/**
 * Orthanc - A Lightweight, RESTful DICOM Store
 * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
 * Department, University Hospital of Liege, Belgium
 * Copyright (C) 2017-2019 Osimis S.A., Belgium
 *
 * This program is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * In addition, as a special exception, the copyright holders of this
 * program give permission to link the code of its release with the
 * OpenSSL project's "OpenSSL" library (or with modified versions of it
 * that use the same license as the "OpenSSL" library), and distribute
 * the linked executables. You must obey the GNU General Public License
 * in all respects for all of the code used other than "OpenSSL". If you
 * modify file(s) with this exception, you may extend this exception to
 * your version of the file(s), but you are not obligated to do so. If
 * you do not wish to do so, delete this exception statement from your
 * version. If you delete this exception statement from all source files
 * in the program, then also delete it here.
 * 
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 **/


// http://en.highscore.de/cpp/boost/stringhandling.html

#include "../PrecompiledHeaders.h"
#include "HttpServer.h"

#include "../ChunkedBuffer.h"
#include "../FileBuffer.h"
#include "../Logging.h"
#include "../OrthancException.h"
#include "../TemporaryFile.h"
#include "HttpToolbox.h"

#if ORTHANC_ENABLE_MONGOOSE == 1
#  include <mongoose.h>

#elif ORTHANC_ENABLE_CIVETWEB == 1
#  include <civetweb.h>
#  define MONGOOSE_USE_CALLBACKS 1
#  if !defined(CIVETWEB_HAS_DISABLE_KEEP_ALIVE)
#    error Macro CIVETWEB_HAS_DISABLE_KEEP_ALIVE must be defined
#  endif

#else
#  error "Either Mongoose or Civetweb must be enabled to compile this file"
#endif

#include <algorithm>
#include <string.h>
#include <boost/lexical_cast.hpp>
#include <boost/algorithm/string.hpp>
#include <iostream>
#include <string.h>
#include <stdio.h>
#include <boost/thread.hpp>

#if !defined(ORTHANC_ENABLE_SSL)
#  error The macro ORTHANC_ENABLE_SSL must be defined
#endif

#if ORTHANC_ENABLE_SSL == 1
#include <openssl/opensslv.h>
#endif

#define ORTHANC_REALM "Orthanc Secure Area"


namespace Orthanc
{
  static const char multipart[] = "multipart/form-data; boundary=";
  static unsigned int multipartLength = sizeof(multipart) / sizeof(char) - 1;


  namespace
  {
    // Anonymous namespace to avoid clashes between compilation modules
    class MongooseOutputStream : public IHttpOutputStream
    {
    private:
      struct mg_connection* connection_;

    public:
      MongooseOutputStream(struct mg_connection* connection) : connection_(connection)
      {
      }

      virtual void Send(bool isHeader, const void* buffer, size_t length)
      {
        if (length > 0)
        {
          int status = mg_write(connection_, buffer, length);
          if (status != static_cast<int>(length))
          {
            // status == 0 when the connection has been closed, -1 on error
            throw OrthancException(ErrorCode_NetworkProtocol);
          }
        }
      }

      virtual void OnHttpStatusReceived(HttpStatus status)
      {
        // Ignore this
      }

      virtual void DisableKeepAlive()
      {
#if ORTHANC_ENABLE_MONGOOSE == 1
        throw OrthancException(ErrorCode_NotImplemented,
                               "Only available if using CivetWeb");

#elif ORTHANC_ENABLE_CIVETWEB == 1
#  if CIVETWEB_HAS_DISABLE_KEEP_ALIVE == 1
        mg_disable_keep_alive(connection_);
#  else
#       warning The function "mg_disable_keep_alive()" is not available, DICOMweb might run slowly
        throw OrthancException(ErrorCode_NotImplemented,
                               "Only available if using a patched version of CivetWeb");
#  endif

#else
#  error Please support your embedded Web server here
#endif
      }
    };


    enum PostDataStatus
    {
      PostDataStatus_Success,
      PostDataStatus_NoLength,
      PostDataStatus_Pending,
      PostDataStatus_Failure
    };
  }


