// 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.

#include "shill/portal_detector.h"

#include <base/bind.h>
#include <base/logging.h>
#include <base/rand_util.h>
#include <base/strings/pattern.h>
#include <base/strings/string_number_conversions.h>
#include <base/strings/string_util.h>
#include <base/strings/stringprintf.h>
#include <chromeos/dbus/service_constants.h>

#include "shill/dns_client.h"
#include "shill/event_dispatcher.h"
#include "shill/logging.h"
#include "shill/metrics.h"

namespace {
const char kLinuxUserAgent[] =
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) "
    "Chrome/89.0.4389.114 Safari/537.36";
const brillo::http::HeaderList kHeaders{
    {brillo::http::request_header::kUserAgent, kLinuxUserAgent},
};

// Base time interval between two portal detection attempts. Should be doubled
// at every new attempt.
constexpr base::TimeDelta kPortalCheckInterval =
    base::TimeDelta::FromSeconds(3);
// Max time interval between two portal detection attempts.
constexpr base::TimeDelta kMaxPortalCheckInterval =
    base::TimeDelta::FromMinutes(5);
}  // namespace

namespace shill {

namespace Logging {
static auto kModuleLogScope = ScopeLogger::kPortal;
static std::string ObjectID(const PortalDetector* pd) {
  return pd->LoggingTag();
}
}  // namespace Logging

const char PortalDetector::kDefaultCheckPortalList[] = "ethernet,wifi,cellular";

const char PortalDetector::kDefaultHttpUrl[] =
    "http://www.gstatic.com/generate_204";
const char PortalDetector::kDefaultHttpsUrl[] =
    "https://www.google.com/generate_204";
const std::vector<std::string> PortalDetector::kDefaultFallbackHttpUrls{
    "http://www.google.com/gen_204",
    "http://play.googleapis.com/generate_204",
    "http://connectivitycheck.gstatic.com/generate_204",
};

PortalDetector::PortalDetector(EventDispatcher* dispatcher,
                               Metrics* metrics,
                               base::Callback<void(const Result&)> callback)
    : attempt_count_(0),
      last_attempt_start_time_(),
      dispatcher_(dispatcher),
      metrics_(metrics),
      weak_ptr_factory_(this),
      portal_result_callback_(callback),
      is_active_(false) {}

PortalDetector::~PortalDetector() {
  Stop();
}

const std::string PortalDetector::PickHttpProbeUrl(const Properties& props) {
  if (attempt_count_ == 0 || props.fallback_http_url_strings.empty()) {
    return props.http_url_string;
  }
  return props.fallback_http_url_strings[base::RandInt(
      0, props.fallback_http_url_strings.size() - 1)];
}

bool PortalDetector::Start(const PortalDetector::Properties& props,
                           const std::string& ifname,
                           const IPAddress& src_address,
                           const std::vector<std::string>& dns_list,
                           base::TimeDelta delay) {
  logging_tag_ =
      ifname + " " + IPAddress::GetAddressFamilyName(src_address.family());

  SLOG(this, 3) << "In " << __func__;

  // This step is rerun on each attempt, but trying it here will allow
  // Start() to abort on any obviously malformed URL strings.
  HttpUrl http_url, https_url;
  http_url_string_ = PickHttpProbeUrl(props);
  https_url_string_ = props.https_url_string;
  if (!http_url.ParseFromString(http_url_string_)) {
    LOG(ERROR) << LoggingTag() << ": Failed to parse HTTP probe URL string: "
               << props.http_url_string;
    return false;
  }

  if (!https_url.ParseFromString(https_url_string_)) {
    LOG(ERROR) << "Failed to parse HTTPS probe URL string: "
               << props.https_url_string;
    return false;
  }

