// Copyright 2019 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.

#ifndef PATCHPANEL_ARC_SERVICE_H_
#define PATCHPANEL_ARC_SERVICE_H_

#include <deque>
#include <map>
#include <memory>
#include <set>
#include <string>
#include <vector>

#include <base/memory/weak_ptr.h>
#include <gtest/gtest_prod.h>  // for FRIEND_TEST

#include "patchpanel/address_manager.h"
#include "patchpanel/datapath.h"
#include "patchpanel/device.h"
#include "patchpanel/ipc.pb.h"
#include "patchpanel/shill_client.h"
#include "patchpanel/traffic_forwarder.h"

namespace patchpanel {

class ArcService {
 public:
  class Impl {
   public:
    virtual ~Impl() = default;

    virtual GuestMessage::GuestType guest() const = 0;
    virtual uint32_t id() const = 0;

    // Returns the list of device configurations that were provided to the
    // implementation at creation time plus the one for the ARC device, if
    // applicable. Currently only ARCVM supports this method.
    virtual std::vector<const Device::Config*> GetDeviceConfigs() const = 0;

    virtual bool Start(uint32_t id) = 0;
    virtual void Stop(uint32_t id) = 0;
    virtual bool IsStarted(uint32_t* id = nullptr) const = 0;
    virtual bool OnStartDevice(Device* device) = 0;
    virtual void OnStopDevice(Device* device) = 0;
    virtual void OnDefaultInterfaceChanged(const std::string& new_ifname,
                                           const std::string& prev_ifname) = 0;

   protected:
    Impl() = default;

    // For now each implementation manages its own ARC device since ARCVM is
    // still single-networked.
    std::unique_ptr<Device> arc_device_;
  };

  // Encapsulates all ARC++ container-specific logic.
  class ContainerImpl : public Impl {
   public:
    ContainerImpl(Datapath* datapath,
                  AddressManager* addr_mgr,
                  TrafficForwarder* forwarder,
                  GuestMessage::GuestType guest);
    ~ContainerImpl() = default;

    GuestMessage::GuestType guest() const override;
    uint32_t id() const override;
    std::vector<const Device::Config*> GetDeviceConfigs() const override {
      return {};
    }

    bool Start(uint32_t pid) override;
    void Stop(uint32_t pid) override;
    bool IsStarted(uint32_t* pid = nullptr) const override;
    bool OnStartDevice(Device* device) override;
    void OnStopDevice(Device* device) override;
    void OnDefaultInterfaceChanged(const std::string& new_ifname,
                                   const std::string& prev_ifname) override;

   private:
    uint32_t pid_;
    Datapath* datapath_;
    AddressManager* addr_mgr_;
    TrafficForwarder* forwarder_;
    GuestMessage::GuestType guest_;

    base::WeakPtrFactory<ContainerImpl> weak_factory_{this};
    DISALLOW_COPY_AND_ASSIGN(ContainerImpl);
  };

  // Encapsulates all ARC VM-specific logic.
  class VmImpl : public Impl {
   public:
    // |configs| is an optional list of device configurations that, if provided,
    // will be used to pre-allocated and associate them, when necessary, to
    // devices as they are added. The caller retains ownership of the pointers.
    VmImpl(ShillClient* shill_client,
           Datapath* datapath,
           AddressManager* addr_mgr,
           TrafficForwarder* forwarder,
           const std::vector<Device::Config*>& configs);
    ~VmImpl() = default;

    GuestMessage::GuestType guest() const override;
    uint32_t id() const override;
    std::vector<const Device::Config*> GetDeviceConfigs() const override;

    bool Start(uint32_t cid) override;
    void Stop(uint32_t cid) override;
    bool IsStarted(uint32_t* cid = nullptr) const override;
    bool OnStartDevice(Device* device) override;
    void OnStopDevice(Device* device) override;
    void OnDefaultInterfaceChanged(const std::string& new_ifname,
                                   const std::string& prev_ifname) override;

   private:
    // TODO(garrick): Remove once ARCVM P is gone.
    bool OnStartArcPDevice();
    void OnStopArcPDevice();

    bool IsMultinetEnabled() const;

    uint32_t cid_;
    const ShillClient* const shill_client_;
    Datapath* datapath_;
    AddressManager* addr_mgr_;
    TrafficForwarder* forwarder_;
    std::vector<Device::Config*> configs_;

