text: // Copyright (c) 2017-2018, The InSPa Project
  // 
  // All rights reserved.
  // 
  // Redistribution and use in source and binary forms, with or without modification, are
  // permitted provided that the following conditions are met:
  // 
  // 1. Redistributions of source code must retain the above copyright notice, this list of
  //    conditions and the following disclaimer.
  // 
  // 2. Redistributions in binary form must reproduce the above copyright notice, this list
  //    of conditions and the following disclaimer in the documentation and/or other
  //    materials provided with the distribution.
  // 
  // 3. Neither the name of the copyright holder nor the names of its contributors may be
  //    used to endorse or promote products derived from this software without specific
  //    prior written permission.
  // 
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
  // EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  // MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
  // THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  // STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
  // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  #include <string>
  #include <atomic>
  #include <boost/filesystem.hpp>
  #include <boost/asio.hpp>
  #include <boost/thread/thread.hpp>
  #include "cryptonote_config.h"
  #include "include_base_utils.h"
  #include "file_io_utils.h"
  #include "net/http_client.h"
  #include "download.h"
  
  #undef INSPA_DEFAULT_LOG_CATEGORY
  #define INSPA_DEFAULT_LOG_CATEGORY "net.dl"
  
  namespace tools
  {
    struct download_thread_control
    {
      const std::string path;
      const std::string uri;
      std::function<void(const std::string&, const std::string&, bool)> result_cb;
      std::function<bool(const std::string&, const std::string&, size_t, ssize_t)> progress_cb;
      bool stop;
      bool stopped;
      bool success;
      boost::thread thread;
      boost::mutex mutex;
  
      download_thread_control(const std::string &path, const std::string &uri, std::function<void(const std::string&, const std::string&, bool)> result_cb, std::function<bool(const std::string&, const std::string&, size_t, ssize_t)> progress_cb):
          path(path), uri(uri), result_cb(result_cb), progress_cb(progress_cb), stop(false), stopped(false), success(false) {}
      ~download_thread_control() { if (thread.joinable()) thread.detach(); }
    };
  
    static void download_thread(download_async_handle control)
    {
      static std::atomic<unsigned int> thread_id(0);
  
      MLOG_SET_THREAD_NAME("DL" + std::to_string(thread_id++));
  
      struct stopped_setter
      {
        stopped_setter(const download_async_handle &control): control(control) {}
        ~stopped_setter() { control->stopped = true; }
        download_async_handle control;
      } stopped_setter(control);
  
      try
      {
        boost::unique_lock<boost::mutex> lock(control->mutex);
        std::ios_base::openmode mode = std::ios_base::out | std::ios_base::binary;
        uint64_t existing_size = 0;
        if (epee::file_io_utils::get_file_size(control->path, existing_size) && existing_size > 0)
        {
          MINFO("Resuming downloading " << control->uri << " to " << control->path << " from " << existing_size);
          mode |= std::ios_base::app;
        }
        else
        {
          MINFO("Downloading " << control->uri << " to " << control->path);
          mode |= std::ios_base::trunc;
        }
        std::ofstream f;
        f.open(control->path, mode);
        if (!f.good()) {
          MERROR("Failed to open file " << control->path);
          control->result_cb(control->path, control->uri, control->success);
          return;
        }
        class download_client: public epee::net_utils::http::http_simple_client
        {
        public:
          download_client(download_async_handle control, std::ofstream &f, uint64_t offset = 0):
            control(control), f(f), content_length(-1), total(0), offset(offset) {}
          virtual ~download_client() { f.close(); }
          virtual bool on_header(const epee::net_utils::http::http_response_info &headers)
          {
            for (const auto &kv: headers.m_header_info.m_etc_fields)
              MDEBUG("Header: " << kv.first << ": " << kv.second);
            ssize_t length;
            if (epee::string_tools::get_xtype_from_string(length, headers.m_header_info.m_content_length) && length >= 0)
            {
              MINFO("Content-Length: " << length);
              content_length = length;
              boost::filesystem::path path(control->path);
              boost::filesystem::space_info si = boost::filesystem::space(path);
              if (si.available < (size_t)content_length)
              {
                const uint64_t avail = (si.available + 1023) / 1024, needed = (content_length + 1023) / 1024;
                MERROR("Not enough space to download " << needed << " kB to " << path << " (" << avail << " kB available)");
                return false;
              }
            }
            if (offset > 0)
            {
              // we requested a range, so check if we're getting it, otherwise truncate
              bool got_range = false;
              const std::string prefix = "bytes=" + std::to_string(offset) + "-";
              for (const auto &kv: headers.m_header_info.m_etc_fields)
              {
                if (kv.first == "Content-Range" && strncmp(kv.second.c_str(), prefix.c_str(), prefix.size()))
                {
                  got_range = true;
                  break;
                }
              }
              if (!got_range)
              {
                MWARNING("We did not get the requested range, downloading from start");
                f.close();
                f.open(control->path, std::ios_base::out | std::ios_base::binary | std::ios_base::trunc);
              }
            }
            return true;
          }
          virtual bool handle_target_data(std::string &piece_of_transfer)
          {
            try
            {
              boost::lock_guard<boost::mutex> lock(control->mutex);
              if (control->stop)
                return false;
              f << piece_of_transfer;
              total += piece_of_transfer.size();
              if (control->progress_cb && !control->progress_cb(control->path, control->uri, total, content_length))
                return false;
              return f.good();
            }
            catch (const std::exception &e)
            {
              MERROR("Error writing data: " << e.what());
              return false;
            }
          }
        private:
          download_async_handle control;
          std::ofstream &f;
          ssize_t content_length;
          size_t total;
          uint64_t offset;
        } client(control, f, existing_size);
        epee::net_utils::http::url_content u_c;
        if (!epee::net_utils::parse_url(control->uri, u_c))
        {
          MERROR("Failed to parse URL " << control->uri);
          control->result_cb(control->path, control->uri, control->success);
          return;
        }
        if (u_c.host.empty())
        {
          MERROR("Failed to determine address from URL " << control->uri);
          control->result_cb(control->path, control->uri, control->success);
          return;
        }
  
