// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MOJO_CORE_NODE_CONTROLLER_H_
#define MOJO_CORE_NODE_CONTROLLER_H_

#include <map>
#include <memory>
#include <optional>
#include <string>
#include <string_view>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#include "base/containers/queue.h"
#include "base/containers/span.h"
#include "base/functional/callback.h"
#include "base/memory/scoped_refptr.h"
#include "base/memory/writable_shared_memory_region.h"
#include "base/process/process.h"
#include "base/task/single_thread_task_runner.h"
#include "build/build_config.h"
#include "mojo/core/atomic_flag.h"
#include "mojo/core/node_channel.h"
#include "mojo/core/ports/event.h"
#include "mojo/core/ports/name.h"
#include "mojo/core/ports/node.h"
#include "mojo/core/ports/node_delegate.h"
#include "mojo/core/system_impl_export.h"
#include "mojo/public/cpp/platform/platform_handle.h"

namespace mojo {
namespace core {

class Broker;
class Core;

// A set of NodeNames that is bounded by a maximum size.
// If the max size is reached, it will delete the older half of stored names.
class BoundedPeerSet {
 public:
  BoundedPeerSet();
  BoundedPeerSet(const BoundedPeerSet&) = delete;
  BoundedPeerSet& operator=(const BoundedPeerSet&) = delete;

  ~BoundedPeerSet();

  void Insert(const ports::NodeName& name);
  bool Contains(const ports::NodeName& name);

 private:
  static constexpr int kHalfSize = 50000;

  std::unordered_set<ports::NodeName> old_set_;
  std::unordered_set<ports::NodeName> new_set_;
};

// The owner of ports::Node which facilitates core EDK implementation. All
// public interface methods are safe to call from any thread.
class MOJO_SYSTEM_IMPL_EXPORT NodeController : public ports::NodeDelegate,
                                               public NodeChannel::Delegate {
 public:
  class PortObserver : public ports::UserData {
   public:
    virtual void OnPortStatusChanged() = 0;

   protected:
    ~PortObserver() override = default;
  };

  // |core| owns and out-lives us.
  NodeController();

  NodeController(const NodeController&) = delete;
  NodeController& operator=(const NodeController&) = delete;

  ~NodeController() override;

  const ports::NodeName& name() const { return name_; }
  ports::Node* node() const { return node_.get(); }
  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner() const {
    return io_task_runner_;
  }

  // Called exactly once, shortly after construction, and before any other
  // methods are called on this object.
  void SetIOTaskRunner(
      scoped_refptr<base::SingleThreadTaskRunner> io_task_runner);

  // Sends an invitation to a remote process (via |connection_params|) to join
  // this process's graph of connected processes as a broker client.
  void SendBrokerClientInvitation(
      base::Process target_process,
      ConnectionParams connection_params,
      const std::vector<std::pair<std::string, ports::PortRef>>& attached_ports,
      const ProcessErrorCallback& process_error_callback);

  // Connects this node to the process which invited it to be a broker client.
  void AcceptBrokerClientInvitation(ConnectionParams connection_params);

  // Connects this node to a peer node. On success, |port| will be merged with
  // the corresponding port in the peer node.
  void ConnectIsolated(ConnectionParams connection_params,
                       const ports::PortRef& port,
                       std::string_view connection_name);

  // Sets a port's observer. If |observer| is null the port's current observer
  // is removed.
  void SetPortObserver(const ports::PortRef& port,
                       scoped_refptr<PortObserver> observer);

  // Closes a port. Use this in lieu of calling Node::ClosePort() directly, as
  // it ensures the port's observer has also been removed.
  void ClosePort(const ports::PortRef& port);

  // Sends a message on a port to its peer.
  int SendUserMessage(const ports::PortRef& port_ref,
                      std::unique_ptr<ports::UserMessageEvent> message);

  // Merges a local port |port| into a port reserved by |name| in the node which
  // invited this node.
  void MergePortIntoInviter(const std::string& name,
                            const ports::PortRef& port);

  // Merges two local ports together.
  int MergeLocalPorts(const ports::PortRef& port0, const ports::PortRef& port1);

  // Creates a new shared buffer for use in the current process.
  base::WritableSharedMemoryRegion CreateSharedBuffer(size_t num_bytes);

  // Request that the Node be shut down cleanly. This may take an arbitrarily
  // long time to complete, at which point |callback| will be called.
  //
  // Note that while it is safe to continue using the NodeController's public
  // interface after requesting shutdown, you do so at your own risk and there
  // is NO guarantee that new messages will be sent or ports will complete
  // transfer.
  void RequestShutdown(base::OnceClosure callback);

  // Notifies the NodeController that we received a bad message from the given
  // node.  To avoid losing error reports the caller should ensure that the
  // source node |HasBadMessageHandler| before calling |NotifyBadMessageFrom|.
  void NotifyBadMessageFrom(const ports::NodeName& source_node,
                            const std::string& error);

