#include "MultiSettings.hpp"

#include <stdexcept>

#include <QObject>
#include <QSettings>
#include <QString>
#include <QStringList>
#include <QDir>
#include <QFont>
#include <QApplication>
#include <QStandardPaths>
#include <QMainWindow>
#include <QMenu>
#include <QAction>
#include <QActionGroup>
#include <QDialog>
#include <QLineEdit>
#include <QRegularExpression>
#include <QRegularExpressionValidator>
#include <QFormLayout>
#include <QVBoxLayout>
#include <QDialogButtonBox>
#include <QPushButton>
#include <QComboBox>
#include <QLabel>
#include <QList>
#include <QMetaObject>

#include "SettingsGroup.hpp"
#include "qt_helpers.hpp"
#include "SettingsGroup.hpp"
#include "MessageBox.hpp"

#include "pimpl_impl.hpp"

namespace
{
  char const * default_string = QT_TRANSLATE_NOOP ("MultiSettings", "Default");
  char const * multi_settings_root_group = "MultiSettings";
  char const * multi_settings_current_group_key = "CurrentMultiSettingsConfiguration";
  char const * multi_settings_current_name_key = "CurrentName";
  char const * multi_settings_place_holder_key = "MultiSettingsPlaceHolder";

  // calculate a useable and unique settings file path
  QString settings_path ()
  {
    auto config_directory = QStandardPaths::writableLocation (QStandardPaths::ConfigLocation);
    QDir config_path {config_directory}; // will be "." if config_directory is empty
    if (!config_path.mkpath ("."))
      {
        throw std::runtime_error {"Cannot find a usable configuration path \"" + config_path.path ().toStdString () + '"'};
      }
    return config_path.absoluteFilePath (QApplication::applicationName () + ".ini");
  }

  //
  // Dialog to get a valid new configuration name
  //
  class NameDialog final
    : public QDialog
  {
  public:
    explicit NameDialog (QString const& current_name,
                         QStringList const& current_names,
                         QWidget * parent = nullptr)
      : QDialog {parent}
    {
      setWindowTitle (tr ("New Configuration Name"));

      auto form_layout = new QFormLayout ();
      form_layout->addRow (tr ("Old name:"), &old_name_label_);
      old_name_label_.setText (current_name);
      form_layout->addRow (tr ("&New name:"), &name_line_edit_);

      auto main_layout = new QVBoxLayout (this);
      main_layout->addLayout (form_layout);

      auto button_box = new QDialogButtonBox {QDialogButtonBox::Ok | QDialogButtonBox::Cancel};
      button_box->button (QDialogButtonBox::Ok)->setEnabled (false);
      main_layout->addWidget (button_box);

      auto * name_validator = new QRegularExpressionValidator {QRegularExpression {R"([^/\\]+)"}, this};
      name_line_edit_.setValidator (name_validator);

      connect (&name_line_edit_, &QLineEdit::textChanged, [current_names, button_box] (QString const& name) {
          bool valid {!current_names.contains (name.trimmed ())};
          button_box->button (QDialogButtonBox::Ok)->setEnabled (valid);
        });
      connect (button_box, &QDialogButtonBox::accepted, this, &QDialog::accept);
      connect (button_box, &QDialogButtonBox::rejected, this, &QDialog::reject);
    }

    QString new_name () const
    {
      return name_line_edit_.text ().trimmed ();
    }

  private:
    QLabel old_name_label_;
    QLineEdit name_line_edit_;
  };

  //
  // Dialog to get a valid new existing name
  //
  class ExistingNameDialog final
    : public QDialog
  {
  public:
    explicit ExistingNameDialog (QStringList const& current_names, QWidget * parent = nullptr)
      : QDialog {parent}
    {
      setWindowTitle (tr ("Configuration to Clone From"));

      name_combo_box_.addItems (current_names);

      auto form_layout = new QFormLayout ();
      form_layout->addRow (tr ("&Source Configuration Name:"), &name_combo_box_);

      auto main_layout = new QVBoxLayout (this);
      main_layout->addLayout (form_layout);

      auto button_box = new QDialogButtonBox {QDialogButtonBox::Ok | QDialogButtonBox::Cancel};
      main_layout->addWidget (button_box);

      connect (button_box, &QDialogButtonBox::accepted, this, &QDialog::accept);
      connect (button_box, &QDialogButtonBox::rejected, this, &QDialog::reject);
    }

    QString name () const
    {
      return name_combo_box_.currentText ();
    }

  private:
    QComboBox name_combo_box_;
  };
}

class MultiSettings::impl final
  : public QObject
{
  Q_OBJECT

public:
  explicit impl ();
  bool reposition ();
  void create_menu_actions (QMainWindow * main_window, QMenu * menu);
  bool exit ();

