{-# LANGUAGE TemplateHaskell #-}
module FFICXX.Runtime.Function.TH where

import Data.List                  ( intercalate )
import Data.Maybe                 ( fromMaybe )
import Foreign.Ptr                ( FunPtr )
import Language.Haskell.TH        ( forImpD, safe )
import Language.Haskell.TH.Syntax ( Body(NormalB), Callconv(CCall), Clause(..)
                                  , Exp(..), Dec(..), ForeignSrcLang(LangCxx)
                                  , Q, Type(..)
                                  , addForeignSource
                                  , addModFinalizer
                                  , addTopDecls
                                  , mkNameS
                                  , newName
                                  )
--
import FFICXX.Runtime.CodeGen.Cxx ( CMacro(..), CStatement(..), renderCMacro, renderCStmt )
import FFICXX.Runtime.TH          ( FunctionParamInfo(..)
                                  , con, mkInstance, mkMember, mkNew, mkTFunc
                                  )
import FFICXX.Runtime.Function.Template ( Function )


mkWrapper :: (Type,String) -> Q Dec
mkWrapper (typ,suffix)
  = do let fn = "wrap_" <> suffix
       n <- newName fn
       d <- forImpD CCall safe "wrapper" n [t| $(pure typ) -> IO (FunPtr ($(pure typ))) |]
       addTopDecls [d]
       pure $
         FunD (mkNameS "wrapFunPtr") [ Clause [] (NormalB (VarE n)) [] ]


t_newFunction :: Type -> String -> Q Exp
t_newFunction typ suffix
  = mkTFunc (typ, suffix, \ n -> "Function_new_" <> n, tyf)
  where tyf _n =
          let t = pure typ
          in [t| FunPtr $( t ) -> IO (Function $( t )) |]

t_call :: Type -> String -> Q Exp
t_call typ suffix
  = mkTFunc (typ, suffix, \ n -> "Function_call_" <> n, tyf)
  where tyf _n =
          let t = pure typ
          in [t| Function $( t ) -> $( t ) |]

t_deleteFunction :: Type -> String -> Q Exp
t_deleteFunction typ suffix
  = mkTFunc (typ, suffix, \ n -> "Function_delete_" <> n, tyf)
  where tyf _n =
          let t = pure typ
          in [t| Function $( t ) -> IO () |]


genFunctionInstanceFor :: Q Type -> FunctionParamInfo -> Q [Dec]
genFunctionInstanceFor qtyp param
  = do let suffix = fpinfoSuffix param
       typ <- qtyp
       f1 <- mkNew "newFunction" t_newFunction typ suffix
       f2 <- mkMember "call" t_call typ suffix
       f3 <- mkMember "deleteFunction" t_deleteFunction typ suffix
       wrap <- mkWrapper (typ,suffix)
       addModFinalizer
         (addForeignSource LangCxx
           ("\n#include \"functional\"\n\n\n#include \"Function.h\"\n\n"
            ++ (let headers = fpinfoCxxHeaders param
                    f x = renderCMacro (Include x)
                in concatMap f headers
               )
            ++ (let nss = fpinfoCxxNamespaces param
                    f x = renderCStmt (UsingNamespace x)
                in concatMap f nss
               )
            ++ (let retstr = fromMaybe "void" (fpinfoCxxRetType param)
                    argstr = let args = fpinfoCxxArgTypes param
                                 vs = case args of
                                        [] -> "(,)"
                                        _ -> intercalate "," $
                                               map (\(t,x) -> "(" ++ t ++ "," ++ x ++ ")") args
                             in "(" ++ vs ++ ")"
                in "Function(" ++ suffix ++ "," ++ retstr ++ "," ++ argstr ++ ")\n"
               )
           )
         )
       let lst = [f1,f2,f3]
       return [ mkInstance [] (AppT (con "IFunction") typ) lst
              , mkInstance [] (AppT (con "FunPtrWrapper") typ) [wrap]
              ]