// Copyright (c) 2011 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.

// NOTE: lifted from src/platform/update_engine and tweaked for cashew
// TODO(vlaviano): see http_fetcher.h

#include "src/libcurl_http_fetcher.h"

#include <config.h>

#include <algorithm>
#include <vector>

#include <glog/logging.h>  // NOLINT

using std::max;
using std::make_pair;
using std::vector;

// This is a concrete implementation of HttpFetcher that uses libcurl to do the
// http work.

namespace cashew {

namespace {
const int kMaxRetriesCount = 20;
const char *kCashewUserAgent = PACKAGE_STRING;
const int kTimeoutCallbackLogInterval = 15;
const int kConnectTimeoutSeconds = 30;
const int kRequestTimeoutSeconds = 30;
}

LibcurlHttpFetcher::~LibcurlHttpFetcher() {
  CleanUp();
}

void LibcurlHttpFetcher::ResumeTransfer(const std::string& url) {
  LOG(INFO) << "Starting/Resuming transfer";
  CHECK(!transfer_in_progress_);
  url_ = url;
  curl_multi_handle_ = curl_multi_init();
  CHECK(curl_multi_handle_);

  curl_handle_ = curl_easy_init();
  CHECK(curl_handle_);

  std::string nameservers_str;
  for (vector<std::string>::const_iterator it(nameservers_.begin());
       it != nameservers_.end(); it++) {
    if (!nameservers_str.empty())
      nameservers_str += ",";
    nameservers_str += *it;
  }
  LOG(INFO) << "LibcurlHttpFetcher: nameservers = " << nameservers_str;

  if (!nameservers_str.empty()) {
    CHECK_EQ(curl_easy_setopt(curl_handle_,
                              CURLOPT_DNS_SERVERS,
                              nameservers_str.c_str()),
             CURLE_OK);
  }

  if (post_data_set_) {
    CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_POST, 1), CURLE_OK);
    CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_POSTFIELDS,
                              &post_data_[0]),
             CURLE_OK);
    CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_POSTFIELDSIZE,
                              post_data_.size()),
             CURLE_OK);
  }

  if (bytes_downloaded_ > 0) {
    // Resume from where we left off
    resume_offset_ = bytes_downloaded_;
    CHECK_EQ(curl_easy_setopt(curl_handle_,
                              CURLOPT_RESUME_FROM_LARGE,
                              bytes_downloaded_), CURLE_OK);
  }

  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_WRITEDATA, this), CURLE_OK);
  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_WRITEFUNCTION,
                            StaticLibcurlWrite), CURLE_OK);
  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_URL, url_.c_str()), CURLE_OK);

  // If the connection drops under 10 bytes/sec for 3 minutes, reconnect.
  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_LOW_SPEED_LIMIT, 10),
           CURLE_OK);
  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_LOW_SPEED_TIME, 3 * 60),
           CURLE_OK);

  // By default, libcurl doesn't follow redirections. Allow up to
  // |kMaxRedirects| redirections.
  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_FOLLOWLOCATION, 1), CURLE_OK);
  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_MAXREDIRS, kMaxRedirects),
           CURLE_OK);

  // Makes sure that peer certificate verification is enabled
  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_SSL_VERIFYPEER, 1), CURLE_OK);

  // Set User-Agent header field since some servers require it to be present.
  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_USERAGENT, kCashewUserAgent),
           CURLE_OK);

  // Set timeout for TCP connections.
  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_CONNECTTIMEOUT,
                            kConnectTimeoutSeconds),
           CURLE_OK);

  // Set timeout for HTTP requests.
  CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_TIMEOUT,
                            kRequestTimeoutSeconds),
           CURLE_OK);

  CHECK_EQ(curl_multi_add_handle(curl_multi_handle_, curl_handle_), CURLM_OK);
  transfer_in_progress_ = true;
}

// Begins the transfer, which must not have already been started.
void LibcurlHttpFetcher::BeginTransfer(const std::string& url) {
  LOG(INFO) << "BeginTransfer";
  transfer_size_ = -1;
  bytes_downloaded_ = 0;
  resume_offset_ = 0;
  retry_count_ = 0;
  http_response_code_ = 0;
  ResumeTransfer(url);
  CurlPerformOnce();
}

void LibcurlHttpFetcher::TerminateTransfer() {
  LOG(INFO) << "TerminateTransfer";
  CleanUp();
}

void LibcurlHttpFetcher::CurlPerformOnce() {
  CHECK(transfer_in_progress_);
  int running_handles = 0;
  CURLMcode retcode = CURLM_CALL_MULTI_PERFORM;

