// Copyright 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.

#import "ios/net/crn_http_protocol_handler.h"

#include "base/command_line.h"
#include "base/logging.h"
#include "base/mac/bind_objc_block.h"
#include "base/mac/scoped_nsobject.h"
#include "base/memory/ref_counted.h"
#include "base/single_thread_task_runner.h"
#include "base/strings/string_util.h"
#include "base/strings/sys_string_conversions.h"
#include "base/strings/utf_string_conversions.h"
#import "ios/net/clients/crn_network_client_protocol.h"
#import "ios/net/crn_http_protocol_handler_proxy_with_client_thread.h"
#import "ios/net/http_protocol_logging.h"
#include "ios/net/nsurlrequest_util.h"
#import "ios/net/protocol_handler_util.h"
#include "ios/net/request_tracker.h"
#include "net/base/auth.h"
#include "net/base/elements_upload_data_stream.h"
#include "net/base/io_buffer.h"
#include "net/base/load_flags.h"
#import "net/base/mac/url_conversions.h"
#include "net/base/net_errors.h"
#include "net/base/net_util.h"
#include "net/base/upload_bytes_element_reader.h"
#include "net/http/http_request_headers.h"
#include "net/url_request/redirect_info.h"
#include "net/url_request/url_request.h"
#include "net/url_request/url_request_context.h"
#include "net/url_request/url_request_context_getter.h"

namespace net {
class HttpProtocolHandlerCore;
}

namespace {

// Size of the buffer used to read the net::URLRequest.
const int kIOBufferSize = 4096;

// Global instance of the HTTPProtocolHandlerDelegate.
net::HTTPProtocolHandlerDelegate* g_protocol_handler_delegate = nullptr;

// Empty callback.
void DoNothing(bool flag) {}

}  // namespace

// Bridge class to forward NSStream events to the HttpProtocolHandlerCore.
// Lives on the IO thread.
@interface CRWHTTPStreamDelegate : NSObject<NSStreamDelegate> {
 @private
  // The object is owned by |_core| and has a weak reference to it.
  __weak net::HttpProtocolHandlerCore* _core;
}
- (instancetype)initWithHttpProtocolHandlerCore:
    (net::HttpProtocolHandlerCore*)core;
// NSStreamDelegate method.
- (void)stream:(NSStream*)theStream handleEvent:(NSStreamEvent)streamEvent;
@end

#pragma mark -
#pragma mark HttpProtocolHandlerCore

namespace net {

// static
void HTTPProtocolHandlerDelegate::SetInstance(
    HTTPProtocolHandlerDelegate* delegate) {
  g_protocol_handler_delegate = delegate;
}

// The HttpProtocolHandlerCore class is the bridge between the URLRequest
// and the NSURLProtocolClient.
// Threading and ownership details:
// - The HttpProtocolHandlerCore is owned by the HttpProtocolHandler
// - The HttpProtocolHandler is owned by the system and can be deleted anytime
// - All the methods of HttpProtocolHandlerCore must be called on the IO thread,
//   except its constructor that can be called from any thread.

// Implementation notes from Apple's "Read Me About CustomHttpProtocolHandler":
//
// An NSURLProtocol subclass is expected to call the various methods of the
// NSURLProtocolClient from the loading thread, including all of the following:
//  -URLProtocol:wasRedirectedToRequest:redirectResponse:
//  -URLProtocol:didReceiveResponse:cacheStoragePolicy:
//  -URLProtocol:didLoadData:
//  -URLProtocol:didFinishLoading:
//  -URLProtocol:didFailWithError:
//  -URLProtocol:didReceiveAuthenticationChallenge:
//  -URLProtocol:didCancelAuthenticationChallenge:
//
// The NSURLProtocol subclass must call the client callbacks in the expected
// order. This breaks down into three phases:
//  o pre-response -- In the initial phase the NSURLProtocol can make any number
//    of -URLProtocol:wasRedirectedToRequest:redirectResponse: and
//    -URLProtocol:didReceiveAuthenticationChallenge: callbacks.
//  o response -- It must then call
//    -URLProtocol:didReceiveResponse:cacheStoragePolicy: to indicate the
//    arrival of a definitive response.
//  o post-response -- After receive a response it may then make any number of
//    -URLProtocol:didLoadData: callbacks, followed by a
//    -URLProtocolDidFinishLoading: callback.
//
// The -URLProtocol:didFailWithError: callback can be made at any time
// (although keep in mind the following point).
//
// The NSProtocol subclass must only send one authentication challenge to the
// client at a time. After calling
// -URLProtocol:didReceiveAuthenticationChallenge:, it must wait for the client
// to resolve the challenge before calling any callbacks other than
// -URLProtocol:didCancelAuthenticationChallenge:. This means that, if the
// connection fails while there is an outstanding authentication challenge, the
// NSURLProtocol subclass must call
// -URLProtocol:didCancelAuthenticationChallenge: before calling
// -URLProtocol:didFailWithError:.
class HttpProtocolHandlerCore
    : public base::RefCountedThreadSafe<HttpProtocolHandlerCore,
                                        HttpProtocolHandlerCore>,
      public URLRequest::Delegate {
 public:
  HttpProtocolHandlerCore(NSURLRequest* request);
  // Starts the network request, and forwards the data downloaded from the
  // network to |base_client|.
  void Start(id<CRNNetworkClientProtocol> base_client);
  // Cancels the request.
  void Cancel();
  // Called by NSStreamDelegate. Used for POST requests having a HTTPBodyStream.
  void HandleStreamEvent(NSStream* stream, NSStreamEvent event);

