// Copyright 2014 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <chromeos/http/http_transport_curl.h>

#include <limits>

#include <base/bind.h>
#include <base/logging.h>
#include <base/message_loop/message_loop.h>
#include <chromeos/http/http_connection_curl.h>
#include <chromeos/http/http_request.h>
#include <chromeos/strings/string_utils.h>

namespace {

const char kChromeOSCACertificatePath[] = "/usr/share/chromeos-ca-certificates";

}  // namespace

namespace chromeos {
namespace http {
namespace curl {

// This is a class that stores connection data on particular CURL socket
// and provides file descriptor watcher to monitor read and/or write operations
// on the socket's file descriptor.
class Transport::SocketPollData : public base::MessageLoopForIO::Watcher {
 public:
  SocketPollData(const std::shared_ptr<CurlInterface>& curl_interface,
                 CURLM* curl_multi_handle,
                 Transport* transport,
                 curl_socket_t socket_fd)
      : curl_interface_(curl_interface),
        curl_multi_handle_(curl_multi_handle),
        transport_(transport),
        socket_fd_(socket_fd) {}

  // Returns the pointer for the socket-specific file descriptor watcher.
  base::MessageLoopForIO::FileDescriptorWatcher* GetWatcher() {
    return &file_descriptor_watcher_;
  }

 private:
  // Overrides from base::MessageLoopForIO::Watcher.
  void OnFileCanReadWithoutBlocking(int fd) override {
    OnSocketReady(fd, CURL_CSELECT_IN);
  }
  void OnFileCanWriteWithoutBlocking(int fd) override {
    OnSocketReady(fd, CURL_CSELECT_OUT);
  }

  // Data on the socket is available to be read from or written to.
  // Notify CURL of the action it needs to take on the socket file descriptor.
  void OnSocketReady(int fd, int action) {
    CHECK_EQ(socket_fd_, fd) << "Unexpected socket file descriptor";
    CURLMcode code = CURLM_OK;
    do {
      int still_running_count = 0;
      // CURL might return CURLM_CALL_MULTI_PERFORM "error" code to indicate
      // that more data is available and can be processed immediately.
      // In this case, just call curl_multi_socket_action() again.
      code = curl_interface_->MultiSocketAction(
          curl_multi_handle_, socket_fd_, action, &still_running_count);
    } while (code == CURLM_CALL_MULTI_PERFORM);

    if (code == CURLM_OK)
      transport_->ProcessAsyncCurlMessages();
  }

  // The CURL interface to use.
  std::shared_ptr<CurlInterface> curl_interface_;
  // CURL multi-handle associated with the transport.
  CURLM* curl_multi_handle_;
  // Transport object itself.
  Transport* transport_;
  // The socket file descriptor for the connection.
  curl_socket_t socket_fd_;
  // File descriptor watcher to notify us of asynchronous I/O on the FD.
  base::MessageLoopForIO::FileDescriptorWatcher file_descriptor_watcher_;

  DISALLOW_COPY_AND_ASSIGN(SocketPollData);
};

// The request data associated with an asynchronous operation on a particular
// connection.
struct Transport::AsyncRequestData {
  // Success/error callbacks to be invoked at the end of the request.
  SuccessCallback success_callback;
  ErrorCallback error_callback;
  // We store a connection here to make sure the object is alive for
  // as long as asynchronous operation is running.
  std::shared_ptr<Connection> connection;
  // The ID of this request.
  RequestID request_id;
};

Transport::Transport(const std::shared_ptr<CurlInterface>& curl_interface)
    : curl_interface_{curl_interface} {
  VLOG(1) << "curl::Transport created";
}

Transport::Transport(const std::shared_ptr<CurlInterface>& curl_interface,
                     const std::string& proxy)
    : curl_interface_{curl_interface}, proxy_{proxy} {
  VLOG(1) << "curl::Transport created with proxy " << proxy;
}