// TODO Move this to external file


  class ChunkedFile : public ChunkedBuffer
  {
  private:
    std::string filename_;

  public:
    ChunkedFile(const std::string& filename) :
      filename_(filename)
    {
    }

    const std::string& GetFilename() const
    {
      return filename_;
    }
  };



  class ChunkStore
  {
  private:
    typedef std::list<ChunkedFile*>  Content;
    Content  content_;
    unsigned int numPlaces_;

    boost::mutex mutex_;
    std::set<std::string> discardedFiles_;

    void Clear()
    {
      for (Content::iterator it = content_.begin();
           it != content_.end(); ++it)
      {
        delete *it;
      }
    }

    Content::iterator Find(const std::string& filename)
    {
      for (Content::iterator it = content_.begin();
           it != content_.end(); ++it)
      {
        if ((*it)->GetFilename() == filename)
        {
          return it;
        }
      }

      return content_.end();
    }

    void Remove(const std::string& filename)
    {
      Content::iterator it = Find(filename);
      if (it != content_.end())
      {
        delete *it;
        content_.erase(it);
      }
    }

  public:
    ChunkStore()
    {
      numPlaces_ = 10;
    }

    ~ChunkStore()
    {
      Clear();
    }

    PostDataStatus Store(std::string& completed,
                         const char* chunkData,
                         size_t chunkSize,
                         const std::string& filename,
                         size_t filesize)
    {
      boost::mutex::scoped_lock lock(mutex_);

      std::set<std::string>::iterator wasDiscarded = discardedFiles_.find(filename);
      if (wasDiscarded != discardedFiles_.end())
      {
        discardedFiles_.erase(wasDiscarded);
        return PostDataStatus_Failure;
      }

      ChunkedFile* f;
      Content::iterator it = Find(filename);
      if (it == content_.end())
      {
        f = new ChunkedFile(filename);

        // Make some room
        if (content_.size() >= numPlaces_)
        {
          discardedFiles_.insert(content_.front()->GetFilename());
          delete content_.front();
          content_.pop_front();
        }

        content_.push_back(f);
      }
      else
      {
        f = *it;
      }

      f->AddChunk(chunkData, chunkSize);

      if (f->GetNumBytes() > filesize)
      {
        Remove(filename);
      }
      else if (f->GetNumBytes() == filesize)
      {
        f->Flatten(completed);
        Remove(filename);
        return PostDataStatus_Success;
      }

      return PostDataStatus_Pending;
    }

    /*void Print() 
      {
      boost::mutex::scoped_lock lock(mutex_);

      printf("ChunkStore status:\n");
      for (Content::const_iterator i = content_.begin();
      i != content_.end(); i++)
      {
      printf("  [%s]: %d\n", (*i)->GetFilename().c_str(), (*i)->GetNumBytes());
      }
      printf("-----\n");
      }*/
  };


  struct HttpServer::PImpl
  {
    struct mg_context *context_;
    ChunkStore chunkStore_;
  };


  ChunkStore& HttpServer::GetChunkStore()
  {
    return pimpl_->chunkStore_;
  }



  static PostDataStatus ReadBody(std::string& postData,
                                 struct mg_connection *connection,
                                 const IHttpHandler::Arguments& headers)
  {
    IHttpHandler::Arguments::const_iterator cs = headers.find("content-length");
    if (cs == headers.end())
    {
      // Store all the individual chunks within a temporary file, then
      // read it back into the memory buffer "postData"
      FileBuffer buffer;

      std::string tmp(1024 * 1024, 0);
      
      for (;;)
      {
        int r = mg_read(connection, &tmp[0], tmp.size());
        if (r < 0)
        {
          return PostDataStatus_Failure;
        }
        else if (r == 0)
        {
          break;
        }
        else
        {
          buffer.Append(tmp.c_str(), r);
        }
      }

      buffer.Read(postData);

