// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "components/sync/engine/net/http_bridge.h"

#include <stddef.h>

#include <utility>

#include "base/functional/bind.h"
#include "base/location.h"
#include "base/metrics/histogram_functions.h"
#include "base/metrics/histogram_macros.h"
#include "base/synchronization/waitable_event.h"
#include "base/task/sequenced_task_runner.h"
#include "base/task/thread_pool.h"
#include "base/threading/thread_restrictions.h"
#include "components/variations/net/variations_http_headers.h"
#include "google_apis/credentials_mode.h"
#include "net/base/load_flags.h"
#include "net/base/net_errors.h"
#include "net/http/http_request_headers.h"
#include "net/http/http_response_headers.h"
#include "net/traffic_annotation/network_traffic_annotation.h"
#include "services/network/public/cpp/resource_request.h"
#include "services/network/public/cpp/simple_url_loader.h"
#include "services/network/public/mojom/url_response_head.mojom.h"
#include "third_party/zlib/google/compression_utils.h"

namespace syncer {

namespace {

// It's possible for an http request to be silently stalled. We set a time
// limit for all http requests, beyond which the request is cancelled and
// treated as a transient failure.
constexpr base::TimeDelta kMaxHttpRequestTime = base::Minutes(5);

// Helper method for logging timeouts via UMA.
void LogTimeout(bool timed_out) {
  UMA_HISTOGRAM_BOOLEAN("Sync.URLFetchTimedOut", timed_out);
}

}  // namespace

HttpBridgeFactory::HttpBridgeFactory(
    const std::string& user_agent,
    std::unique_ptr<network::PendingSharedURLLoaderFactory>
        pending_url_loader_factory)
    : user_agent_(user_agent) {
  // Some tests pass null'ed out pending_url_loader_factory instances.
  if (pending_url_loader_factory) {
    url_loader_factory_ = network::SharedURLLoaderFactory::Create(
        std::move(pending_url_loader_factory));
  }
}

HttpBridgeFactory::~HttpBridgeFactory() = default;

scoped_refptr<HttpPostProvider> HttpBridgeFactory::Create() {
  DCHECK(url_loader_factory_);

  scoped_refptr<HttpPostProvider> http = new HttpBridge(
      user_agent_,
      base::ThreadPool::CreateSequencedTaskRunner({base::MayBlock()}),
      url_loader_factory_->Clone());
  return http;
}

HttpBridge::URLFetchState::URLFetchState() = default;
HttpBridge::URLFetchState::~URLFetchState() = default;

HttpBridge::HttpBridge(
    const std::string& user_agent,
    scoped_refptr<base::SequencedTaskRunner> network_task_runner,
    std::unique_ptr<network::PendingSharedURLLoaderFactory>
        pending_url_loader_factory)
    : user_agent_(user_agent),
      http_post_completed_(base::WaitableEvent::ResetPolicy::AUTOMATIC,
                           base::WaitableEvent::InitialState::NOT_SIGNALED),
      pending_url_loader_factory_(std::move(pending_url_loader_factory)),
      network_task_runner_(network_task_runner) {}

HttpBridge::~HttpBridge() {
  // Note: This may run on either the sync thread or the network thread!
#if DCHECK_IS_ON()
  {
    base::AutoLock lock(fetch_state_lock_);

    // All the network resources must have been destroyed on the network thread
    // *before* the HttpBridge itself gets destroyed (which can happen either on
    // the network thread or on the sync thread).
    DCHECK(!fetch_state_.url_loader);
    DCHECK(!fetch_state_.http_request_timeout_timer);
    DCHECK(!url_loader_factory_);
  }
#endif
}

void HttpBridge::SetExtraRequestHeaders(const char* headers) {
  DCHECK(extra_headers_.empty())
      << "HttpBridge::SetExtraRequestHeaders called twice.";
  extra_headers_.assign(headers);
}

