////////////////////////////////////////////////////////////////////////////////
/// @brief edges request handler
///
/// @file
///
/// DISCLAIMER
///
/// Copyright 2014 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS 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 Michael Hackstein
/// @author Copyright 2014, ArangoDB GmbH, Cologne, Germany
/// @author Copyright 2010-2014, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

#include "RestEdgesHandler.h"
#include "Basics/ScopeGuard.h"
#include "Cluster/ClusterMethods.h"
#include "VocBase/Traverser.h"

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

using namespace triagens::rest;
using namespace triagens::arango;

// -----------------------------------------------------------------------------
// --SECTION--                                      constructors and destructors
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief constructor
////////////////////////////////////////////////////////////////////////////////

RestEdgesHandler::RestEdgesHandler (HttpRequest* request)
  : RestVocbaseBaseHandler(request) {
}

// -----------------------------------------------------------------------------
// --SECTION--                                                   Handler methods
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// {@inheritDoc}
////////////////////////////////////////////////////////////////////////////////

HttpHandler::status_t RestEdgesHandler::execute () {
  // extract the sub-request type
  HttpRequest::HttpRequestType type = _request->requestType();

  // execute one of the CRUD methods
  switch (type) {
    case HttpRequest::HTTP_REQUEST_GET: {
      std::vector<traverser::TraverserExpression*> empty;
      readEdges(empty);
      break;
    }
    case HttpRequest::HTTP_REQUEST_PUT:
      readFilteredEdges();
      break;
    case HttpRequest::HTTP_REQUEST_HEAD:
    case HttpRequest::HTTP_REQUEST_POST:
    case HttpRequest::HTTP_REQUEST_DELETE:
    case HttpRequest::HTTP_REQUEST_ILLEGAL:
    default: {
      generateNotImplemented("ILLEGAL " + EDGES_PATH);
      break;
    }
  }

  // this handler is done
  return status_t(HANDLER_DONE);
}

// -----------------------------------------------------------------------------
// --SECTION--                                                 protected methods
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @startDocuBlock API_EDGE_READINOUTBOUND
/// @brief get edges
///
/// @RESTHEADER{GET /_api/edges/{collection-id}, Read in- or outbound edges}
///
/// @RESTURLPARAMETERS
///
/// @RESTURLPARAM{collection-id,string,required}
/// The id of the collection.
///
/// @RESTQUERYPARAMETERS
///
/// @RESTQUERYPARAM{vertex,string,required}
/// The id of the start vertex.
///
/// @RESTQUERYPARAM{direction,string,optional}
/// Selects *in* or *out* direction for edges. If not set, any edges are
/// returned.
///
/// @RESTDESCRIPTION
/// Returns an array of edges starting or ending in the vertex identified by
/// *vertex-handle*.
///
/// @RESTRETURNCODES
///
/// @RESTRETURNCODE{200}
/// is returned if the edge collection was found and edges were retrieved.
///
/// @RESTRETURNCODE{400}
/// is returned if the request contains invalid parameters.
///
/// @RESTRETURNCODE{404}
/// is returned if the edge collection was not found.
///
/// @EXAMPLES
///
/// Any direction
///
/// @EXAMPLE_ARANGOSH_RUN{RestEdgesReadEdgesAny}
///     var Graph = require("org/arangodb/graph-blueprint").Graph;
///     var g = new Graph("graph", "vertices", "edges");
///     var v1 = g.addVertex(1);
///     var v2 = g.addVertex(2);
///     var v3 = g.addVertex(3);
///     var v4 = g.addVertex(4);
///     g.addEdge(v1, v3, 5, "v1 -> v3");
///     g.addEdge(v2, v1, 6, "v2 -> v1");
///     g.addEdge(v4, v1, 7, "v4 -> v1");
///
///     var url = "/_api/edges/edges?vertex=vertices/1";
///     var response = logCurlRequest('GET', url);
///
///     assert(response.code === 200);
///
///     logJsonResponse(response);
///     db._drop("edges");
///     db._drop("vertices");
///     db._graphs.remove("graph");
/// @END_EXAMPLE_ARANGOSH_RUN
///
/// In edges
///
/// @EXAMPLE_ARANGOSH_RUN{RestEdgesReadEdgesIn}
///     var Graph = require("org/arangodb/graph-blueprint").Graph;
///     var g = new Graph("graph", "vertices", "edges");
///     var v1 = g.addVertex(1);
///     var v2 = g.addVertex(2);
///     var v3 = g.addVertex(3);
///     var v4 = g.addVertex(4);
///     g.addEdge(v1, v3, 5, "v1 -> v3");
///     g.addEdge(v2, v1, 6, "v2 -> v1");
///     g.addEdge(v4, v1, 7, "v4 -> v1");
///
///     var url = "/_api/edges/edges?vertex=vertices/1&direction=in";
///     var response = logCurlRequest('GET', url);
///
///     assert(response.code === 200);
///
///     logJsonResponse(response);
///     db._drop("edges");
///     db._drop("vertices");
///     db._graphs.remove("graph");
/// @END_EXAMPLE_ARANGOSH_RUN
///
/// Out edges
///
/// @EXAMPLE_ARANGOSH_RUN{RestEdgesReadEdgesOut}
///     var Graph = require("org/arangodb/graph-blueprint").Graph;
///     var g = new Graph("graph", "vertices", "edges");
///     var v1 = g.addVertex(1);
///     var v2 = g.addVertex(2);
///     var v3 = g.addVertex(3);
///     var v4 = g.addVertex(4);
///     g.addEdge(v1, v3, 5, "v1 -> v3");
///     g.addEdge(v2, v1, 6, "v2 -> v1");
///     g.addEdge(v4, v1, 7, "v4 -> v1");
///
///     var url = "/_api/edges/edges?vertex=vertices/1&direction=out";
///     var response = logCurlRequest('GET', url);
///
///     assert(response.code === 200);
///
///     logJsonResponse(response);
///     db._drop("edges");
///     db._drop("vertices");
///     db._graphs.remove("graph");
/// @END_EXAMPLE_ARANGOSH_RUN
/// @endDocuBlock
////////////////////////////////////////////////////////////////////////////////