      return PostDataStatus_Success;
    }
    else
    {
      // "Content-Length" is available
      int length;      
      try
      {
        length = boost::lexical_cast<int>(cs->second);
      }
      catch (boost::bad_lexical_cast&)
      {
        return PostDataStatus_NoLength;
      }

      if (length < 0)
      {
        length = 0;
      }

      postData.resize(length);

      size_t pos = 0;
      while (length > 0)
      {
        int r = mg_read(connection, &postData[pos], length);
        if (r <= 0)
        {
          return PostDataStatus_Failure;
        }

        assert(r <= length);
        length -= r;
        pos += r;
      }

      return PostDataStatus_Success;
    }
  }



  static PostDataStatus ParseMultipartPost(std::string &completedFile,
                                           struct mg_connection *connection,
                                           const IHttpHandler::Arguments& headers,
                                           const std::string& contentType,
                                           ChunkStore& chunkStore)
  {
    std::string boundary = "--" + contentType.substr(multipartLength);

    std::string postData;
    PostDataStatus status = ReadBody(postData, connection, headers);

    if (status != PostDataStatus_Success)
    {
      return status;
    }

    /*for (IHttpHandler::Arguments::const_iterator i = headers.begin(); i != headers.end(); i++)
      {
      std::cout << "Header [" << i->first << "] = " << i->second << "\n";
      }
      printf("CHUNK\n");*/

    typedef IHttpHandler::Arguments::const_iterator ArgumentIterator;

    ArgumentIterator requestedWith = headers.find("x-requested-with");
    ArgumentIterator fileName = headers.find("x-file-name");
    ArgumentIterator fileSizeStr = headers.find("x-file-size");

    if (requestedWith != headers.end() &&
        requestedWith->second != "XMLHttpRequest")
    {
      return PostDataStatus_Failure; 
    }

    size_t fileSize = 0;
    if (fileSizeStr != headers.end())
    {
      try
      {
        fileSize = boost::lexical_cast<size_t>(fileSizeStr->second);
      }
      catch (boost::bad_lexical_cast&)
      {
        return PostDataStatus_Failure;
      }
    }

    typedef boost::find_iterator<std::string::iterator> FindIterator;
    typedef boost::iterator_range<char*> Range;

    //chunkStore.Print();

    try
    {
      FindIterator last;
      for (FindIterator it =
             make_find_iterator(postData, boost::first_finder(boundary));
           it!=FindIterator();
           ++it)
      {
        if (last != FindIterator())
        {
          Range part(&last->back(), &it->front());
          Range content = boost::find_first(part, "\r\n\r\n");
          if (/*content != Range()*/!content.empty())
          {
            Range c(&content.back() + 1, &it->front() - 2);
            size_t chunkSize = c.size();

            if (chunkSize > 0)
            {
              const char* chunkData = &c.front();

              if (fileName == headers.end())
              {
                // This file is stored in a single chunk
                completedFile.resize(chunkSize);
                if (chunkSize > 0)
                {
                  memcpy(&completedFile[0], chunkData, chunkSize);
                }
                return PostDataStatus_Success;
              }
              else
              {
                return chunkStore.Store(completedFile, chunkData, chunkSize, fileName->second, fileSize);
              }
            }
          }
        }

        last = it;
      }
    }
    catch (std::length_error&)
    {
      return PostDataStatus_Failure;
    }

    return PostDataStatus_Pending;
  }


  static bool IsAccessGranted(const HttpServer& that,
                              const IHttpHandler::Arguments& headers)
  {
    bool granted = false;

