////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2016 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 Jan Steemann
////////////////////////////////////////////////////////////////////////////////

#include "Aql/AstNode.h"
#include "Aql/Ast.h"
#include "Aql/Executor.h"
#include "Aql/Function.h"
#include "Aql/Quantifier.h"
#include "Aql/Query.h"
#include "Aql/Scopes.h"
#include "Aql/types.h"
#include "Basics/fasthash.h"
#include "Basics/JsonHelper.h"
#include "Basics/json-utilities.h"
#include "Basics/StringBuffer.h"
#include "Basics/Utf8Helper.h"

#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
#include <iostream>
#endif

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

using namespace arangodb::aql;
using JsonHelper = arangodb::basics::JsonHelper;
using Json = arangodb::basics::Json;

/// @brief quick translation array from an AST node value type to a JSON type
std::array<TRI_json_type_e, 5> const JsonTypes{{
    TRI_JSON_NULL,     //    VALUE_TYPE_NULL   = 0,
    TRI_JSON_BOOLEAN,  //    VALUE_TYPE_BOOL   = 1,
    TRI_JSON_NUMBER,   //    VALUE_TYPE_INT    = 2,
    TRI_JSON_NUMBER,   //    VALUE_TYPE_DOUBLE = 3,
    TRI_JSON_STRING    //    VALUE_TYPE_STRING = 4
}};

static_assert(AstNodeValueType::VALUE_TYPE_NULL == 0,
              "incorrect ast node value types");
static_assert(AstNodeValueType::VALUE_TYPE_BOOL == 1,
              "incorrect ast node value types");
static_assert(AstNodeValueType::VALUE_TYPE_INT == 2,
              "incorrect ast node value types");
static_assert(AstNodeValueType::VALUE_TYPE_DOUBLE == 3,
              "incorrect ast node value types");
static_assert(AstNodeValueType::VALUE_TYPE_STRING == 4,
              "incorrect ast node value types");

std::unordered_map<int, std::string const> const AstNode::Operators{
    {static_cast<int>(NODE_TYPE_OPERATOR_UNARY_NOT), "!"},
    {static_cast<int>(NODE_TYPE_OPERATOR_UNARY_PLUS), "+"},
    {static_cast<int>(NODE_TYPE_OPERATOR_UNARY_MINUS), "-"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_AND), "&&"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_OR), "||"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_PLUS), "+"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_MINUS), "-"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_TIMES), "*"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_DIV), "/"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_MOD), "%"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_EQ), "=="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_NE), "!="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_LT), "<"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_LE), "<="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_GT), ">"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_GE), ">="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_IN), "IN"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_NIN), "NOT IN"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_EQ), "array =="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_NE), "array !="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_LT), "array <"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_LE), "array <="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_GT), "array >"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_GE), "array >="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_IN), "array IN"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN), "array NOT IN"}};

/// @brief type names for AST nodes
std::unordered_map<int, std::string const> const AstNode::TypeNames{
    {static_cast<int>(NODE_TYPE_ROOT), "root"},
    {static_cast<int>(NODE_TYPE_FOR), "for"},
    {static_cast<int>(NODE_TYPE_LET), "let"},
    {static_cast<int>(NODE_TYPE_FILTER), "filter"},
    {static_cast<int>(NODE_TYPE_RETURN), "return"},
    {static_cast<int>(NODE_TYPE_REMOVE), "remove"},
    {static_cast<int>(NODE_TYPE_INSERT), "insert"},
    {static_cast<int>(NODE_TYPE_UPDATE), "update"},
    {static_cast<int>(NODE_TYPE_REPLACE), "replace"},
    {static_cast<int>(NODE_TYPE_UPSERT), "upsert"},
    {static_cast<int>(NODE_TYPE_COLLECT), "collect"},
    {static_cast<int>(NODE_TYPE_SORT), "sort"},
    {static_cast<int>(NODE_TYPE_SORT_ELEMENT), "sort element"},
    {static_cast<int>(NODE_TYPE_LIMIT), "limit"},
    {static_cast<int>(NODE_TYPE_VARIABLE), "variable"},
    {static_cast<int>(NODE_TYPE_ASSIGN), "assign"},
    {static_cast<int>(NODE_TYPE_OPERATOR_UNARY_PLUS), "unary plus"},
    {static_cast<int>(NODE_TYPE_OPERATOR_UNARY_MINUS), "unary minus"},
    {static_cast<int>(NODE_TYPE_OPERATOR_UNARY_NOT), "unary not"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_AND), "logical and"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_OR), "logical or"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_PLUS), "plus"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_MINUS), "minus"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_TIMES), "times"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_DIV), "division"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_MOD), "modulus"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_EQ), "compare =="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_NE), "compare !="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_LT), "compare <"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_LE), "compare <="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_GT), "compare >"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_GE), "compare >="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_IN), "compare in"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_NIN), "compare not in"},
    {static_cast<int>(NODE_TYPE_OPERATOR_TERNARY), "ternary"},
    {static_cast<int>(NODE_TYPE_SUBQUERY), "subquery"},
    {static_cast<int>(NODE_TYPE_ATTRIBUTE_ACCESS), "attribute access"},
    {static_cast<int>(NODE_TYPE_BOUND_ATTRIBUTE_ACCESS),
     "bound attribute access"},
    {static_cast<int>(NODE_TYPE_INDEXED_ACCESS), "indexed access"},
    {static_cast<int>(NODE_TYPE_EXPANSION), "expansion"},
    {static_cast<int>(NODE_TYPE_ITERATOR), "iterator"},
    {static_cast<int>(NODE_TYPE_VALUE), "value"},
    {static_cast<int>(NODE_TYPE_ARRAY), "array"},
    {static_cast<int>(NODE_TYPE_OBJECT), "object"},
    {static_cast<int>(NODE_TYPE_OBJECT_ELEMENT), "object element"},
    {static_cast<int>(NODE_TYPE_COLLECTION), "collection"},
    {static_cast<int>(NODE_TYPE_REFERENCE), "reference"},
    {static_cast<int>(NODE_TYPE_PARAMETER), "parameter"},
    {static_cast<int>(NODE_TYPE_FCALL), "function call"},
    {static_cast<int>(NODE_TYPE_FCALL_USER), "user function call"},
    {static_cast<int>(NODE_TYPE_RANGE), "range"},
    {static_cast<int>(NODE_TYPE_NOP), "no-op"},
    {static_cast<int>(NODE_TYPE_COLLECT_COUNT), "collect with count"},
    {static_cast<int>(NODE_TYPE_CALCULATED_OBJECT_ELEMENT),
     "calculated object element"},
    {static_cast<int>(NODE_TYPE_EXAMPLE), "example"},
    {static_cast<int>(NODE_TYPE_PASSTHRU), "passthru"},
    {static_cast<int>(NODE_TYPE_ARRAY_LIMIT), "array limit"},
    {static_cast<int>(NODE_TYPE_DISTINCT), "distinct"},
    {static_cast<int>(NODE_TYPE_TRAVERSAL), "traversal"},
    {static_cast<int>(NODE_TYPE_DIRECTION), "direction"},
    {static_cast<int>(NODE_TYPE_COLLECTION_LIST), "collection list"},
    {static_cast<int>(NODE_TYPE_OPERATOR_NARY_AND), "n-ary and"},
    {static_cast<int>(NODE_TYPE_OPERATOR_NARY_OR), "n-ary or"},
    {static_cast<int>(NODE_TYPE_AGGREGATIONS), "aggregations array"},
    {static_cast<int>(NODE_TYPE_WITH), "with collections"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_EQ), "array compare =="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_NE), "array compare !="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_LT), "array compare <"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_LE), "array compare <="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_GT), "array compare >"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_GE), "array compare >="},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_IN), "array compare in"},
    {static_cast<int>(NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN),
     "array compare not in"},
    {static_cast<int>(NODE_TYPE_QUANTIFIER), "quantifier"},
    {static_cast<int>(NODE_TYPE_SHORTEST_PATH), "shortest path"}};

/// @brief names for AST node value types
std::unordered_map<int, std::string const> const AstNode::ValueTypeNames{
    {static_cast<int>(VALUE_TYPE_NULL), "null"},
    {static_cast<int>(VALUE_TYPE_BOOL), "bool"},
    {static_cast<int>(VALUE_TYPE_INT), "int"},
    {static_cast<int>(VALUE_TYPE_DOUBLE), "double"},
    {static_cast<int>(VALUE_TYPE_STRING), "string"}};

/// @brief resolve an attribute access
static AstNode const* ResolveAttribute(AstNode const* node) {
  TRI_ASSERT(node != nullptr);
  TRI_ASSERT(node->type == NODE_TYPE_ATTRIBUTE_ACCESS);

  std::vector<std::string> attributeNames;

  while (node->type == NODE_TYPE_ATTRIBUTE_ACCESS) {
    attributeNames.emplace_back(node->getString());
    node = node->getMember(0);
  }

  size_t which = attributeNames.size();
  TRI_ASSERT(which > 0);

  while (which > 0) {
    TRI_ASSERT(node->type == NODE_TYPE_VALUE || node->type == NODE_TYPE_ARRAY ||
               node->type == NODE_TYPE_OBJECT);

    bool found = false;

    if (node->type == NODE_TYPE_OBJECT) {
      TRI_ASSERT(which > 0);
      std::string const& attributeName = attributeNames[which - 1];
      --which;

      size_t const n = node->numMembers();
      for (size_t i = 0; i < n; ++i) {
        auto member = node->getMember(i);

        if (member->type == NODE_TYPE_OBJECT_ELEMENT && 
            member->getString() == attributeName) {
          // found the attribute
          node = member->getMember(0);
          if (which == 0) {
            // we found what we looked for
            return node;
          } 
          // we found the correct attribute but there is now an attribute
          // access on the result
          found = true;
          break;
        }
      }
    }

    if (!found) {
      break;
    }
  }

  // attribute not found or non-array
  return Ast::createNodeValueNull();
}

/// @brief get the node type for inter-node comparisons
static TRI_json_type_e GetNodeCompareType(AstNode const* node) {
  TRI_ASSERT(node != nullptr);

  if (node->type == NODE_TYPE_VALUE) {
    return JsonTypes[node->value.type];
  }
  if (node->type == NODE_TYPE_ARRAY) {
    return TRI_JSON_ARRAY;
  }
  if (node->type == NODE_TYPE_OBJECT) {
    return TRI_JSON_OBJECT;
  }

  // we should never get here
  TRI_ASSERT(false);

  // return null in case assertions are turned off
  return TRI_JSON_NULL;
}

/// @brief compare two nodes
/// @return range from -1 to +1 depending:
///  - -1 LHS being  less then   RHS,
///  -  0 LHS being     equal    RHS
///  -  1 LHS being greater then RHS
int arangodb::aql::CompareAstNodes(AstNode const* lhs, AstNode const* rhs,
                                   bool compareUtf8) {
  TRI_ASSERT(lhs != nullptr);
  TRI_ASSERT(rhs != nullptr);

  if (lhs->type == NODE_TYPE_ATTRIBUTE_ACCESS) {
    lhs = ResolveAttribute(lhs);
  }
  if (rhs->type == NODE_TYPE_ATTRIBUTE_ACCESS) {
    rhs = ResolveAttribute(rhs);
  }

  auto lType = GetNodeCompareType(lhs);
  auto rType = GetNodeCompareType(rhs);

  if (lType != rType) {
    int diff = static_cast<int>(lType) - static_cast<int>(rType);

