{-# LANGUAGE CPP #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RoleAnnotations #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE ViewPatterns #-}

#if __GLASGOW_HASKELL__ >= 800
{-# OPTIONS_GHC -fno-warn-redundant-constraints #-}
#endif

module Foreign.JNI.Types
  ( JType(..)
  , IsPrimitiveType
  , IsReferenceType
  , Sing(..)
  , type (<>)
    -- * JNI types
  , J(..)
  , jnull
  , upcast
  , unsafeCast
  , generic
  , unsafeUngeneric
  , jtypeOf
  , referenceTypeName
  , signature
  , methodSignature
  , JVM(..)
  , JNIEnv(..)
  , JMethodID(..)
  , JFieldID(..)
  , JValue(..)
    -- * JNI defined object types
  , JObject
  , JClass
  , JString
  , JArray
  , JObjectArray
  , JBooleanArray
  , JByteArray
  , JCharArray
  , JShortArray
  , JIntArray
  , JLongArray
  , JFloatArray
  , JDoubleArray
  , JThrowable
  -- * inline-c contexts
  , jniCtx
  ) where

import qualified Data.ByteString.Lazy as BSL
import qualified Data.ByteString.Builder as Builder
import qualified Data.ByteString.Builder.Prim as Prim
import Data.ByteString.Builder (Builder)
import Data.Char (chr, ord)
import Data.Int
import Data.Map (fromList)
import Data.Monoid ((<>))
import Data.Singletons
  ( Sing
  , SingI(..)
  , SomeSing(..)
#if !MIN_VERSION_singletons(2,2,0)
  , KProxy(..)
#endif
  )
import Data.Singletons.TypeLits (KnownSymbol, symbolVal)
import Data.String (fromString)
import Data.Word
import Foreign.C (CChar)
import Foreign.JNI.NativeMethod
import qualified Foreign.JNI.String as JNI
import Foreign.Ptr
import Foreign.Storable (Storable(..))
import GHC.TypeLits (Symbol)
import Language.C.Types (TypeSpecifier(TypeName))
import Language.C.Inline.Context (Context(..))

-- | A JVM instance.
newtype JVM = JVM_ (Ptr JVM)
  deriving (Eq, Show, Storable)

-- | The thread-local JNI context. Do not share this object between threads.
newtype JNIEnv = JNIEnv_ (Ptr JNIEnv)
  deriving (Eq, Show, Storable)

-- | A thread-local reference to a field of an object.
newtype JFieldID = JFieldID_ (Ptr JFieldID)
  deriving (Eq, Show, Storable)

-- | A thread-local reference to a method of an object.
newtype JMethodID = JMethodID_ (Ptr JMethodID)
  deriving (Eq, Show, Storable)

-- | Not part of the JNI. The kind of 'J' type indices. Useful to reflect the
-- object's class at the type-level.
data JType
  = Class Symbol                               -- ^ Class name
  | Iface Symbol                               -- ^ Interface name
  | Prim Symbol                                -- ^ Primitive type
  | Array JType                                -- ^ Array type
  | Generic JType [JType]                      -- ^ Parameterized (generic) type
  | Void                                       -- ^ Void special type

-- | The class of Java types that are "unboxed".
class IsPrimitiveType (ty :: JType)
instance IsPrimitiveType ('Prim sym)

class IsReferenceType (ty :: JType)
instance IsReferenceType ('Class sym)
instance IsReferenceType ('Iface sym)
instance IsReferenceType ('Array ty)
instance IsReferenceType ty => IsReferenceType ('Generic ty tys)

data instance Sing (a :: JType) where
  SClass :: JNI.String -> Sing ('Class sym)
  SIface :: JNI.String -> Sing ('Iface sym)
  SPrim :: JNI.String -> Sing ('Prim sym)
  SArray :: Sing ty -> Sing ('Array ty)
  SGeneric :: Sing ty -> Sing tys -> Sing ('Generic ty tys)
  SVoid :: Sing 'Void

-- XXX SingI constraint temporary hack because GHC 7.10 has trouble inferring
-- this constraint in 'signature'.
instance (KnownSymbol sym, SingI sym) => SingI ('Class (sym :: Symbol)) where
  sing = SClass $ fromString $ symbolVal (undefined :: proxy sym)
instance (KnownSymbol sym, SingI sym) => SingI ('Iface (sym :: Symbol)) where
  sing = SIface $ fromString $ symbolVal (undefined :: proxy sym)
instance (KnownSymbol sym, SingI sym) => SingI ('Prim (sym :: Symbol)) where
  sing = SPrim $ fromString $ symbolVal (undefined :: proxy sym)
instance SingI ty => SingI ('Array ty) where
  sing = SArray sing
instance (SingI ty, SingI tys) => SingI ('Generic ty tys) where
  sing = SGeneric sing sing
instance SingI 'Void where
  sing = SVoid