    IHttpHandler::Arguments::const_iterator auth = headers.find("authorization");
    if (auth != headers.end())
    {
      std::string s = auth->second;
      if (s.size() > 6 &&
          s.substr(0, 6) == "Basic ")
      {
        std::string b64 = s.substr(6);
        granted = that.IsValidBasicHttpAuthentication(b64);
      }
    }

    return granted;
  }


  static std::string GetAuthenticatedUsername(const IHttpHandler::Arguments& headers)
  {
    IHttpHandler::Arguments::const_iterator auth = headers.find("authorization");

    if (auth == headers.end())
    {
      return "";
    }

    std::string s = auth->second;
    if (s.size() <= 6 ||
        s.substr(0, 6) != "Basic ")
    {
      return "";
    }

    std::string b64 = s.substr(6);
    std::string decoded;
    Toolbox::DecodeBase64(decoded, b64);
    size_t semicolons = decoded.find(':');

    if (semicolons == std::string::npos)
    {
      // Bad-formatted request
      return "";
    }
    else
    {
      return decoded.substr(0, semicolons);
    }
  }


  static bool ExtractMethod(HttpMethod& method,
                            const struct mg_request_info *request,
                            const IHttpHandler::Arguments& headers,
                            const IHttpHandler::GetArguments& argumentsGET)
  {
    std::string overriden;

    // Check whether some PUT/DELETE faking is done

    // 1. Faking with Google's approach
    IHttpHandler::Arguments::const_iterator methodOverride =
      headers.find("x-http-method-override");

    if (methodOverride != headers.end())
    {
      overriden = methodOverride->second;
    }
    else if (!strcmp(request->request_method, "GET"))
    {
      // 2. Faking with Ruby on Rail's approach
      // GET /my/resource?_method=delete <=> DELETE /my/resource
      for (size_t i = 0; i < argumentsGET.size(); i++)
      {
        if (argumentsGET[i].first == "_method")
        {
          overriden = argumentsGET[i].second;
          break;
        }
      }
    }

    if (overriden.size() > 0)
    {
      // A faking has been done within this request
      Toolbox::ToUpperCase(overriden);

      LOG(INFO) << "HTTP method faking has been detected for " << overriden;

      if (overriden == "PUT")
      {
        method = HttpMethod_Put;
        return true;
      }
      else if (overriden == "DELETE")
      {
        method = HttpMethod_Delete;
        return true;
      }
      else
      {
        return false;
      }
    }

    // No PUT/DELETE faking was present
    if (!strcmp(request->request_method, "GET"))
    {
      method = HttpMethod_Get;
    }
    else if (!strcmp(request->request_method, "POST"))
    {
      method = HttpMethod_Post;
    }
    else if (!strcmp(request->request_method, "DELETE"))
    {
      method = HttpMethod_Delete;
    }
    else if (!strcmp(request->request_method, "PUT"))
    {
      method = HttpMethod_Put;
    }
    else
    {
      return false;
    }    

    return true;
  }


  static void ConfigureHttpCompression(HttpOutput& output,
                                       const IHttpHandler::Arguments& headers)
  {
    // Look if the client wishes HTTP compression
    // https://en.wikipedia.org/wiki/HTTP_compression
    IHttpHandler::Arguments::const_iterator it = headers.find("accept-encoding");
    if (it != headers.end())
    {
      std::vector<std::string> encodings;
      Toolbox::TokenizeString(encodings, it->second, ',');

      for (size_t i = 0; i < encodings.size(); i++)
      {
        std::string s = Toolbox::StripSpaces(encodings[i]);

        if (s == "deflate")
        {
          output.SetDeflateAllowed(true);
        }
        else if (s == "gzip")
        {
          output.SetGzipAllowed(true);
        }
      }
    }
  }


  static void InternalCallback(HttpOutput& output /* out */,
                               HttpMethod& method /* out */,
                               HttpServer& server,
                               struct mg_connection *connection,
                               const struct mg_request_info *request)
  {
    bool localhost;

#if ORTHANC_ENABLE_MONGOOSE == 1
    static const long LOCALHOST = (127ll << 24) + 1ll;
    localhost = (request->remote_ip == LOCALHOST);
#elif ORTHANC_ENABLE_CIVETWEB == 1
    // The "remote_ip" field of "struct mg_request_info" is tagged as
    // deprecated in Civetweb, using "remote_addr" instead.
    localhost = (std::string(request->remote_addr) == "127.0.0.1");
#else
#  error
#endif
    
