//
//  PacketList.cpp
//
//
//  Created by Clement on 7/13/15.
//  Copyright 2015 High Fidelity, Inc.
//
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//

#include "PacketList.h"

#include <QDebug>

#include "../NLPacket.h"

using namespace udt;

PacketList::PacketList(PacketType packetType, QByteArray extendedHeader, bool isReliable, bool isOrdered) :
    _packetType(packetType),
    _isReliable(isReliable),
    _isOrdered(isOrdered),
    _extendedHeader(extendedHeader)
{
    Q_ASSERT_X(!(!_isReliable && _isOrdered), "PacketList", "Unreliable ordered PacketLists are not currently supported");
    QIODevice::open(WriteOnly);
}

PacketList::PacketList(PacketList&& other) :
    _packetType(other._packetType),
    _packets(std::move(other._packets))
{
}

void PacketList::startSegment() {
    _segmentStartIndex = _currentPacket ? _currentPacket->pos() : _extendedHeader.size();
}

void PacketList::endSegment() {
    _segmentStartIndex = -1;
}

size_t PacketList::getDataSize() const {
    size_t totalBytes = 0;
    for (const auto& packet : _packets) {
        totalBytes += packet->getDataSize();
    }

    if (_currentPacket) {
        totalBytes += _currentPacket->getDataSize();
    }

    return totalBytes;
}

std::unique_ptr<PacketList> PacketList::fromReceivedPackets(std::list<std::unique_ptr<Packet>>&& packets) {
    auto packetList = std::unique_ptr<PacketList>(new PacketList(PacketType::Unknown, QByteArray(), true, true));
    packetList->_packets = std::move(packets);
    return packetList;
}

std::unique_ptr<Packet> PacketList::createPacket() {
    // use the static create method to create a new packet
    // If this packet list is supposed to be ordered then we consider this to be part of a message
    bool isPartOfMessage = _isOrdered;
    return Packet::create(-1, _isReliable, isPartOfMessage);
}

std::unique_ptr<Packet> PacketList::createPacketWithExtendedHeader() {
    // use the static create method to create a new packet
    auto packet = createPacket();
    
    if (!_extendedHeader.isEmpty()) {
        // add the extended header to the front of the packet
        if (packet->write(_extendedHeader) == -1) {
            qDebug() << "Could not write extendedHeader in PacketList::createPacketWithExtendedHeader"
                << "- make sure that _extendedHeader is not larger than the payload capacity.";
        }
    }
    
    return packet;
}

QByteArray PacketList::getAllData() {
    size_t sizeBytes = 0;

    for (const auto& packet : _packets) {
        sizeBytes += packet->size();
    }

    QByteArray data;
    data.reserve(sizeBytes);

    for (auto& packet : _packets) {
        data.append(packet->getPayload(), packet->getPayloadSize());
    }

    return data;
}

qint64 PacketList::writeData(const char* data, qint64 maxSize) {
    if (!_currentPacket) {
        // we don't have a current packet, time to set one up
        _currentPacket = createPacketWithExtendedHeader();
    }
    
    // check if this block of data can fit into the currentPacket
    if (maxSize <= _currentPacket->bytesAvailableForWrite()) {
        // it fits, just write it to the current packet
        _currentPacket->write(data, maxSize);
        
        // return the number of bytes written
        return maxSize;
    } else {
        // it does not fit - this may need to be in the next packet
        
        if (!_isOrdered) {
            auto newPacket = createPacketWithExtendedHeader();
            
            if (_segmentStartIndex >= 0) {
                // We in the process of writing a segment for an unordered PacketList.
                // We need to try and pull the first part of the segment out to our new packet
                
                // check now to see if this is an unsupported write
                int numBytesToEnd = _currentPacket->bytesAvailableForWrite();
                
                if ((newPacket->size() - numBytesToEnd) < maxSize) {
                    // this is an unsupported case - the segment is bigger than the size of an individual packet
                    // but the PacketList is not going to be sent ordered
                    qDebug() << "Error in PacketList::writeData - attempted to write a segment to an unordered packet that is"
                    << "larger than the payload size.";
                    Q_ASSERT(false);
                }
                
                int segmentSize = _currentPacket->pos() - _segmentStartIndex;
                
                // copy from currentPacket where the segment started to the beginning of the newPacket
                newPacket->write(_currentPacket->getPayload() + _segmentStartIndex, segmentSize);
                
                // the current segment now starts at the beginning of the new packet
                _segmentStartIndex = _extendedHeader.size();
                
                // shrink the current payload to the actual size of the packet
                _currentPacket->setPayloadSize(_segmentStartIndex);
            }
            
            // move the current packet to our list of packets
            _packets.push_back(std::move(_currentPacket));
            
            // write the data to the newPacket
            newPacket->write(data, maxSize);
            
            // swap our current packet with the new packet
            _currentPacket.swap(newPacket);
            
            // return the number of bytes written to the new packet
            return maxSize;
        } else {
            // we're an ordered PacketList - let's fit what we can into the current packet and then put the leftover
            // into a new packet
            
            int numBytesToEnd = _currentPacket->bytesAvailableForWrite();
            _currentPacket->write(data, numBytesToEnd);
            
            // move the current packet to our list of packets
            _packets.push_back(std::move(_currentPacket));
            
            // recursively call our writeData method for the remaining data to write to a new packet
            return numBytesToEnd + writeData(data + numBytesToEnd, maxSize - numBytesToEnd);
        }
    }
}

void PacketList::closeCurrentPacket(bool shouldSendEmpty) {
    if (shouldSendEmpty && !_currentPacket) {
        _currentPacket = createPacketWithExtendedHeader();
    }
    
    if (_currentPacket) {
        // move the current packet to our list of packets
        _packets.push_back(std::move(_currentPacket));
    }
}