  // URLRequest::Delegate methods:
  void OnReceivedRedirect(URLRequest* request,
                          const RedirectInfo& new_url,
                          bool* defer_redirect) override;
  void OnAuthRequired(URLRequest* request,
                      AuthChallengeInfo* auth_info) override;
  void OnCertificateRequested(URLRequest* request,
                              SSLCertRequestInfo* cert_request_info) override;
  void OnSSLCertificateError(URLRequest* request,
                             const SSLInfo& ssl_info,
                             bool is_hsts_host) override;
  void OnResponseStarted(URLRequest* request) override;
  void OnReadCompleted(URLRequest* request, int bytes_read) override;

 private:
  friend class base::RefCountedThreadSafe<HttpProtocolHandlerCore,
                                          HttpProtocolHandlerCore>;
  friend class base::DeleteHelper<HttpProtocolHandlerCore>;
  ~HttpProtocolHandlerCore() override;

  // RefCountedThreadSafe traits implementation:
  static void Destruct(const HttpProtocolHandlerCore* x);

  void SetLoadFlags();
  void StopNetRequest();
  // Stop listening the delegate on the IO run loop.
  void StopListeningStream(NSStream* stream);
  NSInteger IOSErrorCode(int os_error);
  void StopRequestWithError(NSInteger ns_error_code, int net_error_code);
  // Pass an authentication result provided by a client down to the network
  // request. |auth_ok| is true if the authentication was successful, false
  // otherwise. |username| and |password| should be populated with the correct
  // credentials if |auth_ok| is true.
  void CompleteAuthentication(bool auth_ok,
                              const base::string16& username,
                              const base::string16& password);
  void StripPostSpecificHeaders(NSMutableURLRequest* request);
  void CancelAfterSSLError();
  void ContinueAfterSSLError();
  void SSLErrorCallback(bool carryOn);
  void HostStateCallback(bool carryOn);
  void StartReading();
  // Pushes |client| at the end of the |clients_| array and sets it as the top
  // level client.
  void PushClient(id<CRNNetworkClientProtocol> client);
  // Pushes all of the clients in |clients|, calling PushClient() on each one.
  void PushClients(NSArray* clients);

  base::ThreadChecker thread_checker_;

  // Contains CRNNetworkClientProtocol objects. The first client is the original
  // NSURLProtocol client, and the following clients are ordered such as the
  // ith client is responsible for managing the (i-1)th client.
  base::scoped_nsobject<NSMutableArray> clients_;
  // Weak. This is the last client in |clients_|.
  id<CRNNetworkClientProtocol> top_level_client_;
  scoped_refptr<IOBuffer> buffer_;
  base::scoped_nsobject<NSMutableURLRequest> request_;
  // Stream delegate to read the HTTPBodyStream.
  base::scoped_nsobject<CRWHTTPStreamDelegate> stream_delegate_;
  // Vector of readers used to accumulate a POST data stream.
  ScopedVector<UploadElementReader> post_data_readers_;

  // This cannot be a scoped pointer because it must be deleted on the IO
  // thread.
  URLRequest* net_request_;

  base::WeakPtr<RequestTracker> tracker_;

  DISALLOW_COPY_AND_ASSIGN(HttpProtocolHandlerCore);
};

