{--
JVM-Bridge -- bridge from FP languages and others to the Java VM
Copyright (C) 2001 Ashley Yakeley <ashley@semantic.org>

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
--}

module Foreign.JavaVM.Typed.Value where
{
	import Foreign.JavaVM.Typed.Returnable;
	import Foreign.JavaVM.VM;
	import Platform.JavaVM;
	import Data.Witness;
	
	class (IsJVMReturnable t) => IsJVMValue t where
	{
		getValueType				:: Type t -> ValueType;
		tlConvertVMType :: (forall vmt. (Is VMType vmt) => (vmt -> VM t,t -> VM vmt) -> r) -> r;

		tlNewArray					:: Type t -> Jint -> VM VMRef;
		tlGetArrayElement			:: VMRef -> Jint -> VM t;
		tlGetArrayRegion			:: VMRef -> Jint -> Jint -> VM [t];
		tlSetArrayElement			:: VMRef -> Jint -> t -> VM ();
		tlSetArrayRegion			:: VMRef -> Jint -> [t] -> VM ();
	};


	tlGetVMType :: (IsJVMValue t) => Type t -> (forall vmt. VMType vmt -> r) -> r;
	tlGetVMType tt foo = tlConvertVMType (\(x,_) -> foo (f tt x)) where
	{
		f :: (Is VMType vmt) => Type t -> (vmt -> VM t) -> VMType vmt;
		f _ _ = witness;
	};

	tlToVMType :: (IsJVMValue t) => t -> (forall vmt. (Is VMType vmt) => VM vmt -> r) -> r;
	tlToVMType t foo = tlConvertVMType (\(_,to) -> foo (to t));
	
	tlFromVMType :: (IsJVMValue t) => (forall vmt. (Is VMType vmt) => (vmt -> VM t) -> r) -> r;
	tlFromVMType foo = tlConvertVMType (\(from,_) -> foo from);

	tlExtractValue :: (IsJVMValue t) => Any VMType -> Maybe (VM t);	-- if the JVMValue happens to correspond to the VMType
	tlExtractValue = tlFromVMType foo where
	{
		foo :: forall vmt t. (IsJVMValue t,Is VMType vmt) => (vmt -> VM t) -> Any VMType -> Maybe (VM t);
		foo f (Any vmt) = fmap (\mp -> f (mp vmt)) (matchIs (Type :: Type (VMType ())));
	};

	tlArgumentToValue	:: (IsJVMValue t) => t -> VM (Any VMType);
	tlArgumentToValue t = tlToVMType t foo where
	{
		foo :: forall vmt. (Is VMType vmt) => VM vmt -> VM (Any VMType);
		foo mvmt = fmap Any mvmt;
	};

	tlArgumentToSingleValue	:: (IsJVMValue t) => t -> VM [Any VMType];
	tlArgumentToSingleValue t = do
	{
		arg <- tlArgumentToValue t;
		return [arg];
	};

	tlExtractSingleValue :: (IsJVMValue t) => [Any VMType] -> Maybe (VM t);
	tlExtractSingleValue [arg] = tlExtractValue arg;
	tlExtractSingleValue _ = Nothing;
}