/****************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtQml module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#ifndef QV4BYTECODEGENERATOR_P_H
#define QV4BYTECODEGENERATOR_P_H

//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
#include <private/qv4instr_moth_p.h>

QT_BEGIN_NAMESPACE

namespace QQmlJS {
namespace AST {
class SourceLocation;
}
}

namespace QV4 {
namespace Moth {

class BytecodeGenerator {
public:
    BytecodeGenerator(int line, bool debug)
        : startLine(line), debugMode(debug) {}

    struct Label {
        enum LinkMode {
            LinkNow,
            LinkLater
        };
        Label() = default;
        Label(BytecodeGenerator *generator, LinkMode mode = LinkNow)
            : generator(generator),
              index(generator->labels.size()) {
            generator->labels.append(mode == LinkNow ? generator->instructions.size() : -1);
        }
        static Label returnLabel() {
            Label l;
            l.index = INT_MAX;
            return l;
        }
        bool isReturn() const {
            return index == INT_MAX;
        }

        void link() {
            Q_ASSERT(index >= 0);
            Q_ASSERT(generator->labels[index] == -1);
            generator->labels[index] = generator->instructions.size();
        }

        BytecodeGenerator *generator = nullptr;
        int index = -1;
    };

    struct Jump {
        Jump(BytecodeGenerator *generator, int instruction)
            : generator(generator),
              index(instruction)
        { Q_ASSERT(generator && index != -1); }

        ~Jump() {
            Q_ASSERT(index == -1 || generator->instructions[index].linkedLabel != -1); // make sure link() got called
        }

        Jump(Jump &&j) {
            std::swap(generator, j.generator);
            std::swap(index, j.index);
        }

        BytecodeGenerator *generator = nullptr;
        int index = -1;

        void link() {
            link(generator->label());
        }
        void link(Label l) {
            Q_ASSERT(l.index >= 0);
            Q_ASSERT(generator->instructions[index].linkedLabel == -1);
            generator->instructions[index].linkedLabel = l.index;
        }

    private:
        // make this type move-only:
        Q_DISABLE_COPY(Jump)
        // we never move-assign this type anywhere, so disable it:
        Jump &operator=(Jump &&) = delete;
    };

    struct ExceptionHandler : public Label {
        ExceptionHandler(BytecodeGenerator *generator)
            : Label(generator, LinkLater)
        {
        }
        ~ExceptionHandler()
        {
            Q_ASSERT(generator->currentExceptionHandler != this);
        }
    };

    Label label() {
        return Label(this, Label::LinkNow);
    }

    Label newLabel() {
        return Label(this, Label::LinkLater);
    }

    ExceptionHandler newExceptionHandler() {
        return ExceptionHandler(this);
    }

    template<int InstrT>
    void addInstruction(const InstrData<InstrT> &data)
    {
        Instr genericInstr;
        InstrMeta<InstrT>::setData(genericInstr, data);
        addInstructionHelper(Moth::Instr::Type(InstrT), genericInstr);
    }

    Q_REQUIRED_RESULT Jump jump()
    {
        Instruction::Jump data;
        return addJumpInstruction(data);
    }

    Q_REQUIRED_RESULT Jump jumpTrue()
    {
        Instruction::JumpTrue data;
        return addJumpInstruction(data);
    }

    Q_REQUIRED_RESULT Jump jumpFalse()
    {
        Instruction::JumpFalse data;
        return addJumpInstruction(data);
    }

    void jumpStrictEqual(const StackSlot &lhs, const Label &target)
    {
        Instruction::CmpStrictEqual cmp;
        cmp.lhs = lhs;
        addInstruction(cmp);
        addJumpInstruction(Instruction::JumpTrue()).link(target);
    }

    void jumpStrictNotEqual(const StackSlot &lhs, const Label &target)
    {
        Instruction::CmpStrictNotEqual cmp;
        cmp.lhs = lhs;
        addInstruction(cmp);
        addJumpInstruction(Instruction::JumpTrue()).link(target);
    }

    Q_REQUIRED_RESULT Jump jumpStrictEqualStackSlotInt(const StackSlot &lhs, int rhs)
    {
        Instruction::JumpStrictEqualStackSlotInt data;
        data.lhs = lhs;
        data.rhs = rhs;
        return addJumpInstruction(data);
    }

    Q_REQUIRED_RESULT Jump jumpStrictNotEqualStackSlotInt(const StackSlot &lhs, int rhs)
    {
        Instruction::JumpStrictNotEqualStackSlotInt data;
        data.lhs = lhs;
        data.rhs = rhs;
        return addJumpInstruction(data);
    }

    void setExceptionHandler(ExceptionHandler *handler)
    {
        currentExceptionHandler = handler;
        Instruction::SetExceptionHandler data;
        data.offset = 0;
        if (!handler)
            addInstruction(data);
        else
            addJumpInstruction(data).link(*handler);
    }

    void setLocation(const QQmlJS::AST::SourceLocation &loc);

    ExceptionHandler *exceptionHandler() const {
        return currentExceptionHandler;
    }

    int newRegister();
    int newRegisterArray(int n);
    int registerCount() const { return regCount; }

    void finalize(Compiler::Context *context);

    template<int InstrT>
    Jump addJumpInstruction(const InstrData<InstrT> &data)
    {
        Instr genericInstr;
        InstrMeta<InstrT>::setData(genericInstr, data);
        return Jump(this, addInstructionHelper(Moth::Instr::Type(InstrT), genericInstr, offsetof(InstrData<InstrT>, offset)));
    }

    void addCJumpInstruction(bool jumpOnFalse, const Label *trueLabel, const Label *falseLabel)
    {
        if (jumpOnFalse)
            addJumpInstruction(Instruction::JumpFalse()).link(*falseLabel);
        else
            addJumpInstruction(Instruction::JumpTrue()).link(*trueLabel);
    }

private:
    friend struct Jump;
    friend struct Label;
    friend struct ExceptionHandler;

    int addInstructionHelper(Moth::Instr::Type type, const Instr &i, int offsetOfOffset = -1);

    struct I {
        Moth::Instr::Type type;
        short size;
        uint position;
        int line;
        int offsetForJump;
        int linkedLabel;
        char packed[sizeof(Instr) + 2]; // 2 for instruction and prefix
    };

    void compressInstructions();
    void packInstruction(I &i);
    void adjustJumpOffsets();

    QVector<I> instructions;
    QVector<int> labels;
    ExceptionHandler *currentExceptionHandler;
    int regCount = 0;
public:
    int currentReg = 0;
private:
    int startLine = 0;
    int currentLine = 0;
    bool debugMode = false;
};

}
}

QT_END_NAMESPACE

#endif