HttpProtocolHandlerCore::HttpProtocolHandlerCore(NSURLRequest* request)
    : clients_([[NSMutableArray alloc] init]),
      top_level_client_(nil),
      buffer_(new IOBuffer(kIOBufferSize)),
      net_request_(nullptr) {
  // The request will be accessed from another thread. It is safer to make a
  // copy to avoid conflicts.
  // The copy is mutable, because that request will be given to the client in
  // case of a redirect, but with a different URL. The URL must be created
  // from the absoluteString of the original URL, because mutableCopy only
  // shallowly copies the request, and just retains the non-threadsafe NSURL.
  thread_checker_.DetachFromThread();
  request_.reset([request mutableCopy]);
  [request_ setURL:[NSURL URLWithString:[[request URL] absoluteString]]];
}

void HttpProtocolHandlerCore::HandleStreamEvent(NSStream* stream,
                                                NSStreamEvent event) {
  DCHECK(thread_checker_.CalledOnValidThread());
  DCHECK(stream_delegate_);
  switch (event) {
    case NSStreamEventErrorOccurred:
      DLOG(ERROR)
          << "Failed to read POST data: "
          << base::SysNSStringToUTF8([[stream streamError] description]);
      StopListeningStream(stream);
      StopRequestWithError(NSURLErrorUnknown, ERR_UNEXPECTED);
      break;
    case NSStreamEventEndEncountered:
      StopListeningStream(stream);
      if (!post_data_readers_.empty()) {
        // NOTE: This call will result in |post_data_readers_| being cleared,
        // which is the desired behavior.
        net_request_->set_upload(make_scoped_ptr(
            new ElementsUploadDataStream(post_data_readers_.Pass(), 0)));
        DCHECK(post_data_readers_.empty());
      }
      net_request_->Start();
      if (tracker_)
        tracker_->StartRequest(net_request_);
      break;
    case NSStreamEventHasBytesAvailable: {
      NSUInteger length;
      DCHECK([stream isKindOfClass:[NSInputStream class]]);
      length = [(NSInputStream*)stream read:(unsigned char*)buffer_->data()
                                  maxLength:kIOBufferSize];
      if (length) {
        std::vector<char> owned_data(buffer_->data(), buffer_->data() + length);
        post_data_readers_.push_back(
            new UploadOwnedBytesElementReader(&owned_data));
      }
      break;
    }
    case NSStreamEventNone:
    case NSStreamEventOpenCompleted:
    case NSStreamEventHasSpaceAvailable:
      break;
    default:
      NOTREACHED() << "Unexpected stream event: " << event;
      break;
  }
}

#pragma mark URLRequest::Delegate methods

void HttpProtocolHandlerCore::OnReceivedRedirect(
    URLRequest* request,
    const RedirectInfo& redirect_info,
    bool* /* defer_redirect */) {
  DCHECK(thread_checker_.CalledOnValidThread());

  // Cancel the request and notify UIWebView.
  // If we did nothing, the network stack would follow the redirect
  // automatically, however we do not want this because we need the UIWebView to
  // be notified. The UIWebView will then issue a new request following the
  // redirect.
  DCHECK(request_);
  GURL new_url = redirect_info.new_url;

  if (!new_url.is_valid()) {
    StopRequestWithError(NSURLErrorBadURL, ERR_INVALID_URL);
    return;
  }

  DCHECK(new_url.is_valid());
  NSURL* new_nsurl = NSURLWithGURL(new_url);
  // Stash the original URL in case we need to report it in an error.
  [request_ setURL:new_nsurl];

  if (stream_delegate_.get())
    StopListeningStream([request_ HTTPBodyStream]);

  // TODO(droger): See if we can share some code with URLRequest::Redirect() in
  // net/net_url_request/url_request.cc.

  // For 303 redirects, all request methods except HEAD are converted to GET,
  // as per the latest httpbis draft.  The draft also allows POST requests to
  // be converted to GETs when following 301/302 redirects, for historical
  // reasons. Most major browsers do this and so shall we.
  // See:
  // https://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-17#section-7.3
  const int http_status_code = request->GetResponseCode();
  NSString* method = [request_ HTTPMethod];
  const bool was_post = [method isEqualToString:@"POST"];
  if ((http_status_code == 303 && ![method isEqualToString:@"HEAD"]) ||
      ((http_status_code == 301 || http_status_code == 302) && was_post)) {
    [request_ setHTTPMethod:@"GET"];
    [request_ setHTTPBody:nil];
    [request_ setHTTPBodyStream:nil];
    if (was_post) {
      // If being switched from POST to GET, must remove headers that were
      // specific to the POST and don't have meaning in GET. For example
      // the inclusion of a multipart Content-Type header in GET can cause
      // problems with some servers:
      // http://code.google.com/p/chromium/issues/detail?id=843
      StripPostSpecificHeaders(request_.get());
    }
  }

  NSURLResponse* response = GetNSURLResponseForRequest(request);
#if !defined(NDEBUG)
  DVLOG(2) << "Redirect, to client:";
  LogNSURLResponse(response);
  DVLOG(2) << "Redirect, to client:";
  LogNSURLRequest(request_);
#endif  // !defined(NDEBUG)
  if (tracker_) {
    tracker_->StopRedirectedRequest(request);
    // Add clients from tracker that depend on redirect data.
    PushClients(tracker_->ClientsHandlingRedirect(*request, new_url, response));
  }

