////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2013-2022 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/>.
//
////////////////////////////////////////////////////////////////////////

#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include <sstream>

#include <QDebug>
#include <QLabel>
#include <QMap>
#include <QMessageBox>
#include <QString>
#include <QTableView>

#include "qt-interpreter-events.h"
#include "variable-editor-model.h"

#include "Cell.h"
#include "interpreter.h"
#include "oct-map.h"
#include "ov.h"
#include "parse.h"
#include "pr-flt-fmt.h"
#include "utils.h"
#include "variables.h"

namespace octave
{
  static bool
  cell_is_editable (const octave_value& val)
  {
    if ((val.isnumeric () || val.islogical ()) && val.numel () == 1)
      return true;

    if (val.is_string () && (val.rows () == 1 || val.is_zero_by_zero ()))
      return true;

    return false;
  }

  static char
  get_quote_char (const octave_value& val)
  {
    if (val.is_sq_string ())
      return '\'';

    if (val.is_dq_string ())
      return '"';

    return 0;
  }

  static float_display_format
  get_edit_display_format (const octave_value& val)
  {
    // FIXME: make this limit configurable.

    return (val.numel () > 250000
            ? float_display_format () : val.get_edit_display_format ());
  }

  static bool
  do_requires_sub_editor_sub (const octave_value& elt)
  {
    return (! ((elt.numel () == 1 && (elt.isnumeric () || elt.islogical ()))
               || (elt.is_string () && (elt.rows () == 1 || elt.isempty ()))));
  }

  base_ve_model::base_ve_model (const QString& expr, const octave_value& val)
    : m_name (expr.toStdString ()),
      m_value (val),
      m_data_rows (m_value.rows ()),
      m_data_cols (m_value.columns ()),
      m_display_rows (m_data_rows),
      m_display_cols (m_data_cols),
      m_update_pending (),
      m_valid (m_value.is_defined ()),
      m_display_fmt (get_edit_display_format (m_value))
  { }

  std::string
  base_ve_model::name (void) const
  {
    return m_name;
  }

  bool
  base_ve_model::index_ok (const QModelIndex& idx, int& row, int& col) const
  {
    row = 0;
    col = 0;

    if (! idx.isValid ())
      return false;

    row = idx.row ();
    col = idx.column ();

    return (row < data_rows () && col < data_columns ());
  }

  int
  base_ve_model::column_width (void) const
  {
    int width = 0;

    float_format r_fmt = m_display_fmt.real_format ();
    float_format i_fmt = m_display_fmt.imag_format ();

    int rw = r_fmt.width ();
    int iw = i_fmt.width ();

    if (rw > 0)
      {
        if (m_value.iscomplex ())
          {
            if (iw > 0)
              width = rw + iw + 5;
          }
        else
          width = rw + 2;
      }

    return width;
  }

  int
  base_ve_model::rowCount (const QModelIndex&) const
  {
    return m_valid ? m_display_rows : 1;
  }

  int
  base_ve_model::columnCount (const QModelIndex&) const
  {
    return m_valid ? m_display_cols : 1;
  }

  QString
  base_ve_model::edit_display_sub (const octave_value& elt, int role) const
  {
    std::string str;

    if (cell_is_editable (elt))
      {
        float_display_format fmt;

        if (role == Qt::DisplayRole)
          fmt = get_edit_display_format (elt);
        else
          fmt.set_precision (elt.is_single_type () ? 8 : 16);

        str = elt.edit_display (fmt, 0, 0);
      }
    else
      {
        dim_vector dv = elt.dims ();
        str = "[" + dv.str () + " " + elt.class_name () + "]";
      }

    return QString::fromStdString (str);
  }

  QVariant
  base_ve_model::edit_display (const QModelIndex& idx, int role) const
  {
    int row;
    int col;

    if (! index_ok (idx, row, col))
      return QVariant ();

    float_display_format fmt;
    if (role == Qt::DisplayRole)
      fmt = m_display_fmt;
    else
      fmt.set_precision (m_value.is_single_type () ? 8 : 16);

    std::string str = m_value.edit_display (fmt, row, col);

    return QString::fromStdString (str);
  }

  QVariant
  base_ve_model::data (const QModelIndex& idx, int role) const
  {
    if (idx.isValid () && role == Qt::DisplayRole && update_pending (idx))
      return QVariant (update_pending_data (idx));

    if (! m_valid)
      {
        if (role == Qt::DisplayRole)
          return QVariant (QString ("Variable %1 not found or value can't be edited")
                           .arg (QString::fromStdString (m_name)));

        return QVariant (QString ("x"));
      }

    switch (role)
      {
      case Qt::DisplayRole:
      case Qt::EditRole:
        return edit_display (idx, role);
      }

