wireform-flatbuffers-0.1.0.0: src/FlatBuffers/Registry.hs

{- | User-extensible metadata handler registration for FlatBuffers.

FlatBuffers schemas support metadata (attributes) on table fields.
This module allows users to register custom 'MetadataHandler's that
optionally transform field types and emit extra code during FlatBuffers
code generation.
-}
module FlatBuffers.Registry (
  -- * Registry
  FlatBuffersRegistry (..),
  defaultFlatBuffersRegistry,

  -- * Metadata handlers
  MetadataHandler (..),
  registerFlatBuffersMetadata,
) where

import Data.Map.Strict (Map)
import Data.Map.Strict qualified as Map
import Data.Text (Text)


{- | Handler for a FlatBuffers metadata attribute.  Can transform the
Haskell type of the field and emit extra lines of code.
-}
data MetadataHandler = MetadataHandler
  { hTransformType :: !(Text -> Text)
  , hExtraCode :: !(Text -> Maybe Text -> [Text])
  }


-- | Registry of custom FlatBuffers metadata handlers.
data FlatBuffersRegistry = FlatBuffersRegistry
  { frMetadataHandlers :: !(Map Text MetadataHandler)
  }


instance Semigroup FlatBuffersRegistry where
  a <> b =
    FlatBuffersRegistry
      { frMetadataHandlers = frMetadataHandlers a <> frMetadataHandlers b
      }


instance Monoid FlatBuffersRegistry where
  mempty = FlatBuffersRegistry Map.empty


-- | Default (empty) FlatBuffers registry.
defaultFlatBuffersRegistry :: FlatBuffersRegistry
defaultFlatBuffersRegistry = mempty


-- | Register a metadata handler.
registerFlatBuffersMetadata :: Text -> MetadataHandler -> FlatBuffersRegistry -> FlatBuffersRegistry
registerFlatBuffersMetadata name handler reg =
  reg {frMetadataHandlers = Map.insert name handler (frMetadataHandlers reg)}