package org.saev.deob.trans;

import org.saev.deob.*;
import java.util.*;
import org.apache.bcel.generic.*;
import org.apache.bcel.classfile.*;
import org.apache.bcel.util.*;

public class UnconditionalBranchFolder extends ApplicationTransformer {
    private static final boolean DEBUG = false;

    public UnconditionalBranchFolder() {
        super();
    }

    protected Method internalTransform(MethodGen mg) {
        int n = 0;
        InstructionList il = mg.getInstructionList();
        Iterator<InstructionHandle[]> it = new InstructionFinder(il).search("IfInstruction");

        while(it.hasNext()) {
            InstructionHandle ih = it.next() [0];
            InstructionHandle target = ((BranchHandle) ih).getTarget();

            if(target.getInstruction() instanceof GOTO) {
                n++;
                ((BranchHandle) ih).setTarget(((BranchHandle) target).getTarget());
            }
        }

        if(DEBUG && n > 0) {
            System.out.println("[ " + new org.saev.deob.util.MethodID(mg) +
                " ] retargeted " + n + " instructions");
        }
        it = new InstructionFinder(il).search("GOTO GOTO");

        while(it.hasNext()) {
            InstructionHandle[] match = it.next();

            try {
                il.delete(match[0]);
            } catch(TargetLostException e) {
                InstructionHandle[] targets = e.getTargets();

                for(int j = 0; j < targets.length; j++) {
                    InstructionTargeter[] targeters = targets[j].getTargeters();

                    for(int k = 0; k < targeters.length; k++) {
                        targeters[k].updateTarget(targets[j], match[1]);
                    }
                }
            }
        }

        mg.setInstructionList(il);
        return mg.getMethod();
    }

    public String getName() {
        return "ub-folder";
    }

    public String getDescription() {
        return "folds unconditional branches, ie. if instructions\n" +
            "\tthat target goto instructions are modified to target the\n" +
            "\ttarget of the goto. in some cases the goto can be removed.\n" +
            "\tyes, i realize that description sucks, but its the best i\n" +
            "\tcould come up with.";
    }

    public String getAuthor() {
        return "saevion <saevion at gmail dot com>";
    }
}