add initial version of pandoc filter

langfilter/langfilter.cabal

@@ -0,0 +1,23 @@
+cabal-version: 2.2
+name: langfilter
+version: 0.1.0
+synopsis: filter for conlang stuff
+license: AGPL-3.0-or-later
+
+author: Rhiannon Morris <rhi@rhiannon.website>
+maintainer: Rhiannon Morris <rhi@rhiannon.website>
+
+executable langfilter
+  hs-source-dirs: .
+  main-is: langfilter.hs
+  ghc-options:
+    -Wall -threaded -rtsopts -with-rtsopts=-N
+  default-language: Haskell2010
+  default-extensions:
+    BlockArguments,
+    LambdaCase,
+    PatternSynonyms,
+    ViewPatterns
+  build-depends:
+    base ^>= 4.14.0.0,
+    pandoc-types == 1.17.*

langfilter/langfilter.hs

@@ -0,0 +1,27 @@
+import Text.Pandoc.Definition
+import Text.Pandoc.JSON
+import Text.Pandoc.Builder
+
+main :: IO ()
+main = toJSONFilter \case
+  Code _ txt
+    | Just _ <- enclosed '/' '/' txt ->
+        Span (cls ["ipa", "ipa-broad"]) $ text' txt
+    | Just _ <- enclosed '[' ']' txt ->
+        Span (cls ["ipa", "ipa-narrow"]) $ text' txt
+    | Just txt' <- enclosed '{' '}' txt ->
+        Span (cls ["lang"]) $ text' txt'
+  i -> i
+
+cls :: [String] -> Attr
+cls cs = ("", cs, [])
+
+text' :: String -> [Inline]
+text' = toList . text
+
+
+enclosed :: Char -> Char -> String -> Maybe String
+enclosed o c txt
+  | length txt >= 2, head txt == o, last txt == c
+  = Just $ init $ tail txt
+enclosed _ _ _ = Nothing