network_content.cpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD 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.
 * OpenTTD 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 OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */
 
#include "../stdafx.h"
#include "../rev.h"
#include "../ai/ai.hpp"
#include "../game/game.hpp"
#include "../window_func.h"
#include "../error.h"
#include "../fileio_func.h"
#include "../base_media_base.h"
#include "../settings_type.h"
#include "network_content.h"
 
#include "table/strings.h"
 
#if defined(WITH_ZLIB)
#include <zlib.h>
#endif
 
#ifdef __EMSCRIPTEN__
# include <emscripten.h>
#endif
 
#include "../safeguards.h"
 
extern bool HasScenario(const ContentInfo *ci, bool md5sum);
 
ClientNetworkContentSocketHandler _network_content_client;
 
static bool HasGRFConfig(const ContentInfo *ci, bool md5sum)
{
  return FindGRFConfig(BSWAP32(ci->unique_id), md5sum ? FGCM_EXACT : FGCM_ANY, md5sum ? &ci->md5sum : nullptr) != nullptr;
}
 
typedef bool (*HasProc)(const ContentInfo *ci, bool md5sum);
 
bool ClientNetworkContentSocketHandler::Receive_SERVER_INFO(Packet &p)
{
  ContentInfo *ci = new ContentInfo();
  ci->type     = (ContentType)p.Recv_uint8();
  ci->id       = (ContentID)p.Recv_uint32();
  ci->filesize = p.Recv_uint32();
 
  ci->name        = p.Recv_string(NETWORK_CONTENT_NAME_LENGTH);
  ci->version     = p.Recv_string(NETWORK_CONTENT_VERSION_LENGTH);
  ci->url         = p.Recv_string(NETWORK_CONTENT_URL_LENGTH);
  ci->description = p.Recv_string(NETWORK_CONTENT_DESC_LENGTH, SVS_REPLACE_WITH_QUESTION_MARK | SVS_ALLOW_NEWLINE);
 
  ci->unique_id = p.Recv_uint32();
  p.Recv_bytes(ci->md5sum);
 
  uint dependency_count = p.Recv_uint8();
  ci->dependencies.reserve(dependency_count);
  for (uint i = 0; i < dependency_count; i++) {
    ContentID dependency_cid = (ContentID)p.Recv_uint32();
    ci->dependencies.push_back(dependency_cid);
    this->reverse_dependency_map.emplace(dependency_cid, ci->id);
  }
 
  uint tag_count = p.Recv_uint8();
  ci->tags.reserve(tag_count);
  for (uint i = 0; i < tag_count; i++) ci->tags.push_back(p.Recv_string(NETWORK_CONTENT_TAG_LENGTH));
 
  if (!ci->IsValid()) {
    delete ci;
    this->CloseConnection();
    return false;
  }
 
  /* Find the appropriate check function */
  HasProc proc = nullptr;
  switch (ci->type) {
    case CONTENT_TYPE_NEWGRF:
      proc = HasGRFConfig;
      break;
 
    case CONTENT_TYPE_BASE_GRAPHICS:
      proc = BaseGraphics::HasSet;
      break;
 
    case CONTENT_TYPE_BASE_MUSIC:
      proc = BaseMusic::HasSet;
      break;
 
    case CONTENT_TYPE_BASE_SOUNDS:
      proc = BaseSounds::HasSet;
      break;
 
    case CONTENT_TYPE_AI:
      proc = AI::HasAI; break;
      break;
 
    case CONTENT_TYPE_AI_LIBRARY:
      proc = AI::HasAILibrary; break;
      break;
 
    case CONTENT_TYPE_GAME:
      proc = Game::HasGame; break;
      break;
 
    case CONTENT_TYPE_GAME_LIBRARY:
      proc = Game::HasGameLibrary; break;
      break;
 
    case CONTENT_TYPE_SCENARIO:
    case CONTENT_TYPE_HEIGHTMAP:
      proc = HasScenario;
      break;
 
    default:
      break;
  }
 
  if (proc != nullptr) {
    if (proc(ci, true)) {
      ci->state = ContentInfo::ALREADY_HERE;
    } else {
      ci->state = ContentInfo::UNSELECTED;
      if (proc(ci, false)) ci->upgrade = true;
    }
  } else {
    ci->state = ContentInfo::UNSELECTED;
  }
 