bool RestEdgesHandler::readEdges (std::vector<traverser::TraverserExpression*> const& expressions) {
  std::vector<std::string> const& suffix = _request->suffix();

  if (suffix.size() != 1) {
    generateError(HttpResponse::BAD,
                  TRI_ERROR_HTTP_BAD_PARAMETER,
                  "expected GET " + EDGES_PATH +
                  "/<collection-identifier>?vertex=<vertex-handle>&direction=<direction>");
    return false;
  }

  std::string collectionName = suffix[0];
  CollectionNameResolver resolver(_vocbase);
  TRI_col_type_t colType = resolver.getCollectionTypeCluster(collectionName);
  if (colType == TRI_COL_TYPE_UNKNOWN) {
    generateError(HttpResponse::NOT_FOUND, TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND);
    return false;
  }
  else if (colType != TRI_COL_TYPE_EDGE) {
    generateError(HttpResponse::BAD, TRI_ERROR_ARANGO_COLLECTION_TYPE_INVALID);
    return false;
  }

  bool found;
  char const* dir = _request->value("direction", found);

  if (! found || *dir == '\0') {
    dir = "any";
  }

  std::string dirString(dir);
  TRI_edge_direction_e direction;

  if (dirString == "any") {
    direction = TRI_EDGE_ANY;
  }
  else if (dirString == "out" || dirString == "outbound") {
    direction = TRI_EDGE_OUT;
  }
  else if (dirString == "in" || dirString == "inbound") {
    direction = TRI_EDGE_IN;
  }
  else {
    generateError(HttpResponse::BAD,
                  TRI_ERROR_HTTP_BAD_PARAMETER,
                  "<direction> must by any, in, or out, not: " + dirString);
    return false;
  }

  char const* startVertex = _request->value("vertex", found);

  if (! found || *startVertex == '\0') {
    generateError(HttpResponse::BAD,
                  TRI_ERROR_ARANGO_DOCUMENT_HANDLE_BAD,
                  "illegal document handle");
    return false;
  }

  if (ServerState::instance()->isCoordinator()) {
    std::string vertexString(startVertex);
    triagens::rest::HttpResponse::HttpResponseCode responseCode;
    std::string contentType;
    triagens::basics::Json resultDocument(triagens::basics::Json::Object, 3);
    int res = getFilteredEdgesOnCoordinator(_vocbase->_name,
                                            collectionName,
                                            vertexString,
                                            direction,
                                            expressions,
                                            responseCode,
                                            contentType,
                                            resultDocument);
    if (res != TRI_ERROR_NO_ERROR) {
      generateError(responseCode, res);
      return false;
    }

    resultDocument.set("error", triagens::basics::Json(false));
    resultDocument.set("code", triagens::basics::Json(200));
    generateResult(resultDocument.json());
    return true;
  }

