/**
 * Orthanc - A Lightweight, RESTful DICOM Store
 * Copyright (C) 2012-2014 Medical Physics Department, CHU of Liege,
 * 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 "MongooseServer.h"

#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>
#include <glog/logging.h>

#include "../OrthancException.h"
#include "../ChunkedBuffer.h"
#include "HttpOutput.h"
#include "mongoose.h"

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

#define ORTHANC_REALM "Orthanc Secure Area"

static const long LOCALHOST = (127ll << 24) + 1ll;


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)
        {
          mg_write(connection_, buffer, length);
        }
      }

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


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


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



  static PostDataStatus ReadBody(std::string& postData,
                                 struct mg_connection *connection,
                                 const HttpHandler::Arguments& headers)
  {
    HttpHandler::Arguments::const_iterator cs = headers.find("content-length");
    if (cs == headers.end())
    {
      return PostDataStatus_NoLength;
    }

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

    typedef HttpHandler::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 Authorize(const MongooseServer& that,
                        const HttpHandler::Arguments& headers,
                        HttpOutput& output)
  {
    bool granted = false;

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

    if (!granted)
    {
      output.SendUnauthorized(ORTHANC_REALM);
      return false;
    }
    else
    {
      return true;
    }
  }


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

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

    std::string s = auth->second;
    if (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 HttpHandler::Arguments& headers,
                            const HttpHandler::Arguments& argumentsGET)
  {
    std::string overriden;

    // Check whether some PUT/DELETE faking is done

    // 1. Faking with Google's approach
    HttpHandler::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
      methodOverride = argumentsGET.find("_method");
      if (methodOverride != argumentsGET.end())
      {
        overriden = methodOverride->second;
      }
    }

    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* Callback(enum mg_event event,
                        struct mg_connection *connection,
                        const struct mg_request_info *request)
  {
    if (event == MG_NEW_REQUEST) 
    {
      MongooseServer* that = reinterpret_cast<MongooseServer*>(request->user_data);
      MongooseOutputStream stream(connection);
      HttpOutput output(stream);

      // Check remote calls
      if (!that->IsRemoteAccessAllowed() &&
          request->remote_ip != LOCALHOST)
      {
        output.SendUnauthorized(ORTHANC_REALM);
        return (void*) "";
      }


      // Extract the HTTP headers
      HttpHandler::Arguments headers;
      for (int i = 0; i < request->num_headers; i++)
      {
        std::string name = request->http_headers[i].name;
        std::transform(name.begin(), name.end(), name.begin(), ::tolower);
        headers.insert(std::make_pair(name, request->http_headers[i].value));
      }


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


      // Compute the HTTP method, taking method faking into consideration
      HttpMethod method;
      if (!ExtractMethod(method, request, headers, argumentsGET))
      {
        output.SendHeader(HttpStatus_400_BadRequest);
        return (void*) "";
      }


      // Authenticate this connection
      if (that->IsAuthenticationEnabled() &&
          !Authorize(*that, headers, output))
      {
        return (void*) "";
      }


      // Apply the filter, if it is installed
      const IIncomingHttpRequestFilter *filter = that->GetIncomingHttpRequestFilter();
      if (filter != NULL)
      {
        std::string username = GetAuthenticatedUsername(headers);

        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]);

        if (!filter->IsAllowed(method, request->uri, remoteIp, username.c_str()))
        {
          output.SendUnauthorized(ORTHANC_REALM);
          return (void*) "";
        }
      }


      // Extract the body of the request for PUT and POST
      std::string body;
      if (method == HttpMethod_Post ||
          method == HttpMethod_Put)
      {
        PostDataStatus status;

        HttpHandler::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, that->GetChunkStore());
          }
          else
          {
            status = ReadBody(body, connection, headers);
          }
        }

        switch (status)
        {
          case PostDataStatus_NoLength:
            output.SendHeader(HttpStatus_411_LengthRequired);
            return (void*) "";

          case PostDataStatus_Failure:
            output.SendHeader(HttpStatus_400_BadRequest);
            return (void*) "";

          case PostDataStatus_Pending:
            output.AnswerBufferWithContentType(NULL, 0, "");
            return (void*) "";

          default:
            break;
        }
      }


      // Decompose the URI into its components
      UriComponents uri;
      try
      {
        Toolbox::SplitUriComponents(uri, request->uri);
      }
      catch (OrthancException)
      {
        output.SendHeader(HttpStatus_400_BadRequest);
        return (void*) "";
      }


      // Loop over the candidate handlers for this URI
      LOG(INFO) << EnumerationToString(method) << " " << Toolbox::FlattenUri(uri);
      bool found = false;

      for (MongooseServer::Handlers::const_iterator it = 
             that->GetHandlers().begin(); it != that->GetHandlers().end() && !found; ++it) 
      {
        try
        {
          found = (*it)->Handle(output, method, uri, headers, argumentsGET, body);
        }
        catch (OrthancException& e)
        {
          // Using this candidate handler results in an exception
          LOG(ERROR) << "Exception in the HTTP handler: " << e.What();
          return (void*) "";
        }
        catch (boost::bad_lexical_cast&)
        {
          LOG(ERROR) << "Exception in the HTTP handler: Bad lexical cast";
          return (void*) "";
        }
        catch (std::runtime_error&)
        {
          LOG(ERROR) << "Exception in the HTTP handler: Presumably a bad JSON request";
          return (void*) "";
        }
      }
      
      if (!found)
      {
        output.SendHeader(HttpStatus_404_NotFound);
      }

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


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


  MongooseServer::MongooseServer() : pimpl_(new PImpl)
  {
    pimpl_->context_ = NULL;
    remoteAllowed_ = false;
    authentication_ = false;
    ssl_ = false;
    port_ = 8000;
    filter_ = NULL;

#if ORTHANC_SSL_ENABLED == 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
  }


  MongooseServer::~MongooseServer()
  {
    Stop();
    ClearHandlers();
  }


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

  void MongooseServer::Start()
  {
    if (!IsRunning())
    {
      std::string port = boost::lexical_cast<std::string>(port_);

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

      const char *options[] = {
        "listening_ports", port.c_str(), 
        ssl_ ? "ssl_certificate" : NULL,
        certificate_.c_str(),
        NULL
      };

      pimpl_->context_ = mg_start(&Callback, this, options);
      if (!pimpl_->context_)
      {
        throw OrthancException("Unable to launch the Mongoose server");
      }
    }
  }

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


  void MongooseServer::RegisterHandler(HttpHandler& handler)
  {
    Stop();

    handlers_.push_back(&handler);
  }


  void MongooseServer::ClearHandlers()
  {
    Stop();
  }


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


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

#if ORTHANC_SSL_ENABLED == 0
    if (enabled)
    {
      throw OrthancException("Orthanc has been built without SSL support");
    }
    else
    {
      ssl_ = false;
    }
#else
    ssl_ = enabled;
#endif
  }

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

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

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

  void MongooseServer::SetIncomingHttpRequestFilter(IIncomingHttpRequestFilter& filter)
  {
    Stop();
    filter_ = &filter;
  }

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