  /* Something we don't have and has filesize 0 does not exist in the system */
  if (ci->state == ContentInfo::UNSELECTED && ci->filesize == 0) ci->state = ContentInfo::DOES_NOT_EXIST;
 
  /* Do we already have a stub for this? */
  for (ContentInfo *ici : this->infos) {
    if (ici->type == ci->type && ici->unique_id == ci->unique_id && ci->md5sum == ici->md5sum) {
      /* Preserve the name if possible */
      if (ci->name.empty()) ci->name = ici->name;
      if (ici->IsSelected()) ci->state = ici->state;
 
      /*
       * As ici might be selected by the content window we cannot delete that.
       * However, we want to keep most of the values of ci, except the values
       * we (just) already preserved.
       */
      *ici = *ci;
      delete ci;
 
      this->OnReceiveContentInfo(ici);
      return true;
    }
  }
 
  /* Missing content info? Don't list it */
  if (ci->filesize == 0) {
    delete ci;
    return true;
  }
 
  this->infos.push_back(ci);
 
  /* Incoming data means that we might need to reconsider dependencies */
  ConstContentVector parents;
  this->ReverseLookupTreeDependency(parents, ci);
  for (const ContentInfo *ici : parents) {
    this->CheckDependencyState(const_cast<ContentInfo *>(ici));
  }
 
  this->OnReceiveContentInfo(ci);
 
  return true;
}
 
void ClientNetworkContentSocketHandler::RequestContentList(ContentType type)
{
  if (type == CONTENT_TYPE_END) {
    this->RequestContentList(CONTENT_TYPE_BASE_GRAPHICS);
    this->RequestContentList(CONTENT_TYPE_BASE_MUSIC);
    this->RequestContentList(CONTENT_TYPE_BASE_SOUNDS);
    this->RequestContentList(CONTENT_TYPE_SCENARIO);
    this->RequestContentList(CONTENT_TYPE_HEIGHTMAP);
    this->RequestContentList(CONTENT_TYPE_AI);
    this->RequestContentList(CONTENT_TYPE_AI_LIBRARY);
    this->RequestContentList(CONTENT_TYPE_GAME);
    this->RequestContentList(CONTENT_TYPE_GAME_LIBRARY);
    this->RequestContentList(CONTENT_TYPE_NEWGRF);
    return;
  }
 
  this->Connect();
 
  auto p = std::make_unique<Packet>(this, PACKET_CONTENT_CLIENT_INFO_LIST);
  p->Send_uint8 ((uint8_t)type);
  p->Send_uint32(0xffffffff);
  p->Send_uint8 (1);
  p->Send_string("vanilla");
  p->Send_string(_openttd_content_version);
 
  /* Patchpacks can extend the list with one. In BaNaNaS metadata you can
   * add a branch in the 'compatibility' list, to filter on this. If you want
   * your patchpack to be mentioned in the BaNaNaS web-interface, create an
   * issue on https://github.com/OpenTTD/bananas-api asking for this.
 
  p->Send_string("patchpack"); // Or what-ever the name of your patchpack is.
  p->Send_string(_openttd_content_version_patchpack);
 
   */
 
  this->SendPacket(std::move(p));
}
 
void ClientNetworkContentSocketHandler::RequestContentList(uint count, const ContentID *content_ids)
{
  this->Connect();
 
  while (count > 0) {
    /* We can "only" send a limited number of IDs in a single packet.
     * A packet begins with the packet size and a byte for the type.
     * Then this packet adds a uint16_t for the count in this packet.
     * The rest of the packet can be used for the IDs. */
    uint p_count = std::min<uint>(count, (TCP_MTU - sizeof(PacketSize) - sizeof(uint8_t) - sizeof(uint16_t)) / sizeof(uint32_t));
 
    auto p = std::make_unique<Packet>(this, PACKET_CONTENT_CLIENT_INFO_ID, TCP_MTU);
    p->Send_uint16(p_count);
 
    for (uint i = 0; i < p_count; i++) {
      p->Send_uint32(content_ids[i]);
    }
 
    this->SendPacket(std::move(p));
    count -= p_count;
    content_ids += p_count;
  }
}
 
void ClientNetworkContentSocketHandler::RequestContentList(ContentVector *cv, bool send_md5sum)
{
  if (cv == nullptr) return;
 
  this->Connect();
 