  attempt_count_++;
  if (http_request_ || https_request_) {
    CleanupTrial();
  } else {
    http_request_ =
        std::make_unique<HttpRequest>(dispatcher_, LoggingTag() + " HTTP probe",
                                      ifname, src_address, dns_list);
    // For non-default URLs, allow for secure communication with both Google and
    // non-Google servers.
    bool allow_non_google_https = (https_url_string_ != kDefaultHttpsUrl);
    https_request_ = std::make_unique<HttpRequest>(
        dispatcher_, LoggingTag() + " HTTPS probe", ifname, src_address,
        dns_list, allow_non_google_https);
  }
  trial_.Reset(base::Bind(&PortalDetector::StartTrialTask,
                          weak_ptr_factory_.GetWeakPtr()));
  dispatcher_->PostDelayedTask(FROM_HERE, trial_.callback(),
                               delay.InMilliseconds());
  // |last_attempt_start_time_| is calculated based on the current time and
  // |delay|.  This is used to determine when to schedule the next portal
  // detection attempt after this one.
  last_attempt_start_time_ = base::Time::NowFromSystemTime() + delay;

  return true;
}

void PortalDetector::StartTrialTask() {
  LOG(INFO) << LoggingTag() << ": Starting trial";
  base::Callback<void(std::shared_ptr<brillo::http::Response>)>
      http_request_success_callback(
          base::Bind(&PortalDetector::HttpRequestSuccessCallback,
                     weak_ptr_factory_.GetWeakPtr()));
  base::Callback<void(HttpRequest::Result)> http_request_error_callback(
      base::Bind(&PortalDetector::HttpRequestErrorCallback,
                 weak_ptr_factory_.GetWeakPtr()));
  HttpRequest::Result http_result = http_request_->Start(
      http_url_string_, kHeaders, http_request_success_callback,
      http_request_error_callback);
  if (http_result != HttpRequest::kResultInProgress) {
    // If the http probe fails to start, complete the trial with a failure
    // Result for https.
    LOG(ERROR) << LoggingTag()
               << ": HTTP probe failed to start. Aborting trial.";
    PortalDetector::Result result;
    result.http_phase = GetPortalPhaseForRequestResult(http_result);
    result.http_status = GetPortalStatusForRequestResult(http_result);
    result.https_phase = PortalDetector::Phase::kContent;
    result.https_status = PortalDetector::Status::kFailure;
    CompleteTrial(result);
    return;
  }

  result_ = std::make_unique<Result>();

  base::Callback<void(std::shared_ptr<brillo::http::Response>)>
      https_request_success_callback(
          base::Bind(&PortalDetector::HttpsRequestSuccessCallback,
                     weak_ptr_factory_.GetWeakPtr()));
  base::Callback<void(HttpRequest::Result)> https_request_error_callback(
      base::Bind(&PortalDetector::HttpsRequestErrorCallback,
                 weak_ptr_factory_.GetWeakPtr()));
  HttpRequest::Result https_result = https_request_->Start(
      https_url_string_, kHeaders, https_request_success_callback,
      https_request_error_callback);
  if (https_result != HttpRequest::kResultInProgress) {
    result_->https_phase = GetPortalPhaseForRequestResult(https_result);
    result_->https_status = GetPortalStatusForRequestResult(https_result);
    LOG(ERROR) << LoggingTag() << ": HTTPS probe failed to start";
    // To find the portal sign-in url, wait for the HTTP probe to complete
    // before completing the trial and calling |portal_result_callback_|.
  }
  is_active_ = true;
}

void PortalDetector::CompleteTrial(Result result) {
  LOG(INFO) << LoggingTag()
            << ": Trial completed. HTTP probe: phase=" << result.http_phase
            << ", status=" << result.http_status
            << ". HTTPS probe: phase=" << result.https_phase
            << ", status=" << result.https_status;
  result.num_attempts = attempt_count_;
  metrics_->NotifyPortalDetectionMultiProbeResult(result);
  CleanupTrial();
  portal_result_callback_.Run(result);
}

void PortalDetector::CleanupTrial() {
  result_.reset();
  if (http_request_)
    http_request_->Stop();
  if (https_request_)
    https_request_->Stop();

  is_active_ = false;
}

void PortalDetector::Stop() {
  SLOG(this, 3) << "In " << __func__;

  attempt_count_ = 0;
  if (!http_request_ && !https_request_)
    return;

