#ifndef TRACER_H_
#define TRACER_H_

#include <iostream>
#include <string>
#include <vector>

// Allows readers to track the operations applied to STL container elements.
//
// Tracer assigns a unique and immutable ID to each default-constructed
// instance.  Each instance also contains a list of its ancestors, which can
// be copied from one Tracer to another Tracer.  A Tracer may have a 
//
// These Tracers print messages whenever important events happen, including
// default construction, copy construction, destruction, assignment, and
// "less than" operator invocation.
class Tracer {
 public:
  // Constructors/Destructors.
  Tracer();
  //  Tracer(Tracer&&) = delete;
  ~Tracer();
  Tracer(const Tracer &rhs);

  // Assignment operator.
  Tracer &operator=(const Tracer &rhs);

  // Less-than comparison operator.  This is used for things like sorting
  // or inserting into a map.
  bool operator<(const Tracer &rhs) const;

  // << operator
  friend std::ostream &operator<<(std::ostream &out, const Tracer &rhs);

 private:
  // Returns "(id_,[parents])" as a string.
  std::string PrintID() const;

  // Adds the passed-in list of ancestors to our own.
  void AppendAncestors(const Tracer &t);

  // Return the ID of the original Tracer (ie, the "root" of our ancestry).
  int GetRoot() const;

  // This static (class member) tracks the next id_ to hand out.
  static int nextid_;

  const int id_;
  std::vector<int> ancestors_;
};

#endif  // TRACER_H_