  assert(cv->size() < 255);
  assert(cv->size() < (TCP_MTU - sizeof(PacketSize) - sizeof(uint8_t) - sizeof(uint8_t)) /
      (sizeof(uint8_t) + sizeof(uint32_t) + (send_md5sum ? MD5_HASH_BYTES : 0)));
 
  auto p = std::make_unique<Packet>(this, send_md5sum ? PACKET_CONTENT_CLIENT_INFO_EXTID_MD5 : PACKET_CONTENT_CLIENT_INFO_EXTID, TCP_MTU);
  p->Send_uint8((uint8_t)cv->size());
 
  for (const ContentInfo *ci : *cv) {
    p->Send_uint8((uint8_t)ci->type);
    p->Send_uint32(ci->unique_id);
    if (!send_md5sum) continue;
    p->Send_bytes(ci->md5sum);
  }
 
  this->SendPacket(std::move(p));
 
  for (ContentInfo *ci : *cv) {
    bool found = false;
    for (ContentInfo *ci2 : this->infos) {
      if (ci->type == ci2->type && ci->unique_id == ci2->unique_id &&
          (!send_md5sum || ci->md5sum == ci2->md5sum)) {
        found = true;
        break;
      }
    }
    if (!found) {
      this->infos.push_back(ci);
    } else {
      delete ci;
    }
  }
}
 
void ClientNetworkContentSocketHandler::DownloadSelectedContent(uint &files, uint &bytes, bool fallback)
{
  bytes = 0;
 
  ContentIDList content;
  for (const ContentInfo *ci : this->infos) {
    if (!ci->IsSelected() || ci->state == ContentInfo::ALREADY_HERE) continue;
 
    content.push_back(ci->id);
    bytes += ci->filesize;
  }
 
  files = (uint)content.size();
 
  /* If there's nothing to download, do nothing. */
  if (files == 0) return;
 
  this->isCancelled = false;
 
  if (fallback) {
    this->DownloadSelectedContentFallback(content);
  } else {
    this->DownloadSelectedContentHTTP(content);
  }
}
 
void ClientNetworkContentSocketHandler::DownloadSelectedContentHTTP(const ContentIDList &content)
{
  std::string content_request;
  for (const ContentID &id : content) {
    content_request += std::to_string(id) + "\n";
  }
 
  this->http_response_index = -1;
 
  NetworkHTTPSocketHandler::Connect(NetworkContentMirrorUriString(), this, content_request);
}
 
void ClientNetworkContentSocketHandler::DownloadSelectedContentFallback(const ContentIDList &content)
{
  uint count = (uint)content.size();
  const ContentID *content_ids = content.data();
  this->Connect();
 
  while (count > 0) {
    /* We can "only" send a limited number of IDs in a single packet.
     * A packet begins with the packet size and a byte for the type.
     * Then this packet adds a uint16_t for the count in this packet.
     * The rest of the packet can be used for the IDs. */
    uint p_count = std::min<uint>(count, (TCP_MTU - sizeof(PacketSize) - sizeof(uint8_t) - sizeof(uint16_t)) / sizeof(uint32_t));
 
    auto p = std::make_unique<Packet>(this, PACKET_CONTENT_CLIENT_CONTENT, TCP_MTU);
    p->Send_uint16(p_count);
 
    for (uint i = 0; i < p_count; i++) {
      p->Send_uint32(content_ids[i]);
    }
 
    this->SendPacket(std::move(p));
    count -= p_count;
    content_ids += p_count;
  }
}
 
static std::string GetFullFilename(const ContentInfo *ci, bool compressed)
{
  Subdirectory dir = GetContentInfoSubDir(ci->type);
  if (dir == NO_DIRECTORY) return {};
 
  std::string buf = FioGetDirectory(SP_AUTODOWNLOAD_DIR, dir);
  buf += ci->filename;
  buf += compressed ? ".tar.gz" : ".tar";
 
  return buf;
}
 
static bool GunzipFile(const ContentInfo *ci)
{
#if defined(WITH_ZLIB)
  bool ret = true;
 