    TRI_ASSERT(diff != 0);

    if (diff < 0) {
      return -1;
    } else if (diff > 0) {
      return 1;
    }
    TRI_ASSERT(false);
    return 0;
  }

  if (lType == TRI_JSON_NULL) {
    return 0;
  }

  if (lType == TRI_JSON_BOOLEAN) {
    int diff = static_cast<int>(lhs->getIntValue() - rhs->getIntValue());

    if (diff != 0) {
      if (diff < 0) {
        return -1;
      }
      return 1;
    }
    return 0;
  }

  if (lType == TRI_JSON_NUMBER) {
    double d = lhs->getDoubleValue() - rhs->getDoubleValue();
    if (d < 0.0) {
      return -1;
    } else if (d > 0.0) {
      return 1;
    }
    return 0;
  }

  if (lType == TRI_JSON_STRING) {
    if (compareUtf8) {
      return TRI_compare_utf8(lhs->getStringValue(), lhs->getStringLength(),
                              rhs->getStringValue(), rhs->getStringLength());
    }
    
    size_t const minLength =
        (std::min)(lhs->getStringLength(), rhs->getStringLength());

    int res = memcmp(lhs->getStringValue(), rhs->getStringValue(), minLength);

    if (res != 0) {
      return res;
    }

    int diff = static_cast<int>(lhs->getStringLength()) -
               static_cast<int>(rhs->getStringLength());

    if (diff != 0) {
      return diff < 0 ? -1 : 1;
    }
    return 0;
  }

  if (lType == TRI_JSON_ARRAY) {
    size_t const numLhs = lhs->numMembers();
    size_t const numRhs = rhs->numMembers();
    size_t const n = ((numLhs > numRhs) ? numRhs : numLhs);

    for (size_t i = 0; i < n; ++i) {
      int res = arangodb::aql::CompareAstNodes(lhs->getMember(i),
                                               rhs->getMember(i), compareUtf8);

      if (res != 0) {
        return res;
      }
    }
    if (numLhs < numRhs) {
      return -1;
    } else if (numLhs > numRhs) {
      return 1;
    }
    return 0;
  }

  if (lType == TRI_JSON_OBJECT) {
    // this is a rather exceptional case, so we can
    // afford the inefficiency to convert the node to
    // JSON for comparison
    // (this saves us from writing our own compare function
    // for array AstNodes)
    std::unique_ptr<TRI_json_t> lJson(lhs->toJsonValue(TRI_UNKNOWN_MEM_ZONE));
    std::unique_ptr<TRI_json_t> rJson(rhs->toJsonValue(TRI_UNKNOWN_MEM_ZONE));

    return TRI_CompareValuesJson(lJson.get(), rJson.get(), compareUtf8);
  }

  // all things equal
  return 0;
}

/// @brief returns whether or not the string is empty
static bool IsEmptyString(char const* p, size_t length) {
  char const* e = p + length;

  while (p < e) {
    if (*p != ' ' && *p != '\t' && *p != '\r' && *p != '\n' && *p != '\f' &&
        *p != '\b') {
      return false;
    }
    ++p;
  }

  return true;
}

/// @brief create the node
AstNode::AstNode(AstNodeType type)
    : type(type), flags(0), computedValue(nullptr) {}

/// @brief create a node, with defining a value type
AstNode::AstNode(AstNodeType type, AstNodeValueType valueType) : AstNode(type) {
  value.type = valueType;
  TRI_ASSERT(flags == 0);
  TRI_ASSERT(computedValue == nullptr);
}

/// @brief create a boolean node, with defining a value
AstNode::AstNode(bool v, AstNodeValueType valueType)
    : AstNode(NODE_TYPE_VALUE, valueType) {
  TRI_ASSERT(valueType == VALUE_TYPE_BOOL);
  value.value._bool = v;
  TRI_ASSERT(flags == 0);
  TRI_ASSERT(computedValue == nullptr);
}

/// @brief create an int node, with defining a value
AstNode::AstNode(int64_t v, AstNodeValueType valueType)
    : AstNode(NODE_TYPE_VALUE, valueType) {
  TRI_ASSERT(valueType == VALUE_TYPE_INT);
  value.value._int = v;
  TRI_ASSERT(flags == 0);
  TRI_ASSERT(computedValue == nullptr);
}

/// @brief create a string node, with defining a value
AstNode::AstNode(char const* v, size_t length, AstNodeValueType valueType)
    : AstNode(NODE_TYPE_VALUE, valueType) {
  TRI_ASSERT(valueType == VALUE_TYPE_STRING);
  setStringValue(v, length);
  TRI_ASSERT(flags == 0);
  TRI_ASSERT(computedValue == nullptr);
}

/// @brief create the node from JSON
AstNode::AstNode(Ast* ast, arangodb::basics::Json const& json)
    : AstNode(getNodeTypeFromJson(json)) {
  TRI_ASSERT(flags == 0);
  TRI_ASSERT(computedValue == nullptr);

  auto query = ast->query();

  switch (type) {
    case NODE_TYPE_COLLECTION:
    case NODE_TYPE_PARAMETER:
    case NODE_TYPE_ATTRIBUTE_ACCESS:
    case NODE_TYPE_FCALL_USER: {
      std::string const str(
          JsonHelper::getStringValue(json.json(), "name", ""));
      value.type = VALUE_TYPE_STRING;
      setStringValue(query->registerString(str), str.size());
      break;
    }
    case NODE_TYPE_VALUE: {
      int vType =
          JsonHelper::checkAndGetNumericValue<int>(json.json(), "vTypeID");
      validateValueType(vType);
      value.type = static_cast<AstNodeValueType>(vType);

      switch (value.type) {
        case VALUE_TYPE_NULL:
          break;
        case VALUE_TYPE_BOOL:
          value.value._bool =
              JsonHelper::checkAndGetBooleanValue(json.json(), "value");
          break;
        case VALUE_TYPE_INT:
          setIntValue(JsonHelper::checkAndGetNumericValue<int64_t>(json.json(),
                                                                   "value"));
          break;
        case VALUE_TYPE_DOUBLE:
          setDoubleValue(JsonHelper::checkAndGetNumericValue<double>(
              json.json(), "value"));
          break;
        case VALUE_TYPE_STRING: {
          std::string const str(
              JsonHelper::checkAndGetStringValue(json.json(), "value"));
          setStringValue(query->registerString(str), str.size());
          break;
        }
        default: {}
      }
      break;
    }
    case NODE_TYPE_VARIABLE: {
      // TODO: fix this
      auto builder = JsonHelper::toVelocyPack(json.json());
      auto variable = ast->variables()->createVariable(builder->slice());
      TRI_ASSERT(variable != nullptr);
      setData(variable);
      break;
    }
    case NODE_TYPE_REFERENCE: {
      auto variableId =
          JsonHelper::checkAndGetNumericValue<VariableId>(json.json(), "id");
      auto variable = ast->variables()->getVariable(variableId);

      TRI_ASSERT(variable != nullptr);
      setData(variable);
      break;
    }
    case NODE_TYPE_FCALL: {
      setData(query->executor()->getFunctionByName(
          JsonHelper::getStringValue(json.json(), "name", "")));
      break;
    }
    case NODE_TYPE_OBJECT_ELEMENT: {
      std::string const str(
          JsonHelper::getStringValue(json.json(), "name", ""));
      setStringValue(query->registerString(str), str.size());
      break;
    }
    case NODE_TYPE_EXPANSION: {
      setIntValue(
          JsonHelper::checkAndGetNumericValue<int64_t>(json.json(), "levels"));
      break;
    }
    case NODE_TYPE_OPERATOR_BINARY_IN:
    case NODE_TYPE_OPERATOR_BINARY_NIN: 
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_IN: 
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN: {
      setBoolValue(JsonHelper::getBooleanValue(json.json(), "sorted", false));
      break;
    }
    case NODE_TYPE_ARRAY: {
      bool sorted = JsonHelper::getBooleanValue(json.json(), "sorted", false);
      if (sorted) {
        setFlag(DETERMINED_SORTED, VALUE_SORTED);
      }
      break;
    }
    case NODE_TYPE_QUANTIFIER: {
      std::string const quantifier(JsonHelper::getStringValue(json.json(), "quantifier", ""));
      setIntValue(Quantifier::FromString(quantifier));
      break;
    }
    case NODE_TYPE_OBJECT:
    case NODE_TYPE_ROOT:
    case NODE_TYPE_FOR:
    case NODE_TYPE_LET:
    case NODE_TYPE_FILTER:
    case NODE_TYPE_RETURN:
    case NODE_TYPE_REMOVE:
    case NODE_TYPE_INSERT:
    case NODE_TYPE_UPDATE:
    case NODE_TYPE_REPLACE:
    case NODE_TYPE_UPSERT:
    case NODE_TYPE_COLLECT:
    case NODE_TYPE_COLLECT_COUNT:
    case NODE_TYPE_AGGREGATIONS:
    case NODE_TYPE_SORT:
    case NODE_TYPE_SORT_ELEMENT:
    case NODE_TYPE_LIMIT:
    case NODE_TYPE_ASSIGN:
    case NODE_TYPE_OPERATOR_UNARY_PLUS:
    case NODE_TYPE_OPERATOR_UNARY_MINUS:
    case NODE_TYPE_OPERATOR_UNARY_NOT:
    case NODE_TYPE_OPERATOR_BINARY_AND:
    case NODE_TYPE_OPERATOR_BINARY_OR:
    case NODE_TYPE_OPERATOR_BINARY_PLUS:
    case NODE_TYPE_OPERATOR_BINARY_MINUS:
    case NODE_TYPE_OPERATOR_BINARY_TIMES:
    case NODE_TYPE_OPERATOR_BINARY_DIV:
    case NODE_TYPE_OPERATOR_BINARY_MOD:
    case NODE_TYPE_OPERATOR_BINARY_EQ:
    case NODE_TYPE_OPERATOR_BINARY_NE:
    case NODE_TYPE_OPERATOR_BINARY_LT:
    case NODE_TYPE_OPERATOR_BINARY_LE:
    case NODE_TYPE_OPERATOR_BINARY_GT:
    case NODE_TYPE_OPERATOR_BINARY_GE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_EQ:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_NE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_LT:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_LE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_GT:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_GE: 
    case NODE_TYPE_OPERATOR_TERNARY:
    case NODE_TYPE_SUBQUERY:
    case NODE_TYPE_BOUND_ATTRIBUTE_ACCESS:
    case NODE_TYPE_INDEXED_ACCESS:
    case NODE_TYPE_ITERATOR:
    case NODE_TYPE_RANGE:
    case NODE_TYPE_NOP:
    case NODE_TYPE_CALCULATED_OBJECT_ELEMENT:
    case NODE_TYPE_EXAMPLE:
    case NODE_TYPE_PASSTHRU:
    case NODE_TYPE_ARRAY_LIMIT:
    case NODE_TYPE_DISTINCT:
    case NODE_TYPE_TRAVERSAL:
    case NODE_TYPE_SHORTEST_PATH:
    case NODE_TYPE_DIRECTION:
    case NODE_TYPE_COLLECTION_LIST:
    case NODE_TYPE_OPERATOR_NARY_AND:
    case NODE_TYPE_OPERATOR_NARY_OR:
    case NODE_TYPE_WITH:
      break;
  }

  Json subNodes = json.get("subNodes");

  if (subNodes.isArray()) {
    size_t const len = subNodes.size();

    for (size_t i = 0; i < len; i++) {
      Json subNode(subNodes.at(i));
      int type =
          JsonHelper::checkAndGetNumericValue<int>(subNode.json(), "typeID");
      if (static_cast<AstNodeType>(type) == NODE_TYPE_NOP) {
        // special handling for nop as it is a singleton
        addMember(Ast::getNodeNop());
      } else {
        addMember(new AstNode(ast, subNode));
      }
    }
  }

  ast->query()->addNode(this);
}

/// @brief create the node from JSON
AstNode::AstNode(std::function<void(AstNode*)> registerNode,
                 std::function<char const*(std::string const&)> registerString,
                 arangodb::basics::Json const& json)
    : AstNode(getNodeTypeFromJson(json)) {
  TRI_ASSERT(flags == 0);
  TRI_ASSERT(computedValue == nullptr);

  switch (type) {
    case NODE_TYPE_ATTRIBUTE_ACCESS: {
      std::string const str(
          JsonHelper::getStringValue(json.json(), "name", ""));
      value.type = VALUE_TYPE_STRING;
      auto p = registerString(str);
      TRI_ASSERT(p != nullptr);
      setStringValue(p, str.size());
      break;
    }
    case NODE_TYPE_VALUE: {
      int vType =
          JsonHelper::checkAndGetNumericValue<int>(json.json(), "vTypeID");
      validateValueType(vType);
      value.type = static_cast<AstNodeValueType>(vType);

      switch (value.type) {
        case VALUE_TYPE_NULL:
          break;
        case VALUE_TYPE_BOOL:
          value.value._bool =
              JsonHelper::checkAndGetBooleanValue(json.json(), "value");
          break;
        case VALUE_TYPE_INT:
          setIntValue(JsonHelper::checkAndGetNumericValue<int64_t>(json.json(),
                                                                   "value"));
          break;
        case VALUE_TYPE_DOUBLE:
          setDoubleValue(JsonHelper::checkAndGetNumericValue<double>(
              json.json(), "value"));
          break;
        case VALUE_TYPE_STRING: {
          std::string const str(
              JsonHelper::checkAndGetStringValue(json.json(), "value"));
          setStringValue(registerString(str), str.size());
          break;
        }
        default: {}
      }
      break;
    }
    case NODE_TYPE_REFERENCE: {
      // We use the edge here
      /*
      auto variableId =
      JsonHelper::checkAndGetNumericValue<VariableId>(json.json(), "id");
      auto variable = ast->variables()->getVariable(variableId);

