// Copyright (c) 2009 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.

#include "chrome/common/net/url_fetcher.h"

#include "base/compiler_specific.h"
#include "base/message_loop_proxy.h"
#include "base/string_util.h"
#include "base/thread.h"
#include "chrome/common/net/url_fetcher_protect.h"
#include "chrome/common/net/url_request_context_getter.h"
#include "googleurl/src/gurl.h"
#include "net/base/load_flags.h"
#include "net/base/io_buffer.h"
#include "net/http/http_request_headers.h"
#include "net/http/http_response_headers.h"
#include "net/url_request/url_request.h"
#include "net/url_request/url_request_context.h"

static const int kBufferSize = 4096;

bool URLFetcher::g_interception_enabled = false;

class URLFetcher::Core
    : public base::RefCountedThreadSafe<URLFetcher::Core>,
      public MessageLoop::DestructionObserver,
      public URLRequest::Delegate {
 public:
  // For POST requests, set |content_type| to the MIME type of the content
  // and set |content| to the data to upload.  |flags| are flags to apply to
  // the load operation--these should be one or more of the LOAD_* flags
  // defined in url_request.h.
  Core(URLFetcher* fetcher,
       const GURL& original_url,
       RequestType request_type,
       URLFetcher::Delegate* d);

  // Starts the load.  It's important that this not happen in the constructor
  // because it causes the IO thread to begin AddRef()ing and Release()ing
  // us.  If our caller hasn't had time to fully construct us and take a
  // reference, the IO thread could interrupt things, run a task, Release()
  // us, and destroy us, leaving the caller with an already-destroyed object
  // when construction finishes.
  void Start();

  // Stops any in-progress load and ensures no callback will happen.  It is
  // safe to call this multiple times.
  void Stop();

  // MessageLoop::DestructionObserver implementation.  We are only registered as
  // a DestructionObserver when |request_| exists.
  virtual void WillDestroyCurrentMessageLoop();

  // URLRequest::Delegate implementation.
  virtual void OnResponseStarted(URLRequest* request);
  virtual void OnReadCompleted(URLRequest* request, int bytes_read);

  URLFetcher::Delegate* delegate() const { return delegate_; }

 private:
  friend class base::RefCountedThreadSafe<URLFetcher::Core>;

  ~Core() {}

  // Wrapper functions that allow us to ensure actions happen on the right
  // thread.
  void StartURLRequest();
  void CancelURLRequest();
  void OnCompletedURLRequest(const URLRequestStatus& status);

  URLFetcher* fetcher_;              // Corresponding fetcher object
  GURL original_url_;                // The URL we were asked to fetch
  GURL url_;                         // The URL we eventually wound up at
  RequestType request_type_;         // What type of request is this?
  URLFetcher::Delegate* delegate_;   // Object to notify on completion
  MessageLoop* delegate_loop_;       // Message loop of the creating thread
  scoped_refptr<base::MessageLoopProxy> io_message_loop_proxy_;
                                     // The message loop proxy for the thread
                                     // on which the request IO happens.
  URLRequest* request_;              // The actual request this wraps
  int load_flags_;                   // Flags for the load operation
  int response_code_;                // HTTP status code for the request
  std::string data_;                 // Results of the request
  scoped_refptr<net::IOBuffer> buffer_;
                                     // Read buffer
  scoped_refptr<URLRequestContextGetter> request_context_getter_;
                                     // Cookie/cache info for the request
  ResponseCookies cookies_;          // Response cookies
  net::HttpRequestHeaders extra_request_headers_;
  scoped_refptr<net::HttpResponseHeaders> response_headers_;

  std::string upload_content_;       // HTTP POST payload
  std::string upload_content_type_;  // MIME type of POST payload

  // The overload protection entry for this URL.  This is used to
  // incrementally back off how rapidly we'll send requests to a particular
  // URL, to avoid placing too much demand on the remote resource.  We update
  // this with the status of all requests as they return, and in turn use it
  // to determine how long to wait before making another request.
  URLFetcherProtectEntry* protect_entry_;
  // |num_retries_| indicates how many times we've failed to successfully
  // fetch this URL.  Once this value exceeds the maximum number of retries
  // specified by the protection manager, we'll give up.
  int num_retries_;

  // True if the URLFetcher has been cancelled.
  bool was_cancelled_;

  friend class URLFetcher;
  DISALLOW_COPY_AND_ASSIGN(Core);
};

// static
URLFetcher::Factory* URLFetcher::factory_ = NULL;