Transport::~Transport() {
  ShutDownAsyncCurl();
  VLOG(1) << "curl::Transport destroyed";
}

std::shared_ptr<http::Connection> Transport::CreateConnection(
    const std::string& url,
    const std::string& method,
    const HeaderList& headers,
    const std::string& user_agent,
    const std::string& referer,
    chromeos::ErrorPtr* error) {
  std::shared_ptr<http::Connection> connection;
  CURL* curl_handle = curl_interface_->EasyInit();
  if (!curl_handle) {
    LOG(ERROR) << "Failed to initialize CURL";
    chromeos::Error::AddTo(error,
                           FROM_HERE,
                           http::kErrorDomain,
                           "curl_init_failed",
                           "Failed to initialize CURL");
    return connection;
  }

  LOG(INFO) << "Sending a " << method << " request to " << url;
  CURLcode code = curl_interface_->EasySetOptStr(curl_handle, CURLOPT_URL, url);

  if (code == CURLE_OK) {
    code = curl_interface_->EasySetOptStr(curl_handle, CURLOPT_CAPATH,
                                          kChromeOSCACertificatePath);
  }
  if (code == CURLE_OK && !user_agent.empty()) {
    code = curl_interface_->EasySetOptStr(
        curl_handle, CURLOPT_USERAGENT, user_agent);
  }
  if (code == CURLE_OK && !referer.empty()) {
    code =
        curl_interface_->EasySetOptStr(curl_handle, CURLOPT_REFERER, referer);
  }
  if (code == CURLE_OK && !proxy_.empty()) {
    code = curl_interface_->EasySetOptStr(curl_handle, CURLOPT_PROXY, proxy_);
  }
  if (code == CURLE_OK) {
    int64_t timeout_ms = connection_timeout_.InMillisecondsRoundedUp();

    if (timeout_ms > 0 && timeout_ms <= std::numeric_limits<int>::max()) {
      code = curl_interface_->EasySetOptInt(
          curl_handle, CURLOPT_TIMEOUT_MS,
          static_cast<int>(timeout_ms));
    }
  }

  // Setup HTTP request method and optional request body.
  if (code == CURLE_OK) {
    if (method == request_type::kGet) {
      code = curl_interface_->EasySetOptInt(curl_handle, CURLOPT_HTTPGET, 1);
    } else if (method == request_type::kHead) {
      code = curl_interface_->EasySetOptInt(curl_handle, CURLOPT_NOBODY, 1);
    } else if (method == request_type::kPut) {
      code = curl_interface_->EasySetOptInt(curl_handle, CURLOPT_UPLOAD, 1);
    } else {
      // POST and custom request methods
      code = curl_interface_->EasySetOptInt(curl_handle, CURLOPT_POST, 1);
      if (code == CURLE_OK) {
        code = curl_interface_->EasySetOptPtr(
            curl_handle, CURLOPT_POSTFIELDS, nullptr);
      }
      if (code == CURLE_OK && method != request_type::kPost) {
        code = curl_interface_->EasySetOptStr(
            curl_handle, CURLOPT_CUSTOMREQUEST, method);
      }
    }
  }

  if (code != CURLE_OK) {
    AddEasyCurlError(error, FROM_HERE, code, curl_interface_.get());
    curl_interface_->EasyCleanup(curl_handle);
    return connection;
  }

  connection = std::make_shared<http::curl::Connection>(
      curl_handle, method, curl_interface_, shared_from_this());
  if (!connection->SendHeaders(headers, error)) {
    connection.reset();
  }
  return connection;
}

void Transport::RunCallbackAsync(const tracked_objects::Location& from_here,
                                 const base::Closure& callback) {
  base::MessageLoopForIO::current()->PostTask(from_here, callback);
}

RequestID Transport::StartAsyncTransfer(http::Connection* connection,
                                        const SuccessCallback& success_callback,
                                        const ErrorCallback& error_callback) {
  chromeos::ErrorPtr error;
  if (!SetupAsyncCurl(&error)) {
    RunCallbackAsync(
        FROM_HERE, base::Bind(error_callback, 0, base::Owned(error.release())));
    return 0;
  }