  QSettings settings_;

private:
  using Dictionary = QMap<QString, QVariant>;

  // create a configuration maintenance sub menu
  QMenu * create_sub_menu (QMenu * parent,
                           QString const& menu_title,
                           QActionGroup * = nullptr);

  // extract all settings from the current QSettings group
  Dictionary get_settings () const;

  // write the settings values from the dictionary to the current group
  void load_from (Dictionary const&, bool add_placeholder = true);

  // switch to this configuration
  void select_configuration (QMainWindow *);

  // clone this configuration
  void clone_configuration (QMenu *);

  // update this configuration from another
  void clone_into_configuration (QMainWindow *);

  // reset configuration to default values
  void reset_configuration (QMainWindow *);

  // change configuration name
  void rename_configuration (QMainWindow *);

  // remove a configuration
  void delete_configuration (QMainWindow *);

  QFont original_font_;
  QString current_;

  // action to take on restart
  enum class RepositionType {unchanged, replace, save_and_replace} reposition_type_;
  Dictionary new_settings_;
  bool exit_flag_;              // false means loop around with new
                                // configuration
  QActionGroup * configurations_group_;
  QAction * select_action_;
  QAction * clone_action_;
  QAction * clone_into_action_;
  QAction * reset_action_;
  QAction * rename_action_;
  QAction * delete_action_;
  QList<QMetaObject::Connection> action_connections_;
  QMenu * active_sub_menu_;
};

#include "MultiSettings.moc"

MultiSettings::MultiSettings ()
{
}

MultiSettings::~MultiSettings ()
{
}

QSettings * MultiSettings::settings ()
{
  return &m_->settings_;
}

void MultiSettings::create_menu_actions (QMainWindow * main_window, QMenu * menu)
{
  m_->create_menu_actions (main_window, menu);
}

bool MultiSettings::exit ()
{
  return m_->exit ();
}

MultiSettings::impl::impl ()
  : settings_ {settings_path (), QSettings::IniFormat}
  , reposition_type_ {RepositionType::unchanged}
  , exit_flag_ {true}
  , configurations_group_ {new QActionGroup {this}}
  , select_action_ {new QAction {tr ("&Switch To"), this}}
  , clone_action_ {new QAction {tr ("&Clone"), this}}
  , clone_into_action_ {new QAction {tr ("Clone &Into ..."), this}}
  , reset_action_ {new QAction {tr ("R&eset"), this}}
  , rename_action_ {new QAction {tr ("&Rename ..."), this}}
  , delete_action_ {new QAction {tr ("&Delete"), this}}
  , active_sub_menu_ {nullptr}
{
  if (!settings_.isWritable ())
    {
      throw std::runtime_error {QString {"Cannot access \"%1\" for writing"}
        .arg (settings_.fileName ()).toStdString ()};
    }

  // deal with transient, now defunct, settings key
  if (settings_.contains (multi_settings_current_group_key))
    {
      current_ = settings_.value (multi_settings_current_group_key).toString ();
      settings_.remove (multi_settings_current_group_key);
      if (current_.size ())
        {
          {
            SettingsGroup alternatives {&settings_, multi_settings_root_group};
            {
              SettingsGroup source_group {&settings_, current_};
              new_settings_ = get_settings ();
            }
            settings_.setValue (multi_settings_current_name_key, tr (default_string));
          }
          reposition_type_ = RepositionType::save_and_replace;
          reposition ();
        }
      else
        {
          SettingsGroup alternatives {&settings_, multi_settings_root_group};
          settings_.setValue (multi_settings_current_name_key, tr (default_string));
        }
    }

  // bootstrap
  {
    SettingsGroup alternatives {&settings_, multi_settings_root_group};
    current_ = settings_.value (multi_settings_current_name_key).toString ();
    if (!current_.size ())
      {
        current_ = tr (default_string);
        settings_.setValue (multi_settings_current_name_key, current_);
      }
  }
  settings_.sync ();
}