    // Check remote calls
    if (!server.IsRemoteAccessAllowed() &&
        !localhost)
    {
      output.SendUnauthorized(server.GetRealm());
      return;
    }


    // Extract the HTTP headers
    IHttpHandler::Arguments headers;
    for (int i = 0; i < request->num_headers; i++)
    {
      std::string name = request->http_headers[i].name;
      std::string value = request->http_headers[i].value;

      std::transform(name.begin(), name.end(), name.begin(), ::tolower);
      headers.insert(std::make_pair(name, value));
      VLOG(1) << "HTTP header: [" << name << "]: [" << value << "]";
    }

    if (server.IsHttpCompressionEnabled())
    {
      ConfigureHttpCompression(output, headers);
    }


    // Extract the GET arguments
    IHttpHandler::GetArguments argumentsGET;
    if (!strcmp(request->request_method, "GET"))
    {
      HttpToolbox::ParseGetArguments(argumentsGET, request->query_string);
    }


    // Compute the HTTP method, taking method faking into consideration
    method = HttpMethod_Get;
    if (!ExtractMethod(method, request, headers, argumentsGET))
    {
      output.SendStatus(HttpStatus_400_BadRequest);
      return;
    }


    // Authenticate this connection
    if (server.IsAuthenticationEnabled() && 
        !IsAccessGranted(server, headers))
    {
      output.SendUnauthorized(server.GetRealm());
      return;
    }

    
#if ORTHANC_ENABLE_MONGOOSE == 1
    // Apply the filter, if it is installed
    char remoteIp[24];
    sprintf(remoteIp, "%d.%d.%d.%d", 
            reinterpret_cast<const uint8_t*>(&request->remote_ip) [3], 
            reinterpret_cast<const uint8_t*>(&request->remote_ip) [2], 
            reinterpret_cast<const uint8_t*>(&request->remote_ip) [1], 
            reinterpret_cast<const uint8_t*>(&request->remote_ip) [0]);

    const char* requestUri = request->uri;
      
#elif ORTHANC_ENABLE_CIVETWEB == 1
    const char* remoteIp = request->remote_addr;
    const char* requestUri = request->local_uri;
#else
#  error
#endif

    if (requestUri == NULL)
    {
      requestUri = "";
    }
      
    std::string username = GetAuthenticatedUsername(headers);

    IIncomingHttpRequestFilter *filter = server.GetIncomingHttpRequestFilter();
    if (filter != NULL)
    {
      if (!filter->IsAllowed(method, requestUri, remoteIp,
                             username.c_str(), headers, argumentsGET))
      {
        //output.SendUnauthorized(server.GetRealm());
        output.SendStatus(HttpStatus_403_Forbidden);
        return;
      }
    }


    // Extract the body of the request for PUT and POST

    // TODO Avoid unneccessary memcopy of the body

    std::string body;
    if (method == HttpMethod_Post ||
        method == HttpMethod_Put)
    {
      PostDataStatus status;

      IHttpHandler::Arguments::const_iterator ct = headers.find("content-type");
      if (ct == headers.end())
      {
        // No content-type specified. Assume no multi-part content occurs at this point.
        status = ReadBody(body, connection, headers);          
      }
      else
      {
        std::string contentType = ct->second;
        if (contentType.size() >= multipartLength &&
            !memcmp(contentType.c_str(), multipart, multipartLength))
        {
          status = ParseMultipartPost(body, connection, headers, contentType, server.GetChunkStore());
        }
        else
        {
          status = ReadBody(body, connection, headers);
        }
      }

      switch (status)
      {
        case PostDataStatus_NoLength:
          output.SendStatus(HttpStatus_411_LengthRequired);
          return;

        case PostDataStatus_Failure:
          output.SendStatus(HttpStatus_400_BadRequest);
          return;

        case PostDataStatus_Pending:
          output.AnswerEmpty();
          return;

        default:
          break;
      }
    }


    // Decompose the URI into its components
    UriComponents uri;
    try
    {
      Toolbox::SplitUriComponents(uri, requestUri);
    }
    catch (OrthancException&)
    {
      output.SendStatus(HttpStatus_400_BadRequest);
      return;
    }