    // Invalid.
    return QVariant ();
  }

  bool
  base_ve_model::requires_sub_editor (const QModelIndex&) const
  {
    return false;
  }

  void
  base_ve_model::set_update_pending (const QModelIndex& idx, const QString& str)
  {
    m_update_pending[idx] = str;
  }

  bool
  base_ve_model::update_pending (const QModelIndex& idx) const
  {
    return m_update_pending.contains (idx);
  }

  QString
  base_ve_model::update_pending_data (const QModelIndex& idx) const
  {
    return m_update_pending[idx];
  }

  void
  base_ve_model::clear_update_pending (void)
  {
    return m_update_pending.clear ();
  }

  char
  base_ve_model::quote_char (const QModelIndex&) const
  {
    return 0;
  }

  QVariant
  base_ve_model::header_data (int section, Qt::Orientation, int role) const
  {

    if (role != Qt::DisplayRole)
      return QVariant ();

    return QString::number (section+1);
  }

  QString
  base_ve_model::subscript_expression (const QModelIndex&) const
  {
    return "";
  }

  QString
  base_ve_model::make_description_text (void) const
  {
    QString lbl_txt = QString::fromStdString (m_name);

    if (m_value.is_defined ())
      {
        if (! lbl_txt.isEmpty ())
          lbl_txt += " ";

        dim_vector dv = m_value.dims ();

        lbl_txt += ("["
                    + QString::fromStdString (dv.str ())
                    + " "
                    + QString::fromStdString (m_value.class_name ())
                    + "]");
      }
    else
      lbl_txt += " [undefined]";

    return lbl_txt;
  }

  // Private slots.

  octave_value
  base_ve_model::value_at (const QModelIndex&) const
  {
    return octave_value ();
  }

  class numeric_model : public base_ve_model
  {
  public:

    numeric_model (const QString& expr, const octave_value& val)
      : base_ve_model (expr, val)
    {
      // FIXME: should fill the window and expand on scrolling or
      // resizing.

      maybe_resize_rows (m_data_rows + 16);
      maybe_resize_columns (m_data_cols + 16);
    }

    ~numeric_model (void) = default;

    // No copying!

    numeric_model (const numeric_model&) = delete;

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

    void maybe_resize_rows (int rows)
    {
      if (rows > m_display_rows)
        m_display_rows = rows;
    }

    void maybe_resize_columns (int cols)
    {
      if (cols > m_display_cols)
        m_display_cols = cols;
    }

    QVariant edit_display (const QModelIndex& idx, int role) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return QVariant ();

      float_display_format fmt;
      if (role == Qt::DisplayRole)
        fmt = m_display_fmt;
      else
        fmt.set_precision (m_value.is_single_type () ? 8 : 16);

      std::string str = m_value.edit_display (fmt, row, col);

      return QString::fromStdString (str);
    }

    QString subscript_expression (const QModelIndex& idx) const
    {
      if (! idx.isValid ())
        return "";

      return (QString ("(%1,%2)")
              .arg (idx.row () + 1)
              .arg (idx.column () + 1));
    }
  };

  class string_model : public base_ve_model
  {
  public:

    string_model (const QString& expr, const octave_value& val)
      : base_ve_model (expr, val)
    {
      m_data_rows = 1;
      m_data_cols = 1;

      m_display_rows = 1;
      m_display_cols = 1;
    }

    ~string_model (void) = default;

    // No copying!

    string_model (const string_model&) = delete;

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

    QVariant edit_display (const QModelIndex&, int) const
    {
      // There isn't really a format for strings...

