/*
 * Copyright 2008 Wishnu Prasetya.
 *
 * This file is part of T2.
 * T2 is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License (GPL) as published by the
 * Free Software Foundation; either version 3 of the License, or any
 * later version.
 * 
 * T2 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 General Public License
 * for more details.
 *
 * A copy of the GNU General Public License can be found in T2 distribution.
 * If it is missing, see http://www.gnu.org/licenses.
 */

package t2ext.bcel.utils;

import com.sun.org.apache.bcel.internal.Constants;
import com.sun.org.apache.bcel.internal.generic.ClassGen;
import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.InstructionFactory;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.bcel.internal.generic.MethodGen;
import com.sun.org.apache.bcel.internal.generic.Type;

/**
 * @author Maaike Gerritsen
 */
public class MethodCallInsertion {
	private ClassGen _classGen;
	
	public MethodCallInsertion(ClassGen cGen){
		_classGen = cGen;
	}
	
	public MethodGen addCode(String methodName) {
		InstructionList il = new InstructionList();
		String random = methodName + getRandomNr();
		ConstantPoolGen pgen = _classGen.getConstantPool();
		MethodGen methodGen = new MethodGen(com.sun.org.apache.bcel.internal.Constants.ACC_PUBLIC, Type.VOID,
				Type.NO_ARGS, new String[] {}, random, _classGen.getClassName(),
				il, pgen);
//		InstructionFactory fact = new InstructionFactory(_classGen);
//		il.append(fact.createPrintln(random));
		il.append(InstructionFactory.createReturn(Type.VOID));
		methodGen.setInstructionList(il);
		methodGen.stripAttributes(true);
		methodGen.setMaxStack();
		methodGen.setMaxLocals();
		_classGen.addMethod(methodGen.getMethod());
		return methodGen;
	}
	
	public InstructionList callMethod(String methodName) {
		InstructionFactory ifact = new InstructionFactory(_classGen);
		InstructionList ilist = new InstructionList();
		MethodGen methgen = addCode(methodName);
		Type result = methgen.getReturnType();

		// compute the size of the calling parameters
		Type[] types = methgen.getArgumentTypes();
		int slot = methgen.isStatic() ? 0 : 1;
		for (int i = 0; i < types.length; i++) {
			slot += types[i].getSize();
		}

		// call the wrapped method
		int offset = 0;
		short invoke = Constants.INVOKESTATIC;
		if (!methgen.isStatic()) {
			ilist.append(InstructionFactory.createLoad(Type.OBJECT, 0));
			offset = 1;
			invoke = Constants.INVOKEVIRTUAL;
		}
		for (int i = 0; i < types.length; i++) {
			Type type = types[i];
			ilist.append(InstructionFactory.createLoad(type, offset));
			offset += type.getSize();
		}
		ilist.append(ifact.createInvoke(_classGen.getClassName(), methgen
				.getMethod().getName(), result, types, invoke));

		// store result for return later
		if (result != Type.VOID) {
			ilist.append(InstructionFactory.createStore(result, slot + 2));
		}
		return ilist;
	}

	protected String getRandomNr() {
		Double nr = Math.random();
		String nrS = nr.toString();
		nrS = nrS.replace(".", ":");
		String[] array = nrS.split(":");
		nrS = array[1];
		nrS = nrS.substring(0, 5);
		return nrS;
	}

}