////////////////////////////////////////////////////////////////////////////////
/// @brief Aql, AST node
///
/// @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 Jan Steemann
/// @author Copyright 2014, ArangoDB GmbH, Cologne, Germany
/// @author Copyright 2012-2013, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

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

#ifdef TRI_ENABLE_MAINTAINER_MODE
#include <iostream>
#endif

#include <array>

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

// -----------------------------------------------------------------------------
// --SECTION--                                            static initializations
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @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" }
};

////////////////////////////////////////////////////////////////////////////////
/// @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 count" },
  { static_cast<int>(NODE_TYPE_COLLECT_EXPRESSION),       "collect expression" },
  { 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" }
};

////////////////////////////////////////////////////////////////////////////////
/// @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" }
};

// -----------------------------------------------------------------------------
// --SECTION--                                           static helper functions
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @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) {
    char const* attributeName = node->getStringValue();

    TRI_ASSERT(attributeName != nullptr);
    attributeNames.emplace_back(attributeName);
    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);
      char const* attributeName = attributeNames[which - 1].c_str();
      --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 
            && strcmp(member->getStringValue(), attributeName) == 0) {
          // found the attribute
          node = member->getMember(0);
          if (which == 0) {
            // we found what we looked for
            return node;
          }
          else {
            // 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 triagens::aql::CompareAstNodes (AstNode const* lhs, 
                                    AstNode const* rhs,
                                    bool compareUtf8) {
  TRI_ASSERT_EXPENSIVE(lhs != nullptr);
  TRI_ASSERT_EXPENSIVE(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_EXPENSIVE(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) {
    size_t maxLength = (std::max)(lhs->getStringLength(), rhs->getStringLength());

    if (compareUtf8) {
      return TRI_compare_utf8(lhs->getStringValue(), lhs->getStringLength(), rhs->getStringValue(), rhs->getStringLength());
    }

    int res = strncmp(lhs->getStringValue(), rhs->getStringValue(), maxLength);

    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 = triagens::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 to node to
    // JSON for comparison
    // (this saves us from writing our own compare function
    // for array AstNodes)
    auto lJson = lhs->toJsonValue(TRI_UNKNOWN_MEM_ZONE);
    auto rJson = rhs->toJsonValue(TRI_UNKNOWN_MEM_ZONE);

    int res = TRI_CompareValuesJson(lJson, rJson, compareUtf8);

    if (lJson != nullptr) {
      TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, lJson);
    }
    if (rJson != nullptr) {
      TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, rJson);
    }
    return res;
  }

  // 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;
}

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

////////////////////////////////////////////////////////////////////////////////
/// @brief create the node
////////////////////////////////////////////////////////////////////////////////

AstNode::AstNode (AstNodeType type)
  : type(type),
    flags(0),
    computedJson(nullptr) {
}

////////////////////////////////////////////////////////////////////////////////
/// @brief create a node, with defining a value type
////////////////////////////////////////////////////////////////////////////////

AstNode::AstNode (AstNodeType type,
                  AstNodeValueType valueType)
  : AstNode(type) {

  value.type = valueType;
  TRI_ASSERT_EXPENSIVE(flags == 0);
  TRI_ASSERT_EXPENSIVE(computedJson == 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_EXPENSIVE(flags == 0);
  TRI_ASSERT_EXPENSIVE(computedJson == 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_EXPENSIVE(flags == 0);
  TRI_ASSERT_EXPENSIVE(computedJson == 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_EXPENSIVE(flags == 0);
  TRI_ASSERT_EXPENSIVE(computedJson == nullptr);
}

////////////////////////////////////////////////////////////////////////////////
/// @brief create the node from JSON
////////////////////////////////////////////////////////////////////////////////

AstNode::AstNode (Ast* ast,
                  triagens::basics::Json const& json) 
  : AstNode(getNodeTypeFromJson(json)) {

  TRI_ASSERT_EXPENSIVE(flags == 0);
  TRI_ASSERT_EXPENSIVE(computedJson == 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: {
      auto variable = ast->variables()->createVariable(json);
      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_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_COLLECT_EXPRESSION:
    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_IN:
    case NODE_TYPE_OPERATOR_BINARY_NIN:
    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_ARRAY:
    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_DIRECTION:
    case NODE_TYPE_COLLECTION_LIST:
    case NODE_TYPE_OPERATOR_NARY_AND:
    case NODE_TYPE_OPERATOR_NARY_OR:
      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,
                  triagens::basics::Json const& json) 
  : AstNode(getNodeTypeFromJson(json)) {

  TRI_ASSERT_EXPENSIVE(flags == 0);
  TRI_ASSERT_EXPENSIVE(computedJson == 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_COLLECT_EXPRESSION:
    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_DIRECTION:
    case NODE_TYPE_COLLECTION_LIST:
    case NODE_TYPE_PASSTHRU: {
      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:
      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 (computedJson != nullptr) {
    TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, computedJson);
    computedJson = nullptr;
  }
}