      TRI_ASSERT(variable != nullptr);
      setData(variable);
      */
      break;
    }
    case NODE_TYPE_EXPANSION: {
      setIntValue(
          JsonHelper::checkAndGetNumericValue<int64_t>(json.json(), "levels"));
      break;
    }
    case NODE_TYPE_FCALL_USER:
    case NODE_TYPE_OBJECT_ELEMENT:
    case NODE_TYPE_COLLECTION:
    case NODE_TYPE_PARAMETER:
    case NODE_TYPE_VARIABLE:
    case NODE_TYPE_FCALL:
    case NODE_TYPE_FOR:
    case NODE_TYPE_LET:
    case NODE_TYPE_FILTER:
    case NODE_TYPE_RETURN:
    case NODE_TYPE_REMOVE:
    case NODE_TYPE_INSERT:
    case NODE_TYPE_UPDATE:
    case NODE_TYPE_REPLACE:
    case NODE_TYPE_UPSERT:
    case NODE_TYPE_COLLECT:
    case NODE_TYPE_COLLECT_COUNT:
    case NODE_TYPE_AGGREGATIONS:
    case NODE_TYPE_SORT:
    case NODE_TYPE_SORT_ELEMENT:
    case NODE_TYPE_LIMIT:
    case NODE_TYPE_ASSIGN:
    case NODE_TYPE_SUBQUERY:
    case NODE_TYPE_BOUND_ATTRIBUTE_ACCESS:
    case NODE_TYPE_CALCULATED_OBJECT_ELEMENT:
    case NODE_TYPE_EXAMPLE:
    case NODE_TYPE_DISTINCT:
    case NODE_TYPE_TRAVERSAL:
    case NODE_TYPE_SHORTEST_PATH:
    case NODE_TYPE_DIRECTION:
    case NODE_TYPE_COLLECTION_LIST:
    case NODE_TYPE_PASSTHRU:
    case NODE_TYPE_WITH: {
      THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
                                     "Unsupported node type");
    }
    case NODE_TYPE_OBJECT:
    case NODE_TYPE_ROOT:
    case NODE_TYPE_OPERATOR_UNARY_PLUS:
    case NODE_TYPE_OPERATOR_UNARY_MINUS:
    case NODE_TYPE_OPERATOR_UNARY_NOT:
    case NODE_TYPE_OPERATOR_BINARY_AND:
    case NODE_TYPE_OPERATOR_BINARY_OR:
    case NODE_TYPE_OPERATOR_BINARY_PLUS:
    case NODE_TYPE_OPERATOR_BINARY_MINUS:
    case NODE_TYPE_OPERATOR_BINARY_TIMES:
    case NODE_TYPE_OPERATOR_BINARY_DIV:
    case NODE_TYPE_OPERATOR_BINARY_MOD:
    case NODE_TYPE_OPERATOR_BINARY_EQ:
    case NODE_TYPE_OPERATOR_BINARY_NE:
    case NODE_TYPE_OPERATOR_BINARY_LT:
    case NODE_TYPE_OPERATOR_BINARY_LE:
    case NODE_TYPE_OPERATOR_BINARY_GT:
    case NODE_TYPE_OPERATOR_BINARY_GE:
    case NODE_TYPE_OPERATOR_BINARY_IN:
    case NODE_TYPE_OPERATOR_BINARY_NIN:
    case NODE_TYPE_OPERATOR_TERNARY:
    case NODE_TYPE_INDEXED_ACCESS:
    case NODE_TYPE_ITERATOR:
    case NODE_TYPE_ARRAY:
    case NODE_TYPE_RANGE:
    case NODE_TYPE_NOP:
    case NODE_TYPE_ARRAY_LIMIT:
    case NODE_TYPE_OPERATOR_NARY_AND:
    case NODE_TYPE_OPERATOR_NARY_OR:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_EQ:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_NE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_LT:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_LE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_GT:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_GE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_IN:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN:
    case NODE_TYPE_QUANTIFIER:
      break;
  }

  Json subNodes = json.get("subNodes");

  if (subNodes.isArray()) {
    size_t const len = subNodes.size();
    for (size_t i = 0; i < len; i++) {
      Json subNode(subNodes.at(i));
      addMember(new AstNode(registerNode, registerString, subNode));
    }
  }

  registerNode(this);
}

/// @brief destroy the node
AstNode::~AstNode() {
  if (computedValue != nullptr) {
    delete[] computedValue;
  }
}
  
/// @brief return the string value of a node, as an std::string
std::string AstNode::getString() const {
  TRI_ASSERT(type == NODE_TYPE_VALUE || type == NODE_TYPE_OBJECT_ELEMENT || 
             type == NODE_TYPE_ATTRIBUTE_ACCESS || type == NODE_TYPE_PARAMETER || 
             type == NODE_TYPE_COLLECTION || type == NODE_TYPE_BOUND_ATTRIBUTE_ACCESS ||
             type == NODE_TYPE_FCALL_USER);
  TRI_ASSERT(value.type == VALUE_TYPE_STRING);
  return std::string(getStringValue(), getStringLength());
}

/// @brief test if all members of a node are equality comparisons
bool AstNode::isOnlyEqualityMatch() const {
  if (type != NODE_TYPE_OPERATOR_BINARY_AND &&
      type != NODE_TYPE_OPERATOR_NARY_AND) {
    return false;
  }

  for (size_t i = 0; i < numMembers(); ++i) {
    auto op = getMember(i);
    if (op->type != arangodb::aql::NODE_TYPE_OPERATOR_BINARY_EQ) {
      return false;
    }
  }

  return true;
}

/// @brief computes a hash value for a value node
uint64_t AstNode::hashValue(uint64_t hash) const {
  if (type == NODE_TYPE_VALUE) {
    switch (value.type) {
      case VALUE_TYPE_NULL:
        return fasthash64(static_cast<const void*>("null"), 4, hash);
      case VALUE_TYPE_BOOL:
        if (value.value._bool) {
          return fasthash64(static_cast<const void*>("true"), 4, hash);
        }
        return fasthash64(static_cast<const void*>("false"), 5, hash);
      case VALUE_TYPE_INT:
        return fasthash64(static_cast<const void*>(&value.value._int),
                          sizeof(value.value._int), hash);
      case VALUE_TYPE_DOUBLE:
        return fasthash64(static_cast<const void*>(&value.value._double),
                          sizeof(value.value._double), hash);
      case VALUE_TYPE_STRING:
        return fasthash64(static_cast<const void*>(getStringValue()),
                          getStringLength(), hash);
    }
  }

  size_t const n = numMembers();

  if (type == NODE_TYPE_ARRAY) {
    hash = fasthash64(static_cast<const void*>("array"), 5, hash);
    for (size_t i = 0; i < n; ++i) {
      hash = getMemberUnchecked(i)->hashValue(hash);
    }
    return hash;
  }

  if (type == NODE_TYPE_OBJECT) {
    hash = fasthash64(static_cast<const void*>("object"), 6, hash);
    for (size_t i = 0; i < n; ++i) {
      auto sub = getMemberUnchecked(i);
      if (sub != nullptr) {
        hash = fasthash64(static_cast<const void*>(sub->getStringValue()),
                          sub->getStringLength(), hash);
        hash = sub->getMember(0)->hashValue(hash);
      }
    }
    return hash;
  }

  TRI_ASSERT(false);
  return 0;
}

/// @brief dump the node (for debugging purposes)
#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
void AstNode::dump(int level) const {
  for (int i = 0; i < level; ++i) {
    std::cout << "  ";
  }
  std::cout << "- " << getTypeString();

  if (type == NODE_TYPE_VALUE || type == NODE_TYPE_ARRAY) {
    std::unique_ptr<TRI_json_t> json(toJsonValue(TRI_UNKNOWN_MEM_ZONE));
    std::cout << ": " << json.get();
  } else if (type == NODE_TYPE_ATTRIBUTE_ACCESS) {
    std::cout << ": " << getString();
  } else if (type == NODE_TYPE_REFERENCE) {
    std::cout << ": " << static_cast<Variable const*>(getData())->name;
  }
  std::cout << "\n";

  size_t const n = numMembers();

  for (size_t i = 0; i < n; ++i) {
    auto sub = getMemberUnchecked(i);
    sub->dump(level + 1);
  }
}
#endif

/// @brief compute the value for a constant value node
/// the value is owned by the node and must not be freed by the caller
/// note that the return value might be NULL in case of OOM
VPackSlice AstNode::computeValue() const {
  TRI_ASSERT(isConstant());

  if (computedValue == nullptr) {
    VPackBuilder builder;
    toVelocyPackValue(builder);

    computedValue = new uint8_t[builder.size()];
    memcpy(computedValue, builder.data(), builder.size());
  }

  return VPackSlice(computedValue);
}

/// @brief sort the members of an (array) node
/// this will also set the VALUE_SORTED flag for the node
void AstNode::sort() {
  TRI_ASSERT(type == NODE_TYPE_ARRAY);
  TRI_ASSERT(isConstant());

  std::sort(members.begin(), members.end(),
            [](AstNode const* lhs, AstNode const* rhs) {
              return (arangodb::aql::CompareAstNodes(lhs, rhs, false) < 0);
            });

  setFlag(DETERMINED_SORTED, VALUE_SORTED);
}

/// @brief return the type name of a node
std::string const& AstNode::getTypeString() const {
  auto it = TypeNames.find(static_cast<int>(type));

  if (it != TypeNames.end()) {
    return (*it).second;
  }

  THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_NOT_IMPLEMENTED,
                                 "missing node type in TypeNames");
}

/// @brief return the value type name of a node
std::string const& AstNode::getValueTypeString() const {
  auto it = ValueTypeNames.find(static_cast<int>(value.type));

  if (it != ValueTypeNames.end()) {
    return (*it).second;
  }

  THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_NOT_IMPLEMENTED,
                                 "missing node type in ValueTypeNames");
}

/// @brief stringify the AstNode
std::string AstNode::toString(AstNode const* node) {
  std::unique_ptr<TRI_json_t> json(node->toJson(TRI_UNKNOWN_MEM_ZONE, false));

  return arangodb::basics::JsonHelper::toString(json.get());
}

/// @brief checks whether we know a type of this kind; throws exception if not.
void AstNode::validateType(int type) {
  auto it = TypeNames.find(static_cast<int>(type));

  if (it == TypeNames.end()) {
    THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_NOT_IMPLEMENTED,
                                   "unknown AST node TypeID");
  }
}

/// @brief checks whether we know a value type of this kind;
/// throws exception if not.
void AstNode::validateValueType(int type) {
  auto it = ValueTypeNames.find(static_cast<int>(type));

  if (it == ValueTypeNames.end()) {
    THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_NOT_IMPLEMENTED,
                                   "invalid AST node valueTypeName");
  }
}

/// @brief fetch a node's type from json
AstNodeType AstNode::getNodeTypeFromJson(arangodb::basics::Json const& json) {
  int type = JsonHelper::checkAndGetNumericValue<int>(json.json(), "typeID");
  validateType(type);
  return static_cast<AstNodeType>(type);
}

