/**

 * Back 2 Browser Bytecode Translator

 * Copyright (C) 2012 Jaroslav Tulach <jaroslav.tulach@apidesign.org>

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, version 2 of the License.

 *

 * This program 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.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program. Look for COPYING file in the top folder.

 * If not, see http://opensource.org/licenses/GPL-2.0.

 */

package org.apidesign.vm4brwsr;

import java.io.IOException;

import org.apidesign.javap.RuntimeConstants;

import org.apidesign.javap.TypeArray;

public final class LocalsMapper {

    private final TypeArray argTypeRecords;

    private final TypeArray localTypeRecords;

    public LocalsMapper(final TypeArray stackMapArgs) {

        final TypeArray initTypeRecords = new TypeArray();

        updateRecords(initTypeRecords, stackMapArgs);

        argTypeRecords = initTypeRecords;

        localTypeRecords = new TypeArray(initTypeRecords);

    }

    public void outputArguments(final Appendable out) throws IOException {

        final int argRecordCount = argTypeRecords.getSize();

        if (argRecordCount > 0) {

            Variable variable = getVariable(argTypeRecords, 0);

            out.append(variable);

            int i = variable.isCategory2() ? 2 : 1;

            while (i < argRecordCount) {

                variable = getVariable(argTypeRecords, i);

                out.append(", ");

                out.append(variable);

                i += variable.isCategory2() ? 2 : 1;

            }

        }

    }

    public void syncWithFrameLocals(final TypeArray frameLocals) {

        updateRecords(localTypeRecords, frameLocals);

    }

    public Variable setI(final int index) {

        return setT(index, VarType.INTEGER);

    }

    public Variable setL(final int index) {

        return setT(index, VarType.LONG);

    }

    public Variable setF(final int index) {

        return setT(index, VarType.FLOAT);

    }

    public Variable setD(final int index) {

        return setT(index, VarType.DOUBLE);

    }

    public Variable setA(final int index) {

        return setT(index, VarType.REFERENCE);

    }

    public Variable setT(final int index, final int type) {

        updateRecord(localTypeRecords, index, type);

        return Variable.getLocalVariable(type, index);

    }

    public Variable getI(final int index) {

        return getT(index, VarType.INTEGER);

    }

    public Variable getL(final int index) {

        return getT(index, VarType.LONG);

    }

    public Variable getF(final int index) {

        return getT(index, VarType.FLOAT);

    }

    public Variable getD(final int index) {

        return getT(index, VarType.DOUBLE);

    }

    public Variable getA(final int index) {

        return getT(index, VarType.REFERENCE);

    }

    public Variable getT(final int index, final int type) {

        final int oldRecordValue = localTypeRecords.get(index);

        if ((oldRecordValue & 0xff) != type) {

            throw new IllegalStateException("Type mismatch");

        }

        return Variable.getLocalVariable(type, index);

    }

    private static void updateRecords(final TypeArray typeRecords,

                                      final TypeArray stackMapTypes) {

        final int srcSize = stackMapTypes.getSize();

        for (int i = 0, dstIndex = 0; i < srcSize; ++i) {

            final int smType = stackMapTypes.get(i);

            if (smType == RuntimeConstants.ITEM_Bogus) {

                ++dstIndex;

                continue;

            }

            final int varType = VarType.fromStackMapType(smType);

            updateRecord(typeRecords, dstIndex, varType);

            dstIndex += VarType.isCategory2(varType) ? 2 : 1;

        }

    }

    private static void updateRecord(final TypeArray typeRecords,

                                     final int index, final int type) {

        if (typeRecords.getSize() < (index + 1)) {

            typeRecords.setSize(index + 1);

        }

        final int oldRecordValue = typeRecords.get(index);

        final int usedTypesMask =

                (oldRecordValue >> 8) | (1 << type);

        typeRecords.set(index, (usedTypesMask << 8) | type);

    }

    private static Variable getVariable(final TypeArray typeRecords,

                                        final int index) {

        return Variable.getLocalVariable(typeRecords.get(index) & 0xff, index);

    }

}