// Copyright (c) 2012 The Chromium 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 CHROME_BROWSER_EXTENSIONS_API_DIAL_DIAL_SERVICE_H_
#define CHROME_BROWSER_EXTENSIONS_API_DIAL_DIAL_SERVICE_H_

#include <memory>
#include <string>
#include <vector>

#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "base/threading/thread_checker.h"
#include "base/timer/timer.h"
#include "net/base/ip_address.h"
#include "net/log/net_log.h"
#include "net/udp/udp_socket.h"

namespace net {
class IPEndPoint;
class IOBuffer;
class StringIOBuffer;
struct NetworkInterface;
}

namespace extensions {

class DialDeviceData;

// DialService accepts requests to discover devices, sends multiple M-SEARCH
// requests via UDP multicast, and notifies observers when a DIAL-compliant
// device responds.
//
// Each time Discover() is called, kDialNumRequests M-SEARCH requests are sent
// (with a delay of kDialRequestIntervalMillis in between):
//
// Time    Action
// ----    ------
// T1      Request 1 sent, OnDiscoveryReqest() called
// ...
// Tk      Request kDialNumRequests sent, OnDiscoveryReqest() called
// Tf      OnDiscoveryFinished() called
//
// Any time a valid response is received between T1 and Tf, it is parsed and
// OnDeviceDiscovered() is called with the result.  Tf is set to Tk +
// kDialResponseTimeoutSecs (the response timeout passed in each request).
//
// Calling Discover() again between T1 and Tf has no effect.
//
// All relevant constants are defined in dial_service.cc.
class DialService {
 public:
  enum DialServiceErrorCode {
    DIAL_SERVICE_NO_INTERFACES = 0,
    DIAL_SERVICE_SOCKET_ERROR
  };

  class Observer {
   public:
    // Called when a single discovery request was sent.
    virtual void OnDiscoveryRequest(DialService* service) = 0;

    // Called when a device responds to a request.
    virtual void OnDeviceDiscovered(DialService* service,
                                    const DialDeviceData& device) = 0;

    // Called when we have all responses from the last discovery request.
    virtual void OnDiscoveryFinished(DialService* service) = 0;

    // Called when an error occurs.
    virtual void OnError(DialService* service,
                         const DialServiceErrorCode& code) = 0;

   protected:
    virtual ~Observer() {}
  };

  virtual ~DialService() {}

  // Starts a new round of discovery.  Returns |true| if discovery was started
  // successfully or there is already one active. Returns |false| on error.
  virtual bool Discover() = 0;

  // Called by listeners to this service to add/remove themselves as observers.
  virtual void AddObserver(Observer* observer) = 0;
  virtual void RemoveObserver(Observer* observer) = 0;
  virtual bool HasObserver(const Observer* observer) const = 0;
};

// Implements DialService.
//
// NOTE(mfoltz): It would make this class cleaner to refactor most of the state
// associated with a single discovery cycle into its own |DiscoveryOperation|
// object.  This would also simplify lifetime of the object w.r.t. DialRegistry;
// the Registry would not need to create/destroy the Service on demand.
class DialServiceImpl : public DialService,
                        public base::SupportsWeakPtr<DialServiceImpl> {
 public:
  explicit DialServiceImpl(net::NetLog* net_log);
  ~DialServiceImpl() override;

  // DialService implementation
  bool Discover() override;
  void AddObserver(Observer* observer) override;
  void RemoveObserver(Observer* observer) override;
  bool HasObserver(const Observer* observer) const override;

 private:
  // Represents a socket binding to a single network interface.
  class DialSocket {
   public:
    // TODO(imcheng): Consider writing a DialSocket::Delegate interface that
    // declares methods for these callbacks, and taking a ptr to the delegate
    // here.
    DialSocket(
        const base::Closure& discovery_request_cb,
        const base::Callback<void(const DialDeviceData&)>& device_discovered_cb,
        const base::Closure& on_error_cb);
    ~DialSocket();

    // Creates a socket using |net_log| and |net_log_source| and binds it to
    // |bind_ip_address|.
    bool CreateAndBindSocket(const net::IPAddress& bind_ip_address,
                             net::NetLog* net_log,
                             net::NetLog::Source net_log_source);

    // Sends a single discovery request |send_buffer| to |send_address|
    // over the socket.
    void SendOneRequest(const net::IPEndPoint& send_address,
                        const scoped_refptr<net::StringIOBuffer>& send_buffer);

    // Returns true if the socket is closed.
    bool IsClosed();

   private:
    // Checks the result of a socket operation.  The name of the socket
    // operation is given by |operation| and the result of the operation is
    // given by |result|. If the result is an error, closes the socket,
    // calls |on_error_cb_|, and returns |false|.  Returns
    // |true| otherwise. |operation| and |result| are logged.
    bool CheckResult(const char* operation, int result);

    // Closes the socket.
    void Close();

    // Callback invoked for socket writes.
    void OnSocketWrite(int buffer_size, int result);