  CleanupTrial();
  http_request_.reset();
  https_request_.reset();
}

void PortalDetector::HttpRequestSuccessCallback(
    std::shared_ptr<brillo::http::Response> response) {
  // TODO(matthewmwang): check for 0 length data as well
  int status_code = response->GetStatusCode();
  result_->http_probe_completed = true;
  result_->http_phase = Phase::kContent;
  result_->http_status_code = status_code;
  if (status_code == brillo::http::status_code::NoContent) {
    result_->http_status = Status::kSuccess;
  } else if (status_code == brillo::http::status_code::Redirect) {
    result_->http_status = Status::kRedirect;
    std::string redirect_url_string =
        response->GetHeader(brillo::http::response_header::kLocation);
    if (redirect_url_string.empty()) {
      LOG(ERROR) << LoggingTag() << ": No Location field in redirect header.";
    } else {
      HttpUrl redirect_url;
      if (!redirect_url.ParseFromString(redirect_url_string)) {
        LOG(ERROR) << LoggingTag()
                   << ": Unable to parse redirect URL: " << redirect_url_string;
        result_->http_status = Status::kFailure;
      } else {
        LOG(INFO) << LoggingTag() << ": Redirect URL: " << redirect_url_string;
        result_->redirect_url_string = redirect_url_string;
        result_->probe_url_string = http_url_string_;
      }
    }
  } else {
    result_->http_status = Status::kFailure;
  }
  LOG(INFO) << LoggingTag() << ": HTTP probe response code=" << status_code
            << " status=" << result_->http_status;
  if (result_->IsComplete())
    CompleteTrial(*result_);
}

void PortalDetector::HttpsRequestSuccessCallback(
    std::shared_ptr<brillo::http::Response> response) {
  int status_code = response->GetStatusCode();
  // The HTTPS probe is successful and indicates no portal was present only if
  // it gets the expected 204 status code. Any other result is a failure.
  result_->https_probe_completed = true;
  result_->https_phase = Phase::kContent;
  result_->https_status = (status_code == brillo::http::status_code::NoContent)
                              ? Status::kSuccess
                              : Status::kFailure;
  LOG(INFO) << LoggingTag() << ": HTTPS probe response code=" << status_code
            << " status=" << result_->https_status;
  if (result_->IsComplete())
    CompleteTrial(*result_);
}

void PortalDetector::HttpRequestErrorCallback(HttpRequest::Result http_result) {
  result_->http_probe_completed = true;
  result_->http_phase = GetPortalPhaseForRequestResult(http_result);
  result_->http_status = GetPortalStatusForRequestResult(http_result);
  LOG(INFO) << LoggingTag()
            << ": HTTP probe failed with phase=" << result_->http_phase
            << " status=" << result_->http_status;
  if (result_->IsComplete())
    CompleteTrial(*result_);
}

void PortalDetector::HttpsRequestErrorCallback(
    HttpRequest::Result https_result) {
  result_->https_probe_completed = true;
  result_->https_phase = GetPortalPhaseForRequestResult(https_result);
  result_->https_status = GetPortalStatusForRequestResult(https_result);
  LOG(INFO) << LoggingTag()
            << ": HTTPS probe failed with phase=" << result_->http_phase
            << " status=" << result_->http_status;
  if (result_->IsComplete())
    CompleteTrial(*result_);
}

bool PortalDetector::IsInProgress() {
  return is_active_;
}

base::TimeDelta PortalDetector::GetNextAttemptDelay() {
  if (attempt_count_ == 0)
    return base::TimeDelta();

  base::TimeDelta next_interval =
      kPortalCheckInterval * (1 << (attempt_count_ - 1));
  if (next_interval > kMaxPortalCheckInterval)
    next_interval = kMaxPortalCheckInterval;

