// Copyright 2018 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 SHILL_PORTAL_DETECTOR_H_
#define SHILL_PORTAL_DETECTOR_H_

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

#include <base/callback.h>
#include <base/cancelable_callback.h>
#include <base/memory/ref_counted.h>
#include <base/memory/weak_ptr.h>
#include <brillo/http/http_request.h>
#include <gtest/gtest_prod.h>  // for FRIEND_TEST

#include "shill/http_request.h"
#include "shill/http_url.h"
#include "shill/net/shill_time.h"
#include "shill/net/sockets.h"
#include "shill/refptr_types.h"

namespace shill {

class EventDispatcher;
class Metrics;
class Time;

// The PortalDetector class implements the portal detection
// facility in shill, which is responsible for checking to see
// if a connection has "general internet connectivity".
//
// This information can be used for ranking one connection
// against another, or for informing UI and other components
// outside the connection manager whether the connection seems
// available for "general use" or if further user action may be
// necessary (e.g, click through of a WiFi Hotspot's splash
// page).
//
// This is achieved by using one or more trial attempts
// to access a URL and expecting a specific response.  Any result
// that deviates from this result (DNS or HTTP errors, as well as
// deviations from the expected content) are considered failures.
class PortalDetector {
 public:
  // The Phase enum indicates the phase at which the probe fails.
  enum class Phase {
    kUnknown,
    kConnection,  // Failure to establish connection with server
    kDNS,         // Failure to resolve hostname or DNS server failure
    kHTTP,        // Failure to read or write to server
    kContent      // Content mismatch in response
  };

  enum class Status { kFailure, kSuccess, kTimeout, kRedirect };

  struct Properties {
    Properties()
        : http_url_string(kDefaultHttpUrl),
          https_url_string(kDefaultHttpsUrl),
          fallback_http_url_strings(kDefaultFallbackHttpUrls) {}
    Properties(const std::string& http_url_string,
               const std::string& https_url_string,
               const std::vector<std::string>& fallback_http_url_strings)
        : http_url_string(http_url_string),
          https_url_string(https_url_string),
          fallback_http_url_strings(fallback_http_url_strings) {}
    bool operator==(const Properties& b) const {
      return http_url_string == b.http_url_string &&
             https_url_string == b.https_url_string &&
             std::set<std::string>(fallback_http_url_strings.begin(),
                                   fallback_http_url_strings.end()) ==
                 std::set<std::string>(b.fallback_http_url_strings.begin(),
                                       b.fallback_http_url_strings.end());
    }

    std::string http_url_string;
    std::string https_url_string;
    std::vector<std::string> fallback_http_url_strings;
  };

  struct Result {
    Result() {}
    Result(Phase phase, Status status) : phase(phase), status(status) {}
    Result(Phase phase, Status status, int num_attempts)
        : phase(phase), status(status), num_attempts(num_attempts) {}

    Phase phase = Phase::kUnknown;
    Status status = Status::kFailure;

    // Total number of connectivity trials attempted.
    // This includes failure, timeout and successful attempts.
    int num_attempts = 0;

    // Non-empty redirect URL if status is kRedirect.
    std::string redirect_url_string;

    // Probe URL used to reach redirect URL if status is kRedirect.
    std::string probe_url_string;

    // The HTTP response status code from the http probe.
    int status_code = 0;
  };

  static const char kDefaultHttpUrl[];
  static const char kDefaultHttpsUrl[];
  static const std::vector<std::string> kDefaultFallbackHttpUrls;
  static const int kInitialCheckIntervalSeconds;
  static const int kMaxPortalCheckIntervalSeconds;
  static const char kDefaultCheckPortalList[];

  PortalDetector(
      ConnectionRefPtr connection,
      EventDispatcher* dispatcher,
      Metrics* metrics,
      const base::Callback<void(const PortalDetector::Result& http_result,
                                const PortalDetector::Result& https_result)>&
          callback);
  PortalDetector(const PortalDetector&) = delete;
  PortalDetector& operator=(const PortalDetector&) = delete;

  virtual ~PortalDetector();

  // Static method used to map a portal detection phase to a string.  This
  // includes the phases for connection, DNS, HTTP, returned content and
  // unknown.
  static const std::string PhaseToString(Phase phase);

  // Static method to map from the result of a portal detection phase to a
  // status string. This method supports success, timeout and failure.
  static const std::string StatusToString(Status status);

  // Static method mapping from HttpRequest responses to ConntectivityTrial
  // phases for portal detection. For example, if the HttpRequest result is
  // HttpRequest::kResultDNSFailure, this method returns a
  // PortalDetector::Result with the phase set to
  // Phase::kDNS and the status set to
  // Status::kFailure.
  static Result GetPortalResultForRequestResult(HttpRequest::Result result);

