////////////////////////////////////////////////////////////////////////////////
/// 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 Kaveh Vahedipour
////////////////////////////////////////////////////////////////////////////////

#ifndef ARANGOD_CONSENSUS_NODE_H
#define ARANGOD_CONSENSUS_NODE_H 1

#include "AgencyCommon.h"

#include "Basics/Mutex.h"
#include "Basics/MutexLocker.h"
#include "Basics/Thread.h"
#include "Basics/ConditionVariable.h"

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

#include <type_traits>
#include <utility>
#include <string>
#include <vector>

namespace arangodb {
namespace consensus {

enum NodeType {NODE, LEAF};
enum Operation {SET, INCREMENT, DECREMENT, PUSH, POP,
                PREPEND, SHIFT, OBSERVE, UNOBSERVE};

using namespace arangodb::velocypack;

class StoreException : public std::exception {
public:
  explicit StoreException(std::string const& message) : _message(message) {}
  virtual char const* what() const noexcept override final {
    return _message.c_str(); }
private:
  std::string _message;
};

enum NODE_EXCEPTION {PATH_NOT_FOUND};

class Node;

typedef std::chrono::system_clock::time_point TimePoint;
typedef std::multimap<TimePoint, std::shared_ptr<Node>> TimeTable;

class Store;

/// @brief Simple tree implementation
class Node {
  
public:
  // @brief Slash-segemented path 
  typedef std::vector<std::string> PathType;

  // @brief Child nodes
  typedef std::map<std::string, std::shared_ptr<Node>> Children;
  
  /// @brief Construct with name
  explicit Node (std::string const& name);

  /// @brief Construct with name and introduce to tree under parent
  Node (std::string const& name, Node* parent);
  
  /// @brief Construct with name and introduce to tree under parent
  Node (std::string const& name, Store* store);

  /// @brief Default dtor
  virtual ~Node ();
  
  /// @brief Get name 
  std::string const& name() const;

  /// @brief Get full path
  std::string uri() const;

  /// @brief Apply rhs to this node (deep copy of rhs)
  Node& operator= (Node const& node);

  /// @brief Apply value slice to this node
  Node& operator= (arangodb::velocypack::Slice const&);

  /// @brief Check equality with slice
  bool operator== (arangodb::velocypack::Slice const&) const;

  /// @brief Type of this node (LEAF / NODE)
  NodeType type() const;

  /// @brief Get node specified by path vector  
  Node& operator ()(std::vector<std::string> const& pv);
  /// @brief Get node specified by path vector  
  Node const& operator ()(std::vector<std::string> const& pv) const;
  
  /// @brief Get node specified by path string  
  Node& operator ()(std::string const& path);
  /// @brief Get node specified by path string  
  Node const& operator ()(std::string const& path) const;

  /// @brief Remove child by name
  bool removeChild (std::string const& key);

  /// @brief Remove this node and below from tree
  bool remove();

  /// @brief Get root node
  Node const& root() const;

  /// @brief Get root node
  Node& root();

  /// @brief Dump to ostream
  std::ostream& print (std::ostream&) const;

  /// #brief Get path of this node
  std::string path (); 
  
  /// @brief Apply single operation as defined by "op"
  bool applieOp (arangodb::velocypack::Slice const&);

  /// @brief Apply single slice
  bool applies (arangodb::velocypack::Slice const&);

  /// @brief handle "op" keys in write json
  template<Operation Oper>
  bool handle (arangodb::velocypack::Slice const&);

  /// @brief Create Builder representing this store
  void toBuilder (Builder&) const;

  /// @brief Access children
  Children& children ();

  /// @brief Access children
  Children const& children () const;

  /// @brief Create slice from value
  Slice slice() const;

  /// @brief Get value type  
  ValueType valueType () const;

  /// @brief Add observer for this node
  bool addObserver (std::string const&);
  
  /// @brief Add observer for this node
  void notifyObservers (std::string const& origin) const;

  /// @brief Is this node being observed by url
  bool observedBy (std::string const& url) const;

  Store& store();
  Store const& store() const;

  std::string toJson() const;

protected:

  /// @brief Add time to live entry
  virtual bool addTimeToLive (long millis);

  /// @brief Remove time to live entry
  virtual bool removeTimeToLive ();

  std::string _node_name;              /**< @brief my name */

  Node* _parent;                       /**< @brief parent */
  Store* _store;                       /**< @brief Store */
  Children _children;                  /**< @brief child nodes */
  TimePoint _ttl;                      /**< @brief my expiry */
  Buffer<uint8_t> _value;              /**< @brief my value */

};

inline std::ostream& operator<< (std::ostream& o, Node const& n) {
  return n.print(o);
}

}} // namespaces

#endif