{-# LANGUAGE TemplateHaskell #-}

module Ribosome.Nvim.Api.Generate where

import Control.Monad (join)
import Data.Bifunctor (first)
import Data.Char (toUpper)
import Data.Int (Int64)
import Data.Map (Map)
import qualified Data.Map as Map (fromList, lookup)
import Data.Maybe (fromMaybe)
import Data.MessagePack (Object)
import Language.Haskell.TH
import Neovim.API.Parser (
  NeovimAPI(functions),
  NeovimFunction(NeovimFunction),
  NeovimType(NestedType, SimpleType, Void),
  customTypes,
  parseAPI,
  )

camelcase :: String -> String
camelcase =
  snd . foldr folder (False, "")
  where
    folder '_' (_, z) = (True, z)
    folder a (True, h : t) = (False, a : toUpper h : t)
    folder a (True, []) = (False, [a])
    folder a (False, z) = (False, a : z)

haskellTypes :: Map String TypeQ
haskellTypes =
  Map.fromList [
    ("Boolean", [t|Bool|]),
    ("Integer", [t|Int|]),
    ("Float", [t|Double|]),
    ("String", [t|Text|]),
    ("Array", [t|[Object]|]),
    ("Dictionary", [t|Map Text Object|]),
    ("void", [t|()|])
    ]

haskellType :: NeovimType -> Q Type
haskellType at =
  case at of
    Void -> [t|()|]
    NestedType t Nothing ->
      appT listT $ haskellType t
    NestedType t (Just n) ->
      foldl appT (tupleT n) . replicate n $ haskellType t
    SimpleType t ->
      fromMaybe (conT . mkName $ t) $ Map.lookup t haskellTypes

data FunctionData =
  FunctionData {
    apiName :: String,
    ccName :: Name,
    async :: Bool,
    names :: [Name],
    types :: [Type],
    returnType :: NeovimType
    }
  deriving (Eq, Show)

functionData :: NeovimFunction -> Q FunctionData
functionData (NeovimFunction name parameters _ async returnType) = do
  names <- traverse newName prefixedNames
  types <- traverse haskellType (fst <$> parameters)
  return (FunctionData name (mkName . camelcase $ name) async names types returnType)
  where
    prefix i n = "arg" <> show i <> "_" <> n
    prefixedNames = zipWith prefix [0 :: Int ..] (snd <$> parameters)

generateFromApi :: (FunctionData -> Q [Dec]) -> (Name -> Int64 -> DecsQ) -> Q [Dec]
generateFromApi handleFunction handleExtType = do
  api <- either (fail . show) return =<< runIO parseAPI
  funcs <- traverse functionData (functions api)
  funcDecs <- traverse handleFunction funcs
  tpeDecs <- traverse (uncurry handleExtType) $ first mkName <$> customTypes api
  return $ join (funcDecs <> tpeDecs)