void HttpBridge::SetURL(const GURL& url) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
#if DCHECK_IS_ON()
  {
    base::AutoLock lock(fetch_state_lock_);
    DCHECK(!fetch_state_.request_completed);
  }
  DCHECK(url_for_request_.is_empty())
      << "HttpBridge::SetURL called more than once?!";
#endif
  url_for_request_ = url;
}

void HttpBridge::SetPostPayload(const char* content_type,
                                int content_length,
                                const char* content) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
#if DCHECK_IS_ON()
  {
    base::AutoLock lock(fetch_state_lock_);
    DCHECK(!fetch_state_.request_completed);
  }
  DCHECK(content_type_.empty()) << "Bridge payload already set.";
  DCHECK_GE(content_length, 0) << "Content length < 0";
#endif
  content_type_ = content_type;
  if (!content || (content_length == 0)) {
    DCHECK_EQ(content_length, 0);
    request_content_ = " ";  // TODO(timsteele): URLFetcher requires non-empty
                             // content for POSTs whereas CURL does not, for now
                             // we hack this to support the sync backend.
  } else {
    request_content_.assign(content, content_length);
  }
}

bool HttpBridge::MakeSynchronousPost(int* net_error_code,
                                     int* http_status_code) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
#if DCHECK_IS_ON()
  {
    base::AutoLock lock(fetch_state_lock_);
    DCHECK(!fetch_state_.request_completed);
  }
  DCHECK(url_for_request_.is_valid()) << "Invalid URL for request";
  DCHECK(!content_type_.empty()) << "Payload not set";
#endif

  if (!network_task_runner_->PostTask(
          FROM_HERE,
          base::BindOnce(&HttpBridge::CallMakeAsynchronousPost, this))) {
    // This usually happens when we're in a unit test.
    LOG(WARNING) << "Could not post CallMakeAsynchronousPost task";
    return false;
  }

  // Block until network request completes or is aborted. See
  // OnURLFetchComplete and Abort.
  {
    base::ScopedAllowBaseSyncPrimitives allow_wait;
    http_post_completed_.Wait();
  }

  base::AutoLock lock(fetch_state_lock_);
  DCHECK(fetch_state_.request_completed || fetch_state_.aborted);
  *net_error_code = fetch_state_.net_error_code;
  *http_status_code = fetch_state_.http_status_code;
  return fetch_state_.request_succeeded;
}

scoped_refptr<network::SharedURLLoaderFactory>
HttpBridge::CreateSharedURLLoader() {
  DCHECK(pending_url_loader_factory_);
  return network::SharedURLLoaderFactory::Create(
      std::move(pending_url_loader_factory_));
}

void HttpBridge::MakeAsynchronousPost() {
  DCHECK(network_task_runner_->RunsTasksInCurrentSequence());

  base::AutoLock lock(fetch_state_lock_);
  DCHECK(!fetch_state_.request_completed);
  if (fetch_state_.aborted) {
    return;
  }

  // Start the timer on the network thread (the same thread progress is made
  // on, and on which the url fetcher lives).
  DCHECK(!fetch_state_.http_request_timeout_timer);
  fetch_state_.http_request_timeout_timer = std::make_unique<base::DelayTimer>(
      FROM_HERE, kMaxHttpRequestTime, this, &HttpBridge::OnURLLoadTimedOut);
  fetch_state_.http_request_timeout_timer->Reset();

  url_loader_factory_ = CreateSharedURLLoader();
  DCHECK(url_loader_factory_);