        lock.unlock();
  
        bool ssl = u_c.schema == "https";
        uint16_t port = u_c.port ? u_c.port : ssl ? 443 : 80;
        MDEBUG("Connecting to " << u_c.host << ":" << port);
        client.set_server(u_c.host, std::to_string(port), boost::none, ssl);
        if (!client.connect(std::chrono::seconds(30)))
        {
          boost::lock_guard<boost::mutex> lock(control->mutex);
          MERROR("Failed to connect to " << control->uri);
          control->result_cb(control->path, control->uri, control->success);
          return;
        }
        MDEBUG("GETting " << u_c.uri);
        const epee::net_utils::http::http_response_info *info = NULL;
        epee::net_utils::http::fields_list fields;
        if (existing_size > 0)
        {
          const std::string range = "bytes=" + std::to_string(existing_size) + "-";
          MDEBUG("Asking for range: " << range);
          fields.push_back(std::make_pair("Range", range));
        }
        if (!client.invoke_get(u_c.uri, std::chrono::seconds(30), "", &info, fields))
        {
          boost::lock_guard<boost::mutex> lock(control->mutex);
          MERROR("Failed to connect to " << control->uri);
          client.disconnect();
          control->result_cb(control->path, control->uri, control->success);
          return;
        }
        if (control->stop)
        {
          boost::lock_guard<boost::mutex> lock(control->mutex);
          MDEBUG("Download cancelled");
          client.disconnect();
          control->result_cb(control->path, control->uri, control->success);
          return;
        }
        if (!info)
        {
          boost::lock_guard<boost::mutex> lock(control->mutex);
          MERROR("Failed invoking GET command to " << control->uri << ", no status info returned");
          client.disconnect();
          control->result_cb(control->path, control->uri, control->success);
          return;
        }
        MDEBUG("response code: " << info->m_response_code);
        MDEBUG("response length: " << info->m_header_info.m_content_length);
        MDEBUG("response comment: " << info->m_response_comment);
        MDEBUG("response body: " << info->m_body);
        for (const auto &f: info->m_additional_fields)
          MDEBUG("additional field: " << f.first << ": " << f.second);
        if (info->m_response_code != 200 && info->m_response_code != 206)
        {
          boost::lock_guard<boost::mutex> lock(control->mutex);
          MERROR("Status code " << info->m_response_code);
          client.disconnect();
          control->result_cb(control->path, control->uri, control->success);
          return;
        }
        client.disconnect();
        f.close();
        MDEBUG("Download complete");
        lock.lock();
        control->success = true;
        control->result_cb(control->path, control->uri, control->success);
        return;
      }
      catch (const std::exception &e)
      {
        MERROR("Exception in download thread: " << e.what());
        // fall through and call result_cb not from the catch block to avoid another exception
      }
      boost::lock_guard<boost::mutex> lock(control->mutex);
      control->result_cb(control->path, control->uri, control->success);
    }
  
    bool download(const std::string &path, const std::string &url, std::function<bool(const std::string&, const std::string&, size_t, ssize_t)> cb)
    {
      bool success = false;
      download_async_handle handle = download_async(path, url, [&success](const std::string&, const std::string&, bool result) {success = result;}, cb);
      download_wait(handle);
      return success;
    }
  
    download_async_handle download_async(const std::string &path, const std::string &url, std::function<void(const std::string&, const std::string&, bool)> result, std::function<bool(const std::string&, const std::string&, size_t, ssize_t)> progress)
    {
      download_async_handle control = std::make_shared<download_thread_control>(path, url, result, progress);
      control->thread = boost::thread([control](){ download_thread(control); });
      return control;
    }
  
    bool download_finished(const download_async_handle &control)
    {
      CHECK_AND_ASSERT_MES(control != 0, false, "NULL async download handle");
      boost::lock_guard<boost::mutex> lock(control->mutex);
      return control->stopped;
    }
  
    bool download_error(const download_async_handle &control)
    {
      CHECK_AND_ASSERT_MES(control != 0, false, "NULL async download handle");
      boost::lock_guard<boost::mutex> lock(control->mutex);
      return !control->success;
    }
  
    bool download_wait(const download_async_handle &control)
    {
      CHECK_AND_ASSERT_MES(control != 0, false, "NULL async download handle");
      {
        boost::lock_guard<boost::mutex> lock(control->mutex);
        if (control->stopped)
          return true;
      }
      control->thread.join();
      return true;
    }
  
    bool download_cancel(const download_async_handle &control)
    {
      CHECK_AND_ASSERT_MES(control != 0, false, "NULL async download handle");
      {
        boost::lock_guard<boost::mutex> lock(control->mutex);
        if (control->stopped)
          return true;
        control->stop = true;
      }
      control->thread.join();
      return true;
    }
  }
  