  [top_level_client_ wasRedirectedToRequest:request_
                              nativeRequest:request
                           redirectResponse:response];
  // Don't use |request_| or |response| anymore, as the client may be using them
  // on another thread and they are not re-entrant. As |request_| is mutable, it
  // is also important that it is not modified.
  request_.reset(nil);
  request->Cancel();
  DCHECK_EQ(net_request_, request);
  StopNetRequest();
}

void HttpProtocolHandlerCore::OnAuthRequired(URLRequest* request,
                                             AuthChallengeInfo* auth_info) {
  DCHECK(thread_checker_.CalledOnValidThread());
  // A request with no tab ID should not hit HTTP authentication.
  if (tracker_) {
    // UIWebView does not handle authentication, so there is no point in calling
    // the protocol method didReceiveAuthenticationChallenge.
    // Instead, clients may handle proxy auth or display a UI to handle the
    // challenge.
    // Pass a weak reference, to avoid retain cycles.
    network_client::AuthCallback callback =
        base::Bind(&HttpProtocolHandlerCore::CompleteAuthentication,
                   base::Unretained(this));
    [top_level_client_ didRecieveAuthChallenge:auth_info
                                 nativeRequest:*request
                                      callback:callback];
  } else if (net_request_ != nullptr) {
    net_request_->CancelAuth();
  }
}

void HttpProtocolHandlerCore::OnCertificateRequested(
    URLRequest* request,
    SSLCertRequestInfo* cert_request_info) {
  DCHECK(thread_checker_.CalledOnValidThread());

  // TODO(ios): The network stack does not support SSL client authentication
  // on iOS yet. The request has to be canceled for now.
  request->Cancel();
  StopRequestWithError(NSURLErrorClientCertificateRequired,
                       ERR_SSL_PROTOCOL_ERROR);
}

void HttpProtocolHandlerCore::ContinueAfterSSLError(void) {
  DCHECK(thread_checker_.CalledOnValidThread());
  if (net_request_ != nullptr) {
    // Continue the request and load the data.
    net_request_->ContinueDespiteLastError();
  }
}

void HttpProtocolHandlerCore::CancelAfterSSLError(void) {
  DCHECK(thread_checker_.CalledOnValidThread());
  if (net_request_ != nullptr) {
    // Cancel the request.
    net_request_->Cancel();

    // The request is signalled simply cancelled to the consumer, the
    // presentation of the SSL error will be done via the tracker.
    StopRequestWithError(NSURLErrorCancelled, ERR_BLOCKED_BY_CLIENT);
  }
}

void HttpProtocolHandlerCore::SSLErrorCallback(bool carryOn) {
  DCHECK(thread_checker_.CalledOnValidThread());
  if (carryOn)
    ContinueAfterSSLError();
  else
    CancelAfterSSLError();
}

void HttpProtocolHandlerCore::HostStateCallback(bool carryOn) {
  DCHECK(thread_checker_.CalledOnValidThread());
  if (carryOn)
    StartReading();
  else
    CancelAfterSSLError();
}

void HttpProtocolHandlerCore::OnSSLCertificateError(URLRequest* request,
                                                    const SSLInfo& ssl_info,
                                                    bool is_hsts_host) {
  DCHECK(thread_checker_.CalledOnValidThread());

  if (is_hsts_host) {
    if (tracker_) {
      tracker_->OnSSLCertificateError(request, ssl_info, false,
                                      base::Bind(&DoNothing));
    }
    CancelAfterSSLError();  // High security host do not tolerate any issue.
  } else if (!tracker_) {
    // No tracker, this is a request outside the context of a tab. There is no
    // way to present anything to the user so only allow trivial errors.
    // See ssl_cert_error_handler upstream.
    if (IsCertStatusMinorError(ssl_info.cert_status))
      ContinueAfterSSLError();
    else
      CancelAfterSSLError();
  } else {
    // The tracker will decide, eventually asking the user, and will invoke the
    // callback.
    RequestTracker::SSLCallback callback =
        base::Bind(&HttpProtocolHandlerCore::SSLErrorCallback, this);
    DCHECK(tracker_);
    tracker_->OnSSLCertificateError(request, ssl_info, !is_hsts_host, callback);
  }
}

void HttpProtocolHandlerCore::OnResponseStarted(URLRequest* request) {
  DCHECK(thread_checker_.CalledOnValidThread());

  if (net_request_ == nullptr)
    return;

  const URLRequestStatus& status = request->status();
  if (!status.is_success()) {
    int error = status.error();
    StopRequestWithError(IOSErrorCode(error), error);
    return;
  }

  if (tracker_ && IsCertStatusError(request->ssl_info().cert_status) &&
      !request->context()->GetNetworkSessionParams()->
          ignore_certificate_errors) {
    // The certificate policy cache is captured here because SSL errors do not
    // always trigger OnSSLCertificateError (this is the case when a page comes
    // from the HTTP cache).
    RequestTracker::SSLCallback callback =
        base::Bind(&HttpProtocolHandlerCore::HostStateCallback, this);
    tracker_->CaptureCertificatePolicyCache(request, callback);
    return;
  }