      std::string str = m_value.edit_display (float_display_format (), 0, 0);

      return QString::fromStdString (str);
    }

    char quote_char (const QModelIndex&) const
    {
      return get_quote_char (m_value);
    }
  };

  class cell_model : public base_ve_model
  {
  public:

    cell_model (const QString& expr, const octave_value& val)
      : base_ve_model (expr, val)
    {
      // FIXME: should fill the window and expand on scrolling or
      // resizing.

      maybe_resize_rows (m_data_rows + 16);
      maybe_resize_columns (m_data_cols + 16);
    }

    ~cell_model (void) = default;

    // No copying!

    cell_model (const cell_model&) = delete;

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

    void maybe_resize_rows (int rows)
    {
      if (rows > m_display_rows)
        m_display_rows = rows;
    }

    void maybe_resize_columns (int cols)
    {
      if (cols > m_display_cols)
        m_display_cols = cols;
    }

    QVariant edit_display (const QModelIndex& idx, int role) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return QVariant ();

      Cell cval = m_value.cell_value ();

      return edit_display_sub (cval(row, col), role);
    }

    bool requires_sub_editor (const QModelIndex& idx) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return false;

      Cell cval = m_value.cell_value ();

      return do_requires_sub_editor_sub (cval(row, col));
    }

    char quote_char (const QModelIndex& idx) const
    {
      octave_value ov = value_at (idx);

      if (ov.is_string ())
        return get_quote_char (ov);

      return 0;
    }

    QString subscript_expression (const QModelIndex& idx) const
    {
      if (! idx.isValid ())
        return "";

      return (QString ("{%1,%2}")
              .arg (idx.row () + 1)
              .arg (idx.column () + 1));
    }

    octave_value value_at (const QModelIndex& idx) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return octave_value ();

      Cell cval = m_value.cell_value ();

      return cval(row, col);
    }
  };

  // Scalar struct.  Rows are fields, single column for values.

  class scalar_struct_model : public base_ve_model
  {
  public:

    scalar_struct_model (const QString& expr, const octave_value& val)
      : base_ve_model (expr, val)
    {
      // No extra cells.  We currently don't allow new fields or
      // additional values to be inserted.  If we allow additional values,
      // then the object becomes a vector structure and the display flips
      // (see the vector struct model below).  Do we want that?

      m_data_rows = val.nfields ();
      m_data_cols = 1;

      m_display_rows = m_data_rows;
      m_display_cols = 1;
    }

    ~scalar_struct_model (void) = default;

    // No copying!

    scalar_struct_model (const scalar_struct_model&) = delete;

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

    QVariant edit_display (const QModelIndex& idx, int role) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return QVariant ();

      octave_scalar_map m = m_value.scalar_map_value ();

      return edit_display_sub (m.contents (row), role);
    }

    bool requires_sub_editor (const QModelIndex& idx) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return false;

      octave_scalar_map m = m_value.scalar_map_value ();

      return do_requires_sub_editor_sub (m.contents (row));
    }

    char quote_char (const QModelIndex& idx) const
    {
      octave_value ov = value_at (idx);

      if (ov.is_string ())
        return get_quote_char (ov);

      return 0;
    }

    QVariant header_data (int section, Qt::Orientation orientation,
                          int role) const
    {
      if (role != Qt::DisplayRole)
        return QVariant ();

      switch (orientation)
        {
        case Qt::Horizontal:
          if (section < data_columns ())
            return QString ("Values");
          else
            break;

        case Qt::Vertical:
          if (section < data_rows ())
            {
              octave_scalar_map m = m_value.scalar_map_value ();

              string_vector fields = m.fieldnames ();

              return QString::fromStdString (fields(section));
            }
          else
            break;

        default:
          break;
        }

      return QVariant ();
    }

    QString subscript_expression (const QModelIndex& idx) const
    {
      // Display size and data size match, so all valid indices should
      // also be valid indices for the existing struct.