  // Returns whether |source_node| exists and has a bad message handler.
  bool HasBadMessageHandler(const ports::NodeName& source_node);

  // Force-closes the connection to another process to simulate connection
  // failures for testing. |process_id| must correspond to a process to which
  // this node has an active NodeChannel.
  void ForceDisconnectProcessForTesting(base::ProcessId process_id);

  static void DeserializeRawBytesAsEventForFuzzer(
      base::span<const unsigned char> data);
  static void DeserializeMessageAsEventForFuzzer(Channel::MessagePtr message);

  scoped_refptr<NodeChannel> GetBrokerChannel();

 private:
  friend Core;

  using NodeMap =
      std::unordered_map<ports::NodeName, scoped_refptr<NodeChannel>>;
  using OutgoingMessageQueue = base::queue<Channel::MessagePtr>;
  using PortMap = std::map<std::string, ports::PortRef>;

  struct IsolatedConnection {
    IsolatedConnection();
    IsolatedConnection(const IsolatedConnection& other);
    IsolatedConnection(IsolatedConnection&& other);
    IsolatedConnection(scoped_refptr<NodeChannel> channel,
                       const ports::PortRef& local_port,
                       std::string_view name);
    ~IsolatedConnection();

    IsolatedConnection& operator=(const IsolatedConnection& other);
    IsolatedConnection& operator=(IsolatedConnection&& other);

    // NOTE: |channel| is null once the connection is fully established.
    scoped_refptr<NodeChannel> channel;
    ports::PortRef local_port;
    std::string name;
  };

  void SendBrokerClientInvitationOnIOThread(
      base::Process target_process,
      ConnectionParams connection_params,
      ports::NodeName temporary_node_name,
      const ProcessErrorCallback& process_error_callback);
  void FinishSendBrokerClientInvitationOnIOThread(
      base::Process target_process,
      ConnectionParams connection_params,
      ports::NodeName temporary_node_name,
      Channel::HandlePolicy handle_policy,
      const ProcessErrorCallback& process_error_callback);

  void AcceptBrokerClientInvitationOnIOThread(
      ConnectionParams connection_params,
      std::optional<PlatformHandle> broker_host_handle);

  void ConnectIsolatedOnIOThread(ConnectionParams connection_params,
                                 ports::PortRef port,
                                 const std::string& connection_name);

  scoped_refptr<NodeChannel> GetPeerChannel(const ports::NodeName& name);
  scoped_refptr<NodeChannel> GetInviterChannel();

  void AddPeer(const ports::NodeName& name,
               scoped_refptr<NodeChannel> channel,
               bool start_channel,
               bool allow_name_reuse = false);
  void DropPeer(const ports::NodeName& name, NodeChannel* channel);
  void SendPeerEvent(const ports::NodeName& name, ports::ScopedEvent event);
  void DropAllPeers();

  // ports::NodeDelegate:
  void ForwardEvent(const ports::NodeName& node,
                    ports::ScopedEvent event) override;
  void BroadcastEvent(ports::ScopedEvent event) override;
  void PortStatusChanged(const ports::PortRef& port) override;

  // NodeChannel::Delegate:
  void OnAcceptInvitee(const ports::NodeName& from_node,
                       const ports::NodeName& inviter_name,
                       const ports::NodeName& token) override;
  void OnAcceptInvitation(const ports::NodeName& from_node,
                          const ports::NodeName& token,
                          const ports::NodeName& invitee_name) override;
  void OnAddBrokerClient(const ports::NodeName& from_node,
                         const ports::NodeName& client_name,
                         base::ProcessHandle process_handle) override;
  void OnBrokerClientAdded(const ports::NodeName& from_node,
                           const ports::NodeName& client_name,
                           PlatformHandle broker_channel) override;
  void OnAcceptBrokerClient(const ports::NodeName& from_node,
                            const ports::NodeName& broker_name,
                            PlatformHandle broker_channel,
                            const uint64_t broker_capabilities) override;
  void OnEventMessage(const ports::NodeName& from_node,
                      Channel::MessagePtr message) override;
  void OnRequestPortMerge(const ports::NodeName& from_node,
                          const ports::PortName& connector_port_name,
                          const std::string& token) override;
  void OnRequestIntroduction(const ports::NodeName& from_node,
                             const ports::NodeName& name) override;
  void OnIntroduce(const ports::NodeName& from_node,
                   const ports::NodeName& name,
                   PlatformHandle channel_handle,
                   const uint64_t remote_capailities) override;
  void OnBroadcast(const ports::NodeName& from_node,
                   Channel::MessagePtr message) override;
#if BUILDFLAG(IS_WIN)
  void OnRelayEventMessage(const ports::NodeName& from_node,
                           base::ProcessHandle from_process,
                           const ports::NodeName& destination,
                           Channel::MessagePtr message) override;
  void OnEventMessageFromRelay(const ports::NodeName& from_node,
                               const ports::NodeName& source_node,
                               Channel::MessagePtr message) override;
#endif
  void OnAcceptPeer(const ports::NodeName& from_node,
                    const ports::NodeName& token,
                    const ports::NodeName& peer_name,
                    const ports::PortName& port_name) override;
  void OnChannelError(const ports::NodeName& from_node,
                      NodeChannel* channel) override;

