/*
 *  Copyright (c) 2016, Facebook, Inc.
 *  All rights reserved.
 *
 *  This source code is licensed under the BSD-style license found in the
 *  LICENSE file in the root directory of this source tree. An additional grant
 *  of patent rights can be found in the PATENTS file in the same directory.
 *
 */
#include "EdenServer.h"

#include <boost/filesystem/operations.hpp>
#include <boost/filesystem/path.hpp>
#include <folly/SocketAddress.h>
#include <folly/String.h>
#include <gflags/gflags.h>
#include <thrift/lib/cpp2/server/ThriftServer.h>
#include <wangle/concurrent/CPUThreadPoolExecutor.h>
#include <wangle/concurrent/GlobalExecutor.h>

#include "EdenServiceHandler.h"
#include "eden/fs/config/ClientConfig.h"
#include "eden/fs/inodes/Dirstate.h"
#include "eden/fs/inodes/EdenMount.h"
#include "eden/fs/store/EmptyBackingStore.h"
#include "eden/fs/store/LocalStore.h"
#include "eden/fs/store/git/GitBackingStore.h"
#include "eden/fs/store/hg/HgBackingStore.h"
#include "eden/fuse/MountPoint.h"
#include "eden/fuse/privhelper/PrivHelper.h"

DEFINE_bool(debug, false, "run fuse in debug mode");

DEFINE_int32(num_eden_threads, 12, "the number of eden CPU worker threads");

DEFINE_string(thrift_address, "", "The address for the thrift server socket");
DEFINE_int32(thrift_num_workers, 2, "The number of thrift worker threads");
DEFINE_int32(thrift_max_conns, 100, "Maximum number of thrift connections");
DEFINE_int32(
    thrift_max_requests,
    1000,
    "Maximum number of active thrift requests");
DEFINE_bool(thrift_enable_codel, true, "Enable Codel queuing timeout");
DEFINE_int32(thrift_queue_len, 100, "Maximum number of unprocessed messages");
DEFINE_int32(
    thrift_min_compress_bytes,
    200,
    "Minimum response compression size");

using apache::thrift::ThriftServer;
using folly::StringPiece;
using std::make_shared;
using std::shared_ptr;
using std::string;
using std::unique_ptr;

namespace {
folly::SocketAddress getThriftAddress(
    StringPiece argument,
    StringPiece edenDir);
std::string getPathToUnixDomainSocket(StringPiece edenDir);
}

namespace facebook {
namespace eden {

EdenServer::EdenServer(
    AbsolutePathPiece edenDir,
    AbsolutePathPiece systemConfigDir,
    AbsolutePathPiece configPath,
    AbsolutePathPiece rocksPath)
    : edenDir_(edenDir),
      systemConfigDir_(systemConfigDir),
      configPath_(configPath),
      rocksPath_(rocksPath) {}

EdenServer::~EdenServer() {
  // Stop all of the mount points.
  // They will each call mountFinished() as they exit.
  {
    std::lock_guard<std::mutex> guard(mountPointsMutex_);
    for (const auto& mountPoint : mountPoints_) {
      fusell::privilegedFuseUnmount(mountPoint.first);
    }
  }

  {
    // Wait for all the mounts to stop, and for mountPoints_ to become empty.
    std::unique_lock<std::mutex> lock(mountPointsMutex_);
    while (!mountPoints_.empty()) {
      mountPointsCV_.wait(lock);
    }
  }
}

void EdenServer::run() {
  acquireEdenLock();
  createThriftServer();
  localStore_ = make_shared<LocalStore>(rocksPath_);

  auto pool =
      make_shared<wangle::CPUThreadPoolExecutor>(FLAGS_num_eden_threads);
  wangle::setCPUExecutor(pool);

  reloadConfig();