    DISALLOW_COPY_AND_ASSIGN(VmImpl);
  };

  enum class InterfaceType {
    UNKNOWN,
    ETHERNET,
    WIFI,
    CELL,
  };

  // All pointers are required and cannot be null, and are owned by the caller.
  ArcService(ShillClient* shill_client,
             Datapath* datapath,
             AddressManager* addr_mgr,
             TrafficForwarder* forwarder,
             bool enable_arcvm_multinet);
  ~ArcService();

  bool Start(uint32_t id);
  void Stop(uint32_t id);

  // Returns a list of device configurations. This method only really is useful
  // when ARCVM is running as it enables the caller to discover which
  // configurations, if any, are currently associated to TAP devices.
  std::vector<const Device::Config*> GetDeviceConfigs() const;

 private:
  // Callback from ShillClient, invoked whenever the device list changes.
  // |devices_| will contain all devices currently connected to shill
  // (e.g. "eth0", "wlan0", etc).
  void OnDevicesChanged(const std::set<std::string>& added,
                        const std::set<std::string>& removed);

  // Callback from ShillClient, invoked whenever the default network
  // interface changes or goes away.
  void OnDefaultInterfaceChanged(const std::string& new_ifname,
                                 const std::string& prev_ifname);

  // Build and configure an ARC device for the interface |name| provided by
  // Shill. The new device will be added to |devices_|. If an implementation is
  // already running, the device will be started.
  void AddDevice(const std::string& ifname);

  // Deletes the ARC device; if an implementation is running, the device will be
  // stopped first.
  void RemoveDevice(const std::string& ifname);

  // Starts a device by setting up the bridge and configuring some NAT rules,
  // then invoking the implementation-specific start routine.
  void StartDevice(Device* device);

  // Stops and cleans up any virtual interfaces and associated datapath.
  void StopDevice(Device* device);

  // Creates device configurations for all available IPv4 subnets which will be
  // assigned to devices as they are added.
  void AllocateAddressConfigs();

  // This function will temporarily remove existing devices, reallocate
  // address configurations and re-add existing devices. This is necessary to
  // properly handle the IPv4 addressing binding difference between ARC++ and
  // ARCVM.
  // Returns the list of all configurations ordered by type.
  std::vector<Device::Config*> ReallocateAddressConfigs();

  // Reserve a configuration for an interface.
  std::unique_ptr<Device::Config> AcquireConfig(const std::string& ifname);

  // Returns a configuration to the pool.
  void ReleaseConfig(const std::string& ifname,
                     std::unique_ptr<Device::Config> config);

  ShillClient* shill_client_;
  Datapath* datapath_;
  AddressManager* addr_mgr_;
  TrafficForwarder* forwarder_;
  bool enable_arcvm_multinet_;
  std::unique_ptr<Impl> impl_;
  std::map<InterfaceType, std::deque<std::unique_ptr<Device::Config>>> configs_;
  std::map<std::string, std::unique_ptr<Device>> devices_;

  FRIEND_TEST(ArcServiceTest, StartDevice);
  FRIEND_TEST(ArcServiceTest, StopDevice);
  FRIEND_TEST(ArcServiceTest, VerifyAddrConfigs);
  FRIEND_TEST(ArcServiceTest, VerifyAddrOrder);

  base::WeakPtrFactory<ArcService> weak_factory_{this};
  DISALLOW_COPY_AND_ASSIGN(ArcService);
};

namespace test {
extern GuestMessage::GuestType guest;
}  // namespace test

}  // namespace patchpanel

#endif  // PATCHPANEL_ARC_SERVICE_H_