b) where
+  substitute orig substs = (Fold.fold $ map fst orig',) $ map snd orig'
+    where orig' = map (`substitute` substs) orig
+
+-- | helper: don't substitute anything, don't produce errors
+trivial :: t -> b -> ([a], t)
+trivial = const . ([],)
+
+instance {-# OVERLAPS #-} Substitutable A.Value where
+  substitute = trivial
+
+instance Substitutable Int where
+  substitute = trivial
+
+instance Substitutable GlobalId where
+  substitute = trivial
+
+instance Substitutable LocalId where
+  substitute = trivial
+
+instance Substitutable Double where
+  substitute = trivial
+
+instance Substitutable Float where
+  substitute = trivial
+
+class GSubstitutable i where
+  gsubstitute :: i p -> Map Text Text -> ([SubstitutionError], i p)
+
+instance Substitutable c => GSubstitutable (K1 i c) where
+  gsubstitute (K1 text) = second K1 . substitute text
+
+instance (GSubstitutable a, GSubstitutable b) => GSubstitutable (a :*: b) where
+  gsubstitute (a :*: b) substs = (e1 <> e2, a' :*: b')
+    where (e1, a') = gsubstitute a substs
+          (e2, b') = gsubstitute b substs
+
+instance (GSubstitutable a, GSubstitutable b) => GSubstitutable (a :+: b) where
+  gsubstitute (L1 a) = second L1 . gsubstitute a
+  gsubstitute (R1 a) = second R1 . gsubstitute a
+
+instance (GSubstitutable a) => GSubstitutable (M1 x y a) where
+  gsubstitute (M1 a) = second M1 . gsubstitute a
+
+instance GSubstitutable U1 where
+  gsubstitute = trivial
+
+instance {-# OVERLAPPABLE #-} (GSubstitutable (Rep a), Generic a) => Substitutable a where
+  substitute a substs = second to (gsubstitute (from a) substs)
diff --git a/package.yaml b/package.yaml
index fa34022..2277d29 100644
--- a/package.yaml
+++ b/package.yaml
@@ -79,6 +79,8 @@ executables:
       - filepath
       - containers
       - base64
+      - parsec
+      - mustache
   walint-mapserver:
     main: Main.hs
     source-dirs: 'server'
diff --git a/stack.yaml b/stack.yaml
index dacc540..4448694 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -27,6 +27,8 @@ extra-deps:
  - which-0.2@sha256:db82ca7d83d64cce8ad579756f02d27c5bd289806ee02474726f7fafb87318e8,858
  - cli-git-0.1.0.2@sha256:4e62e6b7357e4fe698df8b58ba53919f9d4a056e9617dbc00c869a365e316387,1122
  - servant-lucid-0.9.0.4@sha256:698db96903a145fdef40cc897f8790728642af917c37b941a98b2da872b65f08,1787
+   # mustache is on stackage, but in a version that doesn't yet support aeson 2.0
+ - mustache-2.4.0@sha256:bd1cfbd027c04d8329877e95413d34dc357d4bee041dd8978cd6a23b114fbda1,3180
 allow-newer: true
 
 # use aeson with a non-hash-floodable implementation
diff --git a/stack.yaml.lock b/stack.yaml.lock
index 05aa1bc..54de1dd 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -81,6 +81,13 @@ packages:
       sha256: 39e0e7b2b25980bfe4df036e89959188f9ef9e8c78c85e241fa9a682d1d78cf3
   original:
     hackage: servant-lucid-0.9.0.4@sha256:698db96903a145fdef40cc897f8790728642af917c37b941a98b2da872b65f08,1787
+- completed:
+    hackage: mustache-2.4.0@sha256:bd1cfbd027c04d8329877e95413d34dc357d4bee041dd8978cd6a23b114fbda1,3180
+    pantry-tree:
+      size: 1182
+      sha256: 44c4d43ecfe1fee11fb03ffd49b0580ed00eec5144067092801ef4256df77ef8
+  original:
+    hackage: mustache-2.4.0@sha256:bd1cfbd027c04d8329877e95413d34dc357d4bee041dd8978cd6a23b114fbda1,3180
 snapshots:
 - completed:
     size: 587393
diff --git a/walint.cabal b/walint.cabal
index 738a748..167a394 100644
--- a/walint.cabal
+++ b/walint.cabal
@@ -82,6 +82,7 @@ executable cwality-maps
   main-is: Main.hs
   other-modules:
       Config
+      Substitute
       Paths_walint
   hs-source-dirs:
       cwality-maps
@@ -98,6 +99,8 @@ executable cwality-maps
     , filepath
     , fmt
     , microlens-platform
+    , mustache
+    , parsec
     , servant
     , servant-server
     , text