  fetch_state_.start_time = base::Time::Now();
  net::NetworkTrafficAnnotationTag traffic_annotation =
      net::DefineNetworkTrafficAnnotation("sync_http_bridge", R"(
        semantics {
          sender: "Chrome Sync"
          description:
            "Chrome Sync synchronizes profile data between Chromium clients "
            "and Google for a given user account."
          trigger:
            "User makes a change to syncable profile data after enabling sync "
            "on the device."
          data:
            "The device and user identifiers, along with any profile data that "
            "is changing."
          destination: GOOGLE_OWNED_SERVICE
        }
        policy {
          cookies_allowed: NO
          setting:
            "Users can disable Chrome Sync by going into the profile settings "
            "and choosing to Sign Out."
          chrome_policy {
            SyncDisabled {
              policy_options {mode: MANDATORY}
              SyncDisabled: true
            }
          }
        })");
  auto resource_request = std::make_unique<network::ResourceRequest>();
  resource_request->url = url_for_request_;
  resource_request->method = "POST";
  resource_request->load_flags =
      net::LOAD_BYPASS_CACHE | net::LOAD_DISABLE_CACHE;
  resource_request->credentials_mode =
      google_apis::GetOmitCredentialsModeForGaiaRequests();

  if (!extra_headers_.empty()) {
    resource_request->headers.AddHeadersFromString(extra_headers_);
  }

  resource_request->headers.SetHeader("Content-Encoding", "gzip");
  resource_request->headers.SetHeader(net::HttpRequestHeaders::kUserAgent,
                                      user_agent_);

  variations::AppendVariationsHeader(
      url_for_request_, variations::InIncognito::kNo,
      variations::SignedIn::kYes, resource_request.get());

  fetch_state_.url_loader = network::SimpleURLLoader::Create(
      std::move(resource_request), traffic_annotation);
  network::SimpleURLLoader* url_loader = fetch_state_.url_loader.get();

  std::string request_to_send;
  compression::GzipCompress(request_content_, &request_to_send);
  url_loader->AttachStringForUpload(request_to_send, content_type_);

  // Sync relies on HTTP errors being detectable (and distinct from
  // net/connection errors).
  url_loader->SetAllowHttpErrorResults(true);

  url_loader->SetOnUploadProgressCallback(
      base::BindRepeating(&HttpBridge::OnURLLoadUploadProgress, this));
  url_loader->DownloadToStringOfUnboundedSizeUntilCrashAndDie(
      url_loader_factory_.get(),
      base::BindOnce(&HttpBridge::OnURLLoadComplete, this));
}

int HttpBridge::GetResponseContentLength() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  base::AutoLock lock(fetch_state_lock_);
  DCHECK(fetch_state_.request_completed);
  return fetch_state_.response_content.size();
}

const char* HttpBridge::GetResponseContent() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  base::AutoLock lock(fetch_state_lock_);
  DCHECK(fetch_state_.request_completed);
  return fetch_state_.response_content.data();
}

const std::string HttpBridge::GetResponseHeaderValue(
    const std::string& name) const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  base::AutoLock lock(fetch_state_lock_);
  DCHECK(fetch_state_.request_completed);

  std::string value;
  fetch_state_.response_headers->EnumerateHeader(nullptr, name, &value);
  return value;
}

void HttpBridge::Abort() {
  base::AutoLock lock(fetch_state_lock_);

  DCHECK(!fetch_state_.aborted);
  if (fetch_state_.aborted || fetch_state_.request_completed) {
    return;
  }

  fetch_state_.aborted = true;

  // Schedule deletion/release of the network resources on the network thread.
  network_task_runner_->DeleteSoon(FROM_HERE,
                                   std::move(fetch_state_.url_loader));
  network_task_runner_->DeleteSoon(
      FROM_HERE, std::move(fetch_state_.http_request_timeout_timer));
  network_task_runner_->ReleaseSoon(FROM_HERE, std::move(url_loader_factory_));

  fetch_state_.net_error_code = net::ERR_ABORTED;
  http_post_completed_.Signal();
}

void HttpBridge::OnURLLoadComplete(std::unique_ptr<std::string> response_body) {
  DCHECK(network_task_runner_->RunsTasksInCurrentSequence());

  base::AutoLock lock(fetch_state_lock_);