// do actions that can only be done once all the windows are closed
bool MultiSettings::impl::reposition ()
{
  switch (reposition_type_)
    {
    case RepositionType::save_and_replace:
      {
        // save the current settings with the other alternatives
        Dictionary saved_settings {get_settings ()};
        SettingsGroup alternatives {&settings_, multi_settings_root_group};
        // get the current configuration name
        auto previous_group_name = settings_.value (multi_settings_current_name_key, tr (default_string)).toString ();
        SettingsGroup save_group {&settings_, previous_group_name};
        load_from (saved_settings);
      }
      // fall through
    case RepositionType::replace:
      // and purge current settings
      for (auto const& key: settings_.allKeys ())
        {
          if (!key.contains (multi_settings_root_group))
            {
              settings_.remove (key);
            }
        }
      // insert the new settings
      load_from (new_settings_, false);
      if (!new_settings_.size ())
        {
          // if we are clearing the current settings then we must
          // reset the application font and the font in the
          // application style sheet, this is necessary since the
          // application instance is not recreated
          qApp->setFont (original_font_);
          qApp->setStyleSheet (qApp->styleSheet () + "* {" + font_as_stylesheet (original_font_) + '}');
        }
      // now we have set up the new current we can safely purge it
      // from the alternatives
      {
        SettingsGroup alternatives {&settings_, multi_settings_root_group};
        {
          SettingsGroup purge_group {&settings_, current_};
          settings_.remove ("");  // purge entire group
        }
        // switch to the specified configuration name
        settings_.setValue (multi_settings_current_name_key, current_);
      }
      settings_.sync ();
      // fall through
    case RepositionType::unchanged:
      new_settings_.clear ();
      break;
    }

  reposition_type_ = RepositionType::unchanged; // reset
  bool exit {exit_flag_};
  exit_flag_ = true;           // reset exit flag so normal exit works
  return exit;
}

// populate a pop up menu with the configurations sub-menus for
// maintenance including select, clone, clone from, delete, rename
// and, reset
void MultiSettings::impl::create_menu_actions (QMainWindow * main_window, QMenu * menu)
{
  SettingsGroup alternatives {&settings_, multi_settings_root_group};
  // get the current configuration name
  auto current_configuration_name = settings_.value (multi_settings_current_name_key, tr (default_string)).toString ();
  // add the default configuration sub menu
  QMenu * default_menu = create_sub_menu (menu, current_configuration_name, configurations_group_);
  // and set as the current configuration
  default_menu->menuAction ()->setChecked (true);

  QStringList available_configurations;
  // get the existing alternatives
  available_configurations = settings_.childGroups ();

  // add all the other configurations
  for (auto const& configuration_name: available_configurations)
    {
      create_sub_menu (menu, configuration_name, configurations_group_);
    }

  // hook up configuration actions
  action_connections_ << connect (select_action_, &QAction::triggered, [this, main_window] (bool) {
      select_configuration (main_window);
    });
  action_connections_ << connect (clone_action_, &QAction::triggered, [this, menu] (bool) {
      clone_configuration (menu);
    });
  action_connections_ << connect (clone_into_action_, &QAction::triggered, [this, main_window] (bool) {
      clone_into_configuration (main_window);
    });
  action_connections_ << connect (rename_action_, &QAction::triggered, [this, main_window] (bool) {
      rename_configuration (main_window);
    });
  action_connections_ << connect (reset_action_, &QAction::triggered, [this, main_window] (bool) {
      reset_configuration (main_window);
    });
  action_connections_ << connect (delete_action_, &QAction::triggered, [this, main_window] (bool) {
      delete_configuration (main_window);
    });
}

// call this at the end of the main program loop to determine if the
// main window really wants to quit or to run again with a new configuration
bool MultiSettings::impl::exit ()
{
  for (auto const& connection: action_connections_)
    {
      disconnect (connection);
    }
  action_connections_.clear ();

  // do any configuration swap required and return exit flag
  return reposition ();
}

QMenu * MultiSettings::impl::create_sub_menu (QMenu * parent_menu,
                                              QString const& menu_title,
                                              QActionGroup * action_group)
{
  QMenu * sub_menu = parent_menu->addMenu (menu_title);
  if (action_group) action_group->addAction (sub_menu->menuAction ());
  sub_menu->menuAction ()->setCheckable (true);
  sub_menu->addAction (select_action_);
  sub_menu->addSeparator ();
  sub_menu->addAction (clone_action_);
  sub_menu->addAction (clone_into_action_);
  sub_menu->addAction (rename_action_);
  sub_menu->addAction (reset_action_);
  sub_menu->addAction (delete_action_);

