{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE UndecidableInstances #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Data.Typeable.Internal
-- Copyright   :  (c) The University of Glasgow, CWI 2001--2011
-- License     :  BSD-style (see the file libraries/base/LICENSE)
--
-- The representations of the types TyCon and TypeRep, and the
-- function mkTyCon which is used by derived instances of Typeable to
-- construct a TyCon.
--
-----------------------------------------------------------------------------

module Data.Typeable.Internal (
    Proxy (..),
    TypeRep(..),
    KindRep,
    Fingerprint(..),
    typeOf, typeOf1, typeOf2, typeOf3, typeOf4, typeOf5, typeOf6, typeOf7,
    Typeable1, Typeable2, Typeable3, Typeable4, Typeable5, Typeable6, Typeable7,
    TyCon(..),
    typeRep,
    mkTyCon,
    mkTyCon3,
    mkTyConApp,
    mkPolyTyConApp,
    mkAppTy,
    typeRepTyCon,
    Typeable(..),
    mkFunTy,
    splitTyConApp,
    splitPolyTyConApp,
    funResultTy,
    typeRepArgs,
    typeRepFingerprint,
    rnfTypeRep,
    showsTypeRep,
    tyConString,
    rnfTyCon,
    listTc, funTc,
    typeRepKinds,
    typeLitTypeRep
  ) where

import GHC.Base
import GHC.Word
import GHC.Show
import Data.Proxy
import GHC.IntWord64 (wordToWord64#)

import GHC.Fingerprint.Type
import {-# SOURCE #-} GHC.Fingerprint
   -- loop: GHC.Fingerprint -> Foreign.Ptr -> Data.Typeable
   -- Better to break the loop here, because we want non-SOURCE imports
   -- of Data.Typeable as much as possible so we can optimise the derived
   -- instances.

-- | A concrete representation of a (monomorphic) type.  'TypeRep'
-- supports reasonably efficient equality.
data TypeRep = TypeRep {-# UNPACK #-} !Fingerprint TyCon [KindRep] [TypeRep]

type KindRep = TypeRep

-- Compare keys for equality
instance Eq TypeRep where
  TypeRep x _ _ _ == TypeRep y _ _ _ = x == y

instance Ord TypeRep where
  TypeRep x _ _ _ <= TypeRep y _ _ _ = x <= y


-- | An abstract representation of a type constructor.  'TyCon' objects can
-- be built using 'mkTyCon'.
data TyCon = TyCon {
   tyConFingerprint :: {-# UNPACK #-} !Fingerprint, -- ^ @since 4.8.0.0
   tyConPackage :: String, -- ^ @since 4.5.0.0
   tyConModule  :: String, -- ^ @since 4.5.0.0
   tyConName    :: String  -- ^ @since 4.5.0.0
 }

instance Eq TyCon where
  (TyCon t1 _ _ _) == (TyCon t2 _ _ _) = t1 == t2

instance Ord TyCon where
  (TyCon k1 _ _ _) <= (TyCon k2 _ _ _) = k1 <= k2

----------------- Construction --------------------

#include "MachDeps.h"

-- mkTyCon is an internal function to make it easier for GHC to
-- generate derived instances.  GHC precomputes the MD5 hash for the
-- TyCon and passes it as two separate 64-bit values to mkTyCon.  The
-- TyCon for a derived Typeable instance will end up being statically
-- allocated.

-- Horrid hack to work around GHC giving us a Word# disguised as a Word64#
w64 :: Word64# -> Word64#
w64 x = wordToWord64# (unsafeCoerce# x)

#if WORD_SIZE_IN_BITS < 64
mkTyCon :: Word64# -> Word64# -> String -> String -> String -> TyCon
#else
mkTyCon :: Word#   -> Word#   -> String -> String -> String -> TyCon
#endif
mkTyCon high# low# pkg modl name
  = TyCon (Fingerprint (W64# (w64 high#)) (W64# (w64 low#))) pkg modl name

-- | Applies a polymorhic type constructor to a sequence of kinds and types
mkPolyTyConApp :: TyCon -> [KindRep] -> [TypeRep] -> TypeRep
mkPolyTyConApp tc@(TyCon tc_k _ _ _) [] [] = TypeRep tc_k tc [] []
mkPolyTyConApp tc@(TyCon tc_k _ _ _) kinds types =
  TypeRep (fingerprintFingerprints (tc_k : arg_ks)) tc kinds types
  where
  arg_ks = [ k | TypeRep k _ _ _ <- kinds ++ types ]

-- | Applies a monomorphic type constructor to a sequence of types
mkTyConApp  :: TyCon -> [TypeRep] -> TypeRep
mkTyConApp tc = mkPolyTyConApp tc []

-- | A special case of 'mkTyConApp', which applies the function
-- type constructor to a pair of types.
mkFunTy  :: TypeRep -> TypeRep -> TypeRep
mkFunTy f a = mkTyConApp funTc [f,a]

