/*******************************************************************************
 * Copyright (c) 2015 Jeff Martin.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser General Public
 * License v3.0 which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/lgpl.html
 * <p>
 * Contributors:
 * Jeff Martin - initial API and implementation
 ******************************************************************************/
package cuchaz.enigma.bytecode;

import cuchaz.enigma.mapping.ArgumentEntry;
import cuchaz.enigma.mapping.BehaviorEntry;
import cuchaz.enigma.mapping.EntryFactory;
import cuchaz.enigma.mapping.Translator;
import javassist.CtBehavior;
import javassist.CtClass;
import javassist.bytecode.*;


public class LocalVariableRenamer {

    private Translator m_translator;

    public LocalVariableRenamer(Translator translator) {
        m_translator = translator;
    }

    public void rename(CtClass c) {
        for (CtBehavior behavior : c.getDeclaredBehaviors()) {

            // if there's a local variable table, just rename everything to v1, v2, v3, ... for now
            CodeAttribute codeAttribute = behavior.getMethodInfo().getCodeAttribute();
            if (codeAttribute == null) {
                continue;
            }

            BehaviorEntry behaviorEntry = EntryFactory.getBehaviorEntry(behavior);
            ConstPool constants = c.getClassFile().getConstPool();

            LocalVariableAttribute table = (LocalVariableAttribute) codeAttribute.getAttribute(LocalVariableAttribute.tag);
            if (table != null) {
                renameLVT(behaviorEntry, constants, table);
            }

            LocalVariableTypeAttribute typeTable = (LocalVariableTypeAttribute) codeAttribute.getAttribute(LocalVariableAttribute.typeTag);
            if (typeTable != null) {
                renameLVTT(typeTable, table);
            }
        }
    }

    // DEBUG
    @SuppressWarnings("unused")
    private void dumpTable(LocalVariableAttribute table) {
        for (int i = 0; i < table.tableLength(); i++) {
            System.out.println(String.format("\t%d (%d): %s %s",
                    i, table.index(i), table.variableName(i), table.descriptor(i)
            ));
        }
    }

    private void renameLVT(BehaviorEntry behaviorEntry, ConstPool constants, LocalVariableAttribute table) {

        // skip empty tables
        if (table.tableLength() <= 0) {
            return;
        }

        // where do we start counting variables?
        int starti = 0;
        if (table.variableName(0).equals("this")) {
            // skip the "this" variable
            starti = 1;
        }

        // rename method arguments first
        int numArgs = 0;
        if (behaviorEntry.getSignature() != null) {
            numArgs = behaviorEntry.getSignature().getArgumentTypes().size();
            for (int i = starti; i < starti + numArgs && i < table.tableLength(); i++) {
                int argi = i - starti;
                String argName = m_translator.translate(new ArgumentEntry(behaviorEntry, argi, ""));
                if (argName == null) {
                    argName = "a" + (argi + 1);
                }
                renameVariable(table, i, constants.addUtf8Info(argName));
            }
        }

        // then rename the rest of the args, if any
        for (int i = starti + numArgs; i < table.tableLength(); i++) {
            int firstIndex = table.index(starti + numArgs);
            renameVariable(table, i, constants.addUtf8Info("v" + (table.index(i) - firstIndex + 1)));
        }
    }

    private void renameLVTT(LocalVariableTypeAttribute typeTable, LocalVariableAttribute table) {
        // rename args to the same names as in the LVT
        for (int i = 0; i < typeTable.tableLength(); i++) {
            renameVariable(typeTable, i, getNameIndex(table, typeTable.index(i)));
        }
    }

    private void renameVariable(LocalVariableAttribute table, int i, int stringId) {
        // based off of LocalVariableAttribute.nameIndex()
        ByteArray.write16bit(stringId, table.get(), i * 10 + 6);
    }

    private int getNameIndex(LocalVariableAttribute table, int index) {
        for (int i = 0; i < table.tableLength(); i++) {
            if (table.index(i) == index) {
                return table.nameIndex(i);
            }
        }
        return 0;
    }
}