      int row;
      int col;

      if (! index_ok (idx, row, col))
        return "";

      octave_scalar_map m = m_value.scalar_map_value ();

      string_vector fields = m.fieldnames ();

      return QString (".%1").arg (QString::fromStdString (fields(row)));
    }

    octave_value value_at (const QModelIndex& idx) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return octave_value ();

      octave_scalar_map m = m_value.scalar_map_value ();

      return m.contents (row);
    }
  };

  class display_only_model : public base_ve_model
  {
  public:

    display_only_model (const QString& expr, const octave_value& val)
      : base_ve_model (expr, val)
    {
      m_data_rows = 1;
      m_data_cols = 1;

      m_display_rows = m_data_rows;
      m_display_cols = m_data_cols;
    }

    ~display_only_model (void) = default;

    // No copying!

    display_only_model (const display_only_model&) = delete;

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

    bool is_editable (void) const { return false; }

    QVariant edit_display (const QModelIndex&, int) const
    {
      if (m_value.is_undefined ())
        return QVariant ();

      std::ostringstream buf;

      octave_value tval = m_value;

      tval.print_with_name (buf, m_name);

      return QString::fromStdString (buf.str ());
    }

    QString make_description_text (void) const
    {
      return (QString ("unable to edit %1")
              .arg (base_ve_model::make_description_text ()));
    }
  };

  // Vector struct.  Columns are fields, rows are values.

  class vector_struct_model : public base_ve_model
  {
  public:

    vector_struct_model (const QString& expr, const octave_value& val)
      : base_ve_model (expr, val)
    {
      // FIXME: should fill the window vertically and expand on scrolling
      // or resizing.  No extra cells horizontally.  New fields must be
      // added specially.

      m_data_rows = val.numel ();
      m_data_cols = val.nfields ();

      maybe_resize_rows (m_data_rows + 16);
      m_display_cols = m_data_cols;
    }

    ~vector_struct_model (void) = default;

    // No copying!

    vector_struct_model (const vector_struct_model&) = delete;

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

    void maybe_resize_rows (int rows)
    {
      if (rows > m_display_rows)
        m_display_rows = rows;
    }

    QVariant edit_display (const QModelIndex& idx, int role) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return QVariant ();

      octave_map m = m_value.map_value ();

      Cell cval = m.contents (col);

      return edit_display_sub (cval(row), role);
    }

    bool requires_sub_editor (const QModelIndex& idx) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return false;

      octave_map m = m_value.map_value ();

      Cell cval = m.contents (col);

      return do_requires_sub_editor_sub (cval(row));
    }

    char quote_char (const QModelIndex& idx) const
    {
      octave_value ov = value_at (idx);

      if (ov.is_string ())
        return get_quote_char (ov);

      return 0;
    }

    QVariant header_data (int section, Qt::Orientation orientation,
                          int role) const
    {
      if (role != Qt::DisplayRole)
        return QVariant ();

      switch (orientation)
        {
        case Qt::Horizontal:
          if (section < data_columns ())
            {
              octave_map m = m_value.map_value ();

              string_vector fields = m.fieldnames ();

              return QString::fromStdString (fields(section));
            }
          else
            break;

        case Qt::Vertical:
          if (section < data_rows ())
            return QString::number (section+1);
          else
            break;

        default:
          break;
        }

      return QVariant ();
    }

    QString subscript_expression (const QModelIndex& idx) const
    {
      if (! idx.isValid ())
        return "";

      octave_map m = m_value.map_value ();

      string_vector fields = m.fieldnames ();

      return (QString ("(%1).%2")
              .arg (idx.row () + 1)
              .arg (QString::fromStdString (fields(idx.column ()))));
    }

    octave_value value_at (const QModelIndex& idx) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return octave_value ();

      octave_map m = m_value.map_value ();

      Cell cval = m.contents (col);

      return cval(row);
    }
  };

  // 2-d struct array.  Rows and columns index individual scalar structs.

  class struct_model : public base_ve_model
  {
  public:

    struct_model (const QString& expr, const octave_value& val)
      : base_ve_model (expr, val)
    {
      // FIXME: should fill the window and expand on scrolling or
      // resizing.

      maybe_resize_rows (m_data_rows + 16);
      maybe_resize_columns (m_data_cols + 16);
    }

    ~struct_model (void) = default;

    // No copying!

    struct_model (const struct_model&) = delete;