  // Start a portal detection test.  Returns true if |props.http_url_string| and
  // |props.https_url_string| correctly parse as URLs.  Returns false (and does
  // not start) if they fail to parse.
  //
  // As each attempt completes the callback handed to the constructor will
  // be called.
  virtual bool StartAfterDelay(const Properties& props, int delay_seconds);

  // End the current portal detection process if one exists, and do not call
  // the callback.
  virtual void Stop();

  // Returns whether portal request is "in progress".
  virtual bool IsInProgress();

  // Method used to adjust the start delay in the event of a retry.
  // Calculates the elapsed time between the most recent attempt and the point
  // the retry is scheduled.  Adjusts the delay to the difference between
  // |delay| and the elapsed time so that the retry starts |delay| seconds after
  // the previous attempt.
  virtual int AdjustStartDelay(int init_delay_seconds);

 private:
  friend class PortalDetectorTest;
  FRIEND_TEST(PortalDetectorTest, StartAttemptFailed);
  FRIEND_TEST(PortalDetectorTest, AdjustStartDelayImmediate);
  FRIEND_TEST(PortalDetectorTest, AdjustStartDelayAfterDelay);
  FRIEND_TEST(PortalDetectorTest, AttemptCount);
  FRIEND_TEST(PortalDetectorTest, RequestSuccess);
  FRIEND_TEST(PortalDetectorTest, RequestHTTPFailureHTTPSSuccess);
  FRIEND_TEST(PortalDetectorTest, RequestFail);
  FRIEND_TEST(PortalDetectorTest, InvalidURL);
  FRIEND_TEST(PortalDetectorTest, IsActive);

  // Picks the HTTP probe URL based on |attempt_count_|. Returns kDefaultHttpUrl
  // if this is the first attempt. Otherwise, randomly returns an element of
  // kDefaultFallbackHttpUrls.
  const std::string PickHttpProbeUrl(const Properties& props);

  // Internal method to update the start time of the next event.  This is used
  // to keep attempts spaced by the right duration in the event of a retry.
  void UpdateAttemptTime(int delay_seconds);

  // Called after each trial to return |http_result| and |https_result| after
  // attempting to determine connectivity status.
  void CompleteAttempt(Result http_result, Result https_result);

  // Start a trial with the supplied delay in ms.
  void StartTrialAfterDelay(int start_delay_milliseconds);

  // Start a portal detection test.  Returns true if |props.http_url_string| and
  // |props.https_url_string| correctly parse as URLs.  Returns false (and does
  // not start) if they fail to parse.
  //
  // After a trial completes, the callback supplied in the constructor is
  // called.
  bool StartTrial(const Properties& props, int start_delay_milliseconds);

  // Internal method used to start the actual connectivity trial, called after
  // the start delay completes.
  void StartTrialTask();

  // Called after a request finishes. Will call CompleteTrial once all probes
  // are done.
  void CompleteRequest();

  // Callback used to return data read from the HTTP HttpRequest.
  void HttpRequestSuccessCallback(
      std::shared_ptr<brillo::http::Response> response);

  // Callback used to return data read from the HTTPS HttpRequest.
  void HttpsRequestSuccessCallback(
      std::shared_ptr<brillo::http::Response> response);

  // Callback used to return the error from the HTTP HttpRequest.
  void HttpRequestErrorCallback(HttpRequest::Result result);

  // Callback used to return the error from the HTTPS HttpRequest.
  void HttpsRequestErrorCallback(HttpRequest::Result result);

  // Internal method used to clean up state and call CompleteAttempt.
  void CompleteTrial(Result http_result, Result https_result);

  // Internal method used to cancel the timeout timer and stop an active
  // HttpRequest.
  void CleanupTrial();

  // Method to return if the connection is being actively tested.
  virtual bool IsActive();

  int attempt_count_;
  struct timeval attempt_start_time_;
  ConnectionRefPtr connection_;
  EventDispatcher* dispatcher_;
  Metrics* metrics_;
  base::WeakPtrFactory<PortalDetector> weak_ptr_factory_;
  base::Callback<void(const Result&, const Result&)> portal_result_callback_;
  Time* time_;
  std::unique_ptr<HttpRequest> http_request_;
  std::unique_ptr<HttpRequest> https_request_;
  std::unique_ptr<Result> http_result_;
  std::unique_ptr<Result> https_result_;

  std::string http_url_string_;
  std::string https_url_string_;
  base::CancelableClosure trial_;
  bool is_active_;
};

}  // namespace shill

#endif  // SHILL_PORTAL_DETECTOR_H_