-- | Splits a type constructor application.
-- Note that if the type construcotr is polymorphic, this will
-- not return the kinds that were used.
-- See 'splitPolyTyConApp' if you need all parts.
splitTyConApp :: TypeRep -> (TyCon,[TypeRep])
splitTyConApp (TypeRep _ tc _ trs) = (tc,trs)

-- | Split a type constructor application
splitPolyTyConApp :: TypeRep -> (TyCon,[KindRep],[TypeRep])
splitPolyTyConApp (TypeRep _ tc ks trs) = (tc,ks,trs)

-- | Applies a type to a function type.  Returns: @'Just' u@ if the
-- first argument represents a function of type @t -> u@ and the
-- second argument represents a function of type @t@.  Otherwise,
-- returns 'Nothing'.
funResultTy :: TypeRep -> TypeRep -> Maybe TypeRep
funResultTy trFun trArg
  = case splitTyConApp trFun of
      (tc, [t1,t2]) | tc == funTc && t1 == trArg -> Just t2
      _ -> Nothing

-- | Adds a TypeRep argument to a TypeRep.
mkAppTy :: TypeRep -> TypeRep -> TypeRep
mkAppTy (TypeRep _ tc ks trs) arg_tr = mkPolyTyConApp tc ks (trs ++ [arg_tr])
   -- Notice that we call mkTyConApp to construct the fingerprint from tc and
   -- the arg fingerprints.  Simply combining the current fingerprint with
   -- the new one won't give the same answer, but of course we want to
   -- ensure that a TypeRep of the same shape has the same fingerprint!
   -- See Trac #5962

-- | Builds a 'TyCon' object representing a type constructor.  An
-- implementation of "Data.Typeable" should ensure that the following holds:
--
-- >  A==A' ^ B==B' ^ C==C' ==> mkTyCon A B C == mkTyCon A' B' C'
--

--
mkTyCon3 :: String       -- ^ package name
         -> String       -- ^ module name
         -> String       -- ^ the name of the type constructor
         -> TyCon        -- ^ A unique 'TyCon' object
mkTyCon3 pkg modl name =
  TyCon (fingerprintString (pkg ++ (' ':modl) ++ (' ':name))) pkg modl name

----------------- Observation ---------------------

-- | Observe the type constructor of a type representation
typeRepTyCon :: TypeRep -> TyCon
typeRepTyCon (TypeRep _ tc _ _) = tc

-- | Observe the argument types of a type representation
typeRepArgs :: TypeRep -> [TypeRep]
typeRepArgs (TypeRep _ _ _ tys) = tys

-- | Observe the argument kinds of a type representation
typeRepKinds :: TypeRep -> [KindRep]
typeRepKinds (TypeRep _ _ ks _) = ks

-- | Observe string encoding of a type representation
{-# DEPRECATED tyConString "renamed to 'tyConName'; 'tyConModule' and 'tyConPackage' are also available." #-} -- deprecated in 7.4
tyConString :: TyCon   -> String
tyConString = tyConName

-- | Observe the 'Fingerprint' of a type representation
--
-- @since 4.8.0.0
typeRepFingerprint :: TypeRep -> Fingerprint
typeRepFingerprint (TypeRep fpr _ _ _) = fpr

-------------------------------------------------------------
--
--      The Typeable class and friends
--
-------------------------------------------------------------

-- | The class 'Typeable' allows a concrete representation of a type to
-- be calculated.
class Typeable a where
  typeRep# :: Proxy# a -> TypeRep

-- | Takes a value of type @a@ and returns a concrete representation
-- of that type.
--
-- @since 4.7.0.0
typeRep :: forall proxy a. Typeable a => proxy a -> TypeRep
typeRep _ = typeRep# (proxy# :: Proxy# a)
{-# INLINE typeRep #-}

-- Keeping backwards-compatibility
typeOf :: forall a. Typeable a => a -> TypeRep
typeOf _ = typeRep (Proxy :: Proxy a)

typeOf1 :: forall t (a :: *). Typeable t => t a -> TypeRep
typeOf1 _ = typeRep (Proxy :: Proxy t)

typeOf2 :: forall t (a :: *) (b :: *). Typeable t => t a b -> TypeRep
typeOf2 _ = typeRep (Proxy :: Proxy t)

typeOf3 :: forall t (a :: *) (b :: *) (c :: *). Typeable t
        => t a b c -> TypeRep
typeOf3 _ = typeRep (Proxy :: Proxy t)

typeOf4 :: forall t (a :: *) (b :: *) (c :: *) (d :: *). Typeable t
        => t a b c d -> TypeRep
typeOf4 _ = typeRep (Proxy :: Proxy t)