  RequestID request_id = ++last_request_id_;

  auto curl_connection = static_cast<http::curl::Connection*>(connection);
  std::unique_ptr<AsyncRequestData> request_data{new AsyncRequestData};
  // Add the request data to |async_requests_| before adding the CURL handle
  // in case CURL feels like calling the socket callback synchronously which
  // will need the data to be in |async_requests_| map already.
  request_data->success_callback = success_callback;
  request_data->error_callback = error_callback;
  request_data->connection =
      std::static_pointer_cast<Connection>(curl_connection->shared_from_this());
  request_data->request_id = request_id;
  async_requests_.emplace(curl_connection, std::move(request_data));
  request_id_map_.emplace(request_id, curl_connection);

  // Add the connection's CURL handle to the multi-handle.
  CURLMcode code = curl_interface_->MultiAddHandle(
      curl_multi_handle_, curl_connection->curl_handle_);
  if (code != CURLM_OK) {
    chromeos::ErrorPtr error;
    AddMultiCurlError(&error, FROM_HERE, code, curl_interface_.get());
    RunCallbackAsync(
        FROM_HERE, base::Bind(error_callback, 0, base::Owned(error.release())));
    async_requests_.erase(curl_connection);
    request_id_map_.erase(request_id);
    return 0;
  }
  return request_id;
}

bool Transport::CancelRequest(RequestID request_id) {
  auto p = request_id_map_.find(request_id);
  if (p == request_id_map_.end()) {
    // The request must have been completed already...
    // This is not necessarily an error condition, so fail gracefully.
    LOG(WARNING) << "HTTP request #" << request_id << " not found";
    return false;
  }
  VLOG(1) << "Canceling HTTP request #" << request_id;
  CleanAsyncConnection(p->second);
  return true;
}

void Transport::SetDefaultTimeout(base::TimeDelta timeout) {
  connection_timeout_ = timeout;
}

void Transport::AddEasyCurlError(chromeos::ErrorPtr* error,
                                 const tracked_objects::Location& location,
                                 CURLcode code,
                                 CurlInterface* curl_interface) {
  chromeos::Error::AddTo(error,
                         location,
                         "curl_easy_error",
                         chromeos::string_utils::ToString(code),
                         curl_interface->EasyStrError(code));
}

void Transport::AddMultiCurlError(chromeos::ErrorPtr* error,
                                  const tracked_objects::Location& location,
                                  CURLMcode code,
                                  CurlInterface* curl_interface) {
  chromeos::Error::AddTo(error,
                         location,
                         "curl_multi_error",
                         chromeos::string_utils::ToString(code),
                         curl_interface->MultiStrError(code));
}

bool Transport::SetupAsyncCurl(chromeos::ErrorPtr* error) {
  if (curl_multi_handle_)
    return true;

  curl_multi_handle_ = curl_interface_->MultiInit();
  if (!curl_multi_handle_) {
    LOG(ERROR) << "Failed to initialize CURL";
    chromeos::Error::AddTo(error,
                           FROM_HERE,
                           http::kErrorDomain,
                           "curl_init_failed",
                           "Failed to initialize CURL");
    return false;
  }

  CURLMcode code = curl_interface_->MultiSetSocketCallback(
      curl_multi_handle_, &Transport::MultiSocketCallback, this);
  if (code == CURLM_OK) {
    code = curl_interface_->MultiSetTimerCallback(
        curl_multi_handle_, &Transport::MultiTimerCallback, this);
  }
  if (code != CURLM_OK) {
    AddMultiCurlError(error, FROM_HERE, code, curl_interface_.get());
    return false;
  }
  return true;
}

void Transport::ShutDownAsyncCurl() {
  if (!curl_multi_handle_)
    return;
  LOG_IF(WARNING, !poll_data_map_.empty())
      << "There are pending requests at the time of transport's shutdown";
  // Make sure we are not leaking any memory here.
  for (const auto& pair : poll_data_map_)
    delete pair.second;
  poll_data_map_.clear();
  curl_interface_->MultiCleanup(curl_multi_handle_);
  curl_multi_handle_ = nullptr;
}

