feat: add RecipeSearchEntry JSON encoding for search payload

src/Roux/RecipeIndex.hs

@@ -1,11 +1,17 @@
+{-# LANGUAGE DeriveGeneric #-}
+
 -- | Scanning and indexing of Cooklang recipe files on disk.
 module Roux.RecipeIndex (
     RecipeInfo (..),
+    RecipeSearchEntry (..),
     scanRecipes,
+    toSearchEntry,
 ) where
 
+import Data.Aeson (ToJSON (..), camelTo2, defaultOptions, fieldLabelModifier, genericToJSON)
 import Data.Text (Text)
 import qualified Data.Text as T
+import GHC.Generics (Generic)
 import System.Directory (listDirectory)
 import System.FilePath (takeBaseName, takeExtension, (</>))
 
@@ -45,9 +51,38 @@ loadRecipe dir filename = do
             , riRecipe = parsed
             }
 
-{- | Extract a display title from the recipe's metadata or fall back to the
+-- | Search payload for type-ahead / recipe search.
-filename.
+data RecipeSearchEntry = RecipeSearchEntry
+    { rseTitle :: !Text
+    , rseFilename :: !Text
+    , rseCourse :: !(Maybe Text)
+    , rseTags :: ![Text]
+    }
+    deriving stock (Generic)
+
+instance ToJSON RecipeSearchEntry where
+    toJSON = genericToJSON defaultOptions{fieldLabelModifier = camelTo2 '_' . drop 3}
+
+{- | Convert a 'RecipeInfo' into a 'RecipeSearchEntry', extracting course and
+     tags from the parsed recipe metadata when available.
 -}
+toSearchEntry :: RecipeInfo -> RecipeSearchEntry
+toSearchEntry info =
+    let (course, tags) = case riRecipe info of
+            Right r ->
+                ( metaCourse (recipeMetadata r)
+                , metaTags (recipeMetadata r)
+                )
+            Left _ -> (Nothing, [])
+     in RecipeSearchEntry
+            { rseTitle = riTitle info
+            , rseFilename = T.pack (riFilename info)
+            , rseCourse = course
+            , rseTags = tags
+            }
+
+-- | Extract a display title from the recipe's metadata or fall back to the
+-- filename.
 extractTitle :: Recipe -> FilePath -> Text
 extractTitle recipe filename =
     case metaTitle (recipeMetadata recipe) of