URLFetcher::URLFetcher(const GURL& url,
                       RequestType request_type,
                       Delegate* d)
    : ALLOW_THIS_IN_INITIALIZER_LIST(
      core_(new Core(this, url, request_type, d))),
      automatically_retry_on_5xx_(true) {
}

URLFetcher::~URLFetcher() {
  core_->Stop();
}

// static
URLFetcher* URLFetcher::Create(int id, const GURL& url,
                               RequestType request_type, Delegate* d) {
  return factory_ ? factory_->CreateURLFetcher(id, url, request_type, d) :
                    new URLFetcher(url, request_type, d);
}

URLFetcher::Core::Core(URLFetcher* fetcher,
                       const GURL& original_url,
                       RequestType request_type,
                       URLFetcher::Delegate* d)
    : fetcher_(fetcher),
      original_url_(original_url),
      request_type_(request_type),
      delegate_(d),
      delegate_loop_(MessageLoop::current()),
      request_(NULL),
      load_flags_(net::LOAD_NORMAL),
      response_code_(-1),
      buffer_(new net::IOBuffer(kBufferSize)),
      protect_entry_(URLFetcherProtectManager::GetInstance()->Register(
          original_url_.host())),
      num_retries_(0),
      was_cancelled_(false) {
}

void URLFetcher::Core::Start() {
  DCHECK(delegate_loop_);
  CHECK(request_context_getter_) << "We need an URLRequestContext!";
  io_message_loop_proxy_ = request_context_getter_->GetIOMessageLoopProxy();
  CHECK(io_message_loop_proxy_.get()) << "We need an IO message loop proxy";
  io_message_loop_proxy_->PostDelayedTask(
      FROM_HERE,
      NewRunnableMethod(this, &Core::StartURLRequest),
          protect_entry_->UpdateBackoff(URLFetcherProtectEntry::SEND));
}

void URLFetcher::Core::Stop() {
  DCHECK_EQ(MessageLoop::current(), delegate_loop_);
  delegate_ = NULL;
  fetcher_ = NULL;
  if (io_message_loop_proxy_.get()) {
    io_message_loop_proxy_->PostTask(
        FROM_HERE, NewRunnableMethod(this, &Core::CancelURLRequest));
  }
}

void URLFetcher::Core::WillDestroyCurrentMessageLoop() {
  CancelURLRequest();
  // Don't bother to try and notify the delegate thread portion of this object,
  // since if the IO thread is shutting down, everything is shutting down, and
  // we just want to avoid leaks.
}

void URLFetcher::Core::OnResponseStarted(URLRequest* request) {
  DCHECK(request == request_);
  DCHECK(io_message_loop_proxy_->BelongsToCurrentThread());
  if (request_->status().is_success()) {
    response_code_ = request_->GetResponseCode();
    response_headers_ = request_->response_headers();
  }

  int bytes_read = 0;
  // Some servers may treat HEAD requests as GET requests.  To free up the
  // network connection as soon as possible, signal that the request has
  // completed immediately, without trying to read any data back (all we care
  // about is the response code and headers, which we already have).
  if (request_->status().is_success() && (request_type_ != HEAD))
    request_->Read(buffer_, kBufferSize, &bytes_read);
  OnReadCompleted(request_, bytes_read);
}

void URLFetcher::Core::OnReadCompleted(URLRequest* request, int bytes_read) {
  DCHECK(request == request_);
  DCHECK(io_message_loop_proxy_->BelongsToCurrentThread());

  url_ = request->url();

  do {
    if (!request_->status().is_success() || bytes_read <= 0)
      break;
    data_.append(buffer_->data(), bytes_read);
  } while (request_->Read(buffer_, kBufferSize, &bytes_read));

  if (request_->status().is_success())
    request_->GetResponseCookies(&cookies_);

  // See comments re: HEAD requests in OnResponseStarted().
  if (!request_->status().is_io_pending() || (request_type_ == HEAD)) {
    delegate_loop_->PostTask(FROM_HERE, NewRunnableMethod(
        this, &Core::OnCompletedURLRequest, request_->status()));
    delete request_;
    request_ = NULL;
    MessageLoop::current()->RemoveDestructionObserver(this);
  }
}

void URLFetcher::Core::StartURLRequest() {
  DCHECK(io_message_loop_proxy_->BelongsToCurrentThread());

  if (was_cancelled_) {
    // Since StartURLRequest() is posted as a *delayed* task, it may
    // run after the URLFetcher was already stopped.
    return;
  }