-- | Shorthand for parametized Java types.
type a <> g = 'Generic a g

-- | Type indexed Java Objects.
newtype J (a :: JType) = J (Ptr (J a))
  deriving (Eq, Show, Storable)

type role J representational

-- | The null reference.
jnull :: J a
jnull = J nullPtr

-- | Any object can be cast to @Object@.
upcast :: J a -> JObject
upcast = unsafeCast

-- | Unsafe type cast. Should only be used to downcast.
unsafeCast :: J a -> J b
unsafeCast (J x) = J (castPtr x)

-- | Parameterize the type of an object, making its type a /generic type/.
generic :: J a -> J (a <> g)
generic = unsafeCast

-- | Get the base type of a generic type.
unsafeUngeneric :: J (a <> g) -> J a
unsafeUngeneric = unsafeCast

-- | A union type for uniformly passing arguments to methods.
data JValue
  = JBoolean Word8
  | JByte CChar
  | JChar Word16
  | JShort Int16
  | JInt Int32
  | JLong Int64
  | JFloat Float
  | JDouble Double
  | forall a. SingI a => JObject {-# UNPACK #-} !(J a)

instance Show JValue where
  show (JBoolean x) = "JBoolean " ++ show x
  show (JByte x) = "JByte " ++ show x
  show (JChar x) = "JChar " ++ show x
  show (JShort x) = "JShort " ++ show x
  show (JInt x) = "JInt " ++ show x
  show (JLong x) = "JLong " ++ show x
  show (JFloat x) = "JFloat " ++ show x
  show (JDouble x) = "JDouble " ++ show x
  show (JObject x) = "JObject " ++ show x

instance Eq JValue where
  (JBoolean x) == (JBoolean y) = x == y
  (JByte x) == (JByte y) = x == y
  (JChar x) == (JChar y) = x == y
  (JShort x) == (JShort y) = x == y
  (JInt x) == (JInt y) = x == y
  (JLong x) == (JLong y) = x == y
  (JFloat x) == (JFloat y) = x == y
  (JDouble x) == (JDouble y) = x == y
  (JObject (J x)) == (JObject (J y)) = castPtr x == castPtr y
  _ == _ = False

instance Storable JValue where
  sizeOf _ = 8
  alignment _ = 8

  poke p (JBoolean x) = poke (castPtr p) x
  poke p (JByte x) = poke (castPtr p) x
  poke p (JChar x) = poke (castPtr p) x
  poke p (JShort x) = poke (castPtr p) x
  poke p (JInt x) = poke (castPtr p) x
  poke p (JLong x) = poke (castPtr p) x
  poke p (JFloat x) = poke (castPtr p) x
  poke p (JDouble x) = poke (castPtr p) x
  poke p (JObject x) = poke (castPtr p :: Ptr (J a)) x

  peek _ = error "Storable JValue: undefined peek"

-- | Get the Java type of a value.
#if MIN_VERSION_singletons(2,2,0)
jtypeOf :: JValue -> SomeSing JType
#else
jtypeOf :: JValue -> SomeSing ('KProxy :: KProxy JType)
#endif
jtypeOf (JBoolean _) = SomeSing (sing :: Sing ('Prim "boolean"))
jtypeOf (JByte _) = SomeSing (sing :: Sing ('Prim "byte"))
jtypeOf (JChar _) = SomeSing (sing :: Sing ('Prim "char"))
jtypeOf (JShort _) = SomeSing (sing :: Sing ('Prim "short"))
jtypeOf (JInt _) = SomeSing (sing :: Sing ('Prim "int"))
jtypeOf (JLong _) = SomeSing (sing :: Sing ('Prim "long"))
jtypeOf (JFloat _) = SomeSing (sing :: Sing ('Prim "float"))
jtypeOf (JDouble _) = SomeSing (sing :: Sing ('Prim "double"))
jtypeOf (JObject (_ :: J ty)) = SomeSing (sing :: Sing ty)

-- | Create a null-terminated string.
build :: Builder -> JNI.String
build =
  JNI.unsafeFromByteString .
  BSL.toStrict .
  Builder.toLazyByteString .
  (<> Builder.char7 '\NUL')

-- | The name of a type, suitable for passing to 'Foreign.JNI.findClass'.
referenceTypeName :: IsReferenceType ty => Sing (ty :: JType) -> JNI.String
referenceTypeName (SClass sym) = build $ classSymbolBuilder sym
referenceTypeName (SIface sym) = build $ classSymbolBuilder sym
referenceTypeName ty@(SArray _) = build $ signatureBuilder ty
referenceTypeName (SGeneric ty@(SClass _) _) = referenceTypeName ty
referenceTypeName (SGeneric ty@(SIface _) _) = referenceTypeName ty
referenceTypeName _ = error "referenceTypeName: Impossible."