/// @brief return a JSON representation of the node value
/// the caller is responsible for freeing the JSON later
TRI_json_t* AstNode::toJsonValue(TRI_memory_zone_t* zone) const {
  if (type == NODE_TYPE_VALUE) {
    // dump value of "value" node
    switch (value.type) {
      case VALUE_TYPE_NULL:
        return TRI_CreateNullJson(zone);
      case VALUE_TYPE_BOOL:
        return TRI_CreateBooleanJson(zone, value.value._bool);
      case VALUE_TYPE_INT:
        return TRI_CreateNumberJson(zone,
                                    static_cast<double>(value.value._int));
      case VALUE_TYPE_DOUBLE:
        return TRI_CreateNumberJson(zone, value.value._double);
      case VALUE_TYPE_STRING:
        return TRI_CreateStringCopyJson(zone, value.value._string,
                                        value.length);
    }
  }

  if (type == NODE_TYPE_ARRAY) {
    size_t const n = numMembers();
    TRI_json_t* array = TRI_CreateArrayJson(zone, n);

    if (array == nullptr) {
      return nullptr;
    }

    for (size_t i = 0; i < n; ++i) {
      auto member = getMemberUnchecked(i);

      if (member != nullptr) {
        TRI_json_t* j = member->toJsonValue(zone);

        if (j != nullptr) {
          TRI_PushBack3ArrayJson(zone, array, j);
        }
      }
    }
    return array;
  }

  if (type == NODE_TYPE_OBJECT) {
    size_t const n = numMembers();
    TRI_json_t* object = TRI_CreateObjectJson(zone, n);

    for (size_t i = 0; i < n; ++i) {
      auto member = getMemberUnchecked(i);

      if (member != nullptr) {
        TRI_json_t* j = member->getMember(0)->toJsonValue(zone);

        if (j != nullptr) {
          TRI_Insert3ObjectJson(zone, object, member->getStringValue(), j);
        }
      }
    }

    return object;
  }

  if (type == NODE_TYPE_ATTRIBUTE_ACCESS) {
    TRI_json_t* j = getMember(0)->toJsonValue(zone);

    if (j != nullptr) {
      if (TRI_IsObjectJson(j)) {
        TRI_json_t const* v = TRI_LookupObjectJson(j, getStringValue());

        if (v != nullptr) {
          TRI_json_t* copy = TRI_CopyJson(zone, v);
          TRI_FreeJson(zone, j);
          return copy;
        }
      }

      TRI_FreeJson(zone, j);

      return TRI_CreateNullJson(zone);
    }
  }

  return nullptr;
}

/// @brief return a JSON representation of the node
/// the caller is responsible for freeing the JSON later
TRI_json_t* AstNode::toJson(TRI_memory_zone_t* zone, bool verbose) const {
  TRI_json_t* node = TRI_CreateObjectJson(zone);

  if (node == nullptr) {
    THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
  }

  // dump node type
  std::string const& typeString(getTypeString());
  TRI_json_t json;
  if (TRI_InitStringCopyJson(zone, &json, typeString.c_str(),
                             typeString.size()) != TRI_ERROR_NO_ERROR) {
    TRI_FreeJson(zone, node);
    THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
  }

  TRI_Insert2ObjectJson(zone, node, "type", &json);

  // add typeId
  if (verbose) {
    TRI_Insert3ObjectJson(zone, node, "typeID",
                          TRI_CreateNumberJson(zone, static_cast<int>(type)));
  }

  if (type == NODE_TYPE_COLLECTION || type == NODE_TYPE_PARAMETER ||
      type == NODE_TYPE_ATTRIBUTE_ACCESS || type == NODE_TYPE_OBJECT_ELEMENT ||
      type == NODE_TYPE_FCALL_USER) {
    // dump "name" of node
    if (TRI_InitStringCopyJson(zone, &json, getStringValue(),
                               getStringLength()) != TRI_ERROR_NO_ERROR) {
      TRI_FreeJson(zone, node);
      THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
    }
    TRI_Insert2ObjectJson(zone, node, "name", &json);
  }

  if (type == NODE_TYPE_FCALL) {
    auto func = static_cast<Function*>(getData());
    TRI_Insert3ObjectJson(
        zone, node, "name",
        TRI_CreateStringCopyJson(zone, func->externalName.c_str(),
                                 func->externalName.size()));
    // arguments are exported via node members
  }

  if (type == NODE_TYPE_ARRAY) {
    if (hasFlag(DETERMINED_SORTED)) {
      // transport information about a node's sortedness
      TRI_Insert3ObjectJson(
          zone, node, "sorted",
          TRI_CreateBooleanJson(TRI_UNKNOWN_MEM_ZONE, hasFlag(VALUE_SORTED)));
    }
  }

  if (type == NODE_TYPE_VALUE) {
    // dump value of "value" node
    auto v = toJsonValue(zone);

    if (v == nullptr) {
      TRI_FreeJson(zone, node);
      THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
    }

    TRI_Insert3ObjectJson(zone, node, "value", v);

    if (verbose) {
      std::string const typeStr(getValueTypeString());
      TRI_Insert3ObjectJson(
          zone, node, "vType",
          TRI_CreateStringCopyJson(zone, typeStr.c_str(), typeStr.size()));
      TRI_Insert3ObjectJson(
          zone, node, "vTypeID",
          TRI_CreateNumberJson(zone, static_cast<int>(value.type)));
    }
  }

  if (type == NODE_TYPE_OPERATOR_BINARY_IN ||
      type == NODE_TYPE_OPERATOR_BINARY_NIN ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_IN ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN) {
    TRI_Insert3ObjectJson(
        zone, node, "sorted",
        TRI_CreateBooleanJson(TRI_UNKNOWN_MEM_ZONE, getBoolValue()));
  }

  if (type == NODE_TYPE_QUANTIFIER) {
    std::string const quantifier(Quantifier::Stringify(getIntValue(true)));
    TRI_Insert3ObjectJson(
        zone, node, "quantifier",
        TRI_CreateStringCopyJson(TRI_UNKNOWN_MEM_ZONE, quantifier.c_str(), quantifier.size()));
  }

  if (type == NODE_TYPE_VARIABLE || type == NODE_TYPE_REFERENCE) {
    auto variable = static_cast<Variable*>(getData());

    TRI_ASSERT(variable != nullptr);

    TRI_Insert3ObjectJson(zone, node, "name",
                          TRI_CreateStringCopyJson(zone, variable->name.c_str(),
                                                   variable->name.size()));
    TRI_Insert3ObjectJson(
        zone, node, "id",
        TRI_CreateNumberJson(zone, static_cast<double>(variable->id)));
  }

  if (type == NODE_TYPE_EXPANSION) {
    TRI_Insert3ObjectJson(
        zone, node, "levels",
        TRI_CreateNumberJson(zone, static_cast<double>(getIntValue(true))));
  }

  // dump sub-nodes
  size_t const n = members.size();

  if (n > 0) {
    TRI_json_t* subNodes = TRI_CreateArrayJson(zone, n);

    if (subNodes == nullptr) {
      TRI_FreeJson(zone, node);
      THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
    }

    try {
      for (size_t i = 0; i < n; ++i) {
        AstNode* member = getMemberUnchecked(i);
        if (member != nullptr) {
          member->toJson(subNodes, zone, verbose);
        }
      }
    } catch (basics::Exception const&) {
      TRI_FreeJson(zone, subNodes);
      TRI_FreeJson(zone, node);
      throw;
    } catch (...) {
      TRI_FreeJson(zone, subNodes);
      TRI_FreeJson(zone, node);
      THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
    }

    TRI_Insert3ObjectJson(zone, node, "subNodes", subNodes);
  }

  return node;
}

/// @brief return a VelocyPack representation of the node value
std::shared_ptr<VPackBuilder> AstNode::toVelocyPackValue() const {
  auto builder = std::make_shared<VPackBuilder>();
  if (builder == nullptr) {
    return nullptr;
  }
  toVelocyPackValue(*builder);
  return builder;
}

/// @brief build a VelocyPack representation of the node value
///        Can throw Out of Memory Error
void AstNode::toVelocyPackValue(VPackBuilder& builder) const {
  if (type == NODE_TYPE_VALUE) {
    // dump value of "value" node
    switch (value.type) {
      case VALUE_TYPE_NULL:
        builder.add(VPackValue(VPackValueType::Null));
        break;
      case VALUE_TYPE_BOOL:
        builder.add(VPackValue(value.value._bool));
        break;
      case VALUE_TYPE_INT:
        builder.add(VPackValue(static_cast<double>(value.value._int)));
        break;
      case VALUE_TYPE_DOUBLE:
        builder.add(VPackValue(value.value._double));
        break;
      case VALUE_TYPE_STRING:
        builder.add(VPackValue(std::string(value.value._string, value.length)));
        break;
    }
    return;
  }
  if (type == NODE_TYPE_ARRAY) {
    {
      VPackArrayBuilder guard(&builder);
      size_t const n = numMembers();
      for (size_t i = 0; i < n; ++i) {
        auto member = getMemberUnchecked(i);
        if (member != nullptr) {
          member->toVelocyPackValue(builder);
        }
      }
    }
    return;
  }

  if (type == NODE_TYPE_OBJECT) {
    {
      size_t const n = numMembers();
      VPackObjectBuilder guard(&builder);

      for (size_t i = 0; i < n; ++i) {
        auto member = getMemberUnchecked(i);
        if (member != nullptr) {
          builder.add(VPackValue(member->getString()));
          member->getMember(0)->toVelocyPackValue(builder);
        }
      }
    }
    return;
  }

  if (type == NODE_TYPE_ATTRIBUTE_ACCESS) {
    // TODO Could this be done more efficiently in the builder in place?
    auto tmp = getMember(0)->toVelocyPackValue();
    if (tmp != nullptr) {
      VPackSlice slice = tmp->slice();
      if (slice.isObject()) {
        slice = slice.get(getString());
        if (!slice.isNone()) {
          builder.add(slice);
          return;
        }
      }
      builder.add(VPackValue(VPackValueType::Null));
    }
  }

  // Do not add anything.
}

/// @brief return a VelocyPack representation of the node
std::shared_ptr<VPackBuilder> AstNode::toVelocyPack(bool verbose) const {
  auto builder = std::make_shared<VPackBuilder>();
  if (builder == nullptr) {
    return nullptr;
  }
  toVelocyPack(*builder, verbose);
  return builder;
}

/// @brief Create a VelocyPack representation of the node
void AstNode::toVelocyPack(VPackBuilder& builder, bool verbose) const {
  try {
    VPackObjectBuilder guard(&builder);

    // dump node type
    builder.add("type", VPackValue(getTypeString()));
    if (verbose) {
      builder.add("typeID", VPackValue(static_cast<int>(type)));
    }
    if (type == NODE_TYPE_COLLECTION || type == NODE_TYPE_PARAMETER ||
        type == NODE_TYPE_ATTRIBUTE_ACCESS ||
        type == NODE_TYPE_OBJECT_ELEMENT || type == NODE_TYPE_FCALL_USER) {
      // dump "name" of node
      builder.add("name", VPackValue(getString()));
    }
    if (type == NODE_TYPE_FCALL) {
      auto func = static_cast<Function*>(getData());
      builder.add("name", VPackValue(func->externalName));
      // arguments are exported via node members
    }

    if (type == NODE_TYPE_ARRAY && hasFlag(DETERMINED_SORTED)) {
      // transport information about a node's sortedness
      builder.add("sorted", VPackValue(hasFlag(VALUE_SORTED)));
    }
 
    if (type == NODE_TYPE_VALUE) {
      // dump value of "value" node
      builder.add(VPackValue("value"));
      toVelocyPackValue(builder);

      if (verbose) {
        builder.add("vType", VPackValue(getValueTypeString()));
        builder.add("vTypeID", VPackValue(static_cast<int>(value.type)));
      }
    }

    if (type == NODE_TYPE_OPERATOR_BINARY_IN ||
        type == NODE_TYPE_OPERATOR_BINARY_NIN ||
        type == NODE_TYPE_OPERATOR_BINARY_ARRAY_IN ||
        type == NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN) {
      builder.add("sorted", VPackValue(getBoolValue()));
    }
    if (type == NODE_TYPE_QUANTIFIER) {
      std::string const quantifier(Quantifier::Stringify(getIntValue(true)));
      builder.add("quantifier", VPackValue(quantifier));
    }

    if (type == NODE_TYPE_VARIABLE || type == NODE_TYPE_REFERENCE) {
      auto variable = static_cast<Variable*>(getData());

      TRI_ASSERT(variable != nullptr);
      builder.add("name", VPackValue(variable->name));
      builder.add("id", VPackValue(static_cast<double>(variable->id)));
    }

    if (type == NODE_TYPE_EXPANSION) {
      builder.add("levels", VPackValue(static_cast<double>(getIntValue(true))));
    }

    // dump sub-nodes
    size_t const n = members.size();
    if (n > 0) {
      builder.add(VPackValue("subNodes"));
      VPackArrayBuilder guard(&builder);
      for (size_t i = 0; i < n; ++i) {
        AstNode* member = getMemberUnchecked(i);
        if (member != nullptr) {
          member->toVelocyPack(builder, verbose);
        }
      }
    }
  } catch (...) {
    THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
  }
}