  /* Need to open the file with fopen() to support non-ASCII on Windows. */
  auto ftmp = FileHandle::Open(GetFullFilename(ci, true), "rb");
  if (!ftmp.has_value()) return false;
  /* Duplicate the handle, and close the FILE*, to avoid double-closing the handle later. */
  int fdup = dup(fileno(*ftmp));
  gzFile fin = gzdopen(fdup, "rb");
  ftmp.reset();
 
  auto fout = FileHandle::Open(GetFullFilename(ci, false), "wb");
 
  if (fin == nullptr || !fout.has_value()) {
    ret = false;
  } else {
    uint8_t buff[8192];
    for (;;) {
      int read = gzread(fin, buff, sizeof(buff));
      if (read == 0) {
        /* If gzread() returns 0, either the end-of-file has been
         * reached or an underlying read error has occurred.
         *
         * gzeof() can't be used, because:
         * 1.2.5 - it is safe, 1 means 'everything was OK'
         * 1.2.3.5, 1.2.4 - 0 or 1 is returned 'randomly'
         * 1.2.3.3 - 1 is returned for truncated archive
         *
         * So we use gzerror(). When proper end of archive
         * has been reached, then:
         * errnum == Z_STREAM_END in 1.2.3.3,
         * errnum == 0 in 1.2.4 and 1.2.5 */
        int errnum;
        gzerror(fin, &errnum);
        if (errnum != 0 && errnum != Z_STREAM_END) ret = false;
        break;
      }
      if (read < 0 || static_cast<size_t>(read) != fwrite(buff, 1, read, *fout)) {
        /* If gzread() returns -1, there was an error in archive */
        ret = false;
        break;
      }
      /* DO NOT DO THIS! It will fail to detect broken archive with 1.2.3.3!
       * if (read < sizeof(buff)) break; */
    }
  }
 
  if (fin != nullptr) {
    gzclose(fin);
  } else if (fdup != -1) {
    /* Failing gzdopen does not close the passed file descriptor. */
    close(fdup);
  }
 
  return ret;
#else
  NOT_REACHED();
#endif /* defined(WITH_ZLIB) */
}
 
static inline ssize_t TransferOutFWrite(std::optional<FileHandle> &file, const char *buffer, size_t amount)
{
  return fwrite(buffer, 1, amount, *file);
}
 
bool ClientNetworkContentSocketHandler::Receive_SERVER_CONTENT(Packet &p)
{
  if (!this->curFile.has_value()) {
    delete this->curInfo;
    /* When we haven't opened a file this must be our first packet with metadata. */
    this->curInfo = new ContentInfo;
    this->curInfo->type     = (ContentType)p.Recv_uint8();
    this->curInfo->id       = (ContentID)p.Recv_uint32();
    this->curInfo->filesize = p.Recv_uint32();
    this->curInfo->filename = p.Recv_string(NETWORK_CONTENT_FILENAME_LENGTH);
 
    if (!this->BeforeDownload()) {
      this->CloseConnection();
      return false;
    }
  } else {
    /* We have a file opened, thus are downloading internal content */
    size_t toRead = p.RemainingBytesToTransfer();
    if (toRead != 0 && static_cast<size_t>(p.TransferOut(TransferOutFWrite, std::ref(this->curFile))) != toRead) {
      CloseWindowById(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_CONTENT_DOWNLOAD);
      ShowErrorMessage(STR_CONTENT_ERROR_COULD_NOT_DOWNLOAD, STR_CONTENT_ERROR_COULD_NOT_DOWNLOAD_FILE_NOT_WRITABLE, WL_ERROR);
      this->CloseConnection();
      this->curFile.reset();
 
      return false;
    }
 
    this->OnDownloadProgress(this->curInfo, (int)toRead);
 
    if (toRead == 0) this->AfterDownload();
  }
 
  return true;
}
 
bool ClientNetworkContentSocketHandler::BeforeDownload()
{
  if (!this->curInfo->IsValid()) {
    delete this->curInfo;
    this->curInfo = nullptr;
    return false;
  }
 
  if (this->curInfo->filesize != 0) {
    /* The filesize is > 0, so we are going to download it */
    std::string filename = GetFullFilename(this->curInfo, true);
    if (filename.empty() || !(this->curFile = FileHandle::Open(filename, "wb")).has_value()) {
      /* Unless that fails of course... */
      CloseWindowById(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_CONTENT_DOWNLOAD);
      ShowErrorMessage(STR_CONTENT_ERROR_COULD_NOT_DOWNLOAD, STR_CONTENT_ERROR_COULD_NOT_DOWNLOAD_FILE_NOT_WRITABLE, WL_ERROR);
      return false;
    }
  }
  return true;
}
 
void ClientNetworkContentSocketHandler::AfterDownload()
{
  /* We read nothing; that's our marker for end-of-stream.
   * Now gunzip the tar and make it known. */
  this->curFile.reset();
 
  if (GunzipFile(this->curInfo)) {
    FioRemove(GetFullFilename(this->curInfo, true));
 
