////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2012-2021 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Octave is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
// <https://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////

#if ! defined (octave_profiler_h)
#define octave_profiler_h 1

#include "octave-config.h"

#include <cstddef>
#include <map>
#include <set>
#include <string>
#include <vector>

class octave_value;

namespace octave
{
  class
  OCTINTERP_API
  profiler
  {
  public:

    // This is a utility class that can be used to call the enter/exit
    // functions in a manner protected from stack unwinding.
    template <typename T> class enter
    {
    private:

      profiler& m_profiler;
      std::string m_fcn;
      bool m_enabled;

    public:

      enter (profiler& p, const T& t) : m_profiler (p)
      {
        // A profiling block cannot be active if the profiler is not
        m_enabled = m_profiler.enabled ();

        if (m_enabled)
          {
            m_fcn = t.profiler_name ();

            // NOTE: The test f != "" must be kept to prevent a blank
            // line showing up in profiler statistics.  See bug
            // #39524.  The root cause is that the function name is
            // not set for the recurring readline hook function.
            if (m_fcn == "")
              m_enabled = false;  // Inactive profiling block
            else
              m_profiler.enter_function (m_fcn);
          }
      }

      // No copying!

      enter (const enter&) = delete;

      enter& operator = (const enter&) = delete;

      ~enter (void)
      {
        if (m_enabled)
          m_profiler.exit_function (m_fcn);
      }
    };

    profiler (void);

    // No copying!

    profiler (const profiler&) = delete;

    profiler& operator = (const profiler&) = delete;

    virtual ~profiler (void);

    bool enabled (void) const { return m_enabled; }
    void set_active (bool);

    void reset (void);

    octave_value get_flat (void) const;
    octave_value get_hierarchical (void) const;

  private:

    // One entry in the flat profile (i.e., a collection of data for a single
    // function).  This is filled in when building the flat profile from the
    // hierarchical call tree.
    struct stats
    {
      stats (void);

      double m_time;
      std::size_t m_calls;

      bool m_recursive;

      typedef std::set<octave_idx_type> function_set;
      function_set m_parents;
      function_set m_children;

      // Convert a function_set list to an Octave array of indices.
      static octave_value function_set_value (const function_set&);
    };

    typedef std::vector<stats> flat_profile;

    // Store data for one node in the call-tree of the hierarchical profiler
    // data we collect.
    class tree_node
    {
    public:

      tree_node (tree_node*, octave_idx_type);

      virtual ~tree_node (void);

      // No copying!

      tree_node (const tree_node&) = delete;

      tree_node& operator = (const tree_node&) = delete;

      void add_time (double dt) { m_time += dt; }

      // Enter a child function.  It is created in the list of children if it
      // wasn't already there.  The now-active child node is returned.
      tree_node *enter (octave_idx_type);

      // Exit function.  As a sanity-check, it is verified that the currently
      // active function actually is the one handed in here.  Returned is the
      // then-active node, which is our parent.
      tree_node *exit (octave_idx_type);

      void build_flat (flat_profile&) const;

      // Get the hierarchical profile for this node and its children.  If total
      // is set, accumulate total time of the subtree in that variable as
      // additional return value.
      octave_value get_hierarchical (double *total = nullptr) const;

    private:

      tree_node *m_parent;
      octave_idx_type m_fcn_id;

      typedef std::map<octave_idx_type, tree_node*> child_map;
      child_map m_children;

      // This is only time spent *directly* on this level, excluding children!
      double m_time;

      std::size_t m_calls;
    };

    // Each function we see in the profiler is given a unique index (which
    // simply counts starting from 1).  We thus have to map profiler-names to
    // those indices.  For all other stuff, we identify functions by their index.

    typedef std::vector<std::string> function_set;
    typedef std::map<std::string, octave_idx_type> fcn_index_map;

    function_set m_known_functions;
    fcn_index_map m_fcn_index;

    bool m_enabled;

    tree_node *m_call_tree;
    tree_node *m_active_fcn;

    // Store last timestamp we had, when the currently active function was called.
    double m_last_time;

    // These are private as only the unwind-protecting inner class enter
    // should be allowed to call them.
    void enter_function (const std::string&);
    void exit_function (const std::string&);

    // Query a timestamp, used for timing calls (obviously).
    // This is not static because in the future, maybe we want a flag
    // in the profiler or something to choose between cputime, wall-time,
    // user-time, system-time, ...
    double query_time (void) const;

    // Add the time elapsed since last_time to the function we're currently in.
    // This is called from two different positions, thus it is useful to have
    // it as a separate function.
    void add_current_time (void);
  };
}

#endif