  StartReading();
}

void HttpProtocolHandlerCore::StartReading() {
  DCHECK(thread_checker_.CalledOnValidThread());
  if (net_request_ == nullptr)
    return;

  NSURLResponse* response = GetNSURLResponseForRequest(net_request_);
#if !defined(NDEBUG)
  DVLOG(2) << "To client:";
  LogNSURLResponse(response);
#endif  // !defined(NDEBUG)

  if (tracker_) {
    tracker_->CaptureHeaders(net_request_);
    long long expectedContentLength = [response expectedContentLength];
    if (expectedContentLength > 0)
      tracker_->CaptureExpectedLength(net_request_, expectedContentLength);

    // Add clients from tracker.
    PushClients(
        tracker_->ClientsHandlingRequestAndResponse(*net_request_, response));
  }

  // Don't call any function on the response from now on, as the client may be
  // using it and the object is not re-entrant.
  [top_level_client_ didReceiveResponse:response];

  int bytes_read = 0;

  if (net_request_->Read(buffer_.get(), kIOBufferSize, &bytes_read)) {
    OnReadCompleted(net_request_, bytes_read);
  } else if (!net_request_->status().is_success()) {
    int error = net_request_->status().error();
    StopRequestWithError(IOSErrorCode(error), error);
  }
}

void HttpProtocolHandlerCore::OnReadCompleted(URLRequest* request,
                                              int bytes_read) {
  DCHECK(thread_checker_.CalledOnValidThread());

  if (net_request_ == nullptr)
    return;

  base::scoped_nsobject<NSMutableData> data([[NSMutableData alloc] init]);

  // Read all we can from the socket and put it into data.
  // TODO(droger): It may be possible to avoid some of the copies (using
  // WrappedIOBuffer for example).
  NSUInteger data_length;
  bool loop = (bytes_read > 0);
  bool io_pending = false;
  uint64_t total_byte_read = loop ? bytes_read : 0;
  while (loop) {
    data_length = [data length];  // Assumes that getting the length is fast.
    [data increaseLengthBy:bytes_read];
    memcpy(reinterpret_cast<char*>([data mutableBytes]) + data_length,
           buffer_->data(), bytes_read);
    io_pending = !request->Read(buffer_.get(), kIOBufferSize, &bytes_read);
    loop = !io_pending && (bytes_read > 0);
    total_byte_read += bytes_read;
  }

  if (tracker_)
    tracker_->CaptureReceivedBytes(request, total_byte_read);

  // Notify the client.
  const URLRequestStatus& status = request->status();
  if (status.is_success()) {
    if ([data length] > 0) {
      // If the data is not encoded in UTF8, the NSString is nil.
      DVLOG(3) << "To client:" << std::endl
               << base::SysNSStringToUTF8([[[NSString alloc]
                      initWithData:data
                          encoding:NSUTF8StringEncoding] autorelease]);
      [top_level_client_ didLoadData:data];
    }
    if (bytes_read == 0 && !io_pending) {
      DCHECK_EQ(net_request_, request);
      // There is nothing more to read.
      StopNetRequest();
      [top_level_client_ didFinishLoading];
    }
  } else {
    // Request failed (not canceled).
    int error = status.error();
    StopRequestWithError(IOSErrorCode(error), error);
  }
}

HttpProtocolHandlerCore::~HttpProtocolHandlerCore() {
  DCHECK(thread_checker_.CalledOnValidThread());
  [top_level_client_ cancelAuthRequest];
  DCHECK(!net_request_);
  DCHECK(!stream_delegate_);
}

// static
void HttpProtocolHandlerCore::Destruct(const HttpProtocolHandlerCore* x) {
  scoped_refptr<base::SingleThreadTaskRunner> task_runner =
      g_protocol_handler_delegate->GetDefaultURLRequestContext()
          ->GetNetworkTaskRunner();
  if (task_runner->BelongsToCurrentThread())
    delete x;
  else
    task_runner->DeleteSoon(FROM_HERE, x);
}

void HttpProtocolHandlerCore::SetLoadFlags() {
  DCHECK(thread_checker_.CalledOnValidThread());

  int load_flags = LOAD_VERIFY_EV_CERT;
  // TODO(droger) Support MAIN_FRAME and SUB_FRAME flags.
  if (![request_ HTTPShouldHandleCookies])
    load_flags |= LOAD_DO_NOT_SEND_COOKIES | LOAD_DO_NOT_SAVE_COOKIES;