/// @brief iterates whether a node of type "searchType" can be found
bool AstNode::containsNodeType(AstNodeType searchType) const {
  if (type == searchType) {
    return true;
  }

  // iterate sub-nodes
  size_t const n = members.size();

  if (n > 0) {
    for (size_t i = 0; i < n; ++i) {
      AstNode* member = getMemberUnchecked(i);

      if (member != nullptr && member->containsNodeType(searchType)) {
        return true;
      }
    }
  }

  return false;
}

/// @brief convert the node's value to a boolean value
/// this may create a new node or return the node itself if it is already a
/// boolean value node
AstNode* AstNode::castToBool(Ast* ast) {
  TRI_ASSERT(type == NODE_TYPE_VALUE || type == NODE_TYPE_ARRAY ||
             type == NODE_TYPE_OBJECT);

  if (type == NODE_TYPE_VALUE) {
    switch (value.type) {
      case VALUE_TYPE_NULL:
        // null => false
        return ast->createNodeValueBool(false);
      case VALUE_TYPE_BOOL:
        // already a boolean
        return this;
      case VALUE_TYPE_INT:
        return ast->createNodeValueBool(value.value._int != 0);
      case VALUE_TYPE_DOUBLE:
        return ast->createNodeValueBool(value.value._double != 0.0);
      case VALUE_TYPE_STRING:
        return ast->createNodeValueBool(value.length > 0);
      default: {}
    }
    // fall-through intentional
  } else if (type == NODE_TYPE_ARRAY) {
    return ast->createNodeValueBool(true);
  } else if (type == NODE_TYPE_OBJECT) {
    return ast->createNodeValueBool(true);
  }

  return ast->createNodeValueBool(false);
}

/// @brief convert the node's value to a number value
/// this may create a new node or return the node itself if it is already a
/// numeric value node
AstNode* AstNode::castToNumber(Ast* ast) {
  TRI_ASSERT(type == NODE_TYPE_VALUE || type == NODE_TYPE_ARRAY ||
             type == NODE_TYPE_OBJECT);

  if (type == NODE_TYPE_VALUE) {
    switch (value.type) {
      case VALUE_TYPE_NULL:
        // null => 0
        return ast->createNodeValueInt(0);
      case VALUE_TYPE_BOOL:
        // false => 0, true => 1
        return ast->createNodeValueInt(value.value._bool ? 1 : 0);
      case VALUE_TYPE_INT:
      case VALUE_TYPE_DOUBLE:
        // already numeric!
        return this;
      case VALUE_TYPE_STRING:
        try {
          // try converting string to number
          double v = std::stod(std::string(value.value._string, value.length));
          return ast->createNodeValueDouble(v);
        } catch (...) {
          if (IsEmptyString(value.value._string, value.length)) {
            // empty string => 0
            return ast->createNodeValueInt(0);
          }
          // conversion failed
        }
        // fall-through intentional
    }
    // fall-through intentional
  } else if (type == NODE_TYPE_ARRAY) {
    size_t const n = numMembers();
    if (n == 0) {
      // [ ] => 0
      return ast->createNodeValueInt(0);
    } else if (n == 1) {
      auto member = getMember(0);
      // convert only member to number
      return member->castToNumber(ast);
    }
    // fall-through intentional
  } else if (type == NODE_TYPE_OBJECT) {
    // fall-through intentional
  }

  return ast->createNodeValueInt(0);
}

/// @brief adds a JSON representation of the node to the JSON list specified
/// in the first argument
void AstNode::toJson(TRI_json_t* json, TRI_memory_zone_t* zone,
                     bool verbose) const {
  TRI_ASSERT(TRI_IsArrayJson(json));

  TRI_json_t* node = toJson(zone, verbose);

  if (node == nullptr) {
    THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
  }

  TRI_PushBack3ArrayJson(zone, json, node);
}

/// @brief get the integer value of a node, provided the node is a value node
/// this will return 0 for all non-value nodes and for all non-int value nodes!!
int64_t AstNode::getIntValue() const {
  if (type == NODE_TYPE_VALUE) {
    switch (value.type) {
      case VALUE_TYPE_BOOL:
        return (value.value._bool ? 1 : 0);
      case VALUE_TYPE_INT:
        return value.value._int;
      case VALUE_TYPE_DOUBLE:
        return static_cast<int64_t>(value.value._double);
      default: {}
    }
  }

  return 0;
}

/// @brief get the double value of a node, provided the node is a value node
double AstNode::getDoubleValue() const {
  if (type == NODE_TYPE_VALUE) {
    switch (value.type) {
      case VALUE_TYPE_BOOL:
        return (value.value._bool ? 1.0 : 0.0);
      case VALUE_TYPE_INT:
        return static_cast<double>(value.value._int);
      case VALUE_TYPE_DOUBLE:
        return value.value._double;
      default: {}
    }
  }

  return 0.0;
}

/// @brief whether or not the node value is trueish
bool AstNode::isTrue() const {
  if (type == NODE_TYPE_VALUE) {
    switch (value.type) {
      case VALUE_TYPE_NULL:
        return false;
      case VALUE_TYPE_BOOL:
        return value.value._bool;
      case VALUE_TYPE_INT:
        return (value.value._int != 0);
      case VALUE_TYPE_DOUBLE:
        return (value.value._double != 0.0);
      case VALUE_TYPE_STRING:
        return (value.length != 0);
    }
  } else if (type == NODE_TYPE_ARRAY || type == NODE_TYPE_OBJECT) {
    return true;
  } else if (type == NODE_TYPE_OPERATOR_BINARY_OR) {
    if (getMember(0)->isTrue()) {
      return true;
    }
    return getMember(1)->isTrue();
  } else if (type == NODE_TYPE_OPERATOR_BINARY_AND) {
    if (!getMember(0)->isTrue()) {
      return false;
    }
    return getMember(1)->isTrue();
  } else if (type == NODE_TYPE_OPERATOR_UNARY_NOT) {
    if (getMember(0)->isFalse()) {
      // ! false => true
      return true;
    }
  }

  return false;
}

/// @brief whether or not the node value is falsey
bool AstNode::isFalse() const {
  if (type == NODE_TYPE_VALUE) {
    switch (value.type) {
      case VALUE_TYPE_NULL:
        return true;
      case VALUE_TYPE_BOOL:
        return (!value.value._bool);
      case VALUE_TYPE_INT:
        return (value.value._int == 0);
      case VALUE_TYPE_DOUBLE:
        return (value.value._double == 0.0);
      case VALUE_TYPE_STRING:
        return (value.length == 0);
    }
  } else if (type == NODE_TYPE_ARRAY || type == NODE_TYPE_OBJECT) {
    return false;
  } else if (type == NODE_TYPE_OPERATOR_BINARY_OR) {
    if (!getMember(0)->isFalse()) {
      return false;
    }
    return getMember(1)->isFalse();
  } else if (type == NODE_TYPE_OPERATOR_BINARY_AND) {
    if (getMember(0)->isFalse()) {
      return true;
    }
    return getMember(1)->isFalse();
  } else if (type == NODE_TYPE_OPERATOR_UNARY_NOT) {
    if (getMember(0)->isTrue()) {
      // ! true => false
      return true;
    }
  }

  return false;
}

/// @brief whether or not a value node is of type attribute access that
/// refers to any variable reference
/// returns true if yes, and then also returns variable reference and array
/// of attribute names in the parameter passed by reference
bool AstNode::isAttributeAccessForVariable(
    std::pair<Variable const*, std::vector<arangodb::basics::AttributeName>>&
        result) const {
  if (type != NODE_TYPE_ATTRIBUTE_ACCESS && type != NODE_TYPE_EXPANSION) {
    return false;
  }

  // initialize
  bool expandNext = false;
  result.first = nullptr;
  if (!result.second.empty()) {
    result.second.clear();
  }
  auto node = this;

  while (node->type == NODE_TYPE_ATTRIBUTE_ACCESS ||
         node->type == NODE_TYPE_EXPANSION) {
    if (node->type == NODE_TYPE_ATTRIBUTE_ACCESS) {
      result.second.insert(
          result.second.begin(),
          arangodb::basics::AttributeName(node->getString(), expandNext));
      node = node->getMember(0);
      expandNext = false;
    } else {
      // expansion, i.e. [*]
      TRI_ASSERT(node->type == NODE_TYPE_EXPANSION);
      TRI_ASSERT(node->numMembers() >= 2);

      // check if the expansion uses a projection. if yes, we cannot use an
      // index for it
      if (node->getMember(4) != Ast::getNodeNop()) {
        // [* RETURN projection]
        result.second.clear();
        return false;
      }

      if (node->getMember(1)->type != NODE_TYPE_REFERENCE) {
        if (!node->getMember(1)->isAttributeAccessForVariable(result)) {
          result.second.clear();
          return false;
        }
      }
      expandNext = true;

      TRI_ASSERT(node->getMember(0)->type == NODE_TYPE_ITERATOR);

      node = node->getMember(0)->getMember(1);
    }
  }

  if (node->type != NODE_TYPE_REFERENCE) {
    result.second.clear();
    return false;
  }

  result.first = static_cast<Variable const*>(node->getData());
  return true;
}

/// @brief recursively clear flags
void AstNode::clearFlagsRecursive() {
  clearFlags();
  size_t const n = numMembers();

  for (size_t i = 0; i < n; ++i) {
    auto member = getMemberUnchecked(i);
    member->clearFlagsRecursive();
  }
}

/// @brief whether or not a node is simple enough to be used in a simple
/// expression
bool AstNode::isSimple() const {
  if (hasFlag(DETERMINED_SIMPLE)) {
    // fast track exit
    return hasFlag(VALUE_SIMPLE);
  }

  if (type == NODE_TYPE_REFERENCE || type == NODE_TYPE_VALUE ||
      type == NODE_TYPE_VARIABLE || type == NODE_TYPE_NOP) {
    setFlag(DETERMINED_SIMPLE, VALUE_SIMPLE);
    return true;
  }

  if (type == NODE_TYPE_ARRAY || type == NODE_TYPE_OBJECT ||
      type == NODE_TYPE_EXPANSION || type == NODE_TYPE_ITERATOR ||
      type == NODE_TYPE_ARRAY_LIMIT || type == NODE_TYPE_CALCULATED_OBJECT_ELEMENT) {
    size_t const n = numMembers();

    for (size_t i = 0; i < n; ++i) {
      auto member = getMemberUnchecked(i);

      if (!member->isSimple()) {
        setFlag(DETERMINED_SIMPLE);
        return false;
      }
    }

    setFlag(DETERMINED_SIMPLE, VALUE_SIMPLE);
    return true;
  }

  if (type == NODE_TYPE_OBJECT_ELEMENT || type == NODE_TYPE_ATTRIBUTE_ACCESS ||
      type == NODE_TYPE_OPERATOR_UNARY_NOT) {
    TRI_ASSERT(numMembers() == 1);

    if (!getMember(0)->isSimple()) {
      setFlag(DETERMINED_SIMPLE);
      return false;
    }

    setFlag(DETERMINED_SIMPLE, VALUE_SIMPLE);
    return true;
  }

  if (type == NODE_TYPE_BOUND_ATTRIBUTE_ACCESS) {
    if (!getMember(0)->isSimple()) {
      setFlag(DETERMINED_SIMPLE);
      return false;
    }

    setFlag(DETERMINED_SIMPLE, VALUE_SIMPLE);
    return true;
  }

  if (type == NODE_TYPE_FCALL) {
    // some functions have C++ handlers
    // check if the called function is one of them
    auto func = static_cast<Function*>(getData());
    TRI_ASSERT(func != nullptr);

    if (func->implementation == nullptr) {
      // no C++ handler available for function
      setFlag(DETERMINED_SIMPLE);
      return false;
    }

    TRI_ASSERT(func->implementation != nullptr);

    TRI_ASSERT(numMembers() == 1);

    // check if there is a C++ function handler condition
    if (func->condition != nullptr && !func->condition()) {
      // function execution condition is false
      setFlag(DETERMINED_SIMPLE);
      return false;
    }