int Transport::MultiSocketCallback(CURL* easy,
                                   curl_socket_t s,
                                   int what,
                                   void* userp,
                                   void* socketp) {
  auto transport = static_cast<Transport*>(userp);
  CHECK(transport) << "Transport must be set for this callback";
  auto poll_data = static_cast<SocketPollData*>(socketp);
  if (!poll_data) {
    // We haven't attached polling data to this socket yet. Let's do this now.
    poll_data = new SocketPollData{transport->curl_interface_,
                                   transport->curl_multi_handle_,
                                   transport,
                                   s};
    transport->poll_data_map_.emplace(std::make_pair(easy, s), poll_data);
    transport->curl_interface_->MultiAssign(
        transport->curl_multi_handle_, s, poll_data);
  }

  if (what == CURL_POLL_NONE) {
    return 0;
  } else if (what == CURL_POLL_REMOVE) {
    // Remove the attached data from the socket.
    transport->curl_interface_->MultiAssign(
        transport->curl_multi_handle_, s, nullptr);
    transport->poll_data_map_.erase(std::make_pair(easy, s));
    // This method can be called indirectly from SocketPollData::OnSocketReady,
    // so delay destruction of SocketPollData object till the next loop cycle.
    base::MessageLoopForIO::current()->DeleteSoon(FROM_HERE, poll_data);
    return 0;
  }

  base::MessageLoopForIO::Mode watch_mode = base::MessageLoopForIO::WATCH_READ;
  switch (what) {
    case CURL_POLL_IN:
      watch_mode = base::MessageLoopForIO::WATCH_READ;
      break;
    case CURL_POLL_OUT:
      watch_mode = base::MessageLoopForIO::WATCH_WRITE;
      break;
    case CURL_POLL_INOUT:
      watch_mode = base::MessageLoopForIO::WATCH_READ_WRITE;
      break;
    default:
      LOG(FATAL) << "Unknown CURL socket action: " << what;
      break;
  }

  // WatchFileDescriptor() can be called with the same controller object
  // (watcher) to amend the watch mode, however this has cumulative effect.
  // For example, if we were watching a file descriptor for READ operations
  // and now call it to watch for WRITE, it will end up watching for both
  // READ and WRITE. This is not what we want here, so stop watching the
  // file descriptor on previous controller before starting with a different
  // mode.
  if (!poll_data->GetWatcher()->StopWatchingFileDescriptor())
    LOG(WARNING) << "Failed to stop watching the previous socket descriptor";
  CHECK(base::MessageLoopForIO::current()->WatchFileDescriptor(
      s, true, watch_mode, poll_data->GetWatcher(), poll_data))
      << "Failed to watch the CURL socket.";
  return 0;
}

// CURL actually uses "long" types in callback signatures, so we must comply.
int Transport::MultiTimerCallback(CURLM* multi,
                                  long timeout_ms,  // NOLINT(runtime/int)
                                  void* userp) {
  auto transport = static_cast<Transport*>(userp);
  if (timeout_ms > 0) {
    transport->timer_delay_ = base::TimeDelta::FromMilliseconds(timeout_ms);
    transport->ScheduleTimer(++transport->current_timer_id_);
  } else {
    // This will effectively cancel the next invocation of the timer.
    ++transport->current_timer_id_;
  }
  return 0;
}

void Transport::OnTimer(int timer_id) {
  if (curl_multi_handle_) {
    int still_running_count = 0;
    curl_interface_->MultiSocketAction(
        curl_multi_handle_, CURL_SOCKET_TIMEOUT, 0, &still_running_count);
    ProcessAsyncCurlMessages();
  }

  if (timer_id == current_timer_id_) {
    // Reschedule a periodic check only if this is the latest timer event.
    // If not, a newer event has already been scheduled, so there is nothing
    // else to do here.
    ScheduleTimer(timer_id);
  }
}