  // libcurl may request that we immediately call curl_multi_perform after it
  // returns, so we do. libcurl promises that curl_multi_perform will not block.
  while (CURLM_CALL_MULTI_PERFORM == retcode) {
    retcode = curl_multi_perform(curl_multi_handle_, &running_handles);
  }
  if (0 == running_handles) {
    GetHttpResponseCode();
    if (http_response_code_) {
      LOG(INFO) << "HTTP response code: " << http_response_code_;
    } else {
      LOG(WARNING) << "Unable to get http response code.";
    }

    CheckRequestStatus();

    // we're done!
    CleanUp();

    if ((transfer_size_ >= 0) && (bytes_downloaded_ < transfer_size_)) {
      // Need to restart transfer
      retry_count_++;
      LOG(INFO) << "Restarting transfer b/c we finished, had downloaded "
                << bytes_downloaded_ << " bytes, but transfer_size_ is "
                << transfer_size_ << ". retry_count: " << retry_count_;
      if (retry_count_ > kMaxRetriesCount) {
        if (delegate_)
          delegate_->TransferComplete(this, false);  // success
      } else {
        g_timeout_add_seconds(retry_seconds_,
                              &LibcurlHttpFetcher::StaticRetryTimeoutCallback,
                              this);
      }
      return;
    } else {
      if (delegate_) {
        // success is when http_response_code_ is 2xx
        bool success = (http_response_code_ >= 200) &&
            (http_response_code_ < 300);
        delegate_->TransferComplete(this, success);
      }
    }
  } else {
    // set up callback
    SetupMainloopSources();
  }
}

size_t LibcurlHttpFetcher::LibcurlWrite(void *ptr, size_t size, size_t nmemb) {
  GetHttpResponseCode();
  LOG(INFO) << "LibcurlWrite";
  {
    double transfer_size_double;
    CHECK_EQ(curl_easy_getinfo(curl_handle_,
                               CURLINFO_CONTENT_LENGTH_DOWNLOAD,
                               &transfer_size_double), CURLE_OK);
    off_t new_transfer_size = static_cast<off_t>(transfer_size_double);
    if (new_transfer_size > 0) {
      transfer_size_ = resume_offset_ + new_transfer_size;
    }
  }
  bytes_downloaded_ += size * nmemb;
  if (delegate_)
    delegate_->ReceivedBytes(this, reinterpret_cast<char*>(ptr), size * nmemb);
  return size * nmemb;
}

void LibcurlHttpFetcher::Pause() {
  LOG(INFO) << "Pause";
  CHECK(curl_handle_);
  CHECK(transfer_in_progress_);
  CHECK_EQ(curl_easy_pause(curl_handle_, CURLPAUSE_ALL), CURLE_OK);
}

void LibcurlHttpFetcher::Unpause() {
  LOG(INFO) << "Unpause";
  CHECK(curl_handle_);
  CHECK(transfer_in_progress_);
  CHECK_EQ(curl_easy_pause(curl_handle_, CURLPAUSE_CONT), CURLE_OK);
}

// This method sets up callbacks with the glib main loop.
void LibcurlHttpFetcher::SetupMainloopSources() {
  fd_set fd_read;
  fd_set fd_write;
  fd_set fd_exc;

  FD_ZERO(&fd_read);
  FD_ZERO(&fd_write);
  FD_ZERO(&fd_exc);

  int fd_max = 0;

  // Ask libcurl for the set of file descriptors we should track on its
  // behalf.
  CHECK_EQ(curl_multi_fdset(curl_multi_handle_, &fd_read, &fd_write,
                            &fd_exc, &fd_max), CURLM_OK);

  // We should iterate through all file descriptors up to libcurl's fd_max or
  // the highest one we're tracking, whichever is larger.
  for (size_t t = 0; t < arraysize(io_channels_); ++t) {
    if (!io_channels_[t].empty())
      fd_max = max(fd_max, io_channels_[t].rbegin()->first);
  }

  // For each fd, if we're not tracking it, track it. If we are tracking it, but
  // libcurl doesn't care about it anymore, stop tracking it. After this loop,
  // there should be exactly as many GIOChannel objects in io_channels_[0|1] as
  // there are read/write fds that we're tracking.
  for (int fd = 0; fd <= fd_max; ++fd) {
    // Note that fd_exc is unused in the current version of libcurl so is_exc
    // should always be false.
    bool is_exc = FD_ISSET(fd, &fd_exc) != 0;
    bool must_track[2] = {
      is_exc || (FD_ISSET(fd, &fd_read) != 0),  // track 0 -- read
      is_exc || (FD_ISSET(fd, &fd_write) != 0)  // track 1 -- write
    };

    for (size_t t = 0; t < arraysize(io_channels_); ++t) {
      bool tracked = io_channels_[t].find(fd) != io_channels_[t].end();

      if (!must_track[t]) {
        // If we have an outstanding io_channel, remove it.
        if (tracked) {
          g_source_remove(io_channels_[t][fd].second);
          g_io_channel_unref(io_channels_[t][fd].first);
          io_channels_[t].erase(io_channels_[t].find(fd));
        }
        continue;
      }