    // Establishes the callback to read from the socket.  Returns true if
    // successful.
    bool ReadSocket();

    // Callback invoked for socket reads.
    void OnSocketRead(int result);

    // Callback invoked for socket reads.
    void HandleResponse(int bytes_read);

    // Parses a response into a DialDeviceData object. If the DIAL response is
    // invalid or does not contain enough information, then the return
    // value will be false and |device| is not changed.
    static bool ParseResponse(const std::string& response,
                              const base::Time& response_time,
                              DialDeviceData* device);

    // The UDP socket.
    std::unique_ptr<net::UDPSocket> socket_;

    // Buffer for socket reads.
    scoped_refptr<net::IOBufferWithSize> recv_buffer_;

    // The source of of the last socket read.
    net::IPEndPoint recv_address_;

    // Thread checker.
    base::ThreadChecker thread_checker_;

    // The callback to be invoked when a discovery request was made.
    base::Closure discovery_request_cb_;

    // The callback to be invoked when a device has been discovered.
    base::Callback<void(const DialDeviceData&)> device_discovered_cb_;

    // The callback to be invoked when there is an error with socket operations.
    base::Closure on_error_cb_;

    // Marks whether there is an active write callback.
    bool is_writing_;

    // Marks whether there is an active read callback.
    bool is_reading_;

    FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestNotifyOnError);
    FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestOnDeviceDiscovered);
    FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestOnDiscoveryRequest);
    FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestResponseParsing);
    DISALLOW_COPY_AND_ASSIGN(DialSocket);
  };

  // Starts the control flow for one discovery cycle.
  void StartDiscovery();

  // For each network interface in |list|, finds all unqiue IPv4 network
  // interfaces and call |DiscoverOnAddresses()| with their IP addresses.
  void SendNetworkList(const net::NetworkInterfaceList& list);

  // Calls |BindAndAddSocket()| for each address in |ip_addresses|, calls
  // |SendOneRequest()|, and start the timer to finish discovery if needed.
  // The (Address family, interface index) of each address in |ip_addresses|
  // must be unique. If |ip_address| is empty, calls |FinishDiscovery()|.
  void DiscoverOnAddresses(const net::IPAddressList& ip_addresses);

  // Creates a DialSocket, binds it to |bind_ip_address| and if
  // successful, add the DialSocket to |dial_sockets_|.
  void BindAndAddSocket(const net::IPAddress& bind_ip_address);

  // Creates a DialSocket with callbacks to this object.
  std::unique_ptr<DialSocket> CreateDialSocket();

  // Sends a single discovery request to every socket that are currently open.
  void SendOneRequest();

  // Notify observers that a discovery request was made.
  void NotifyOnDiscoveryRequest();

  // Notify observers a device has been discovered.
  void NotifyOnDeviceDiscovered(const DialDeviceData& device_data);

  // Notify observers that there has been an error with one of the DialSockets.
  void NotifyOnError();

  // Called from finish_timer_ when we are done with the current round of
  // discovery.
  void FinishDiscovery();

  // Returns |true| if there are open sockets.
  bool HasOpenSockets();

  // DialSockets for each network interface whose ip address was
  // successfully bound.
  std::vector<std::unique_ptr<DialSocket>> dial_sockets_;

  // The NetLog for this service.
  net::NetLog* net_log_;

  // The NetLog source for this service.
  net::NetLog::Source net_log_source_;

  // The multicast address:port for search requests.
  net::IPEndPoint send_address_;

  // Buffer for socket writes.
  scoped_refptr<net::StringIOBuffer> send_buffer_;

  // True when we are currently doing discovery.
  bool discovery_active_;

  // The number of requests that have been sent in the current discovery.
  int num_requests_sent_;

  // The maximum number of requests to send per discovery cycle.
  int max_requests_;

  // Timer for finishing discovery.
  base::OneShotTimer finish_timer_;

  // The delay for |finish_timer_|; how long to wait for discovery to finish.
  // Setting this to zero disables the timer.
  base::TimeDelta finish_delay_;

  // Timer for sending multiple requests at fixed intervals.
  base::RepeatingTimer request_timer_;

  // The delay for |request_timer_|; how long to wait between successive
  // requests.
  base::TimeDelta request_interval_;

  // List of observers.
  base::ObserverList<Observer> observer_list_;

  // Thread checker.
  base::ThreadChecker thread_checker_;

  friend class DialServiceTest;
  FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestSendMultipleRequests);
  FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestMultipleNetworkInterfaces);
  FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestNotifyOnError);
  FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestOnDeviceDiscovered);
  FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestOnDiscoveryFinished);
  FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestOnDiscoveryRequest);
  FRIEND_TEST_ALL_PREFIXES(DialServiceTest, TestResponseParsing);
  DISALLOW_COPY_AND_ASSIGN(DialServiceImpl);
};

}  // namespace extensions

#endif  // CHROME_BROWSER_EXTENSIONS_API_DIAL_DIAL_SERVICE_H_