  // Cache flags.
  if (tracker_) {
    RequestTracker::CacheMode cache_mode = tracker_->GetCacheMode();
    switch (cache_mode) {
      case RequestTracker::CACHE_RELOAD:
        load_flags |= LOAD_VALIDATE_CACHE;
        break;
      case RequestTracker::CACHE_HISTORY:
        load_flags |= LOAD_PREFERRING_CACHE;
        break;
      case RequestTracker::CACHE_BYPASS:
        load_flags |= LOAD_DISABLE_CACHE | LOAD_BYPASS_CACHE;
        break;
      case RequestTracker::CACHE_ONLY:
        load_flags |= LOAD_ONLY_FROM_CACHE;
        break;
      case RequestTracker::CACHE_NORMAL:
        // Do nothing, normal load.
        break;
    }
  } else {
    switch ([request_ cachePolicy]) {
      case NSURLRequestReloadIgnoringLocalAndRemoteCacheData:
        load_flags |= LOAD_BYPASS_CACHE;
      case NSURLRequestReloadIgnoringLocalCacheData:
        load_flags |= LOAD_DISABLE_CACHE;
        break;
      case NSURLRequestReturnCacheDataElseLoad:
        load_flags |= LOAD_PREFERRING_CACHE;
        break;
      case NSURLRequestReturnCacheDataDontLoad:
        load_flags |= LOAD_ONLY_FROM_CACHE;
        break;
      case NSURLRequestReloadRevalidatingCacheData:
        load_flags |= LOAD_VALIDATE_CACHE;
        break;
      default:
        // For the NSURLRequestUseProtocolCachePolicy case.
        break;
    }
  }
  net_request_->SetLoadFlags(load_flags);
}

void HttpProtocolHandlerCore::Start(id<CRNNetworkClientProtocol> base_client) {
  DCHECK(thread_checker_.CalledOnValidThread());
  DCHECK(!top_level_client_);
  DCHECK_EQ(0u, [clients_ count]);
  DCHECK(base_client);
  top_level_client_ = base_client;
  [clients_ addObject:base_client];
  GURL url = GURLWithNSURL([request_ URL]);

  bool valid_tracker = RequestTracker::GetRequestTracker(request_, &tracker_);
  if (!valid_tracker) {
    // The request is associated with a tracker that does not exist, cancel it.
    // NSURLErrorCancelled avoids triggering any error page.
    [top_level_client_ didFailWithNSErrorCode:NSURLErrorCancelled
                                 netErrorCode:ERR_ABORTED];
    return;
  }

  if (tracker_) {
    // Set up any clients that can operate regardless of the request
    PushClients(tracker_->ClientsHandlingAnyRequest());
  } else {
    // There was no request_group_id, so the request was from something like a
    // data: or file: URL.
    // Attach any global clients to the request.
    PushClients(RequestTracker::GlobalClientsHandlingAnyRequest());
  }

  // Now that all of the network clients are set up, if there was an error with
  // the URL, it can be raised and all of the clients will have a chance to
  // handle it.
  if (!url.is_valid()) {
    DLOG(ERROR) << "Trying to load an invalid URL: "
                << base::SysNSStringToUTF8([[request_ URL] absoluteString]);
    [top_level_client_ didFailWithNSErrorCode:NSURLErrorBadURL
                                 netErrorCode:ERR_INVALID_URL];
    return;
  }

  const URLRequestContext* context =
      tracker_ ? tracker_->GetRequestContext()
               : g_protocol_handler_delegate->GetDefaultURLRequestContext()
                     ->GetURLRequestContext();
  DCHECK(context);

  net_request_ =
      context->CreateRequest(url, DEFAULT_PRIORITY, this).release();
  net_request_->set_method(base::SysNSStringToUTF8([request_ HTTPMethod]));

  net_request_->set_first_party_for_cookies(
      GURLWithNSURL([request_ mainDocumentURL]));

#if !defined(NDEBUG)
  DVLOG(2) << "From client:";
  LogNSURLRequest(request_);
#endif  // !defined(NDEBUG)

  CopyHttpHeaders(request_, net_request_);

  // Add network clients.
  if (tracker_)
    PushClients(tracker_->ClientsHandlingRequest(*net_request_));