  // Remount existing mount points
  folly::dynamic dirs = folly::dynamic::object();
  try {
    dirs = ClientConfig::loadClientDirectoryMap(edenDir_);
  } catch (const std::exception& ex) {
    LOG(ERROR) << "Could not parse config.json file: " << ex.what()
               << " Skipping remount step.";
  }
  for (auto& client : dirs.items()) {
    auto mountInfo = std::make_unique<MountInfo>();
    mountInfo->mountPoint = client.first.c_str();
    auto edenClientPath = edenDir_ + PathComponent("clients") +
        PathComponent(client.second.c_str());
    mountInfo->edenClientPath = edenClientPath.stringPiece().str();
    try {
      handler_->mount(std::move(mountInfo));
    } catch (const std::exception& ex) {
      LOG(ERROR) << "Failed to perform remount for " << client.first.c_str()
                 << ": " << ex.what();
    }
  }
  prepareThriftAddress();
  runThriftServer();
}

void EdenServer::mount(shared_ptr<EdenMount> edenMount) {
  // Add the mount point to mountPoints_.
  // This also makes sure we don't have this path mounted already
  auto mountPath = edenMount->getPath().stringPiece();
  {
    std::lock_guard<std::mutex> guard(mountPointsMutex_);
    auto ret = mountPoints_.emplace(mountPath, edenMount);
    if (!ret.second) {
      // This mount point already exists.
      throw EdenError(folly::to<string>(
          "mount point \"", mountPath, "\" is already mounted"));
    }
  }

  auto onFinish = [this, edenMount]() { this->mountFinished(edenMount.get()); };
  try {
    edenMount->getMountPoint()->start(FLAGS_debug, onFinish);
  } catch (...) {
    // If we fail to start the mount point, call mountFinished()
    // to make sure it gets removed from mountPoints_.
    //
    // Note that we can't perform this clean-up using SCOPE_FAIL() for now, due
    // to a bug in some versions of gcc:
    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62258
    this->mountFinished(edenMount.get());
    throw;
  }

  // Perform all of the bind mounts associated with the client.
  for (auto& bindMount : edenMount->getBindMounts()) {
    auto pathInMountDir = bindMount.pathInMountDir;
    try {
      // If pathInMountDir does not exist, then it must be created before the
      // bind mount is performed.
      boost::system::error_code errorCode;
      boost::filesystem::path mountDir = pathInMountDir.c_str();
      boost::filesystem::create_directories(mountDir, errorCode);

      fusell::privilegedBindMount(
          bindMount.pathInClientDir.c_str(), pathInMountDir.c_str());
    } catch (...) {
      // Consider recording all failed bind mounts in a way that can be
      // communicated back to the caller in a structured way.
      LOG(ERROR) << "Failed to perform bind mount for "
                 << pathInMountDir.stringPiece() << ".";
    }
  }
}

void EdenServer::unmount(StringPiece mountPath) {
  try {
    fusell::privilegedFuseUnmount(mountPath);
  } catch (const std::exception& ex) {
    LOG(ERROR) << "Failed to perform unmount for \"" << mountPath
               << "\": " << folly::exceptionStr(ex);
    throw ex;
  }
}

void EdenServer::mountFinished(EdenMount* edenMount) {
  auto mountPath = edenMount->getPath().stringPiece();
  LOG(INFO) << "mount point \"" << mountPath << "\" stopped";
  {
    std::lock_guard<std::mutex> guard(mountPointsMutex_);
    auto numErased = mountPoints_.erase(mountPath);
    CHECK_EQ(numErased, 1);
    // This notify and the erase above MUST happen while holding
    // mountPointsMutex_ otherwise we can have a race in the case that there
    // are two threads in mountFinished().  If the erasure and the notify are
    // not done under the lock, the predicate check in ~EdenServer will see
    // that mountPoints_ is empty and proceed to delete mountPointsCV_ out
    // from under the other thread(s) as they attempt to call notify_all() on
    // it.
    mountPointsCV_.notify_all();
  }
}

EdenServer::MountList EdenServer::getMountPoints() const {
  MountList results;
  {
    std::lock_guard<std::mutex> guard(mountPointsMutex_);
    for (const auto& entry : mountPoints_) {
      results.emplace_back(entry.second);
    }
  }
  return results;
}

shared_ptr<EdenMount> EdenServer::getMount(StringPiece mountPath) const {
  std::lock_guard<std::mutex> guard(mountPointsMutex_);
  auto it = mountPoints_.find(mountPath);
  if (it == mountPoints_.end()) {
    return nullptr;
  }
  return it->second;
}

void EdenServer::reloadConfig() {
  *configData_.wlock() = make_shared<ConfigData>(ClientConfig::loadConfigData(
      systemConfigDir_.piece(), configPath_.piece()));
}

shared_ptr<EdenServer::ConfigData> EdenServer::getConfig() {
  return *configData_.rlock();
}

shared_ptr<BackingStore> EdenServer::getBackingStore(
    StringPiece type,
    StringPiece name) {
  BackingStoreKey key{type.str(), name.str()};
  SYNCHRONIZED(lockedStores, backingStores_) {
    auto it = lockedStores.find(key);
    if (it != lockedStores.end()) {
      return it->second;
    }

    auto store = createBackingStore(type, name);
    lockedStores.emplace(key, store);
    return store;
  }