    // check simplicity of function arguments
    auto args = getMember(0);
    size_t const n = args->numMembers();

    for (size_t i = 0; i < n; ++i) {
      auto member = args->getMemberUnchecked(i);
      auto conversion = func->getArgumentConversion(i);

      if (member->type == NODE_TYPE_COLLECTION &&
          (conversion == Function::CONVERSION_REQUIRED ||
           conversion == Function::CONVERSION_OPTIONAL)) {
        // collection attribute: no need to check for member simplicity
        continue;
      } else {
        // check for member simplicity the usual way
        if (!member->isSimple()) {
          setFlag(DETERMINED_SIMPLE);
          return false;
        }
      }
    }

    setFlag(DETERMINED_SIMPLE, VALUE_SIMPLE);
    return true;
  }

  if (type == NODE_TYPE_OPERATOR_BINARY_PLUS ||
      type == NODE_TYPE_OPERATOR_BINARY_MINUS ||
      type == NODE_TYPE_OPERATOR_BINARY_TIMES ||
      type == NODE_TYPE_OPERATOR_BINARY_DIV ||
      type == NODE_TYPE_OPERATOR_BINARY_MOD) {
    if (!getMember(0)->isSimple() || !getMember(1)->isSimple()) {
      setFlag(DETERMINED_SIMPLE);
      return false;
    }
    setFlag(DETERMINED_SIMPLE, VALUE_SIMPLE);
    return true;
  }

  if (type == NODE_TYPE_OPERATOR_BINARY_AND ||
      type == NODE_TYPE_OPERATOR_BINARY_OR ||
      type == NODE_TYPE_OPERATOR_BINARY_EQ ||
      type == NODE_TYPE_OPERATOR_BINARY_NE ||
      type == NODE_TYPE_OPERATOR_BINARY_LT ||
      type == NODE_TYPE_OPERATOR_BINARY_LE ||
      type == NODE_TYPE_OPERATOR_BINARY_GT ||
      type == NODE_TYPE_OPERATOR_BINARY_GE ||
      type == NODE_TYPE_OPERATOR_BINARY_IN ||
      type == NODE_TYPE_OPERATOR_BINARY_NIN || 
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_EQ ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_NE ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_LT ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_LE ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_GT ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_GE ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_IN ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN ||
      type == NODE_TYPE_RANGE ||
      type == NODE_TYPE_INDEXED_ACCESS || type == NODE_TYPE_PASSTHRU) {
    // a logical operator is simple if its operands are simple
    // a comparison operator is simple if both bounds are simple
    // a range is simple if both bounds are simple
    if (!getMember(0)->isSimple() || !getMember(1)->isSimple()) {
      setFlag(DETERMINED_SIMPLE);
      return false;
    }

    setFlag(DETERMINED_SIMPLE, VALUE_SIMPLE);
    return true;
  }

  setFlag(DETERMINED_SIMPLE);
  return false;
}

/// @brief whether or not a node has a constant value
bool AstNode::isConstant() const {
  if (hasFlag(DETERMINED_CONSTANT)) {
    // fast track exit
    return hasFlag(VALUE_CONSTANT);
  }

  if (type == NODE_TYPE_VALUE) {
    setFlag(DETERMINED_CONSTANT, VALUE_CONSTANT);
    return true;
  }

  if (type == NODE_TYPE_ARRAY) {
    size_t const n = numMembers();

    for (size_t i = 0; i < n; ++i) {
      auto member = getMember(i);

      if (!member->isConstant()) {
        setFlag(DETERMINED_CONSTANT);
        return false;
      }
    }

    setFlag(DETERMINED_CONSTANT, VALUE_CONSTANT);
    return true;
  }

  if (type == NODE_TYPE_OBJECT) {
    size_t const n = numMembers();

    for (size_t i = 0; i < n; ++i) {
      auto member = getMember(i);
      if (member->type == NODE_TYPE_OBJECT_ELEMENT) {
        auto value = member->getMember(0);

        if (!value->isConstant()) {
          setFlag(DETERMINED_CONSTANT);
          return false;
        }
      } else {
        // definitely not const!
        TRI_ASSERT(member->type == NODE_TYPE_CALCULATED_OBJECT_ELEMENT);
        setFlag(DETERMINED_CONSTANT);
        return false;
      }
    }

    setFlag(DETERMINED_CONSTANT, VALUE_CONSTANT);
    return true;
  }

  if (type == NODE_TYPE_ATTRIBUTE_ACCESS ||
      type == NODE_TYPE_BOUND_ATTRIBUTE_ACCESS) {
    if (getMember(0)->isConstant()) {
      setFlag(DETERMINED_CONSTANT, VALUE_CONSTANT);
      return true;
    }
  }

  setFlag(DETERMINED_CONSTANT);
  return false;
}

/// @brief whether or not a node is a simple comparison operator
bool AstNode::isSimpleComparisonOperator() const {
  return (type == NODE_TYPE_OPERATOR_BINARY_EQ ||
          type == NODE_TYPE_OPERATOR_BINARY_NE ||
          type == NODE_TYPE_OPERATOR_BINARY_LT ||
          type == NODE_TYPE_OPERATOR_BINARY_LE ||
          type == NODE_TYPE_OPERATOR_BINARY_GT ||
          type == NODE_TYPE_OPERATOR_BINARY_GE);
}

/// @brief whether or not a node is a comparison operator
bool AstNode::isComparisonOperator() const {
  return (type == NODE_TYPE_OPERATOR_BINARY_EQ ||
          type == NODE_TYPE_OPERATOR_BINARY_NE ||
          type == NODE_TYPE_OPERATOR_BINARY_LT ||
          type == NODE_TYPE_OPERATOR_BINARY_LE ||
          type == NODE_TYPE_OPERATOR_BINARY_GT ||
          type == NODE_TYPE_OPERATOR_BINARY_GE ||
          type == NODE_TYPE_OPERATOR_BINARY_IN ||
          type == NODE_TYPE_OPERATOR_BINARY_NIN);
}

/// @brief whether or not a node is an array comparison operator
bool AstNode::isArrayComparisonOperator() const {
  return (type == NODE_TYPE_OPERATOR_BINARY_ARRAY_EQ ||
          type == NODE_TYPE_OPERATOR_BINARY_ARRAY_NE ||
          type == NODE_TYPE_OPERATOR_BINARY_ARRAY_LT ||
          type == NODE_TYPE_OPERATOR_BINARY_ARRAY_LE ||
          type == NODE_TYPE_OPERATOR_BINARY_ARRAY_GT ||
          type == NODE_TYPE_OPERATOR_BINARY_ARRAY_GE ||
          type == NODE_TYPE_OPERATOR_BINARY_ARRAY_IN ||
          type == NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN);
}

/// @brief whether or not a node (and its subnodes) can throw a runtime
/// exception
bool AstNode::canThrow() const {
  if (hasFlag(DETERMINED_THROWS)) {
    // fast track exit
    return hasFlag(VALUE_THROWS);
  }

  // check sub-nodes first
  size_t const n = numMembers();
  for (size_t i = 0; i < n; ++i) {
    auto member = getMember(i);
    if (member->canThrow()) {
      // if any sub-node may throw, the whole branch may throw
      setFlag(DETERMINED_THROWS);
      return true;
    }
  }

  // no sub-node throws, now check ourselves

  if (type == NODE_TYPE_FCALL) {
    auto func = static_cast<Function*>(getData());

    // built-in functions may or may not throw
    // we are currently reporting non-deterministic functions as
    // potentially throwing. This is not correct on the one hand, but on
    // the other hand we must not optimize or move non-deterministic functions
    // during optimization
    if (func->canThrow) {
      setFlag(DETERMINED_THROWS, VALUE_THROWS);
      return true;
    }

    setFlag(DETERMINED_THROWS);
    return false;
  }

  if (type == NODE_TYPE_FCALL_USER) {
    // user functions can always throw
    setFlag(DETERMINED_THROWS, VALUE_THROWS);
    return true;
  }

  // everything else does not throw!
  setFlag(DETERMINED_THROWS);
  return false;
}

/// @brief whether or not a node (and its subnodes) can safely be executed on
/// a DB server
bool AstNode::canRunOnDBServer() const {
  if (hasFlag(DETERMINED_RUNONDBSERVER)) {
    // fast track exit
    return hasFlag(VALUE_RUNONDBSERVER);
  }

  // check sub-nodes first
  size_t const n = numMembers();
  for (size_t i = 0; i < n; ++i) {
    auto member = getMember(i);
    if (!member->canRunOnDBServer()) {
      // if any sub-node cannot run on a DB server, we can't either
      setFlag(DETERMINED_RUNONDBSERVER);
      return false;
    }
  }

  // now check ourselves
  if (type == NODE_TYPE_FCALL) {
    // built-in function
    auto func = static_cast<Function*>(getData());
    if (func->canRunOnDBServer) {
      setFlag(DETERMINED_RUNONDBSERVER, VALUE_RUNONDBSERVER);
    } else {
      setFlag(DETERMINED_RUNONDBSERVER);
    }
    return func->canRunOnDBServer;
  }

  if (type == NODE_TYPE_FCALL_USER) {
    // user function. we don't know anything about it
    setFlag(DETERMINED_RUNONDBSERVER);
    return false;
  }

  // everyhing else can run everywhere
  setFlag(DETERMINED_RUNONDBSERVER, VALUE_RUNONDBSERVER);
  return true;
}

/// @brief whether or not an object's keys must be checked for uniqueness
bool AstNode::mustCheckUniqueness() const {
  if (hasFlag(DETERMINED_CHECKUNIQUENESS)) {
    // fast track exit
    return hasFlag(VALUE_CHECKUNIQUENESS);
  }

  TRI_ASSERT(type == NODE_TYPE_OBJECT);

  bool mustCheck = false;

  // check the actual key members now
  size_t const n = numMembers();

  if (n >= 2) {
    std::unordered_set<std::string> keys;

    // only useful to check when there are 2 or more keys
    for (size_t i = 0; i < n; ++i) {
      auto member = getMemberUnchecked(i);

      if (member->type == NODE_TYPE_OBJECT_ELEMENT) {
        // constant key
        if (!keys.emplace(member->getString()).second) {
          // duplicate key
          mustCheck = true;
          break;
        }
      } else if (member->type == NODE_TYPE_CALCULATED_OBJECT_ELEMENT) {
        // dynamic key... we don't know the key yet, so there's no
        // way around check it at runtime later
        mustCheck = true;
        break;
      }
    }
  }
        
  if (mustCheck) {
    // we have duplicate keys, or we can't tell yet
    setFlag(DETERMINED_CHECKUNIQUENESS, VALUE_CHECKUNIQUENESS);
  } else {
    // all keys unique, or just one or zero keys in object
    setFlag(DETERMINED_CHECKUNIQUENESS);
  }
  return mustCheck;
}

/// @brief whether or not a node (and its subnodes) is deterministic
bool AstNode::isDeterministic() const {
  if (hasFlag(DETERMINED_NONDETERMINISTIC)) {
    // fast track exit
    return !hasFlag(VALUE_NONDETERMINISTIC);
  }

  if (isConstant()) {
    return true;
  }

  // check sub-nodes first
  size_t const n = numMembers();

  for (size_t i = 0; i < n; ++i) {
    auto member = getMemberUnchecked(i);

    if (!member->isDeterministic()) {
      // if any sub-node is non-deterministic, we are neither
      setFlag(DETERMINED_NONDETERMINISTIC, VALUE_NONDETERMINISTIC);
      return false;
    }
  }

  if (type == NODE_TYPE_FCALL) {
    // built-in functions may or may not be deterministic
    auto func = static_cast<Function*>(getData());

    if (!func->isDeterministic) {
      setFlag(DETERMINED_NONDETERMINISTIC, VALUE_NONDETERMINISTIC);
      return false;
    }

    setFlag(DETERMINED_NONDETERMINISTIC);
    return true;
  }

  if (type == NODE_TYPE_FCALL_USER) {
    // user functions are always non-deterministic
    setFlag(DETERMINED_NONDETERMINISTIC, VALUE_NONDETERMINISTIC);
    return false;
  }

  // everything else is deterministic
  setFlag(DETERMINED_NONDETERMINISTIC);
  return true;
}

/// @brief whether or not a node (and its subnodes) is cacheable
bool AstNode::isCacheable() const {
  if (isConstant()) {
    return true;
  }

