module HsDev.Tools.GhcMod.InferType (
	untyped, inferType, inferTypes
	) where

import Control.Monad.Error
import Data.Traversable (traverse)

import HsDev.Cabal
import HsDev.Project
import HsDev.Symbols
import HsDev.Tools.GhcMod

-- | Is declaration untyped
untyped :: DeclarationInfo -> Bool
untyped (Function Nothing _) = True
untyped _ = False

-- | Infer type of declaration
inferType :: [String] -> Cabal -> FilePath -> Maybe Project -> String -> Declaration -> ErrorT String IO Declaration
inferType opts cabal src mproj mname decl
	| untyped (declaration decl) = infer
	| otherwise = return decl
	where
		infer = do
			inferred <- liftM declaration $ info opts cabal src mproj mname (declarationName decl)
			return decl {
				declaration = setType (declaration decl) (getType inferred) }

		setType :: DeclarationInfo -> Maybe String -> DeclarationInfo
		setType (Function _ ds) newType = Function newType ds
		setType info _ = info

		getType :: DeclarationInfo -> Maybe String
		getType (Function fType _) = fType
		getType _ = Nothing

-- | Infer types for module
inferTypes :: [String] -> Cabal -> Module -> ErrorT String IO Module
inferTypes opts cabal m = case moduleLocation m of
	FileModule src p -> do
		inferredDecls <- traverse (inferType opts cabal src p (moduleName m)) $ moduleDeclarations m
		return m { moduleDeclarations = inferredDecls }
	_ -> throwError "Type infer works only for source files"