{--
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.Class
	(
	Class_JClass,
	JClass,
	findClassByName,
	findClass,
	getClass,
	isInstanceOfClass,
	isInstanceOf,
	SubJavaClassMarker(..)
	) where
	{
	import Foreign.JavaVM.Typed.Object;
	import Foreign.JavaVM.Typed.Reference;
	import Foreign.JavaVM.VM;
	import Platform.JavaVM;
	import Data.Subtype;
	import Data.Witness;

	data Class_JClass;
	instance IsJavaClassMarker Class_JClass where
		{
		cName Type = "java/lang/Class";
		};
	type JClass = ObjectRef Class_JClass;

	findClassByName :: ClassName -> VM JClass;
	findClassByName cname = do
		{
		classRef <- vmFindClass cname;
		return (MkTLRef classRef);
		};
	
	findClass :: (IsJVMReference t) => Type t -> VM JClass;
	findClass t = findClassByName (findClassName t);
	
	getClass :: (IsJVMReference t) => t -> VM JClass;
	getClass obj = findClass (getWitness obj);
	
	isInstanceOfClass :: (IsJVMReference t) => JClass -> t -> VM Bool;
	isInstanceOfClass (MkTLRef cl) obj = do
		{
		vmObj <- tlToRef obj;
		vmIsInstanceOf vmObj cl;
		};
	
	isInstanceOf :: (IsJVMReference ct, IsJVMReference ot) => Type ct -> ot -> VM Bool;
	isInstanceOf t obj = do
		{
		cl <- findClass t;
		isInstanceOfClass cl obj;
		};

	class (IsJavaClassMarker super,IsJavaClassMarker sub) => SubJavaClassMarker super sub where
		{
		objUpcast :: ObjectRef sub -> ObjectRef super;
		objUpcast sub = castTLRef sub;

		objDowncast :: ObjectRef super -> VM (Maybe (ObjectRef sub));
		objDowncast obj = do
			{
			isObj <- objIs (Type :: Type (ObjectRef sub)) obj;
			return (if isObj then (Just (castTLRef obj)) else Nothing);
			};

		objIs :: Type (ObjectRef sub) -> ObjectRef super -> VM Bool;
		objIs = isInstanceOf;
		};

	instance
		(
		SubJavaClassMarker super sub
		) =>
	 IsA (ObjectRef super) (ObjectRef sub) where
		{
		convert	= objUpcast;
		};

	instance
		(
		SubJavaClassMarker super sub
		) =>
	 JVMIsA (ObjectRef super) (ObjectRef sub) where
		{
		jvmConvert sub	= return (upcast sub);
		};
	}