  [top_level_client_ didCreateNativeRequest:net_request_];
  SetLoadFlags();

  if ([request_ HTTPBodyStream]) {
    NSInputStream* input_stream = [request_ HTTPBodyStream];
    stream_delegate_.reset(
        [[CRWHTTPStreamDelegate alloc] initWithHttpProtocolHandlerCore:this]);
    [input_stream setDelegate:stream_delegate_];
    [input_stream scheduleInRunLoop:[NSRunLoop currentRunLoop]
                            forMode:NSDefaultRunLoopMode];
    [input_stream open];
    // The request will be started when the stream is fully read.
    return;
  }

  NSData* body = [request_ HTTPBody];
  const NSUInteger body_length = [body length];
  if (body_length > 0) {
    const char* source_bytes = reinterpret_cast<const char*>([body bytes]);
    std::vector<char> owned_data(source_bytes, source_bytes + body_length);
    scoped_ptr<UploadElementReader> reader(
        new UploadOwnedBytesElementReader(&owned_data));
    net_request_->set_upload(
        ElementsUploadDataStream::CreateWithReader(reader.Pass(), 0));
  }

  net_request_->Start();
  if (tracker_)
    tracker_->StartRequest(net_request_);
}

void HttpProtocolHandlerCore::Cancel() {
  DCHECK(thread_checker_.CalledOnValidThread());
  if (net_request_ == nullptr)
    return;

  DVLOG(2) << "Client canceling request: " << net_request_->url().spec();
  net_request_->Cancel();
  StopNetRequest();
}

void HttpProtocolHandlerCore::StopNetRequest() {
  DCHECK(thread_checker_.CalledOnValidThread());
  if (tracker_)
    tracker_->StopRequest(net_request_);
  delete net_request_;
  net_request_ = nullptr;
  if (stream_delegate_.get())
    StopListeningStream([request_ HTTPBodyStream]);
}

void HttpProtocolHandlerCore::StopListeningStream(NSStream* stream) {
  DCHECK(thread_checker_.CalledOnValidThread());
  DCHECK(stream);
  DCHECK(stream_delegate_);
  DCHECK([stream delegate] == stream_delegate_.get());
  [stream setDelegate:nil];
  [stream removeFromRunLoop:[NSRunLoop currentRunLoop]
                    forMode:NSDefaultRunLoopMode];
  stream_delegate_.reset(nil);
  // Close the stream if needed.
  switch ([stream streamStatus]) {
    case NSStreamStatusOpening:
    case NSStreamStatusOpen:
    case NSStreamStatusReading:
    case NSStreamStatusWriting:
    case NSStreamStatusAtEnd:
      [stream close];
      break;
    case NSStreamStatusNotOpen:
    case NSStreamStatusClosed:
    case NSStreamStatusError:
      break;
    default:
      NOTREACHED() << "Unexpected stream status: " << [stream streamStatus];
      break;
  }
}

NSInteger HttpProtocolHandlerCore::IOSErrorCode(int os_error) {
  DCHECK(thread_checker_.CalledOnValidThread());
  switch (os_error) {
    case ERR_SSL_PROTOCOL_ERROR:
      return NSURLErrorClientCertificateRequired;
    case ERR_CONNECTION_RESET:
    case ERR_NETWORK_CHANGED:
      return NSURLErrorNetworkConnectionLost;
    case ERR_UNEXPECTED:
      return NSURLErrorUnknown;
    default:
      return NSURLErrorCannotConnectToHost;
  }
}

void HttpProtocolHandlerCore::StopRequestWithError(NSInteger ns_error_code,
                                                   int net_error_code) {
  DCHECK(net_request_ != nullptr);
  DCHECK(thread_checker_.CalledOnValidThread());

  // Don't show an error message on ERR_ABORTED because this is error is often
  // fired when switching profiles (see RequestTracker::CancelRequests()).
  DLOG_IF(ERROR, net_error_code != ERR_ABORTED)
      << "HttpProtocolHandlerCore - Network error: "
      << ErrorToString(net_error_code) << " (" << net_error_code << ")";

  [top_level_client_ didFailWithNSErrorCode:ns_error_code
                               netErrorCode:net_error_code];
  StopNetRequest();
}

void HttpProtocolHandlerCore::CompleteAuthentication(
    bool auth_ok,
    const base::string16& username,
    const base::string16& password) {
  DCHECK(thread_checker_.CalledOnValidThread());
  if (net_request_ == nullptr)
    return;
  if (auth_ok) {
    net_request_->SetAuth(AuthCredentials(username, password));
  } else {
    net_request_->CancelAuth();
  }
}

