Start extracting titles from recipes

byg/src/Functions/Pandoc.hs

@@ -1,6 +1,7 @@
 module Functions.Pandoc
   ( readMarkdown
   , writeHtml
+  , extractTitle
   ) where
 
 import Types (IsFunction(..), Token)
@@ -8,6 +9,8 @@ import DependencyGenerator (DepGenM, TokenableTo(..), runFunction)
 
 import Data.Text (Text)
 import Text.Pandoc.Definition (Pandoc)
+import qualified Text.Pandoc.Definition as PD
+import qualified Text.Pandoc.Shared as PS
 import qualified Text.Pandoc as P
 
 runPandoc :: P.PandocPure a -> a
@@ -33,3 +36,13 @@ instance IsFunction WriteHtml Pandoc Text where
 
 writeHtml :: TokenableTo Pandoc a => a -> DepGenM (Token Text)
 writeHtml a = runFunction WriteHtml =<< toToken a
+
+
+data ExtractTitle = ExtractTitle deriving Show
+instance IsFunction ExtractTitle Pandoc Text where
+  evalFunction ExtractTitle (PD.Pandoc _ blocks) = case blocks of
+    (PD.Header 1 _ inlines : _) -> PS.stringify inlines
+    _ -> error "unexpected"
+
+extractTitle :: TokenableTo Pandoc a => a -> DepGenM (Token Text)
+extractTitle a = runFunction ExtractTitle =<< toToken a