#include <limits.h>
#include <stdlib.h>
#include <unistd.h>

#include <fstream>
#include <memory>
#include <sstream>

#include <gflags/gflags.h>
#include <glog/logging.h>
#include <libvirt/libvirt.h>

#include "common/libs/fs/shared_select.h"
#include "host/config/file_partition.h"
#include "host/config/guest_config.h"
#include "host/ivserver/ivserver.h"
#include "host/ivserver/options.h"
#include "host/vadb/usbip/server.h"
#include "host/vadb/virtual_adb_server.h"

namespace {
std::string StringFromEnv(const char *varname, std::string defval) {
  const char* const valstr = getenv(varname);
  if (!valstr) {
    return defval;
  }
  return valstr;
}
}  // namespace

DEFINE_int32(instance, 1, "Instance number. Must be unique.");
DEFINE_int32(cpus, 2, "Virtual CPU count.");
DEFINE_int32(memory_mb, 2048,
             "Total amount of memory available for guest, MB.");
DEFINE_string(layout, "/usr/share/cuttlefish-common/vsoc_mem.json",
              "Location of the vsoc_mem.json file.");
DEFINE_string(mempath, "/dev/shm/ivshmem",
              "Target location for the shmem file.");
DEFINE_int32(shmsize, 0, "(ignored)");
DEFINE_string(qemusocket, "/tmp/ivshmem_socket_qemu", "QEmu socket path");
DEFINE_string(clientsocket, "/tmp/ivshmem_socket_client", "Client socket path");

DEFINE_string(system_image_dir, StringFromEnv("HOME", "."),
              "Location of the system partition images.");
DEFINE_string(kernel, "", "Location of cuttlefish kernel file.");
DEFINE_string(kernel_command_line, "",
              "Location of a text file with the kernel command line.");
DEFINE_string(initrd, "", "Location of cuttlefish initrd file.");
DEFINE_string(data_image, "", "Location of the data partition image.");
DEFINE_string(cache_image, "", "Location of the cache partition image.");

DEFINE_string(usbipsocket, "android_usbip", "Name of the USB/IP socket.");

namespace {
constexpr char kLibVirtQemuTarget[] = "qemu:///system";

Json::Value LoadLayoutFile(const std::string& file) {
  char real_file_path[PATH_MAX];
  if (realpath(file.c_str(), real_file_path) == nullptr) {
    LOG(FATAL) << "Could not get real path for file " << file << ": "
               << strerror(errno);
  }

  Json::Value result;
  Json::Reader reader;
  std::ifstream ifs(real_file_path);
  if (!reader.parse(ifs, result)) {
    LOG(FATAL) << "Could not read layout file " << file << ": "
               << reader.getFormattedErrorMessages();
  }
  return result;
}

// VirtualUSBManager manages virtual USB device presence for Cuttlefish.
class VirtualUSBManager {
 public:
  VirtualUSBManager(const std::string& usbsocket)
      : adb_{usbsocket, FLAGS_usbipsocket},
        usbip_{FLAGS_usbipsocket, adb_.Pool()} {}

  ~VirtualUSBManager() = default;

  // Initialize Virtual USB and start USB management thread.
  void Start() {
    CHECK(adb_.Init()) << "Could not initialize Virtual ADB server";
    CHECK(usbip_.Init()) << "Could not start USB/IP server";
    thread_.reset(new std::thread([this]() { Thread(); }));
  }

 private:
  void Thread() {
    for (;;) {
      avd::SharedFDSet fd_read;
      fd_read.Zero();

      adb_.BeforeSelect(&fd_read);
      usbip_.BeforeSelect(&fd_read);

      int ret = avd::Select(&fd_read, nullptr, nullptr, nullptr);
      if (ret <= 0) continue;

      adb_.AfterSelect(fd_read);
      usbip_.AfterSelect(fd_read);
    }
  }

  vadb::VirtualADBServer adb_;
  vadb::usbip::Server usbip_;
  std::unique_ptr<std::thread> thread_;

  VirtualUSBManager(const VirtualUSBManager&) = delete;
  VirtualUSBManager& operator=(const VirtualUSBManager&) = delete;
};

// IVServerManager takes care of serving shared memory segments between
// Cuttlefish and host-side daemons.
class IVServerManager {
 public:
  IVServerManager(const Json::Value& json_root)
      : server_(ivserver::IVServerOptions(FLAGS_layout, FLAGS_mempath,
                                          FLAGS_qemusocket, FLAGS_clientsocket),
                json_root) {}

  ~IVServerManager() = default;

  // Start IVServer thread.
  void Start() {
    thread_.reset(new std::thread([this]() { server_.Serve(); }));
  }

 private:
  ivserver::IVServer server_;
  std::unique_ptr<std::thread> thread_;

  IVServerManager(const IVServerManager&) = delete;
  IVServerManager& operator=(const IVServerManager&) = delete;
};