    Subdirectory sd = GetContentInfoSubDir(this->curInfo->type);
    if (sd == NO_DIRECTORY) NOT_REACHED();
 
    TarScanner ts;
    std::string fname = GetFullFilename(this->curInfo, false);
    ts.AddFile(sd, fname);
 
    if (this->curInfo->type == CONTENT_TYPE_BASE_MUSIC) {
      /* Music can't be in a tar. So extract the tar! */
      ExtractTar(fname, BASESET_DIR);
      FioRemove(fname);
    }
 
#ifdef __EMSCRIPTEN__
    EM_ASM(if (window["openttd_syncfs"]) openttd_syncfs());
#endif
 
    this->OnDownloadComplete(this->curInfo->id);
  } else {
    ShowErrorMessage(STR_CONTENT_ERROR_COULD_NOT_EXTRACT, INVALID_STRING_ID, WL_ERROR);
  }
}
 
bool ClientNetworkContentSocketHandler::IsCancelled() const
{
  return this->isCancelled;
}
 
/* Also called to just clean up the mess. */
void ClientNetworkContentSocketHandler::OnFailure()
{
  this->http_response.clear();
  this->http_response.shrink_to_fit();
  this->http_response_index = -2;
 
  if (this->curFile.has_value()) {
    this->OnDownloadProgress(this->curInfo, -1);
 
    this->curFile.reset();
  }
 
  /* If we fail, download the rest via the 'old' system. */
  if (!this->isCancelled) {
    uint files, bytes;
 
    this->DownloadSelectedContent(files, bytes, true);
  }
}
 
void ClientNetworkContentSocketHandler::OnReceiveData(std::unique_ptr<char[]> data, size_t length)
{
  assert(data.get() == nullptr || length != 0);
 
  /* Ignore any latent data coming from a connection we closed. */
  if (this->http_response_index == -2) {
    return;
  }
 
  if (this->http_response_index == -1) {
    if (data != nullptr) {
      /* Append the rest of the response. */
      this->http_response.insert(this->http_response.end(), data.get(), data.get() + length);
      return;
    } else {
      /* Make sure the response is properly terminated. */
      this->http_response.push_back('\0');
 
      /* And prepare for receiving the rest of the data. */
      this->http_response_index = 0;
    }
  }
 
  if (data != nullptr) {
    /* We have data, so write it to the file. */
    if (fwrite(data.get(), 1, length, *this->curFile) != length) {
      /* Writing failed somehow, let try via the old method. */
      this->OnFailure();
    } else {
      /* Just received the data. */
      this->OnDownloadProgress(this->curInfo, (int)length);
    }
 
    /* Nothing more to do now. */
    return;
  }
 
  if (this->curFile.has_value()) {
    /* We've finished downloading a file. */
    this->AfterDownload();
  }
 
  if ((uint)this->http_response_index >= this->http_response.size()) {
    /* It's not a real failure, but if there's
     * nothing more to download it helps with
     * cleaning up the stuff we allocated. */
    this->OnFailure();
    return;
  }
 
  delete this->curInfo;
  /* When we haven't opened a file this must be our first packet with metadata. */
  this->curInfo = new ContentInfo;
 
#define check_not_null(p) { if ((p) == nullptr) { this->OnFailure(); return; } }
 
#define check_and_terminate(p) { check_not_null(p); *(p) = '\0'; }
 
  for (;;) {
    char *str = this->http_response.data() + this->http_response_index;
    char *p = strchr(str, '\n');
    check_and_terminate(p);
 
    /* Update the index for the next one */
    this->http_response_index += (int)strlen(str) + 1;
 
    /* Read the ID */
    p = strchr(str, ',');
    check_and_terminate(p);
    this->curInfo->id = (ContentID)atoi(str);
 
    /* Read the type */
    str = p + 1;
    p = strchr(str, ',');
    check_and_terminate(p);
    this->curInfo->type = (ContentType)atoi(str);
 