  // find and load collection given by name or identifier
  SingleCollectionReadOnlyTransaction trx(new StandaloneTransactionContext(), _vocbase, collectionName);

  // .............................................................................
  // inside read transaction
  // .............................................................................

  int res = trx.begin();
  if (res != TRI_ERROR_NO_ERROR) {
    generateTransactionError(collectionName, res);
    return false;
  }

  TRI_voc_cid_t const cid = trx.cid();

  // If we are a DBserver, we want to use the cluster-wide collection
  // name for error reporting:
  if (ServerState::instance()->isDBServer()) {
    collectionName = trx.resolver()->getCollectionName(cid);
  }

  triagens::arango::traverser::VertexId start;
  std::string startVertexString(startVertex);

  start = triagens::arango::traverser::IdStringToVertexId (
    trx.resolver(),
    startVertexString
  );

  TRI_transaction_collection_t* collection = trx.trxCollection();

  size_t filtered = 0;
  std::vector<TRI_doc_mptr_copy_t>&& edges = TRI_LookupEdgesDocumentCollection(
    &trx,
    collection->_collection->_collection,
    direction,
    start.cid,
    const_cast<char*>(start.key)
  );


  // generate result
  triagens::basics::Json documents(triagens::basics::Json::Array);
  documents.reserve(edges.size());
  TRI_document_collection_t* docCol = collection->_collection->_collection;

  if (expressions.empty()) {
    for (auto& e : edges) {
      DocumentAccessor da(trx.resolver(), docCol, &e);
      documents.add(da.toJson());
    }
  }
  else {
    for (auto& e : edges) {
      bool add = true;
      // Expressions symbolize an and, so all have to be matched
      for (auto& exp : expressions) {
        if (exp->isEdgeAccess && ! exp->matchesCheck(e, docCol, trx.resolver())) {
          ++filtered;
          add = false;
          break;
        }
      }
      if (add) {
        DocumentAccessor da(trx.resolver(), docCol, &e);
        documents.add(da.toJson());
      }
    }
  }

  res = trx.finish(res);
  if (res != TRI_ERROR_NO_ERROR) {
    generateTransactionError(collectionName, res);
    return false;
  }

  triagens::basics::Json result(triagens::basics::Json::Object, 4);
  result("edges", documents);
  result("error", triagens::basics::Json(false));
  result("code", triagens::basics::Json(200));
  triagens::basics::Json stats(triagens::basics::Json::Object, 2);

  stats("scannedIndex", triagens::basics::Json(static_cast<int32_t>(edges.size())));
  stats("filtered", triagens::basics::Json(static_cast<int32_t>(filtered)));
  result("stats", stats);

  // and generate a response
  generateResult(result.json());

  return true;
}

////////////////////////////////////////////////////////////////////////////////
/// Internal function for optimized edge retrieval.
/// Allows to send an TraverserExpression for filtering in the body
/// Not publicly documented on purpose.
////////////////////////////////////////////////////////////////////////////////

bool RestEdgesHandler::readFilteredEdges () {
  std::vector<traverser::TraverserExpression*> expressions;
  bool parseSuccess = true;
  std::shared_ptr<VPackBuilder> parsedBody = parseVelocyPackBody(parseSuccess);
  if (! parseSuccess) {
    // We continue unfiltered
    // Filter could be done by caller
    delete _response;
    _response = nullptr;
    return readEdges(expressions);
  }
  VPackSlice body = parsedBody->slice();
  triagens::basics::ScopeGuard guard{
    []() -> void { },
    [&expressions]() -> void {
      for (auto& e : expressions) {
        delete e;
      }
    }
  };

  if (! body.isArray()) {
    generateError(HttpResponse::BAD,
                  TRI_ERROR_HTTP_BAD_PARAMETER,
                  "Expected an array of traverser expressions as body parameter");
    return false;
  }

  expressions.reserve(body.length());

  for (auto const& exp : VPackArrayIterator(body)) {
    if (exp.isObject()) {
      std::unique_ptr<traverser::TraverserExpression> expression(new traverser::TraverserExpression(exp));
      expressions.emplace_back(expression.get());
      expression.release();
    }
  }
  return readEdges(expressions);
}