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

    void maybe_resize_rows (int rows)
    {
      if (rows > m_display_rows)
        m_display_rows = rows;
    }

    void maybe_resize_columns (int cols)
    {
      if (cols > m_display_cols)
        m_display_cols = cols;
    }

    QVariant edit_display (const QModelIndex& idx, int) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return QVariant ();

      std::string str = m_value.edit_display (m_display_fmt, row, col);
      return QString::fromStdString (str);
    }

    bool requires_sub_editor (const QModelIndex& idx) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return false;

      octave_map m = m_value.map_value ();

      return do_requires_sub_editor_sub (m(row, col));
    }

    char quote_char (const QModelIndex& idx) const
    {
      octave_value ov = value_at (idx);

      if (ov.is_string ())
        return get_quote_char (ov);

      return 0;
    }

    QString subscript_expression (const QModelIndex& idx) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return "";

      return (QString ("(%1,%2)")
              .arg (row + 1)
              .arg (col + 1));
    }

    octave_value value_at (const QModelIndex& idx) const
    {
      int row;
      int col;

      if (! index_ok (idx, row, col))
        return octave_value ();

      octave_map m = m_value.map_value ();

      return m(row, col);
    }
  };

  base_ve_model *
  variable_editor_model::create (const QString& expr, const octave_value& val)
  {
    // Choose specific model based on type of val.

    if ((val.isnumeric () || val.islogical ()) && val.ndims () == 2)
      return new numeric_model (expr, val);
    else if (val.is_string () && (val.rows () == 1 || val.is_zero_by_zero ()))
      return new string_model (expr, val);
    else if (val.iscell ())
      return new cell_model (expr, val);
    else if (val.isstruct ())
      {
        if (val.numel () == 1)
          return new scalar_struct_model (expr, val);
        else if (val.ndims () == 2)
          {
            if (val.rows () == 1 || val.columns () == 1)
              return new vector_struct_model (expr, val);
            else
              return new struct_model (expr, val);
          }
      }

    return new display_only_model (expr, val);
  }

  variable_editor_model::variable_editor_model (const QString& expr,
                                                const octave_value& val,
                                                QObject *parent)
    : QAbstractTableModel (parent), rep (create (expr, val))
  {
    update_description ();

    connect (this, &variable_editor_model::user_error_signal,
             this, &variable_editor_model::user_error);

    connect (this, &variable_editor_model::update_data_signal,
             this, &variable_editor_model::update_data);

    connect (this, &variable_editor_model::data_error_signal,
             this, &variable_editor_model::data_error);

    if (is_editable ())
      {
        int new_rows = display_rows ();

        if (new_rows > 0)
          {
            beginInsertRows (QModelIndex (), 0, new_rows-1);
            endInsertRows ();
          }

        int new_cols = display_columns ();

        if (new_cols > 0)
          {
            beginInsertColumns (QModelIndex (), 0, new_cols-1);
            endInsertColumns ();
          }
      }
  }

  bool
  variable_editor_model::setData (const QModelIndex& idx,
                                  const QVariant& v_user_input, int role)
  {
    if (role != Qt::EditRole || ! v_user_input.canConvert (QMetaType::QString)
        || ! idx.isValid ())
      return false;

    // Initially, set value to whatever the user entered.

    QString user_input = v_user_input.toString ();

    char qc = quote_char (idx);

    // FIXME: maybe we need a better way to ask whether empty input is
    // valid than to rely on whether there is a quote character (meaning
    // we are editing a character string)?
    if (user_input.isEmpty () && ! qc)
      return false;

    set_update_pending (idx, user_input);

    std::ostringstream os;

    std::string nm = name ();
    os << nm;

    QString tmp = subscript_expression (idx);
    os << tmp.toStdString () << "=";

    if (qc)
      os << qc;

    os << user_input.toStdString ();

    if (qc)
      os << qc;

    std::string expr = os.str ();

    emit interpreter_event
      ([=] (interpreter& interp)
       {
         // INTERPRETER THREAD

         try
           {
             int parse_status = 0;
             interp.eval_string (expr, true, parse_status);

             octave_value val = retrieve_variable (interp, nm);

             emit update_data_signal (val);
           }
         catch (const execution_exception&)
           {
             clear_update_pending ();

             evaluation_error (expr);