  // Ugh.  The SYNCHRONIZED() macro is super lame.
  // We have to return something here, since the compiler can't figure out
  // that we always return inside SYNCHRONIZED.
  LOG(FATAL) << "unreached";
  abort();
}

shared_ptr<BackingStore> EdenServer::createBackingStore(
    StringPiece type,
    StringPiece name) {
  if (type == "null") {
    return make_shared<EmptyBackingStore>();
  } else if (type == "hg") {
    return make_shared<HgBackingStore>(name, localStore_.get());
  } else if (type == "git") {
    return make_shared<GitBackingStore>(name, localStore_.get());
  } else {
    throw std::domain_error(
        folly::to<string>("unsupported backing store type: ", type));
  }
}

void EdenServer::createThriftServer() {
  auto address = getThriftAddress(FLAGS_thrift_address, edenDir_.stringPiece());

  server_ = make_shared<ThriftServer>();
  server_->setMaxConnections(FLAGS_thrift_max_conns);
  server_->setMaxRequests(FLAGS_thrift_max_requests);
  server_->setNumIOWorkerThreads(FLAGS_thrift_num_workers);
  server_->setEnableCodel(FLAGS_thrift_enable_codel);
  server_->setMaxNumPendingConnectionsPerWorker(FLAGS_thrift_queue_len);
  server_->setMinCompressBytes(FLAGS_thrift_min_compress_bytes);

  handler_ = make_shared<EdenServiceHandler>(this);
  server_->setInterface(handler_);
  server_->setAddress(address);
}

void EdenServer::acquireEdenLock() {
  boost::filesystem::path edenPath{edenDir_.stringPiece().str()};
  boost::filesystem::path lockPath = edenPath / "lock";
  lockFile_ = folly::File(lockPath.string(), O_WRONLY | O_CREAT);
  if (!lockFile_.try_lock()) {
    throw std::runtime_error(
        "another instance of Eden appears to be running for " +
        edenDir_.stringPiece().str());
  }
}

void EdenServer::prepareThriftAddress() {
  // If we are serving on a local Unix socket, remove any old socket file
  // that may be left over from a previous instance.
  // We have already acquired the mount point lock at this time, so we know
  // that any existing socket is unused and safe to remove.
  const auto& addr = server_->getAddress();
  if (addr.getFamily() != AF_UNIX) {
    return;
  }
  int rc = unlink(addr.getPath().c_str());
  if (rc != 0 && errno != ENOENT) {
    // This might happen if we don't have permission to remove the file.
    folly::throwSystemError(
        "unable to remove old Eden thrift socket ", addr.getPath());
  }
}

void EdenServer::stop() const {
  server_->stop();
}
}
} // facebook::eden

namespace {

/*
 * Parse the --thrift_address argument, and return a SocketAddress object
 */
folly::SocketAddress getThriftAddress(
    StringPiece argument,
    StringPiece edenDir) {
  folly::SocketAddress addr;

  // If the argument is empty, default to a Unix socket placed next
  // to the mount point
  if (argument.empty()) {
    auto socketPath = getPathToUnixDomainSocket(edenDir);
    addr.setFromPath(socketPath);
    return addr;
  }

  // Check to see if the argument looks like a port number
  uint16_t port;
  bool validPort{false};
  try {
    port = folly::to<uint16_t>(argument);
    validPort = true;
  } catch (const std::range_error& ex) {
    // validPort = false
  }
  if (validPort) {
    addr.setFromLocalPort(port);
    return addr;
  }

  // TODO: also support IPv4:PORT or [IPv6]:PORT

  // Otherwise assume the address refers to a local unix socket path
  addr.setFromPath(argument);
  return addr;
}

std::string getPathToUnixDomainSocket(StringPiece edenDir) {
  boost::filesystem::path edenPath{edenDir.str()};
  boost::filesystem::path socketPath = edenPath / "socket";
  return socketPath.string();
}

} // unnamed namespace