    LOG(INFO) << EnumerationToString(method) << " " << Toolbox::FlattenUri(uri);

    bool found = false;

    if (server.HasHandler())
    {
      found = server.GetHandler().Handle(output, RequestOrigin_RestApi, remoteIp, username.c_str(), 
                                         method, uri, headers, argumentsGET, body.c_str(), body.size());
    }

    if (!found)
    {
      throw OrthancException(ErrorCode_UnknownResource);
    }
  }


  static void ProtectedCallback(struct mg_connection *connection,
                                const struct mg_request_info *request)
  {
    try
    {
#if ORTHANC_ENABLE_MONGOOSE == 1
      void *that = request->user_data;
      const char* requestUri = request->uri;
#elif ORTHANC_ENABLE_CIVETWEB == 1
      // https://github.com/civetweb/civetweb/issues/409
      void *that = mg_get_user_data(mg_get_context(connection));
      const char* requestUri = request->local_uri;
#else
#  error
#endif

      if (requestUri == NULL)
      {
        requestUri = "";
      }
      
      HttpServer* server = reinterpret_cast<HttpServer*>(that);

      if (server == NULL)
      {
        MongooseOutputStream stream(connection);
        HttpOutput output(stream, false /* assume no keep-alive */);
        output.SendStatus(HttpStatus_500_InternalServerError);
        return;
      }

      MongooseOutputStream stream(connection);
      HttpOutput output(stream, server->IsKeepAliveEnabled());
      HttpMethod method = HttpMethod_Get;

      try
      {
        try
        {
          InternalCallback(output, method, *server, connection, request);
        }
        catch (OrthancException&)
        {
          throw;  // Pass the exception to the main handler below
        }
        // Now convert native exceptions as OrthancException
        catch (boost::bad_lexical_cast&)
        {
          throw OrthancException(ErrorCode_BadParameterType,
                                 "Syntax error in some user-supplied data");
        }
        catch (std::runtime_error&)
        {
          // Presumably an error while parsing the JSON body
          throw OrthancException(ErrorCode_BadRequest);
        }
        catch (std::bad_alloc&)
        {
          throw OrthancException(ErrorCode_NotEnoughMemory,
                                 "The server hosting Orthanc is running out of memory");
        }
        catch (...)
        {
          throw OrthancException(ErrorCode_InternalError,
                                 "An unhandled exception was generated inside the HTTP server");
        }
      }
      catch (OrthancException& e)
      {
        assert(server != NULL);

        // Using this candidate handler results in an exception
        try
        {
          if (server->GetExceptionFormatter() == NULL)
          {
            LOG(ERROR) << "Exception in the HTTP handler: " << e.What();
            output.SendStatus(e.GetHttpStatus());
          }
          else
          {
            server->GetExceptionFormatter()->Format(output, e, method, requestUri);
          }
        }
        catch (OrthancException&)
        {
          // An exception here reflects the fact that the status code
          // was already set by the HTTP handler.
        }
      }
    }
    catch (...)
    {
      // We should never arrive at this point, where it is even impossible to send an answer
      LOG(ERROR) << "Catastrophic error inside the HTTP server, giving up";
    }
  }


#if MONGOOSE_USE_CALLBACKS == 0
  static void* Callback(enum mg_event event,
                        struct mg_connection *connection,
                        const struct mg_request_info *request)
  {
    if (event == MG_NEW_REQUEST) 
    {
      ProtectedCallback(connection, request);

      // Mark as processed
      return (void*) "";
    }
    else
    {
      return NULL;
    }
  }

#elif MONGOOSE_USE_CALLBACKS == 1
  static int Callback(struct mg_connection *connection)
  {
    const struct mg_request_info *request = mg_get_request_info(connection);

    ProtectedCallback(connection, request);

    return 1;  // Do not let Mongoose handle the request by itself
  }

#else
#  error Please set MONGOOSE_USE_CALLBACKS
#endif





  bool HttpServer::IsRunning() const
  {
    return (pimpl_->context_ != NULL);
  }