             // This will cause the data in the cell to be reset
             // from the cached octave_value object.

             emit dataChanged (idx, idx);
           }
       });

    return true;
  }

  bool
  variable_editor_model::clear_content (const QModelIndex& idx)
  {
    int row = idx.row ();
    int col = idx.column ();

    if (row < data_rows () && col < data_columns ())
      return setData (idx, QVariant ("0"));

    return false;
  }

  Qt::ItemFlags
  variable_editor_model::flags (const QModelIndex& idx) const
  {
    if (! is_valid ())
      return Qt::NoItemFlags;

    Qt::ItemFlags retval = QAbstractTableModel::flags (idx);

    if (! requires_sub_editor (idx))
      retval |= Qt::ItemIsEditable;

    return retval;
  }

  bool
  variable_editor_model::insertRows (int row, int count, const QModelIndex&)
  {
    // FIXME: cells?

    eval_expr_event
      (QString ("%1 = [%1(1:%2,:); zeros(%3,columns(%1)); %1(%2+%3:end,:)]")
       .arg (QString::fromStdString (name ()))
       .arg (row)
       .arg (count));

    return true;
  }

  bool
  variable_editor_model::removeRows (int row, int count, const QModelIndex&)
  {
    if (row + count > data_rows ())
      {
        qDebug () << "Tried to remove too many rows "
                  << data_rows () << " "
                  << count << " (" << row << ")";
        return false;
      }

    eval_expr_event
      (QString ("%1(%2:%3,:) = []")
       .arg (QString::fromStdString (name ()))
       .arg (row)
       .arg (row + count));

    return true;
  }

  bool
  variable_editor_model::insertColumns (int col, int count, const QModelIndex&)
  {
    eval_expr_event
      (QString ("%1 = [%1(:,1:%2); zeros(rows(%1),%3) %1(:,%2+%3:end)]")
       .arg (QString::fromStdString (name ()))
       .arg (col)
       .arg (count));

    return true;
  }

  bool
  variable_editor_model::removeColumns (int col, int count, const QModelIndex&)
  {
    if (col + count > data_columns ())
      {
        qDebug () << "Tried to remove too many cols "
                  << data_columns () << " "
                  << count << " (" << col << ")";
        return false;
      }

    eval_expr_event
      (QString ("%1(:,%2:%3) = []")
       .arg (QString::fromStdString (name ()))
       .arg (col)
       .arg (col + count));

    return true;
  }

  void
  variable_editor_model::init_from_oct (interpreter& interp)
  {
    // INTERPRETER THREAD

    std::string nm = name ();

    try
      {
        octave_value val = retrieve_variable (interp, nm);

        emit update_data_signal (val);
      }
    catch (const execution_exception&)
      {
        QString msg = (QString ("variable '%1' is invalid or undefined")
                       .arg (QString::fromStdString (nm)));

        emit data_error_signal (msg);
      }
  }

  void
  variable_editor_model::eval_expr_event (const QString& expr_arg)
  {
    std::string expr = expr_arg.toStdString ();

    emit interpreter_event
      ([=] (interpreter& interp)
       {
         // INTERPRETER THREAD

         try
           {
             int parse_status = 0;
             interp.eval_string (expr, true, parse_status);

             init_from_oct (interp);
           }
         catch (const execution_exception&)
           {
             evaluation_error (expr);
           }
       });
  }

  // If the variable exists, load it into the data model.  If it doesn't
  // exist, flag the data model as referring to a nonexistent variable.
  // This allows the variable to be opened before it is created.

  // This function should only be called within other functions that
  // execute in the interpreter thread.  It should also be called in a
  // try-catch block that catches execution exceptions.