void HttpProtocolHandlerCore::StripPostSpecificHeaders(
    NSMutableURLRequest* request) {
  DCHECK(thread_checker_.CalledOnValidThread());
  DCHECK(request);
  [request setValue:nil forHTTPHeaderField:base::SysUTF8ToNSString(
      HttpRequestHeaders::kContentLength)];
  [request setValue:nil forHTTPHeaderField:base::SysUTF8ToNSString(
      HttpRequestHeaders::kContentType)];
  [request setValue:nil forHTTPHeaderField:base::SysUTF8ToNSString(
      HttpRequestHeaders::kOrigin)];
}

void HttpProtocolHandlerCore::PushClient(id<CRNNetworkClientProtocol> client) {
  DCHECK(thread_checker_.CalledOnValidThread());
  [client setUnderlyingClient:top_level_client_];
  [clients_ addObject:client];
  top_level_client_ = client;
}

void HttpProtocolHandlerCore::PushClients(NSArray* clients) {
  DCHECK(thread_checker_.CalledOnValidThread());
  for (id<CRNNetworkClientProtocol> client in clients)
    PushClient(client);
}

}  // namespace net

#pragma mark -
#pragma mark CRWHTTPStreamDelegate

@implementation CRWHTTPStreamDelegate
- (instancetype)initWithHttpProtocolHandlerCore:
    (net::HttpProtocolHandlerCore*)core {
  DCHECK(core);
  self = [super init];
  if (self)
    _core = core;
  return self;
}

- (void)stream:(NSStream*)theStream handleEvent:(NSStreamEvent)streamEvent {
  _core->HandleStreamEvent(theStream, streamEvent);
}
@end

#pragma mark -
#pragma mark HttpProtocolHandler

// The HttpProtocolHandler is called by the iOS system to handle the
// NSURLRequest.
@implementation CRNHTTPProtocolHandler {
  scoped_refptr<net::HttpProtocolHandlerCore> _core;
  base::scoped_nsprotocol<id<CRNHTTPProtocolHandlerProxy>> _protocolProxy;
  BOOL _supportedURL;
}

#pragma mark NSURLProtocol methods

+ (BOOL)canInitWithRequest:(NSURLRequest*)request {
  DVLOG(5) << "canInitWithRequest " << net::FormatUrlRequestForLogging(request);
  return g_protocol_handler_delegate->CanHandleRequest(request);
}

+ (NSURLRequest*)canonicalRequestForRequest:(NSURLRequest*)request {
  // TODO(droger): Is this used if we disable the cache of UIWebView? If it is,
  // then we need a real implementation, even though Chrome network stack does
  // not need it (GURLs are automatically canonized).
  return request;
}

- (instancetype)initWithRequest:(NSURLRequest*)request
                 cachedResponse:(NSCachedURLResponse*)cachedResponse
                         client:(id<NSURLProtocolClient>)client {
  DCHECK(!cachedResponse);
  self = [super initWithRequest:request
                 cachedResponse:cachedResponse
                         client:client];
  if (self) {
    _supportedURL = g_protocol_handler_delegate->IsRequestSupported(request);
    _core = new net::HttpProtocolHandlerCore(request);
  }
  return self;
}

#pragma mark NSURLProtocol overrides.

- (NSCachedURLResponse*)cachedResponse {
  // We do not use the UIWebView cache.
  // TODO(droger): Disable the UIWebView cache.
  return nil;
}

- (void)startLoading {
  // If the scheme is not valid, just return an error right away.
  if (!_supportedURL) {
    NSMutableDictionary* dictionary = [NSMutableDictionary dictionary];

    // It is possible for URL to be nil, so check for that
    // before creating the error object. See http://crbug/349051
    NSURL* url = [[self request] URL];
    if (url)
      [dictionary setObject:url forKey:NSURLErrorKey];

    NSError* error = [NSError errorWithDomain:NSURLErrorDomain
                                         code:NSURLErrorUnsupportedURL
                                     userInfo:dictionary];
    [[self client] URLProtocol:self didFailWithError:error];
    return;
  }

  _protocolProxy.reset([[CRNHTTPProtocolHandlerProxyWithClientThread alloc]
      initWithProtocol:self
          clientThread:[NSThread currentThread]
           runLoopMode:[[NSRunLoop currentRunLoop] currentMode]]);
  g_protocol_handler_delegate->GetDefaultURLRequestContext()
      ->GetNetworkTaskRunner()
      ->PostTask(FROM_HERE, base::Bind(&net::HttpProtocolHandlerCore::Start,
                                       _core, _protocolProxy));
}

- (void)stopLoading {
  g_protocol_handler_delegate->GetDefaultURLRequestContext()
      ->GetNetworkTaskRunner()
      ->PostTask(FROM_HERE,
                 base::Bind(&net::HttpProtocolHandlerCore::Cancel, _core));
  [_protocolProxy invalidate];
  _protocolProxy.reset();
}

@end