  HttpServer::HttpServer() : pimpl_(new PImpl)
  {
    pimpl_->context_ = NULL;
    handler_ = NULL;
    remoteAllowed_ = false;
    authentication_ = false;
    ssl_ = false;
    port_ = 8000;
    filter_ = NULL;
    keepAlive_ = false;
    httpCompression_ = true;
    exceptionFormatter_ = NULL;
    realm_ = ORTHANC_REALM;
    threadsCount_ = 50;  // Default value in mongoose
    tcpNoDelay_ = true;

#if ORTHANC_ENABLE_MONGOOSE == 1
    LOG(INFO) << "This Orthanc server uses Mongoose as its embedded HTTP server";
#endif

#if ORTHANC_ENABLE_CIVETWEB == 1
    LOG(INFO) << "This Orthanc server uses CivetWeb as its embedded HTTP server";
#endif

#if ORTHANC_ENABLE_SSL == 1
    // Check for the Heartbleed exploit
    // https://en.wikipedia.org/wiki/OpenSSL#Heartbleed_bug
    if (OPENSSL_VERSION_NUMBER <  0x1000107fL  /* openssl-1.0.1g */ &&
        OPENSSL_VERSION_NUMBER >= 0x1000100fL  /* openssl-1.0.1 */) 
    {
      LOG(WARNING) << "This version of OpenSSL is vulnerable to the Heartbleed exploit";
    }
#endif
  }


  HttpServer::~HttpServer()
  {
    Stop();
  }


  void HttpServer::SetPortNumber(uint16_t port)
  {
    Stop();
    port_ = port;
  }

  void HttpServer::Start()
  {
#if ORTHANC_ENABLE_MONGOOSE == 1
    LOG(INFO) << "Starting embedded Web server using Mongoose";
#elif ORTHANC_ENABLE_CIVETWEB == 1
    LOG(INFO) << "Starting embedded Web server using Civetweb";
#else
#  error
#endif  

    if (!IsRunning())
    {
      std::string port = boost::lexical_cast<std::string>(port_);
      std::string numThreads = boost::lexical_cast<std::string>(threadsCount_);

      if (ssl_)
      {
        port += "s";
      }

      const char *options[] = {
        // Set the TCP port for the HTTP server
        "listening_ports", port.c_str(), 
        
        // Optimization reported by Chris Hafey
        // https://groups.google.com/d/msg/orthanc-users/CKueKX0pJ9E/_UCbl8T-VjIJ
        "enable_keep_alive", (keepAlive_ ? "yes" : "no"),

#if ORTHANC_ENABLE_CIVETWEB == 1
        // https://github.com/civetweb/civetweb/blob/master/docs/UserManual.md#enable_keep_alive-no
        "keep_alive_timeout_ms", (keepAlive_ ? "500" : "0"),
#endif

#if ORTHANC_ENABLE_CIVETWEB == 1
        // Disable TCP Nagle's algorithm to maximize speed (this
        // option is not available in Mongoose).
        // https://groups.google.com/d/topic/civetweb/35HBR9seFjU/discussion
        // https://eklitzke.org/the-caveats-of-tcp-nodelay
        "tcp_nodelay", (tcpNoDelay_ ? "1" : "0"),
#endif

        // Set the number of threads
        "num_threads", numThreads.c_str(),
        
        // Set the SSL certificate, if any. This must be the last option.
        ssl_ ? "ssl_certificate" : NULL,
        certificate_.c_str(),
        NULL
      };

#if MONGOOSE_USE_CALLBACKS == 0
      pimpl_->context_ = mg_start(&Callback, this, options);

#elif MONGOOSE_USE_CALLBACKS == 1
      struct mg_callbacks callbacks;
      memset(&callbacks, 0, sizeof(callbacks));
      callbacks.begin_request = Callback;
      pimpl_->context_ = mg_start(&callbacks, this, options);