    /* Read the file size */
    str = p + 1;
    p = strchr(str, ',');
    check_and_terminate(p);
    this->curInfo->filesize = atoi(str);
 
    /* Read the URL */
    str = p + 1;
    /* Is it a fallback URL? If so, just continue with the next one. */
    if (strncmp(str, "ottd", 4) == 0) {
      if ((uint)this->http_response_index >= this->http_response.size()) {
        /* Have we gone through all lines? */
        this->OnFailure();
        return;
      }
      continue;
    }
 
    p = strrchr(str, '/');
    check_not_null(p);
    p++; // Start after the '/'
 
    std::string filename = p;
    /* Remove the extension from the string. */
    for (uint i = 0; i < 2; i++) {
      auto pos = filename.find_last_of('.');
      if (pos == std::string::npos) {
        this->OnFailure();
        return;
      }
      filename.erase(pos);
    }
 
    /* Copy the string, without extension, to the filename. */
    this->curInfo->filename = std::move(filename);
 
    /* Request the next file. */
    if (!this->BeforeDownload()) {
      this->OnFailure();
      return;
    }
 
    NetworkHTTPSocketHandler::Connect(str, this);
    return;
  }
 
#undef check
#undef check_and_terminate
}
 
ClientNetworkContentSocketHandler::ClientNetworkContentSocketHandler() :
  NetworkContentSocketHandler(),
  http_response_index(-2),
  curFile(std::nullopt),
  curInfo(nullptr),
  isConnecting(false),
  isCancelled(false)
{
  this->lastActivity = std::chrono::steady_clock::now();
}
 
ClientNetworkContentSocketHandler::~ClientNetworkContentSocketHandler()
{
  delete this->curInfo;
 
  for (ContentInfo *ci : this->infos) delete ci;
}
 
class NetworkContentConnecter : public TCPConnecter {
public:
  NetworkContentConnecter(const std::string &connection_string) : TCPConnecter(connection_string, NETWORK_CONTENT_SERVER_PORT) {}
 
  void OnFailure() override
  {
    _network_content_client.isConnecting = false;
    _network_content_client.OnConnect(false);
  }
 
  void OnConnect(SOCKET s) override
  {
    assert(_network_content_client.sock == INVALID_SOCKET);
    _network_content_client.lastActivity = std::chrono::steady_clock::now();
    _network_content_client.isConnecting = false;
    _network_content_client.sock = s;
    _network_content_client.Reopen();
    _network_content_client.OnConnect(true);
  }
};
 
void ClientNetworkContentSocketHandler::Connect()
{
  if (this->sock != INVALID_SOCKET || this->isConnecting) return;
 
  this->isCancelled = false;
  this->isConnecting = true;
 
  TCPConnecter::Create<NetworkContentConnecter>(NetworkContentServerConnectionString());
}
 
NetworkRecvStatus ClientNetworkContentSocketHandler::CloseConnection(bool)
{
  NetworkContentSocketHandler::CloseConnection();
 
  if (this->sock == INVALID_SOCKET) return NETWORK_RECV_STATUS_OKAY;
 
  this->CloseSocket();
  this->OnDisconnect();
 
  return NETWORK_RECV_STATUS_OKAY;
}
 
void ClientNetworkContentSocketHandler::Cancel(void)
{
  this->isCancelled = true;
  this->CloseConnection();
}
 
void ClientNetworkContentSocketHandler::SendReceive()
{
  if (this->sock == INVALID_SOCKET || this->isConnecting) return;
 
  /* Close the connection to the content server after inactivity; there can still be downloads pending via HTTP. */
  if (std::chrono::steady_clock::now() > this->lastActivity + IDLE_TIMEOUT) {
    this->CloseConnection();
    return;
  }
 
  if (this->CanSendReceive()) {
    if (this->ReceivePackets()) {
      /* Only update activity once a packet is received, instead of every time we try it. */
      this->lastActivity = std::chrono::steady_clock::now();
    }
  }
 
  this->SendPackets();
}
 
void ClientNetworkContentSocketHandler::DownloadContentInfo(ContentID cid)
{
  /* When we tried to download it already, don't try again */
  if (std::find(this->requested.begin(), this->requested.end(), cid) != this->requested.end()) return;
 