}  // anonymous namespace

int main(int argc, char** argv) {
  google::InitGoogleLogging(argv[0]);
  google::InstallFailureSignalHandler();
  google::ParseCommandLineFlags(&argc, &argv, true);

  // Log all messages with level WARNING and above to stderr.
  google::SetStderrLogging(google::GLOG_WARNING);

  LOG_IF(FATAL, FLAGS_system_image_dir.empty())
      << "--system_image_dir must be specified.";

  // If user did not specify location of either of these files, expect them to
  // be placed in --system_image_dir location.
  if (FLAGS_kernel.empty()) {
    FLAGS_kernel = FLAGS_system_image_dir + "/kernel";
  }

  if (FLAGS_kernel_command_line.empty()) {
    FLAGS_kernel_command_line = FLAGS_system_image_dir + "/cmdline";
  }

  if (FLAGS_initrd.empty()) {
    FLAGS_initrd = FLAGS_system_image_dir + "/ramdisk.img";
  }

  if (FLAGS_cache_image.empty()) {
    FLAGS_cache_image = FLAGS_system_image_dir + "/cache.img";
  }

  if (FLAGS_data_image.empty()) {
    FLAGS_data_image = FLAGS_system_image_dir + "/userdata.img";
  }

  CHECK(virInitialize() == 0) << "Could not initialize libvirt.";

  Json::Value json_root = LoadLayoutFile(FLAGS_layout);

  // Each of these calls is free to fail and terminate launch if file does not
  // exist or could not be created.
  auto system_partition = config::FilePartition::ReuseExistingFile(
      FLAGS_system_image_dir + "/system.img");
  auto data_partition = config::FilePartition::ReuseExistingFile(
      FLAGS_data_image);
  auto cache_partition =  config::FilePartition::ReuseExistingFile(
      FLAGS_cache_image);

  std::ifstream t(FLAGS_kernel_command_line);
  if (!t) {
    LOG(FATAL) << "Unable to open " << FLAGS_kernel_command_line;
  }
  t.seekg(0, std::ios::end);
  size_t commandline_size = t.tellg();
  if (commandline_size < 1) {
    LOG(FATAL) << "no command line data found at " << FLAGS_kernel_command_line;
  }
  std::string cmdline;
  cmdline.reserve(commandline_size);
  t.seekg(0, std::ios::beg);
  cmdline.assign((std::istreambuf_iterator<char>(t)),
             std::istreambuf_iterator<char>());
  t.close();

  unsigned long libvirt_version;
  CHECK(virGetVersion(&libvirt_version, nullptr, nullptr) == 0)
      << "Could not query libvirt.";

  std::string entropy_source = "/dev/urandom";
  // There seems to be no macro turning major/minor/patch to a number, but
  // headers explain this as major * 1'000'000 + minor * 1'000 + patch.
  if (libvirt_version <= 1003003) {
    entropy_source = "/dev/random";
    LOG(WARNING) << "Your system supplies old version of libvirt, that is "
                 << "not able to use /dev/urandom as entropy source.";
    LOG(WARNING) << "This may affect performance of your virtual instance.";
  }

  config::GuestConfig cfg;
  cfg.SetID(FLAGS_instance)
      .SetVCPUs(FLAGS_cpus)
      .SetMemoryMB(FLAGS_memory_mb)
      .SetKernelName(FLAGS_kernel)
      .SetInitRDName(FLAGS_initrd)
      .SetKernelArgs(cmdline)
      .SetIVShMemSocketPath(FLAGS_qemusocket)
      .SetIVShMemVectorCount(json_root["vsoc_device_regions"].size())
      .SetSystemPartitionPath(system_partition->GetName())
      .SetCachePartitionPath(cache_partition->GetName())
      .SetDataPartitionPath(data_partition->GetName())
      .SetMobileBridgeName("abr0")
      .SetEntropySource(entropy_source)
      .SetEmulator(json_root["guest"]["vmm_path"].asString());

  std::string xml = cfg.Build();
  VLOG(1) << "Using XML:\n" << xml;

  auto libvirt_connection = virConnectOpen(kLibVirtQemuTarget);
  CHECK(libvirt_connection)
      << "Could not connect to libvirt backend: " << kLibVirtQemuTarget;

  VirtualUSBManager vadb(cfg.GetUSBSocketName());
  vadb.Start();
  IVServerManager ivshmem(json_root);
  ivshmem.Start();

  sleep(1);

  auto domain = virDomainCreateXML(
      libvirt_connection, xml.c_str(),
      VIR_DOMAIN_START_PAUSED | VIR_DOMAIN_START_AUTODESTROY);
  CHECK(domain) << "Could not create libvirt domain.";

  CHECK(virDomainResume(domain) == 0) << "Could not start domain.";
  pause();
}