void Transport::ScheduleTimer(int timer_id) {
  base::MessageLoopForIO::current()->PostDelayedTask(
      FROM_HERE,
      base::Bind(&Transport::OnTimer, weak_ptr_factory_.GetWeakPtr(), timer_id),
      timer_delay_);
}

void Transport::ProcessAsyncCurlMessages() {
  CURLMsg* msg = nullptr;
  int msgs_left = 0;
  while ((msg = curl_interface_->MultiInfoRead(curl_multi_handle_,
                                               &msgs_left))) {
    if (msg->msg == CURLMSG_DONE) {
      // Async I/O complete for a connection. Invoke the user callbacks.
      Connection* connection = nullptr;
      CHECK_EQ(CURLE_OK,
               curl_interface_->EasyGetInfoPtr(
                   msg->easy_handle,
                   CURLINFO_PRIVATE,
                   reinterpret_cast<void**>(&connection)));
      CHECK(connection != nullptr);
      OnTransferComplete(connection, msg->data.result);
    }
  }
}

void Transport::OnTransferComplete(Connection* connection, CURLcode code) {
  auto p = async_requests_.find(connection);
  CHECK(p != async_requests_.end()) << "Unknown connection";
  AsyncRequestData* request_data = p->second.get();
  if (code != CURLE_OK) {
    chromeos::ErrorPtr error;
    AddEasyCurlError(&error, FROM_HERE, code, curl_interface_.get());
    RunCallbackAsync(FROM_HERE,
                     base::Bind(request_data->error_callback,
                                p->second->request_id,
                                base::Owned(error.release())));
  } else {
    chromeos::ErrorPtr error;
    // Rewind the response data stream to the beginning so the clients can
    // read the data back.
    if (request_data->connection->response_data_ &&
        !request_data->connection->response_data_->SetPosition(0, &error)) {
      RunCallbackAsync(FROM_HERE,
                       base::Bind(request_data->error_callback,
                                  p->second->request_id,
                                  base::Owned(error.release())));
    } else {
      std::unique_ptr<Response> resp{new Response{request_data->connection}};
      RunCallbackAsync(FROM_HERE,
                       base::Bind(request_data->success_callback,
                                  p->second->request_id,
                                  base::Passed(&resp)));
    }
  }
  // In case of an error on CURL side, we would have dispatched the error
  // callback and we need to clean up the current connection, however the
  // error callback has no reference to the connection itself and
  // |async_requests_| is the only reference to the shared pointer that
  // maintains the lifetime of |connection| and possibly even this Transport
  // object instance. As a result, if we call CleanAsyncConnection() directly,
  // there is a chance that this object might be deleted.
  // Instead, schedule an asynchronous task to clean up the connection.
  RunCallbackAsync(FROM_HERE,
                   base::Bind(&Transport::CleanAsyncConnection,
                              weak_ptr_factory_.GetWeakPtr(),
                              connection));
}

void Transport::CleanAsyncConnection(Connection* connection) {
  auto p = async_requests_.find(connection);
  CHECK(p != async_requests_.end()) << "Unknown connection";
  // Remove the request data from the map first, since this might be the only
  // reference to the Connection class and even possibly to this Transport.
  auto request_data = std::move(p->second);

  // Remove associated request ID.
  request_id_map_.erase(request_data->request_id);

  // Remove the connection's CURL handle from multi-handle.
  curl_interface_->MultiRemoveHandle(curl_multi_handle_,
                                     connection->curl_handle_);

  // Remove all the socket data associated with this connection.
  auto iter = poll_data_map_.begin();
  while (iter != poll_data_map_.end()) {
    if (iter->first.first == connection->curl_handle_)
      iter = poll_data_map_.erase(iter);
    else
      ++iter;
  }
  // Remove pending asynchronous request data.
  // This must be last since there is a chance of this object being
  // destroyed as the result. See the comment in Transport::OnTransferComplete.
  async_requests_.erase(p);
}

}  // namespace curl
}  // namespace http
}  // namespace chromeos