  this->requested.push_back(cid);
  this->RequestContentList(1, &cid);
}
 
ContentInfo *ClientNetworkContentSocketHandler::GetContent(ContentID cid) const
{
  for (ContentInfo *ci : this->infos) {
    if (ci->id == cid) return ci;
  }
  return nullptr;
}
 
 
void ClientNetworkContentSocketHandler::Select(ContentID cid)
{
  ContentInfo *ci = this->GetContent(cid);
  if (ci == nullptr || ci->state != ContentInfo::UNSELECTED) return;
 
  ci->state = ContentInfo::SELECTED;
  this->CheckDependencyState(ci);
}
 
void ClientNetworkContentSocketHandler::Unselect(ContentID cid)
{
  ContentInfo *ci = this->GetContent(cid);
  if (ci == nullptr || !ci->IsSelected()) return;
 
  ci->state = ContentInfo::UNSELECTED;
  this->CheckDependencyState(ci);
}
 
void ClientNetworkContentSocketHandler::SelectAll()
{
  for (ContentInfo *ci : this->infos) {
    if (ci->state == ContentInfo::UNSELECTED) {
      ci->state = ContentInfo::SELECTED;
      this->CheckDependencyState(ci);
    }
  }
}
 
void ClientNetworkContentSocketHandler::SelectUpgrade()
{
  for (ContentInfo *ci : this->infos) {
    if (ci->state == ContentInfo::UNSELECTED && ci->upgrade) {
      ci->state = ContentInfo::SELECTED;
      this->CheckDependencyState(ci);
    }
  }
}
 
void ClientNetworkContentSocketHandler::UnselectAll()
{
  for (ContentInfo *ci : this->infos) {
    if (ci->IsSelected() && ci->state != ContentInfo::ALREADY_HERE) ci->state = ContentInfo::UNSELECTED;
  }
}
 
void ClientNetworkContentSocketHandler::ToggleSelectedState(const ContentInfo *ci)
{
  switch (ci->state) {
    case ContentInfo::SELECTED:
    case ContentInfo::AUTOSELECTED:
      this->Unselect(ci->id);
      break;
 
    case ContentInfo::UNSELECTED:
      this->Select(ci->id);
      break;
 
    default:
      break;
  }
}
 
void ClientNetworkContentSocketHandler::ReverseLookupDependency(ConstContentVector &parents, const ContentInfo *child) const
{
  auto range = this->reverse_dependency_map.equal_range(child->id);
 
  for (auto iter = range.first; iter != range.second; ++iter) {
    parents.push_back(GetContent(iter->second));
  }
}
 
void ClientNetworkContentSocketHandler::ReverseLookupTreeDependency(ConstContentVector &tree, const ContentInfo *child) const
{
  tree.push_back(child);
 
  /* First find all direct parents. We can't use the "normal" iterator as
   * we are including stuff into the vector and as such the vector's data
   * store can be reallocated (and thus move), which means out iterating
   * pointer gets invalid. So fall back to the indices. */
  for (uint i = 0; i < tree.size(); i++) {
    ConstContentVector parents;
    this->ReverseLookupDependency(parents, tree[i]);
 
    for (const ContentInfo *ci : parents) {
      include(tree, ci);
    }
  }
}
 
void ClientNetworkContentSocketHandler::CheckDependencyState(ContentInfo *ci)
{
  if (ci->IsSelected() || ci->state == ContentInfo::ALREADY_HERE) {
    /* Selection is easy; just walk all children and set the
     * autoselected state. That way we can see what we automatically
     * selected and thus can unselect when a dependency is removed. */
    for (auto &dependency : ci->dependencies) {
      ContentInfo *c = this->GetContent(dependency);
      if (c == nullptr) {
        this->DownloadContentInfo(dependency);
      } else if (c->state == ContentInfo::UNSELECTED) {
        c->state = ContentInfo::AUTOSELECTED;
        this->CheckDependencyState(c);
      }
    }
    return;
  }
 
  if (ci->state != ContentInfo::UNSELECTED) return;
 
