/***
    Copyright (C) 2021 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: ByteBuffer.cpp
    Date: 2021-8-28
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "ByteBuffer.hpp"

namespace Aurora::Memory
{
    AuList<AuUInt8> ByteBuffer::ToVector()
    {
        AuList<AuUInt8> vec;
        vec.resize(length);
        if (flagCircular)
        {
            return RemainingBytesToVector(false);
        }
        else
        {
            std::memcpy(vec.data(), base, length);
        }
        return vec;
    }

    AUKN_SYM bool ByteBuffer::WriterTryGoForward(AuUInt32 offset)
    {
        auto n = Write(nullptr, offset);
        SysAssert(n == offset); // TODO: writer go back
        return true;
    }


    bool ByteBuffer::ReaderTryGoForward(AuUInt32 offset)
    {
        auto n = Read(nullptr, offset, false);
        if (n != offset)
        {
            SysAssert(ReaderTryGoBack(n));
            return false;
        }
        return true;
    }

    AuOptional<AuUInt8 *> ByteBuffer::WriterTryGetWriteHeadFor(AuUInt32 nBytes)
    {
        if (writePtr == base + length)
        {
            writePtr = base;
        }

        if (flagCircular)
        {
            AuUInt32 linearOverhead;
            if (writePtr < readPtr)
            {
                linearOverhead = readPtr - writePtr;
            }
            else
            {
                linearOverhead = length - (writePtr - base);
            }

            if (linearOverhead < nBytes)
            {
                return {};
            }
        }
        else
        {
            if (length - (writePtr - base) < nBytes)
            {
                return {};
            }
        }

        return writePtr;
    }

    bool ByteBuffer::ReaderTryGoBack(AuUInt32 offset)
    {
        if (flagCircular)
        {
            auto readOffset = readPtr - base;

            if (readOffset < offset)
            {
                auto absPosition = offset - readOffset;
                auto goAround    = absPosition;
                auto backIdx     = length - goAround;

                auto writeOffset = writePtr - base;
                if (writeOffset > backIdx)
                {
                    return false;
                }

                readPtr = base + backIdx;
            }
            else
            {
                auto writeOffset = writePtr - base;
                auto backIdx     = readOffset - offset;

                if (writeOffset > backIdx)
                {
                    return false;
                }
                    
                readPtr = base + backIdx;
            }

            return true;
        }
        else
        {
            auto readOffset = readPtr - base;

            if (readOffset < offset)
            {
                return false;
            }

            readPtr -= offset;

            return true;
        }
    }

    AuUInt8 *ByteBuffer::begin()
    {
        SysAssert(!flagCircular, "::begin is only available for linear buffers");
        return base;
    }
    
    AuUInt8 *ByteBuffer::end()
    {
        SysAssert(!flagCircular, "::end is only available for linear buffers");
        return base + length;
    }
}