  // If the fetch completes in the window between Abort() and
  // DestroyURLLoaderOnIOThread() this will still run. Abort() has already
  // reported the result, so no extra work is needed.
  if (fetch_state_.aborted) {
    return;
  }

  network::SimpleURLLoader* url_loader = fetch_state_.url_loader.get();

  int http_status_code = -1;
  if (url_loader->ResponseInfo() && url_loader->ResponseInfo()->headers) {
    http_status_code = url_loader->ResponseInfo()->headers->response_code();
    fetch_state_.response_headers = url_loader->ResponseInfo()->headers;
  }

  OnURLLoadCompleteInternal(http_status_code, url_loader->NetError(),
                            url_loader->GetFinalURL(),
                            std::move(response_body));
}

void HttpBridge::OnURLLoadCompleteInternal(
    int http_status_code,
    int net_error_code,
    const GURL& final_url,
    std::unique_ptr<std::string> response_body) {
  DCHECK(network_task_runner_->RunsTasksInCurrentSequence());
  DCHECK(!fetch_state_.aborted);

  // Stop the request timer now that the request completed.
  fetch_state_.http_request_timeout_timer = nullptr;

  fetch_state_.end_time = base::Time::Now();
  fetch_state_.request_completed = true;
  fetch_state_.request_succeeded =
      net_error_code == net::OK && http_status_code != -1;
  fetch_state_.http_status_code = http_status_code;
  fetch_state_.net_error_code = net_error_code;

  if (fetch_state_.request_succeeded) {
    LogTimeout(false);
  }
  base::UmaHistogramSparse("Sync.URLFetchResponse",
                           fetch_state_.request_succeeded
                               ? fetch_state_.http_status_code
                               : fetch_state_.net_error_code);

  // Use a real (non-debug) log to facilitate troubleshooting in the wild.
  VLOG(2) << "HttpBridge::OnURLFetchComplete for: " << final_url.spec();
  VLOG(1) << "HttpBridge received response code: "
          << fetch_state_.http_status_code;

  if (response_body) {
    fetch_state_.response_content = std::move(*response_body);
  }

  fetch_state_.url_loader.reset();
  url_loader_factory_ = nullptr;

  // Wake the blocked syncer thread in MakeSynchronousPost.
  // WARNING: DONT DO ANYTHING AFTER THIS CALL! `this` may be deleted!
  http_post_completed_.Signal();
}

void HttpBridge::OnURLLoadUploadProgress(uint64_t position, uint64_t total) {
  DCHECK(network_task_runner_->RunsTasksInCurrentSequence());
  // Reset the delay when forward progress is made.
  base::AutoLock lock(fetch_state_lock_);
  if (fetch_state_.http_request_timeout_timer) {
    fetch_state_.http_request_timeout_timer->Reset();
  }
}

void HttpBridge::OnURLLoadTimedOut() {
  DCHECK(network_task_runner_->RunsTasksInCurrentSequence());

  base::AutoLock lock(fetch_state_lock_);
  if (!fetch_state_.url_loader) {
    return;
  }

  LogTimeout(true);
  DVLOG(1) << "Sync url fetch timed out. Canceling.";

  fetch_state_.end_time = base::Time::Now();
  fetch_state_.request_completed = true;
  fetch_state_.request_succeeded = false;
  fetch_state_.http_status_code = -1;
  fetch_state_.net_error_code = net::ERR_TIMED_OUT;

  // This method is called by the timer, not the url fetcher implementation,
  // so it's safe to delete the fetcher here.
  fetch_state_.url_loader.reset();
  url_loader_factory_ = nullptr;

  // Timer is smart enough to handle being deleted as part of the invoked task.
  fetch_state_.http_request_timeout_timer = nullptr;

  // Wake the blocked syncer thread in MakeSynchronousPost.
  // WARNING: DONT DO ANYTHING AFTER THIS CALL! `this` may be deleted!
  http_post_completed_.Signal();
}

}  // namespace syncer