  // Cancels all pending port merges. These are merges which are supposed to
  // be requested from the inviter ASAP, and they may be cancelled if the
  // connection to the inviter is broken or never established.
  void CancelPendingPortMerges();

  // Marks this NodeController for destruction when the IO thread shuts down.
  // This is used in case Core is torn down before the IO thread. Must only be
  // called on the IO thread.
  void DestroyOnIOThreadShutdown();

  // If there is a registered shutdown callback (meaning shutdown has been
  // requested, this checks the Node's status to see if clean shutdown is
  // possible. If so, shutdown is performed and the shutdown callback is run.
  void AttemptShutdownIfRequested();

  // See |ForceDisconnectProcessForTesting()|.
  void ForceDisconnectProcessForTestingOnIOThread(base::ProcessId process_id);

  // Mark a port that it is about to be merged. This allows us to do a security
  // check on the incoming port merge that this port was intended to be merged.
  void RecordPendingPortMerge(const ports::PortRef& port);

  // These are safe to access from any thread as long as the Node is alive.
  const ports::NodeName name_;
  const std::unique_ptr<ports::Node> node_;
  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;

  // Guards |peers_| and |pending_peer_messages_|.
  base::Lock peers_lock_;

  // Channels to known peers, including inviter and invitees, if any.
  NodeMap peers_;
  BoundedPeerSet dropped_peers_;

  // Outgoing message queues for peers we've heard of but can't yet talk to.
  std::unordered_map<ports::NodeName, OutgoingMessageQueue>
      pending_peer_messages_;

  // Guards |reserved_ports_|.
  base::Lock reserved_ports_lock_;

  // Ports reserved by name, per peer.
  std::map<ports::NodeName, PortMap> reserved_ports_;

  // Guards |pending_port_merges_| and |reject_pending_merges_|.
  base::Lock pending_port_merges_lock_;

  // A set of port merge requests awaiting inviter connection.
  std::vector<std::pair<std::string, ports::PortRef>> pending_port_merges_;

  // Indicates that new merge requests should be rejected because the inviter
  // has disconnected.
  bool reject_pending_merges_ = false;

  // Guards |inviter_name_| and |bootstrap_inviter_channel_|.
  base::Lock inviter_lock_;

  // The name of the node which invited us to join its network, if any.
  ports::NodeName inviter_name_;

  // A temporary reference to the inviter channel before we know their name.
  scoped_refptr<NodeChannel> bootstrap_inviter_channel_;

  // Guards |broker_name_|, |pending_broker_clients_|, and
  // |pending_relay_messages_|.
  base::Lock broker_lock_;

  // The name of our broker node, if any.
  ports::NodeName broker_name_;

  // A queue of remote broker clients waiting to be connected to the broker.
  base::queue<ports::NodeName> pending_broker_clients_;

  // Messages waiting to be relayed by the broker once it's known.
  std::unordered_map<ports::NodeName, OutgoingMessageQueue>
      pending_relay_messages_;

  // Guards |shutdown_callback_|.
  base::Lock shutdown_lock_;

  // Set by RequestShutdown(). If this is non-null, the controller will
  // begin polling the Node to see if clean shutdown is possible any time the
  // Node's state is modified by the controller.
  base::OnceClosure shutdown_callback_;
  // Flag to fast-path checking |shutdown_callback_|.
  AtomicFlag shutdown_callback_flag_;

  // All other fields below must only be accessed on the I/O thread, i.e., the
  // thread on which `io_task_runner_` runs tasks.

  // Channels to invitees during handshake.
  NodeMap pending_invitations_;

  std::map<ports::NodeName, IsolatedConnection> pending_isolated_connections_;
  std::map<std::string, ports::NodeName> named_isolated_connections_;

  // Indicates whether this object should delete itself on IO thread shutdown.
  // Must only be accessed from the IO thread.
  bool destroy_on_io_thread_shutdown_ = false;

#if !BUILDFLAG(IS_APPLE) && !BUILDFLAG(IS_NACL) && !BUILDFLAG(IS_FUCHSIA)
  // Broker for sync shared buffer creation on behalf of broker clients.
  std::unique_ptr<Broker> broker_;
#endif
};

}  // namespace core
}  // namespace mojo

#endif  // MOJO_CORE_NODE_CONTROLLER_H_