////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2016 ArangoDB GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///     http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Simon Grätzer
////////////////////////////////////////////////////////////////////////////////

#include "RestPregelHandler.h"

#include "ApplicationFeatures/ApplicationServer.h"
#include "Rest/HttpRequest.h"

#include <velocypack/Builder.h>
#include <velocypack/velocypack-aliases.h>

#include "Pregel/PregelFeature.h"
#include "Pregel/Conductor.h"
#include "Pregel/Worker.h"
#include "Pregel/Utils.h"

using namespace arangodb;
using namespace arangodb::basics;
using namespace arangodb::rest;
using namespace arangodb::pregel;

RestPregelHandler::RestPregelHandler(GeneralRequest* request, GeneralResponse* response)
: RestVocbaseBaseHandler(request, response) {}

RestStatus RestPregelHandler::execute() {
  try {    
    bool parseSuccess = true;
    std::shared_ptr<VPackBuilder> parsedBody =
    parseVelocyPackBody(&VPackOptions::Defaults, parseSuccess);
    VPackSlice body(parsedBody->start());// never nullptr
    
    if (!parseSuccess || !body.isObject()) {
      LOG(ERR) << "Bad request body\n";
      generateError(rest::ResponseCode::BAD,
                    TRI_ERROR_NOT_IMPLEMENTED, "illegal request for /_api/pregel");
    } else if (_request->requestType() == rest::RequestType::POST) {
      
      std::vector<std::string> const& suffix = _request->suffix();
      VPackSlice sExecutionNum = body.get(Utils::executionNumberKey);
      if (!sExecutionNum.isInteger()) {
        LOG(ERR) << "Invalid execution number";
        generateError(rest::ResponseCode::NOT_FOUND, TRI_ERROR_HTTP_NOT_FOUND);
        return RestStatus::DONE;
      }
      
      unsigned int executionNumber = sExecutionNum.getUInt();
      if (suffix.size() != 1) {
        LOG(ERR) << "Invalid suffix";
        generateError(rest::ResponseCode::NOT_FOUND,
                      TRI_ERROR_HTTP_NOT_FOUND);
        return RestStatus::DONE;
      } else if (suffix[0] == Utils::finishedGSSPath) {
        Conductor *exe = PregelFeature::instance()->conductor(executionNumber);
        if (exe) {
          exe->finishedGlobalStep(body);
        } else {
          LOG(ERR) << "Conductor not found: " << executionNumber;
        }
      } else if (suffix[0] == Utils::nextGSSPath) {
        IWorker *w = PregelFeature::instance()->worker(executionNumber);
        if (!w) {// can happen if gss == 0
          LOG(INFO) << "creating worker";
          w = IWorker::createWorker(_vocbase, body);
          PregelFeature::instance()->addWorker(w, executionNumber);
        }
        w->nextGlobalStep(body);
      } else if (suffix[0] == Utils::messagesPath) {
        LOG(INFO) << "messages";
        IWorker *exe = PregelFeature::instance()->worker(executionNumber);
        if (exe) {
          exe->receivedMessages(body);
        }
      } else if (suffix[0] == Utils::finalizeExecutionPath) {
        IWorker *exe = PregelFeature::instance()->worker(executionNumber);
        if (exe) {
          exe->finalizeExecution(body);
          PregelFeature::instance()->cleanup(executionNumber);
        }
      }
      
      VPackBuilder result;
      result.add(VPackValue("thanks"));
      generateResult(rest::ResponseCode::OK, result.slice());
      
    } else {
      generateError(rest::ResponseCode::METHOD_NOT_ALLOWED,
                    TRI_ERROR_NOT_IMPLEMENTED, "illegal method for /_api/pregel");
    }
  } catch (std::exception const &e) {
    LOG(ERR) << e.what();
  } catch(...) {
    LOG(ERR) << "Exception";
  }
    
  return RestStatus::DONE;
}