classSymbolBuilder :: JNI.String -> Builder
classSymbolBuilder sym =
    Prim.primMapByteStringFixed (subst Prim.>$< Prim.word8) (JNI.toByteString sym)
  where
    subst (chr . fromIntegral -> '.') = fromIntegral (ord '/')
    subst x = x

signatureBuilder :: Sing (ty :: JType) -> Builder
signatureBuilder (SClass sym) = Builder.char7 'L' <> classSymbolBuilder sym <> Builder.char7 ';'
signatureBuilder (SIface sym) = Builder.char7 'L' <> classSymbolBuilder sym <> Builder.char7 ';'
signatureBuilder (SPrim "boolean") = Builder.char7 'Z'
signatureBuilder (SPrim "byte") = Builder.char7 'B'
signatureBuilder (SPrim "char") = Builder.char7 'C'
signatureBuilder (SPrim "short") = Builder.char7 'S'
signatureBuilder (SPrim "int") = Builder.char7 'I'
signatureBuilder (SPrim "long") = Builder.char7 'J'
signatureBuilder (SPrim "float") = Builder.char7 'F'
signatureBuilder (SPrim "double") = Builder.char7 'D'
signatureBuilder (SPrim sym) = error $ "Unknown primitive: " ++ show sym
signatureBuilder (SArray ty) = Builder.char7 '[' <> signatureBuilder ty
signatureBuilder (SGeneric ty _) = signatureBuilder ty
signatureBuilder SVoid = Builder.char7 'V'

-- | Construct a JNI type signature from a Java type.
signature :: Sing (ty :: JType) -> JNI.String
signature = build . signatureBuilder

-- | Construct a method's JNI type signature, given the type of the arguments
-- and the return type.
methodSignature
#if MIN_VERSION_singletons(2,2,0)
  :: [SomeSing JType]
#else
  :: [SomeSing ('KProxy :: KProxy JType)]
#endif
  -> Sing (ty :: JType)
  -> JNI.String
methodSignature args ret =
    build $
    Builder.char7 '(' <>
    mconcat (map (\(SomeSing s) -> signatureBuilder s) args) <>
    Builder.char7 ')' <>
    signatureBuilder ret

type JObject = J ('Class "java.lang.Object")
type JClass = J ('Class "java.lang.Class")
type JString = J ('Class "java.lang.String")
type JThrowable = J ('Class "java.lang.Throwable")
type JArray a = J ('Array a)
type JObjectArray = JArray ('Class "java.lang.Object")
type JBooleanArray = JArray ('Prim "boolean")
type JByteArray = JArray ('Prim "byte")
type JCharArray = JArray ('Prim "char")
type JShortArray = JArray ('Prim "short")
type JIntArray = JArray ('Prim "int")
type JLongArray = JArray ('Prim "long")
type JFloatArray = JArray ('Prim "float")
type JDoubleArray = JArray ('Prim "double")

jniCtx :: Context
jniCtx = mempty { ctxTypesTable = fromList tytab }
  where
    tytab =
      [ -- Primitive types
        (TypeName "jboolean", [t| Word8 |])
      , (TypeName "jbyte", [t| CChar |])
      , (TypeName "jchar", [t| Word16 |])
      , (TypeName "jshort", [t| Int16 |])
      , (TypeName "jint", [t| Int32 |])
      , (TypeName "jlong", [t| Int64 |])
      , (TypeName "jfloat", [t| Float |])
      , (TypeName "jdouble", [t| Double |])
      -- Reference types
      , (TypeName "jobject", [t| JObject |])
      , (TypeName "jclass", [t| JClass |])
      , (TypeName "jstring", [t| JString |])
      , (TypeName "jarray", [t| JObject |])
      , (TypeName "jobjectArray", [t| JObjectArray |])
      , (TypeName "jbooleanArray", [t| JBooleanArray |])
      , (TypeName "jbyteArray", [t| JByteArray |])
      , (TypeName "jcharArray", [t| JCharArray |])
      , (TypeName "jshortArray", [t| JShortArray |])
      , (TypeName "jintArray", [t| JIntArray |])
      , (TypeName "jlongArray", [t| JLongArray |])
      , (TypeName "jfloatArray", [t| JFloatArray |])
      , (TypeName "jdoubleArray", [t| JDoubleArray |])
      , (TypeName "jthrowable", [t| JThrowable |])
      -- Internal types
      , (TypeName "JavaVM", [t| JVM |])
      , (TypeName "JNIEnv", [t| JNIEnv |])
      , (TypeName "JNINativeMethod", [t| JNINativeMethod |])
      , (TypeName "jfieldID", [t| JFieldID |])
      , (TypeName "jmethodID", [t| JMethodID |])
      , (TypeName "jsize", [t| Int32 |])
      , (TypeName "jvalue", [t| JValue |])
      ]