// -----------------------------------------------------------------------------
// --SECTION--                                                    public methods
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief dump the node (for debugging purposes)
////////////////////////////////////////////////////////////////////////////////

#ifdef TRI_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();
  }
  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 JSON for a constant value node
/// the JSON 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
////////////////////////////////////////////////////////////////////////////////

TRI_json_t* AstNode::computeJson () const {
  TRI_ASSERT(isConstant());

  if (computedJson == nullptr) {
    // note: the following may fail but we do not need to 
    // check that here
    computedJson = toJsonValue(TRI_UNKNOWN_MEM_ZONE);
  }

  return computedJson;
}

////////////////////////////////////////////////////////////////////////////////
/// @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_EXPENSIVE(isConstant());

  std::sort(members.begin(), members.end(), [] (AstNode const* lhs, AstNode const* rhs) {
    return (triagens::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 triagens::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 (triagens::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);
        // TODO: can we get away with a string reference only??
        // this would speed things up considerably!
        // return TRI_CreateStringReferenceJson(zone, value.value._string, strlen(value.value._string));
    }
  }
  
  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_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_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 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) {
        if (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.value._string) != '\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->createNodeValueNull();
}

////////////////////////////////////////////////////////////////////////////////
/// @brief convert the node's value to a string value
/// this may create a new node or return the node itself if it is already a
/// string value node
////////////////////////////////////////////////////////////////////////////////

AstNode* AstNode::castToString (Ast* ast) {
  TRI_ASSERT(type == NODE_TYPE_VALUE || 
             type == NODE_TYPE_ARRAY || 
             type == NODE_TYPE_OBJECT);

  if (type == NODE_TYPE_VALUE && value.type == VALUE_TYPE_STRING) {
    // already a string
    return this;
  }

  TRI_ASSERT(isConstant());

  // stringify node
  triagens::basics::StringBuffer buffer(TRI_UNKNOWN_MEM_ZONE);
  stringify(&buffer, false, false);

  char const* value = ast->query()->registerString(buffer.c_str(), buffer.length());
  TRI_ASSERT(value != nullptr);
  return ast->createNodeValueString(value, buffer.length());
}

////////////////////////////////////////////////////////////////////////////////
/// @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<triagens::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(), 
        triagens::basics::AttributeName(std::string(node->getStringValue(), node->getStringLength()), 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 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) {
    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_CALCULATED_OBJECT_ELEMENT) {
    // this one is explicitly non-simple!
    setFlag(DETERMINED_SIMPLE);
    return false;
  } 

  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_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 (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 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 (triagens::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);
    } 

    if (verbose || n > 0) {
      if (verbose || n > 1) {
        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);
        }
      }
      if (verbose || n > 1) {
        buffer->appendChar(']');
      }
    }
    return;
  }

  if (type == NODE_TYPE_OBJECT) {
    // must be JavaScript-compatible!
    if (verbose) {
      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->appendChar('"');
          buffer->appendJsonEncoded(member->getStringValue(), member->getStringLength());
          buffer->appendText(TRI_CHAR_LENGTH_PAIR("\":"));

          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('}');
    }
    else {
      buffer->appendText(TRI_CHAR_LENGTH_PAIR("[object Object]"));
    }
    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());
    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());
    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 && filterNode != 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 && filterNode != Ast::getNodeNop()) {
      buffer->appendText(TRI_CHAR_LENGTH_PAIR(" RETURN "));
      returnNode->getMember(0)->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_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 {
   triagens::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_COLLECT_EXPRESSION:
    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_COLLECTION_LIST:
    case NODE_TYPE_DIRECTION:
      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_COLLECT_EXPRESSION:
  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_COLLECTION_LIST:
  case NODE_TYPE_DIRECTION:
  case NODE_TYPE_OPERATOR_NARY_AND:
  case NODE_TYPE_OPERATOR_NARY_OR:
    break;
  }
  return ret;
}

// -----------------------------------------------------------------------------
// --SECTION--                                                   private methods
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @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 (triagens::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: {
      buffer->appendDecimal(value.value._double);
      break;
    }

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

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

// -----------------------------------------------------------------------------
// --SECTION--                                       public non-member functions
// -----------------------------------------------------------------------------

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

////////////////////////////////////////////////////////////////////////////////
/// @brief append the AstNode to an output stream
////////////////////////////////////////////////////////////////////////////////

std::ostream& operator<< (std::ostream& stream,
                          triagens::aql::AstNode const& node) {
  stream << triagens::aql::AstNode::toString(&node);
  return stream;
}

// -----------------------------------------------------------------------------
// --SECTION--                                                       END-OF-FILE
// -----------------------------------------------------------------------------

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