      // If we are already tracking this fd, continue -- nothing to do.
      if (tracked)
        continue;

      // Set conditions appropriately -- read for track 0, write for track 1.
      GIOCondition condition = static_cast<GIOCondition>(
          ((t == 0) ? (G_IO_IN | G_IO_PRI) : G_IO_OUT) | G_IO_ERR | G_IO_HUP);

      // Track a new fd.
      GIOChannel* io_channel = g_io_channel_unix_new(fd);
      guint tag =
          g_io_add_watch(io_channel, condition, &StaticFDCallback, this);

      io_channels_[t][fd] = make_pair(io_channel, tag);
      static int io_counter = 0;
      io_counter++;
      if (io_counter % 50 == 0) {
        LOG(INFO) << "io_counter = " << io_counter;
      }
    }
  }

  // Set up a timeout callback for libcurl.
  if (!timeout_source_) {
    LOG(INFO) << "Setting up timeout source: " << idle_seconds_ << " seconds.";
    timeout_source_ = g_timeout_source_new_seconds(idle_seconds_);
    g_source_set_callback(timeout_source_, StaticTimeoutCallback, this, NULL);
    g_source_attach(timeout_source_, NULL);
  }
}

bool LibcurlHttpFetcher::FDCallback(GIOChannel *source,
                                    GIOCondition condition) {
  CurlPerformOnce();
  // We handle removing of this source elsewhere, so we always return true.
  // The docs say, "the function should return FALSE if the event source
  // should be removed."
  // http://www.gtk.org/api/2.6/glib/glib-IO-Channels.html#GIOFunc
  return true;
}

gboolean LibcurlHttpFetcher::RetryTimeoutCallback() {
  LOG(INFO) << "RetryTimeoutCallback";
  ResumeTransfer(url_);
  CurlPerformOnce();
  return FALSE;  // Don't have glib auto call this callback again
}

gboolean LibcurlHttpFetcher::TimeoutCallback() {
  LOG_EVERY_N(INFO, kTimeoutCallbackLogInterval) << "TimeoutCallback ("
      << google::COUNTER << ")";
  // We always return true, even if we don't want glib to call us back.
  // We will remove the event source separately if we don't want to
  // be called back.
  if (!transfer_in_progress_)
    return TRUE;
  CurlPerformOnce();
  return TRUE;
}

void LibcurlHttpFetcher::CleanUp() {
  if (timeout_source_) {
    g_source_destroy(timeout_source_);
    timeout_source_ = NULL;
  }

  for (size_t t = 0; t < arraysize(io_channels_); ++t) {
    for (IOChannels::iterator it = io_channels_[t].begin();
         it != io_channels_[t].end(); ++it) {
      g_source_remove(it->second.second);
      g_io_channel_unref(it->second.first);
    }
    io_channels_[t].clear();
  }

  if (curl_handle_) {
    if (curl_multi_handle_) {
      CHECK_EQ(curl_multi_remove_handle(curl_multi_handle_, curl_handle_),
               CURLM_OK);
    }
    curl_easy_cleanup(curl_handle_);
    curl_handle_ = NULL;
  }
  if (curl_multi_handle_) {
    CHECK_EQ(curl_multi_cleanup(curl_multi_handle_), CURLM_OK);
    curl_multi_handle_ = NULL;
  }
  transfer_in_progress_ = false;
}

void LibcurlHttpFetcher::GetHttpResponseCode() {
  long http_response_code = 0;  // NOLINT
  CURLcode result = curl_easy_getinfo(curl_handle_,
                                      CURLINFO_RESPONSE_CODE,
                                      &http_response_code);
  if (result == CURLE_OK) {
    http_response_code_ = static_cast<int>(http_response_code);
  } else {
    LOG(WARNING) << "GetHttpResponseCode: curl_easy_getinfo failed: "
        << curl_easy_strerror(result);
  }
}

void LibcurlHttpFetcher::CheckRequestStatus() {
  int remaining_updates;
  CURLMsg *request_status;
  while ((request_status =
      curl_multi_info_read(curl_multi_handle_, &remaining_updates)) != NULL) {
    if (request_status->msg != CURLMSG_DONE) {
      continue;
    }
    CURLcode code = static_cast<CURLcode>(request_status->data.result);
    LOG(WARNING) << "CheckRequestStatus: result = " << code << ": "
        << curl_easy_strerror(code);
  }
}

}  // namespace cashew