typeOf5 :: forall t (a :: *) (b :: *) (c :: *) (d :: *) (e :: *). Typeable t
        => t a b c d e -> TypeRep
typeOf5 _ = typeRep (Proxy :: Proxy t)

typeOf6 :: forall t (a :: *) (b :: *) (c :: *) (d :: *) (e :: *) (f :: *).
                Typeable t => t a b c d e f -> TypeRep
typeOf6 _ = typeRep (Proxy :: Proxy t)

typeOf7 :: forall t (a :: *) (b :: *) (c :: *) (d :: *) (e :: *) (f :: *)
                (g :: *). Typeable t => t a b c d e f g -> TypeRep
typeOf7 _ = typeRep (Proxy :: Proxy t)

type Typeable1 (a :: * -> *)                               = Typeable a
type Typeable2 (a :: * -> * -> *)                          = Typeable a
type Typeable3 (a :: * -> * -> * -> *)                     = Typeable a
type Typeable4 (a :: * -> * -> * -> * -> *)                = Typeable a
type Typeable5 (a :: * -> * -> * -> * -> * -> *)           = Typeable a
type Typeable6 (a :: * -> * -> * -> * -> * -> * -> *)      = Typeable a
type Typeable7 (a :: * -> * -> * -> * -> * -> * -> * -> *) = Typeable a

{-# DEPRECATED Typeable1 "renamed to 'Typeable'" #-} -- deprecated in 7.8
{-# DEPRECATED Typeable2 "renamed to 'Typeable'" #-} -- deprecated in 7.8
{-# DEPRECATED Typeable3 "renamed to 'Typeable'" #-} -- deprecated in 7.8
{-# DEPRECATED Typeable4 "renamed to 'Typeable'" #-} -- deprecated in 7.8
{-# DEPRECATED Typeable5 "renamed to 'Typeable'" #-} -- deprecated in 7.8
{-# DEPRECATED Typeable6 "renamed to 'Typeable'" #-} -- deprecated in 7.8
{-# DEPRECATED Typeable7 "renamed to 'Typeable'" #-} -- deprecated in 7.8


----------------- Showing TypeReps --------------------

instance Show TypeRep where
  showsPrec p (TypeRep _ tycon kinds tys) =
    case tys of
      [] -> showsPrec p tycon
      [x]   | tycon == listTc -> showChar '[' . shows x . showChar ']'
      [a,r] | tycon == funTc  -> showParen (p > 8) $
                                 showsPrec 9 a .
                                 showString " -> " .
                                 showsPrec 8 r
      xs | isTupleTyCon tycon -> showTuple xs
         | otherwise         ->
            showParen (p > 9) $
            showsPrec p tycon .
            showChar ' '      .
            showArgs (showChar ' ') (kinds ++ tys)

showsTypeRep :: TypeRep -> ShowS
showsTypeRep = shows

instance Show TyCon where
  showsPrec _ t = showString (tyConName t)

isTupleTyCon :: TyCon -> Bool
isTupleTyCon (TyCon _ _ _ ('(':',':_)) = True
isTupleTyCon _                         = False

-- | Helper to fully evaluate 'TypeRep' for use as @NFData(rnf)@ implementation
--
-- @since 4.8.0.0
rnfTypeRep :: TypeRep -> ()
rnfTypeRep (TypeRep _ tyc krs tyrs) = rnfTyCon tyc `seq` go krs `seq` go tyrs
  where
    go [] = ()
    go (x:xs) = rnfTypeRep x `seq` go xs

-- | Helper to fully evaluate 'TyCon' for use as @NFData(rnf)@ implementation
--
-- @since 4.8.0.0
rnfTyCon :: TyCon -> ()
rnfTyCon (TyCon _ tcp tcm tcn) = go tcp `seq` go tcm `seq` go tcn
  where
    go [] = ()
    go (x:xs) = x `seq` go xs

-- Some (Show.TypeRep) helpers:

showArgs :: Show a => ShowS -> [a] -> ShowS
showArgs _   []     = id
showArgs _   [a]    = showsPrec 10 a
showArgs sep (a:as) = showsPrec 10 a . sep . showArgs sep as

showTuple :: [TypeRep] -> ShowS
showTuple args = showChar '('
               . showArgs (showChar ',') args
               . showChar ')'

listTc :: TyCon
listTc = typeRepTyCon (typeOf [()])

funTc :: TyCon
funTc = typeRepTyCon (typeRep (Proxy :: Proxy (->)))



-- | An internal function, to make representations for type literals.
typeLitTypeRep :: String -> TypeRep
typeLitTypeRep nm = rep
    where
    rep = mkTyConApp tc []
    tc = TyCon
           { tyConFingerprint = fingerprintString (mk pack modu nm)
           , tyConPackage  = pack
           , tyConModule   = modu
           , tyConName     = nm
           }
    pack = "base"
    modu = "GHC.TypeLits"
    mk a b c = a ++ " " ++ b ++ " " ++ c