  /* For unselection we need to find the parents of us. We need to
   * unselect them. After that we unselect all children that we
   * depend on and are not used as dependency for us, but only when
   * we automatically selected them. */
  ConstContentVector parents;
  this->ReverseLookupDependency(parents, ci);
  for (const ContentInfo *c : parents) {
    if (!c->IsSelected()) continue;
 
    this->Unselect(c->id);
  }
 
  for (auto &dependency : ci->dependencies) {
    const ContentInfo *c = this->GetContent(dependency);
    if (c == nullptr) {
      DownloadContentInfo(dependency);
      continue;
    }
    if (c->state != ContentInfo::AUTOSELECTED) continue;
 
    /* Only unselect when WE are the only parent. */
    parents.clear();
    this->ReverseLookupDependency(parents, c);
 
    /* First check whether anything depends on us */
    int sel_count = 0;
    bool force_selection = false;
    for (const ContentInfo *parent_ci : parents) {
      if (parent_ci->IsSelected()) sel_count++;
      if (parent_ci->state == ContentInfo::SELECTED) force_selection = true;
    }
    if (sel_count == 0) {
      /* Nothing depends on us */
      this->Unselect(c->id);
      continue;
    }
    /* Something manually selected depends directly on us */
    if (force_selection) continue;
 
    /* "Flood" search to find all items in the dependency graph*/
    parents.clear();
    this->ReverseLookupTreeDependency(parents, c);
 
    /* Is there anything that is "force" selected?, if so... we're done. */
    for (const ContentInfo *parent_ci : parents) {
      if (parent_ci->state != ContentInfo::SELECTED) continue;
 
      force_selection = true;
      break;
    }
 
    /* So something depended directly on us */
    if (force_selection) continue;
 
    /* Nothing depends on us, mark the whole graph as unselected.
     * After that's done run over them once again to test their children
     * to unselect. Don't do it immediately because it'll do exactly what
     * we're doing now. */
    for (const ContentInfo *parent : parents) {
      if (parent->state == ContentInfo::AUTOSELECTED) this->Unselect(parent->id);
    }
    for (const ContentInfo *parent : parents) {
      this->CheckDependencyState(this->GetContent(parent->id));
    }
  }
}
 
void ClientNetworkContentSocketHandler::Clear()
{
  for (ContentInfo *c : this->infos) delete c;
 
  this->infos.clear();
  this->requested.clear();
  this->reverse_dependency_map.clear();
}
 
/*** CALLBACK ***/
 
void ClientNetworkContentSocketHandler::OnConnect(bool success)
{
  for (size_t i = 0; i < this->callbacks.size(); /* nothing */) {
    ContentCallback *cb = this->callbacks[i];
    /* the callback may remove itself from this->callbacks */
    cb->OnConnect(success);
    if (i != this->callbacks.size() && this->callbacks[i] == cb) i++;
  }
}
 
void ClientNetworkContentSocketHandler::OnDisconnect()
{
  for (size_t i = 0; i < this->callbacks.size(); /* nothing */) {
    ContentCallback *cb = this->callbacks[i];
    cb->OnDisconnect();
    if (i != this->callbacks.size() && this->callbacks[i] == cb) i++;
  }
}
 
void ClientNetworkContentSocketHandler::OnReceiveContentInfo(const ContentInfo *ci)
{
  for (size_t i = 0; i < this->callbacks.size(); /* nothing */) {
    ContentCallback *cb = this->callbacks[i];
    /* the callback may add items and/or remove itself from this->callbacks */
    cb->OnReceiveContentInfo(ci);
    if (i != this->callbacks.size() && this->callbacks[i] == cb) i++;
  }
}
 
void ClientNetworkContentSocketHandler::OnDownloadProgress(const ContentInfo *ci, int bytes)
{
  for (size_t i = 0; i < this->callbacks.size(); /* nothing */) {
    ContentCallback *cb = this->callbacks[i];
    cb->OnDownloadProgress(ci, bytes);
    if (i != this->callbacks.size() && this->callbacks[i] == cb) i++;
  }
}
 
void ClientNetworkContentSocketHandler::OnDownloadComplete(ContentID cid)
{
  ContentInfo *ci = this->GetContent(cid);
  if (ci != nullptr) {
    ci->state = ContentInfo::ALREADY_HERE;
  }
 
  for (size_t i = 0; i < this->callbacks.size(); /* nothing */) {
    ContentCallback *cb = this->callbacks[i];
    /* the callback may remove itself from this->callbacks */
    cb->OnDownloadComplete(cid);
    if (i != this->callbacks.size() && this->callbacks[i] == cb) i++;
  }
}