/*

Copyright (C) 1996-2016 John W. Eaton

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
<http://www.gnu.org/licenses/>.

*/

#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif

#include "error.h"
#include "defun.h"
#include "ovl.h"
#include "ov.h"
#include "profiler.h"
#include "pt-binop.h"
#include "pt-bp.h"
#include "pt-walk.h"
#include "variables.h"

// TRUE means we mark | and & expressions for braindead short-circuit
// behavior.
static bool Vdo_braindead_shortcircuit_evaluation = true;

// Binary expressions.

octave_value_list
tree_binary_expression::rvalue (int nargout)
{
  octave_value_list retval;

  if (nargout > 1)
    error ("binary operator '%s': invalid number of output arguments",
           oper ().c_str ());

  retval = rvalue1 (nargout);

  return retval;
}

void
tree_binary_expression::matlab_style_short_circuit_warning (const char *op)
{
  warning_with_id ("Octave:possible-matlab-short-circuit-operator",
                   "Matlab-style short-circuit operation performed for operator %s",
                   op);

  braindead_shortcircuit_warning_issued = true;
}

octave_value
tree_binary_expression::rvalue1 (int)
{
  octave_value retval;

  if (Vdo_braindead_shortcircuit_evaluation
      && eligible_for_braindead_shortcircuit)
    {
      if (op_lhs)
        {
          octave_value a = op_lhs->rvalue1 ();

          if (a.ndims () == 2 && a.rows () == 1 && a.columns () == 1)
            {
              bool result = false;

              bool a_true = a.is_true ();

              if (a_true)
                {
                  if (etype == octave_value::op_el_or)
                    {
                      matlab_style_short_circuit_warning ("|");
                      return octave_value (true);
                    }
                }
              else
                {
                  if (etype == octave_value::op_el_and)
                    {
                      matlab_style_short_circuit_warning ("&");
                      return octave_value (false);
                    }
                }

              if (op_rhs)
                {
                  octave_value b = op_rhs->rvalue1 ();

                  result = b.is_true ();
                }

              return octave_value (result);
            }
        }
    }

  if (op_lhs)
    {
      octave_value a = op_lhs->rvalue1 ();

      if (a.is_defined () && op_rhs)
        {
          octave_value b = op_rhs->rvalue1 ();

          if (b.is_defined ())
            {
              BEGIN_PROFILER_BLOCK (tree_binary_expression)

              // Note: The profiler does not catch the braindead
              // short-circuit evaluation code above, but that should be
              // ok.  The evaluation of operands and the operator itself
              // is entangled and it's not clear where to start/stop
              // timing the operator to make it reasonable.

              retval = ::do_binary_op (etype, a, b);

              END_PROFILER_BLOCK
            }
        }
    }

  return retval;
}

std::string
tree_binary_expression::oper (void) const
{
  return octave_value::binary_op_as_string (etype);
}

tree_expression *
tree_binary_expression::dup (symbol_table::scope_id scope,
                             symbol_table::context_id context) const
{
  tree_binary_expression *new_be
    = new tree_binary_expression (op_lhs ? op_lhs->dup (scope, context) : 0,
                                  op_rhs ? op_rhs->dup (scope, context) : 0,
                                  line (), column (), etype);

  new_be->copy_base (*this);

  return new_be;
}

void
tree_binary_expression::accept (tree_walker& tw)
{
  tw.visit_binary_expression (*this);
}

// Boolean expressions.

octave_value_list
tree_boolean_expression::rvalue (int nargout)
{
  octave_value_list retval;

  if (nargout > 1)
    error ("binary operator '%s': invalid number of output arguments",
           oper ().c_str ());

  retval = rvalue1 (nargout);

  return retval;
}

octave_value
tree_boolean_expression::rvalue1 (int)
{
  octave_value retval;

  bool result = false;

  // This evaluation is not caught by the profiler, since we can't find
  // a reasonable place where to time.  Note that we don't want to
  // include evaluation of LHS or RHS into the timing, but this is
  // entangled together with short-circuit evaluation here.

  if (op_lhs)
    {
      octave_value a = op_lhs->rvalue1 ();

      bool a_true = a.is_true ();

      if (a_true)
        {
          if (etype == bool_or)
            return octave_value (true);
        }
      else
        {
          if (etype == bool_and)
            return octave_value (false);
        }

      if (op_rhs)
        {
          octave_value b = op_rhs->rvalue1 ();

          result = b.is_true ();
        }

      retval = octave_value (result);
    }

  return retval;
}

std::string
tree_boolean_expression::oper (void) const
{
  std::string retval = "<unknown>";

  switch (etype)
    {
    case bool_and:
      retval = "&&";
      break;

    case bool_or:
      retval = "||";
      break;

    default:
      break;
    }

  return retval;
}

tree_expression *
tree_boolean_expression::dup (symbol_table::scope_id scope,
                              symbol_table::context_id context) const
{
  tree_boolean_expression *new_be
    = new tree_boolean_expression (op_lhs ? op_lhs->dup (scope, context) : 0,
                                   op_rhs ? op_rhs->dup (scope, context) : 0,
                                   line (), column (), etype);

  new_be->copy_base (*this);

  return new_be;
}

DEFUN (do_braindead_shortcircuit_evaluation, args, nargout,
       doc: /* -*- texinfo -*-
@deftypefn  {} {@var{val} =} do_braindead_shortcircuit_evaluation ()
@deftypefnx {} {@var{old_val} =} do_braindead_shortcircuit_evaluation (@var{new_val})
@deftypefnx {} {} do_braindead_shortcircuit_evaluation (@var{new_val}, "local")
Query or set the internal variable that controls whether Octave will
do short-circuit evaluation of @samp{|} and @samp{&} operators inside the
conditions of if or while statements.

This feature is only provided for compatibility with @sc{matlab} and should
not be used unless you are porting old code that relies on this feature.

To obtain short-circuit behavior for logical expressions in new programs,
you should always use the @samp{&&} and @samp{||} operators.

When called from inside a function with the @qcode{"local"} option, the
variable is changed locally for the function and any subroutines it calls.
The original variable value is restored when exiting the function.
@end deftypefn */)
{
  static bool warned = false;
  if (! warned)
    {
      warned = true;
      warning_with_id ("Octave:deprecated-function",
                       "do_braindead_shortcircuit_evaluation is obsolete and will be removed from a future version of Octave");
    }

  return SET_INTERNAL_VARIABLE (do_braindead_shortcircuit_evaluation);
}

/*
%!test
%! x = 0;
%! do_braindead_shortcircuit_evaluation (0);
%! if (1 | (x = 1))
%! endif
%! assert (x, 1);
%! do_braindead_shortcircuit_evaluation (1);
%! if (1 | (x = 0))
%! endif
%! assert (x, 1);
*/