  const auto next_attempt = last_attempt_start_time_ + next_interval;
  const auto now = base::Time::NowFromSystemTime();
  if (next_attempt < now)
    return base::TimeDelta();

  return next_attempt - now;
}

// static
const std::string PortalDetector::PhaseToString(Phase phase) {
  switch (phase) {
    case Phase::kConnection:
      return kPortalDetectionPhaseConnection;
    case Phase::kDNS:
      return kPortalDetectionPhaseDns;
    case Phase::kHTTP:
      return kPortalDetectionPhaseHttp;
    case Phase::kContent:
      return kPortalDetectionPhaseContent;
    case Phase::kUnknown:
    default:
      return kPortalDetectionPhaseUnknown;
  }
}

// static
const std::string PortalDetector::StatusToString(Status status) {
  switch (status) {
    case Status::kSuccess:
      return kPortalDetectionStatusSuccess;
    case Status::kTimeout:
      return kPortalDetectionStatusTimeout;
    case Status::kRedirect:
      return kPortalDetectionStatusRedirect;
    case Status::kFailure:
    default:
      return kPortalDetectionStatusFailure;
  }
}

// static
PortalDetector::Phase PortalDetector::GetPortalPhaseForRequestResult(
    HttpRequest::Result result) {
  switch (result) {
    case HttpRequest::kResultSuccess:
      return Phase::kContent;
    case HttpRequest::kResultDNSFailure:
      return Phase::kDNS;
    case HttpRequest::kResultDNSTimeout:
      return Phase::kDNS;
    case HttpRequest::kResultConnectionFailure:
      return Phase::kConnection;
    case HttpRequest::kResultHTTPFailure:
      return Phase::kHTTP;
    case HttpRequest::kResultHTTPTimeout:
      return Phase::kHTTP;
    case HttpRequest::kResultInvalidInput:
    case HttpRequest::kResultUnknown:
    default:
      return Phase::kUnknown;
  }
}

// static
PortalDetector::Status PortalDetector::GetPortalStatusForRequestResult(
    HttpRequest::Result result) {
  switch (result) {
    case HttpRequest::kResultSuccess:
      // The request completed without receiving the expected payload.
      return Status::kFailure;
    case HttpRequest::kResultDNSFailure:
      return Status::kFailure;
    case HttpRequest::kResultDNSTimeout:
      return Status::kTimeout;
    case HttpRequest::kResultConnectionFailure:
      return Status::kFailure;
    case HttpRequest::kResultHTTPFailure:
      return Status::kFailure;
    case HttpRequest::kResultHTTPTimeout:
      return Status::kTimeout;
    case HttpRequest::kResultInvalidInput:
    case HttpRequest::kResultUnknown:
    default:
      return Status::kFailure;
  }
}

Service::ConnectState PortalDetector::Result::GetConnectionState() const {
  if (http_phase != PortalDetector::Phase::kContent) {
    return Service::kStateNoConnectivity;
  }
  if (http_status == PortalDetector::Status::kSuccess &&
      https_status == PortalDetector::Status::kSuccess) {
    return Service::kStateOnline;
  }
  if (http_status == PortalDetector::Status::kRedirect) {
    return redirect_url_string.empty() ? Service::kStatePortalSuspected
                                       : Service::kStateRedirectFound;
  }
  if (http_status == PortalDetector::Status::kTimeout &&
      https_status != PortalDetector::Status::kSuccess) {
    return Service::kStateNoConnectivity;
  }
  return Service::kStatePortalSuspected;
}

std::string PortalDetector::LoggingTag() const {
  return logging_tag_ + " attempt=" + std::to_string(attempt_count_);
}

bool PortalDetector::Result::IsComplete() const {
  return http_probe_completed && https_probe_completed;
}

std::ostream& operator<<(std::ostream& stream, PortalDetector::Phase phase) {
  return stream << PortalDetector::PhaseToString(phase);
}

std::ostream& operator<<(std::ostream& stream, PortalDetector::Status status) {
  return stream << PortalDetector::StatusToString(status);
}

}  // namespace shill