  octave_value
  variable_editor_model::retrieve_variable (interpreter& interp,
                                            const std::string& x)
  {
    // INTERPRETER THREAD

    std::string name = x;

    name = name.substr (0, name.find ("."));

    if (name.back () == ')' || name.back () == '}')
      name = name.substr (0, name.find (name.back () == ')' ? "(" : "{"));

    if (symbol_exist (name, "var") > 0)
      {
        int parse_status = 0;

        octave_value result = interp.eval_string (x, true, parse_status);

        if (result.is_cs_list ())
          error ("evaluation produced c-s list");

        return result;
      }

    return octave_value ();
  }

  void
  variable_editor_model::evaluation_error (const std::string& expr) const
  {
    emit user_error_signal ("Evaluation failed",
                            QString ("failed to evaluate expression: '%1' or result can't be edited")
                            .arg (QString::fromStdString (expr)));
  }

  void
  variable_editor_model::user_error (const QString& title, const QString& msg)
  {
    QMessageBox::critical (nullptr, title, msg);
  }

  void
  variable_editor_model::update_data_cache (void)
  {
    emit interpreter_event
      ([=] (interpreter& interp)
       {
         // INTERPRETER_THREAD

         init_from_oct (interp);
       });
  }

  void
  variable_editor_model::update_data (const octave_value& val)
  {
    if (val.is_undefined ())
      {
        QString msg = (QString ("variable '%1' is invalid or undefined")
                       .arg (QString::fromStdString (name ())));

        emit data_error_signal (msg);

        return;
      }

    // Add or remove rows and columns when the size changes.

    int old_rows = display_rows ();
    int old_cols = display_columns ();

    reset (val);

    int new_rows = display_rows ();
    int new_cols = display_columns ();

    if (new_rows != old_rows || new_cols != old_cols)
      change_display_size (old_rows, old_cols, new_rows, new_cols);

    // Even if the size doesn't change, we still need to update here
    // because the data may have changed.  But only if we have some data
    // to display.

    if (new_rows > 0 && new_cols > 0)
      emit dataChanged (QAbstractTableModel::index (0, 0),
                        QAbstractTableModel::index (new_rows-1, new_cols-1));

    clear_update_pending ();
  }

  void
  variable_editor_model::change_display_size (int old_rows, int old_cols,
                                              int new_rows, int new_cols)
  {
    if (new_rows < old_rows)
      {
        beginRemoveRows (QModelIndex (), new_rows, old_rows-1);
        endRemoveRows ();
      }
    else if (new_rows > old_rows)
      {
        beginInsertRows (QModelIndex (), old_rows, new_rows-1);
        endInsertRows ();
      }

    if (new_cols < old_cols)
      {
        beginRemoveColumns (QModelIndex (), new_cols, old_cols-1);
        endRemoveColumns ();
      }
    else if (new_cols > old_cols)
      {
        beginInsertColumns (QModelIndex (), old_cols, new_cols-1);
        endInsertColumns ();
      }
  }

  void
  variable_editor_model::maybe_resize_rows (int rows)
  {
    int old_rows = display_rows ();
    int old_cols = display_columns ();

    rep->maybe_resize_rows (rows);

    int new_rows = display_rows ();
    int new_cols = display_columns ();

    if (new_rows != old_rows)
      change_display_size (old_rows, old_cols, new_rows, new_cols);
  }

  void
  variable_editor_model::maybe_resize_columns (int cols)
  {
    int old_rows = display_rows ();
    int old_cols = display_columns ();

    rep->maybe_resize_columns (cols);

    int new_rows = display_rows ();
    int new_cols = display_columns ();

    if (new_cols != old_cols)
      change_display_size (old_rows, old_cols, new_rows, new_cols);
  }

  void
  variable_editor_model::data_error (const QString& msg)
  {
    invalidate ();

    update_description (msg);
  }

  void
  variable_editor_model::reset (const octave_value& val)
  {
    base_ve_model *old_rep = rep;

    rep = create (QString::fromStdString (name ()), val);

    delete old_rep;

    update_description ();

    emit set_editable_signal (is_editable ());
  }

  void
  variable_editor_model::invalidate (void)
  {
    beginResetModel ();

    reset (octave_value ());

    endResetModel ();
  }

  void
  variable_editor_model::update_description (const QString& description)
  {
    emit description_changed (description.isEmpty ()
                              ? make_description_text () : description);
  }

  void
  variable_editor_model::double_click (const QModelIndex& idx)
  {
    if (requires_sub_editor (idx))
      {
        QString name = QString::fromStdString(rep->name ());
        emit edit_variable_signal (name + subscript_expression (idx),
                                   value_at (idx));
      }
  }
}