#else
#  error Please set MONGOOSE_USE_CALLBACKS
#endif

      if (!pimpl_->context_)
      {
        throw OrthancException(ErrorCode_HttpPortInUse,
                               " (port = " + boost::lexical_cast<std::string>(port_) + ")");
      }

      LOG(WARNING) << "HTTP server listening on port: " << GetPortNumber()
                   << " (HTTPS encryption is "
                   << (IsSslEnabled() ? "enabled" : "disabled")
                   << ", remote access is "
                   << (IsRemoteAccessAllowed() ? "" : "not ")
                   << "allowed)";
    }
  }

  void HttpServer::Stop()
  {
    if (IsRunning())
    {
      mg_stop(pimpl_->context_);
      pimpl_->context_ = NULL;
    }
  }


  void HttpServer::ClearUsers()
  {
    Stop();
    registeredUsers_.clear();
  }


  void HttpServer::RegisterUser(const char* username,
                                const char* password)
  {
    Stop();

    std::string tag = std::string(username) + ":" + std::string(password);
    std::string encoded;
    Toolbox::EncodeBase64(encoded, tag);
    registeredUsers_.insert(encoded);
  }

  void HttpServer::SetSslEnabled(bool enabled)
  {
    Stop();

#if ORTHANC_ENABLE_SSL == 0
    if (enabled)
    {
      throw OrthancException(ErrorCode_SslDisabled);
    }
    else
    {
      ssl_ = false;
    }
#else
    ssl_ = enabled;
#endif
  }


  void HttpServer::SetKeepAliveEnabled(bool enabled)
  {
    Stop();
    keepAlive_ = enabled;
    LOG(INFO) << "HTTP keep alive is " << (enabled ? "enabled" : "disabled");

#if ORTHANC_ENABLE_MONGOOSE == 1
    if (enabled)
    {
      LOG(WARNING) << "You should disable HTTP keep alive, as you are using Mongoose";
    }
#endif
  }


  void HttpServer::SetAuthenticationEnabled(bool enabled)
  {
    Stop();
    authentication_ = enabled;
  }

  void HttpServer::SetSslCertificate(const char* path)
  {
    Stop();
    certificate_ = path;
  }

  void HttpServer::SetRemoteAccessAllowed(bool allowed)
  {
    Stop();
    remoteAllowed_ = allowed;
  }

  void HttpServer::SetHttpCompressionEnabled(bool enabled)
  {
    Stop();
    httpCompression_ = enabled;
    LOG(WARNING) << "HTTP compression is " << (enabled ? "enabled" : "disabled");
  }
  
  void HttpServer::SetIncomingHttpRequestFilter(IIncomingHttpRequestFilter& filter)
  {
    Stop();
    filter_ = &filter;
  }


  void HttpServer::SetHttpExceptionFormatter(IHttpExceptionFormatter& formatter)
  {
    Stop();
    exceptionFormatter_ = &formatter;
  }


  bool HttpServer::IsValidBasicHttpAuthentication(const std::string& basic) const
  {
    return registeredUsers_.find(basic) != registeredUsers_.end();
  }


  void HttpServer::Register(IHttpHandler& handler)
  {
    Stop();
    handler_ = &handler;
  }


  IHttpHandler& HttpServer::GetHandler() const
  {
    if (handler_ == NULL)
    {
      throw OrthancException(ErrorCode_InternalError);
    }

    return *handler_;
  }


  void HttpServer::SetThreadsCount(unsigned int threads)
  {
    if (threads <= 0)
    {
      throw OrthancException(ErrorCode_ParameterOutOfRange);
    }
    
    Stop();
    threadsCount_ = threads;

    LOG(INFO) << "The embedded HTTP server will use " << threads << " threads";
  }


  void HttpServer::SetTcpNoDelay(bool tcpNoDelay)
  {
    Stop();
    tcpNoDelay_ = tcpNoDelay;
    LOG(INFO) << "TCP_NODELAY for the HTTP sockets is set to "
              << (tcpNoDelay ? "true" : "false");
  }
}