  CHECK(request_context_getter_);
  DCHECK(!request_);

  MessageLoop::current()->AddDestructionObserver(this);

  request_ = new URLRequest(original_url_, this);
  int flags = request_->load_flags() | load_flags_;
  if (!g_interception_enabled) {
    flags = flags | net::LOAD_DISABLE_INTERCEPT;
  }
  request_->set_load_flags(flags);
  request_->set_context(request_context_getter_->GetURLRequestContext());

  switch (request_type_) {
    case GET:
      break;

    case POST:
      DCHECK(!upload_content_.empty());
      DCHECK(!upload_content_type_.empty());

      request_->set_method("POST");
      extra_request_headers_.SetHeader(net::HttpRequestHeaders::kContentType,
                                       upload_content_type_);
      request_->AppendBytesToUpload(upload_content_.data(),
                                    static_cast<int>(upload_content_.size()));
      break;

    case HEAD:
      request_->set_method("HEAD");
      break;

    default:
      NOTREACHED();
  }

  if (!extra_request_headers_.IsEmpty())
    request_->SetExtraRequestHeaders(extra_request_headers_);

  request_->Start();
}

void URLFetcher::Core::CancelURLRequest() {
  DCHECK(io_message_loop_proxy_->BelongsToCurrentThread());

  if (request_) {
    request_->Cancel();
    delete request_;
    request_ = NULL;
    MessageLoop::current()->RemoveDestructionObserver(this);
  }
  // Release the reference to the request context. There could be multiple
  // references to URLFetcher::Core at this point so it may take a while to
  // delete the object, but we cannot delay the destruction of the request
  // context.
  request_context_getter_ = NULL;
  was_cancelled_ = true;
}

void URLFetcher::Core::OnCompletedURLRequest(const URLRequestStatus& status) {
  DCHECK(MessageLoop::current() == delegate_loop_);

  // Checks the response from server.
  if (response_code_ >= 500) {
    // When encountering a server error, we will send the request again
    // after backoff time.
    int64 back_off_time =
        protect_entry_->UpdateBackoff(URLFetcherProtectEntry::FAILURE);
    if (delegate_) {
      fetcher_->backoff_delay_ =
          base::TimeDelta::FromMilliseconds(back_off_time);
    }
    ++num_retries_;
    // Restarts the request if we still need to notify the delegate.
    if (delegate_) {
      if (fetcher_->automatically_retry_on_5xx_ &&
          num_retries_ <= protect_entry_->max_retries()) {
        io_message_loop_proxy_->PostDelayedTask(
            FROM_HERE,
            NewRunnableMethod(this, &Core::StartURLRequest), back_off_time);
      } else {
        delegate_->OnURLFetchComplete(fetcher_, url_, status, response_code_,
                                      cookies_, data_);
      }
    }
  } else {
    protect_entry_->UpdateBackoff(URLFetcherProtectEntry::SUCCESS);
    if (delegate_) {
      fetcher_->backoff_delay_ = base::TimeDelta();
      delegate_->OnURLFetchComplete(fetcher_, url_, status, response_code_,
                                    cookies_, data_);
    }
  }
}

void URLFetcher::set_upload_data(const std::string& upload_content_type,
                     const std::string& upload_content) {
  core_->upload_content_type_ = upload_content_type;
  core_->upload_content_ = upload_content;
}

const std::string& URLFetcher::upload_data() const {
  return core_->upload_content_;
}

void URLFetcher::set_load_flags(int load_flags) {
  core_->load_flags_ = load_flags;
}

int URLFetcher::load_flags() const {
  return core_->load_flags_;
}

void URLFetcher::set_extra_request_headers(
    const std::string& extra_request_headers) {
  core_->extra_request_headers_.Clear();
  core_->extra_request_headers_.AddHeadersFromString(extra_request_headers);
}

void URLFetcher::set_request_context(
    URLRequestContextGetter* request_context_getter) {
  core_->request_context_getter_ = request_context_getter;
}

void URLFetcher::set_automatcally_retry_on_5xx(bool retry) {
  automatically_retry_on_5xx_ = retry;
}

net::HttpResponseHeaders* URLFetcher::response_headers() const {
  return core_->response_headers_;
}

void URLFetcher::Start() {
  core_->Start();
}

const GURL& URLFetcher::url() const {
  return core_->url_;
}

URLFetcher::Delegate* URLFetcher::delegate() const {
  return core_->delegate();
}