  // check sub-nodes first
  size_t const n = numMembers();

  for (size_t i = 0; i < n; ++i) {
    auto member = getMemberUnchecked(i);

    if (!member->isCacheable()) {
      return false;
    }
  }

  if (type == NODE_TYPE_FCALL) {
    // built-in functions may or may not be cacheable
    auto func = static_cast<Function*>(getData());
    return func->isCacheable;
  }

  if (type == NODE_TYPE_FCALL_USER) {
    // user functions are always non-cacheable
    return false;
  }

  // everything else is cacheable
  return true;
}

/// @brief whether or not a node (and its subnodes) may contain a call to a
/// user-defined function
bool AstNode::callsUserDefinedFunction() const {
  if (isConstant()) {
    return true;
  }

  // check sub-nodes first
  size_t const n = numMembers();

  for (size_t i = 0; i < n; ++i) {
    auto member = getMemberUnchecked(i);

    if (!member->callsUserDefinedFunction()) {
      return false;
    }
  }

  return (type == NODE_TYPE_FCALL_USER);
}

/// @brief whether or not the object node contains dynamically named attributes
/// on its first level
bool AstNode::containsDynamicAttributeName() const {
  TRI_ASSERT(type == NODE_TYPE_OBJECT);

  size_t const n = numMembers();
  for (size_t i = 0; i < n; ++i) {
    if (getMember(i)->type == NODE_TYPE_CALCULATED_OBJECT_ELEMENT) {
      return true;
    }
  }

  return false;
}

/// @brief clone a node, recursively
AstNode* AstNode::clone(Ast* ast) const { return ast->clone(this); }

/// @brief append a string representation of the node to a string buffer
/// the string representation does not need to be JavaScript-compatible
/// except for node types NODE_TYPE_VALUE, NODE_TYPE_ARRAY and NODE_TYPE_OBJECT
/// (only for objects that do not contain dynamic attributes)
void AstNode::stringify(arangodb::basics::StringBuffer* buffer, bool verbose,
                        bool failIfLong) const {
  // any arrays/objects with more values than this will not be stringified if
  // failIfLonf is set to true!
  static size_t const TooLongThreshold = 80;

  if (type == NODE_TYPE_VALUE) {
    // must be JavaScript-compatible!
    appendValue(buffer);
    return;
  }

  if (type == NODE_TYPE_ARRAY) {
    // must be JavaScript-compatible!
    size_t const n = numMembers();

    if (failIfLong && n > TooLongThreshold) {
      // intentionally do not stringify this node because the output would be
      // too long
      THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
    }

    buffer->appendChar('[');
    for (size_t i = 0; i < n; ++i) {
      if (i > 0) {
        buffer->appendChar(',');
      }

      AstNode* member = getMember(i);
      if (member != nullptr) {
        member->stringify(buffer, verbose, failIfLong);
      }
    }
    buffer->appendChar(']');
    return;
  }

  if (type == NODE_TYPE_OBJECT) {
    // must be JavaScript-compatible!
    buffer->appendChar('{');
    size_t const n = numMembers();

    if (failIfLong && n > TooLongThreshold) {
      // intentionally do not stringify this node because the output would be
      // too long
      THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
    }

    for (size_t i = 0; i < n; ++i) {
      if (i > 0) {
        buffer->appendChar(',');
      }

      AstNode* member = getMember(i);

      if (member->type == NODE_TYPE_OBJECT_ELEMENT) {
        TRI_ASSERT(member->numMembers() == 1);

        buffer->appendJsonEncoded(member->getStringValue(),
                                  member->getStringLength());
        buffer->appendChar(':');

        member->getMember(0)->stringify(buffer, verbose, failIfLong);
      } else if (member->type == NODE_TYPE_CALCULATED_OBJECT_ELEMENT) {
        TRI_ASSERT(member->numMembers() == 2);

        buffer->appendText(TRI_CHAR_LENGTH_PAIR("$["));
        member->getMember(0)->stringify(buffer, verbose, failIfLong);
        buffer->appendText(TRI_CHAR_LENGTH_PAIR("]:"));
        member->getMember(1)->stringify(buffer, verbose, failIfLong);
      } else {
        TRI_ASSERT(false);
      }
    }
    buffer->appendChar('}');
    return;
  }

  if (type == NODE_TYPE_REFERENCE || type == NODE_TYPE_VARIABLE) {
    // not used by V8
    auto variable = static_cast<Variable*>(getData());
    TRI_ASSERT(variable != nullptr);
    // we're intentionally not using the variable name as it is not necessarily
    // unique within a query (hey COLLECT, I am looking at you!)
    buffer->appendChar('$');
    buffer->appendInteger(variable->id);
    return;
  }

  if (type == NODE_TYPE_INDEXED_ACCESS) {
    // not used by V8
    auto member = getMember(0);
    auto index = getMember(1);
    member->stringify(buffer, verbose, failIfLong);
    buffer->appendChar('[');
    index->stringify(buffer, verbose, failIfLong);
    buffer->appendChar(']');
    return;
  }

  if (type == NODE_TYPE_ATTRIBUTE_ACCESS) {
    // not used by V8
    auto member = getMember(0);
    member->stringify(buffer, verbose, failIfLong);
    buffer->appendChar('.');
    buffer->appendText(getStringValue(), getStringLength());
    return;
  }

  if (type == NODE_TYPE_BOUND_ATTRIBUTE_ACCESS) {
    // not used by V8
    getMember(0)->stringify(buffer, verbose, failIfLong);
    buffer->appendChar('.');
    getMember(1)->stringify(buffer, verbose, failIfLong);
    return;
  }

  if (type == NODE_TYPE_PARAMETER) {
    // not used by V8
    buffer->appendChar('@');
    buffer->appendText(getStringValue(), getStringLength());
    return;
  }

  if (type == NODE_TYPE_FCALL) {
    // not used by V8
    auto func = static_cast<Function*>(getData());
    buffer->appendText(func->externalName);
    buffer->appendChar('(');
    getMember(0)->stringify(buffer, verbose, failIfLong);
    buffer->appendChar(')');
    return;
  }

  if (type == NODE_TYPE_ARRAY_LIMIT) {
    // not used by V8
    buffer->appendText(TRI_CHAR_LENGTH_PAIR("_LIMIT("));
    getMember(0)->stringify(buffer, verbose, failIfLong);
    buffer->appendChar(',');
    getMember(1)->stringify(buffer, verbose, failIfLong);
    buffer->appendChar(')');
    return;
  }

  if (type == NODE_TYPE_EXPANSION) {
    // not used by V8
    buffer->appendText(TRI_CHAR_LENGTH_PAIR("_EXPANSION("));
    getMember(0)->stringify(buffer, verbose, failIfLong);
    buffer->appendChar(',');
    getMember(1)->stringify(buffer, verbose, failIfLong);
    // filter
    buffer->appendChar(',');

    auto filterNode = getMember(2);
    if (filterNode != nullptr && filterNode != Ast::getNodeNop()) {
      buffer->appendText(TRI_CHAR_LENGTH_PAIR(" FILTER "));
      filterNode->getMember(0)->stringify(buffer, verbose, failIfLong);
    }
    auto limitNode = getMember(3);
    if (limitNode != nullptr && limitNode != Ast::getNodeNop()) {
      buffer->appendText(TRI_CHAR_LENGTH_PAIR(" LIMIT "));
      limitNode->getMember(0)->stringify(buffer, verbose, failIfLong);
      buffer->appendChar(',');
      limitNode->getMember(1)->stringify(buffer, verbose, failIfLong);
    }
    auto returnNode = getMember(4);
    if (returnNode != nullptr && returnNode != Ast::getNodeNop()) {
      buffer->appendText(TRI_CHAR_LENGTH_PAIR(" RETURN "));
      returnNode->stringify(buffer, verbose, failIfLong);
    }

    buffer->appendChar(')');
    return;
  }

  if (type == NODE_TYPE_ITERATOR) {
    // not used by V8
    buffer->appendText(TRI_CHAR_LENGTH_PAIR("_ITERATOR("));
    getMember(1)->stringify(buffer, verbose, failIfLong);
    buffer->appendChar(',');
    getMember(0)->stringify(buffer, verbose, failIfLong);
    buffer->appendChar(')');
    return;
  }

  if (type == NODE_TYPE_OPERATOR_UNARY_NOT ||
      type == NODE_TYPE_OPERATOR_UNARY_PLUS ||
      type == NODE_TYPE_OPERATOR_UNARY_MINUS) {
    // not used by V8
    TRI_ASSERT(numMembers() == 1);
    auto it = Operators.find(static_cast<int>(type));
    TRI_ASSERT(it != Operators.end());
    buffer->appendChar(' ');
    buffer->appendText((*it).second);

    getMember(0)->stringify(buffer, verbose, failIfLong);
    return;
  }

  if (type == NODE_TYPE_OPERATOR_BINARY_AND ||
      type == NODE_TYPE_OPERATOR_BINARY_OR ||
      type == NODE_TYPE_OPERATOR_BINARY_PLUS ||
      type == NODE_TYPE_OPERATOR_BINARY_MINUS ||
      type == NODE_TYPE_OPERATOR_BINARY_TIMES ||
      type == NODE_TYPE_OPERATOR_BINARY_DIV ||
      type == NODE_TYPE_OPERATOR_BINARY_MOD ||
      type == NODE_TYPE_OPERATOR_BINARY_EQ ||
      type == NODE_TYPE_OPERATOR_BINARY_NE ||
      type == NODE_TYPE_OPERATOR_BINARY_LT ||
      type == NODE_TYPE_OPERATOR_BINARY_LE ||
      type == NODE_TYPE_OPERATOR_BINARY_GT ||
      type == NODE_TYPE_OPERATOR_BINARY_GE ||
      type == NODE_TYPE_OPERATOR_BINARY_IN ||
      type == NODE_TYPE_OPERATOR_BINARY_NIN) {
    // not used by V8
    TRI_ASSERT(numMembers() == 2);
    auto it = Operators.find(type);
    TRI_ASSERT(it != Operators.end());

    getMember(0)->stringify(buffer, verbose, failIfLong);
    buffer->appendChar(' ');
    buffer->appendText((*it).second);
    buffer->appendChar(' ');
    getMember(1)->stringify(buffer, verbose, failIfLong);
    return;
  }

  if (type == NODE_TYPE_OPERATOR_BINARY_ARRAY_EQ ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_NE ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_LT ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_LE ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_GT ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_GE ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_IN ||
      type == NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN) {
    // not used by V8
    TRI_ASSERT(numMembers() == 3);
    auto it = Operators.find(type);
    TRI_ASSERT(it != Operators.end());

    getMember(0)->stringify(buffer, verbose, failIfLong);
    buffer->appendChar(' ');
    buffer->appendText(Quantifier::Stringify(getMember(2)->getIntValue(true)));
    buffer->appendChar(' ');
    buffer->appendText((*it).second);
    buffer->appendChar(' ');
    getMember(1)->stringify(buffer, verbose, failIfLong);
    return;
  }

  if (type == NODE_TYPE_RANGE) {
    // not used by V8
    TRI_ASSERT(numMembers() == 2);
    getMember(0)->stringify(buffer, verbose, failIfLong);
    buffer->appendText(TRI_CHAR_LENGTH_PAIR(".."));
    getMember(1)->stringify(buffer, verbose, failIfLong);
    return;
  }

  std::string message("stringification not supported for node type ");
  message.append(getTypeString());

  THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL, message);
}

std::string AstNode::toString() const {
  arangodb::basics::StringBuffer buffer(TRI_UNKNOWN_MEM_ZONE);
  stringify(&buffer, false, false);
  return std::string(buffer.c_str(), buffer.length());
}

/// @brief locate a variable including the direct path vector leading to it.
void AstNode::findVariableAccess(
    std::vector<AstNode const*>& currentPath,
    std::vector<std::vector<AstNode const*>>& paths,
    Variable const* findme) const {
  currentPath.push_back(this);
  switch (type) {
    case NODE_TYPE_VARIABLE:
    case NODE_TYPE_REFERENCE: {
      auto variable = static_cast<Variable*>(getData());
      TRI_ASSERT(variable != nullptr);
      if (variable->id == findme->id) {
        paths.emplace_back(currentPath);
      }
    } break;

    case NODE_TYPE_OPERATOR_NARY_AND:
    case NODE_TYPE_OPERATOR_NARY_OR:
    case NODE_TYPE_OBJECT:  // yes, keys can't be vars, but...
    case NODE_TYPE_ARRAY: {
      size_t const n = numMembers();
      for (size_t i = 0; (i < n); ++i) {
        AstNode* member = getMember(i);
        if (member != nullptr) {
          member->findVariableAccess(currentPath, paths, findme);
        }
      }
    } break;

    // One subnode:
    case NODE_TYPE_FCALL:
    case NODE_TYPE_ATTRIBUTE_ACCESS:
    case NODE_TYPE_OPERATOR_UNARY_PLUS:
    case NODE_TYPE_OPERATOR_UNARY_MINUS:
    case NODE_TYPE_OPERATOR_UNARY_NOT:
      getMember(0)->findVariableAccess(currentPath, paths, findme);
      break;

    // two subnodes to inspect:
    case NODE_TYPE_RANGE:
    case NODE_TYPE_ITERATOR:
    case NODE_TYPE_ARRAY_LIMIT:
    case NODE_TYPE_INDEXED_ACCESS:
    case NODE_TYPE_BOUND_ATTRIBUTE_ACCESS:
    case NODE_TYPE_OPERATOR_BINARY_AND:
    case NODE_TYPE_OPERATOR_BINARY_OR:
    case NODE_TYPE_OPERATOR_BINARY_PLUS:
    case NODE_TYPE_OPERATOR_BINARY_MINUS:
    case NODE_TYPE_OPERATOR_BINARY_TIMES:
    case NODE_TYPE_OPERATOR_BINARY_DIV:
    case NODE_TYPE_OPERATOR_BINARY_MOD:
    case NODE_TYPE_OPERATOR_BINARY_EQ:
    case NODE_TYPE_OPERATOR_BINARY_NE:
    case NODE_TYPE_OPERATOR_BINARY_LT:
    case NODE_TYPE_OPERATOR_BINARY_LE:
    case NODE_TYPE_OPERATOR_BINARY_GT:
    case NODE_TYPE_OPERATOR_BINARY_GE:
    case NODE_TYPE_OPERATOR_BINARY_IN:
    case NODE_TYPE_OPERATOR_BINARY_NIN:
      getMember(0)->findVariableAccess(currentPath, paths, findme);
      getMember(1)->findVariableAccess(currentPath, paths, findme);
      break;

    case NODE_TYPE_EXPANSION: {
      getMember(0)->findVariableAccess(currentPath, paths, findme);
      getMember(1)->findVariableAccess(currentPath, paths, findme);
      auto filterNode = getMember(2);
      if (filterNode != nullptr) {
        filterNode->findVariableAccess(currentPath, paths, findme);
      }
      auto limitNode = getMember(3);
      if (limitNode != nullptr) {
        limitNode->findVariableAccess(currentPath, paths, findme);
      }
      auto returnNode = getMember(4);
      if (returnNode != nullptr) {
        returnNode->findVariableAccess(currentPath, paths, findme);
      }
    } break;
    // no sub nodes, not a variable:
    case NODE_TYPE_OPERATOR_TERNARY:
    case NODE_TYPE_SUBQUERY:
    case NODE_TYPE_VALUE:
    case NODE_TYPE_ROOT:
    case NODE_TYPE_FOR:
    case NODE_TYPE_LET:
    case NODE_TYPE_FILTER:
    case NODE_TYPE_RETURN:
    case NODE_TYPE_REMOVE:
    case NODE_TYPE_INSERT:
    case NODE_TYPE_UPDATE:
    case NODE_TYPE_REPLACE:
    case NODE_TYPE_COLLECT:
    case NODE_TYPE_SORT:
    case NODE_TYPE_SORT_ELEMENT:
    case NODE_TYPE_LIMIT:
    case NODE_TYPE_ASSIGN:
    case NODE_TYPE_OBJECT_ELEMENT:
    case NODE_TYPE_COLLECTION:
    case NODE_TYPE_PARAMETER:
    case NODE_TYPE_FCALL_USER:
    case NODE_TYPE_NOP:
    case NODE_TYPE_COLLECT_COUNT:
    case NODE_TYPE_AGGREGATIONS:
    case NODE_TYPE_CALCULATED_OBJECT_ELEMENT:
    case NODE_TYPE_UPSERT:
    case NODE_TYPE_EXAMPLE:
    case NODE_TYPE_PASSTHRU:
    case NODE_TYPE_DISTINCT:
    case NODE_TYPE_TRAVERSAL:
    case NODE_TYPE_SHORTEST_PATH:
    case NODE_TYPE_COLLECTION_LIST:
    case NODE_TYPE_DIRECTION:
    case NODE_TYPE_WITH:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_EQ:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_NE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_LT:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_LE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_GT:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_GE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_IN:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN:
    case NODE_TYPE_QUANTIFIER:
      break;
  }

  currentPath.pop_back();
}

AstNode const* AstNode::findReference(AstNode const* findme) const {
  if (this == findme) {
    return this;
  }

  const AstNode* ret = nullptr;
  switch (type) {
    case NODE_TYPE_OBJECT:  // yes, keys can't be vars, but...
    case NODE_TYPE_ARRAY: {
      size_t const n = numMembers();
      for (size_t i = 0; i < n; ++i) {
        AstNode* member = getMember(i);
        if (member == findme) {
          return this;
        }
        if (member != nullptr) {
          ret = member->findReference(findme);
          if (ret != nullptr) { 
            return ret;
          }
        }
      }
    } break;

    // One subnode:
    case NODE_TYPE_FCALL:
    case NODE_TYPE_ATTRIBUTE_ACCESS:
    case NODE_TYPE_OPERATOR_UNARY_PLUS:
    case NODE_TYPE_OPERATOR_UNARY_MINUS:
    case NODE_TYPE_OPERATOR_UNARY_NOT:
      if (getMember(0) == findme) {
        return this;
      }
      return getMember(0)->findReference(findme);

    // two subnodes to inspect:
    case NODE_TYPE_RANGE:
    case NODE_TYPE_ITERATOR:
    case NODE_TYPE_ARRAY_LIMIT:
    case NODE_TYPE_INDEXED_ACCESS:
    case NODE_TYPE_BOUND_ATTRIBUTE_ACCESS:
    case NODE_TYPE_OPERATOR_BINARY_AND:
    case NODE_TYPE_OPERATOR_BINARY_OR:
    case NODE_TYPE_OPERATOR_BINARY_PLUS:
    case NODE_TYPE_OPERATOR_BINARY_MINUS:
    case NODE_TYPE_OPERATOR_BINARY_TIMES:
    case NODE_TYPE_OPERATOR_BINARY_DIV:
    case NODE_TYPE_OPERATOR_BINARY_MOD:
    case NODE_TYPE_OPERATOR_BINARY_EQ:
    case NODE_TYPE_OPERATOR_BINARY_NE:
    case NODE_TYPE_OPERATOR_BINARY_LT:
    case NODE_TYPE_OPERATOR_BINARY_LE:
    case NODE_TYPE_OPERATOR_BINARY_GT:
    case NODE_TYPE_OPERATOR_BINARY_GE:
    case NODE_TYPE_OPERATOR_BINARY_IN:
    case NODE_TYPE_OPERATOR_BINARY_NIN:
      if (getMember(0) == findme) {
        return this;
      }
      ret = getMember(0)->findReference(findme);
      if (ret != nullptr) {
        return ret;
      }
      if (getMember(1) == findme) {
        return this;
      }
      ret = getMember(1)->findReference(findme);
      break;

    case NODE_TYPE_EXPANSION: {
      if (getMember(0) == findme) {
        return this;
      }
      ret = getMember(0)->findReference(findme);
      if (ret != nullptr) {
        return ret;
      }
      if (getMember(1) == findme) {
        return this;
      }
      ret = getMember(1)->findReference(findme);
      if (ret != nullptr) {
        return ret;
      }
      auto filterNode = getMember(2);
      if (filterNode != nullptr) {
        if (filterNode->getMember(0) == findme) {
          return this;
        }

        ret = filterNode->getMember(0)->findReference(findme);
        if (ret != nullptr) {
          return ret;
        }
      }
      auto limitNode = getMember(3);
      if (limitNode != nullptr) {
        if (limitNode->getMember(0) == findme) {
          return this;
        }
        ret = limitNode->getMember(0)->findReference(findme);
        if (ret != nullptr) {
          return ret;
        }
        ret = limitNode->getMember(1)->findReference(findme);
        if (ret != nullptr) {
          return ret;
        }
      }
      auto returnNode = getMember(4);
      if (returnNode != nullptr) {
        if (returnNode->getMember(0) == findme) {
          return this;
        }
        ret = returnNode->getMember(0)->findReference(findme);
      }
    } break;

    // no subnodes here:
    case NODE_TYPE_OPERATOR_TERNARY:
    case NODE_TYPE_SUBQUERY:
    case NODE_TYPE_VALUE:
    case NODE_TYPE_ROOT:
    case NODE_TYPE_FOR:
    case NODE_TYPE_LET:
    case NODE_TYPE_FILTER:
    case NODE_TYPE_RETURN:
    case NODE_TYPE_REMOVE:
    case NODE_TYPE_INSERT:
    case NODE_TYPE_UPDATE:
    case NODE_TYPE_REPLACE:
    case NODE_TYPE_COLLECT:
    case NODE_TYPE_SORT:
    case NODE_TYPE_SORT_ELEMENT:
    case NODE_TYPE_LIMIT:
    case NODE_TYPE_ASSIGN:
    case NODE_TYPE_VARIABLE:
    case NODE_TYPE_REFERENCE:
    case NODE_TYPE_OBJECT_ELEMENT:
    case NODE_TYPE_COLLECTION:
    case NODE_TYPE_PARAMETER:
    case NODE_TYPE_FCALL_USER:
    case NODE_TYPE_NOP:
    case NODE_TYPE_COLLECT_COUNT:
    case NODE_TYPE_AGGREGATIONS:
    case NODE_TYPE_CALCULATED_OBJECT_ELEMENT:
    case NODE_TYPE_UPSERT:
    case NODE_TYPE_EXAMPLE:
    case NODE_TYPE_PASSTHRU:
    case NODE_TYPE_DISTINCT:
    case NODE_TYPE_TRAVERSAL:
    case NODE_TYPE_SHORTEST_PATH:
    case NODE_TYPE_COLLECTION_LIST:
    case NODE_TYPE_DIRECTION:
    case NODE_TYPE_OPERATOR_NARY_AND:
    case NODE_TYPE_OPERATOR_NARY_OR:
    case NODE_TYPE_WITH:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_EQ:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_NE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_LT:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_LE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_GT:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_GE:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_IN:
    case NODE_TYPE_OPERATOR_BINARY_ARRAY_NIN:
    case NODE_TYPE_QUANTIFIER:
      break;
  }
  return ret;
}

/// @brief stringify the value of a node into a string buffer
/// this creates an equivalent to what JSON.stringify() would do
/// this method is used when generated JavaScript code for the node!
void AstNode::appendValue(arangodb::basics::StringBuffer* buffer) const {
  TRI_ASSERT(type == NODE_TYPE_VALUE);

  switch (value.type) {
    case VALUE_TYPE_BOOL: {
      if (value.value._bool) {
        buffer->appendText(TRI_CHAR_LENGTH_PAIR("true"));
      } else {
        buffer->appendText(TRI_CHAR_LENGTH_PAIR("false"));
      }
      break;
    }

    case VALUE_TYPE_INT: {
      buffer->appendInteger(value.value._int);
      break;
    }

    case VALUE_TYPE_DOUBLE: {
      double const v = value.value._double;
      if (std::isnan(v) || !std::isfinite(v) || v == HUGE_VAL || v == -HUGE_VAL) {
        buffer->appendText(TRI_CHAR_LENGTH_PAIR("null"));
      } else {
        buffer->appendDecimal(value.value._double);
      }
      break;
    }

    case VALUE_TYPE_STRING: {
      buffer->appendJsonEncoded(value.value._string, value.length);
      break;
    }

    case VALUE_TYPE_NULL:
    default: {
      buffer->appendText(TRI_CHAR_LENGTH_PAIR("null"));
      break;
    }
  }
}

/// @brief append the AstNode to an output stream
std::ostream& operator<<(std::ostream& stream,
                         arangodb::aql::AstNode const* node) {
  if (node != nullptr) {
    stream << arangodb::aql::AstNode::toString(node);
  }
  return stream;
}

/// @brief append the AstNode to an output stream
std::ostream& operator<<(std::ostream& stream,
                         arangodb::aql::AstNode const& node) {
  stream << arangodb::aql::AstNode::toString(&node);
  return stream;
}