  // disable disallowed actions before showing sub menu
  connect (sub_menu, &QMenu::aboutToShow, [this, sub_menu] () {
      bool is_current {sub_menu->menuAction ()->text () == current_};
      select_action_->setEnabled (!is_current);
      delete_action_->setEnabled (!is_current);
      SettingsGroup alternatives {&settings_, multi_settings_root_group};
      clone_into_action_->setEnabled (settings_.childGroups ().size ());
      active_sub_menu_ = sub_menu;
    });

  return sub_menu;
}

auto MultiSettings::impl::get_settings () const -> Dictionary
{
  Dictionary settings;
  for (auto const& key: settings_.allKeys ())
    {
      // filter out multi settings group and empty settings
      // placeholder
      if (!key.contains (multi_settings_root_group)
          && !key.contains (multi_settings_place_holder_key))
        {
          settings[key] = settings_.value (key);
        }
    }
  return settings;
}

void MultiSettings::impl::load_from (Dictionary const& dictionary, bool add_placeholder)
{
  if (dictionary.size ())
    {
      for (Dictionary::const_iterator iter = dictionary.constBegin ();
           iter != dictionary.constEnd (); ++iter)
        {
          settings_.setValue (iter.key (), iter.value ());
        }
    }
  else if (add_placeholder)
    {
      // add a placeholder key to stop the alternative configuration
      // name from disappearing
      settings_.setValue (multi_settings_place_holder_key, QVariant {});
    }
  settings_.sync ();
}

void MultiSettings::impl::select_configuration (QMainWindow * main_window)
{
  if (active_sub_menu_)
    {
      auto const& target_name = active_sub_menu_->title ();

      if (target_name != current_)
        {
          {
            // position to the alternative settings
            SettingsGroup alternatives {&settings_, multi_settings_root_group};
            // save the target settings
            SettingsGroup target_group {&settings_, target_name};
            new_settings_ = get_settings ();
          }
          // and set up the restart
          current_ = target_name;
          reposition_type_ = RepositionType::save_and_replace;
          exit_flag_ = false;
          main_window->close ();
        }
    }
}

void MultiSettings::impl::clone_configuration (QMenu * menu)
{
  if (active_sub_menu_)
    {
      auto const& source_name = active_sub_menu_->title ();

      // settings to clone
      Dictionary source_settings;
      if (source_name == current_)
        {
          // grab the data to clone from the current settings
          source_settings = get_settings ();
        }
      SettingsGroup alternatives {&settings_, multi_settings_root_group};
      if (source_name != current_)
        {
          SettingsGroup source_group {&settings_, source_name};
          source_settings = get_settings ();
        }

      // find a new unique name
      QString new_name_root {source_name + " - Copy"};;
      QString new_name {new_name_root};
      unsigned index {0};
      do
        {
          if (index++) new_name = new_name_root + '(' + QString::number (index) + ')';
        }
      while (settings_.childGroups ().contains (new_name));
      SettingsGroup new_group {&settings_, new_name};
      load_from (source_settings);

      // insert the new configuration sub menu in the parent menu
      create_sub_menu (menu, new_name, configurations_group_);
    }
}

void MultiSettings::impl::clone_into_configuration (QMainWindow * main_window)
{
  if (active_sub_menu_)
    {
      auto const& target_name = active_sub_menu_->title ();

      // get the current configuration name
      QString current_group_name;
      QStringList sources;
      {
        SettingsGroup alternatives {&settings_, multi_settings_root_group};
        current_group_name = settings_.value (multi_settings_current_name_key).toString ();

        {
          // get the source configuration name for the clone
          sources = settings_.childGroups ();
          sources << current_group_name;
          sources.removeOne (target_name);
        }
      }

      // pick a source configuration
      ExistingNameDialog dialog {sources, main_window};
      if (sources.size () && (1 == sources.size () || QDialog::Accepted == dialog.exec ()))
        {
          QString source_name {1 == sources.size () ? sources.at (0) : dialog.name ()};
          if (MessageBox::Yes == MessageBox::query_message (main_window,
                                                            tr ("Clone Into Configuration"),
                                                            tr ("Confirm overwrite of all values for configuration \"%1\" with values from \"%2\"?")
                                                            .arg (target_name)
                                                            .arg (source_name)))
            {
              // grab the data to clone from
              if (source_name == current_group_name)
                {
                  // grab the data to clone from the current settings
                  new_settings_ = get_settings ();
                }
              else
                {
                  SettingsGroup alternatives {&settings_, multi_settings_root_group};
                  SettingsGroup source_group {&settings_, source_name};
                  new_settings_ = get_settings ();
                }

              // purge target settings and replace
              if (target_name == current_)
                {
                  // restart with new settings
                  reposition_type_ = RepositionType::replace;
                  exit_flag_ = false;
                  main_window->close ();
                }
              else
                {
                  SettingsGroup alternatives {&settings_, multi_settings_root_group};
                  SettingsGroup target_group {&settings_, target_name};
                  settings_.remove (""); // purge entire group
                  load_from (new_settings_);
                  new_settings_.clear ();
                }
            }
        }
    }
}

void MultiSettings::impl::reset_configuration (QMainWindow * main_window)
{
  if (active_sub_menu_)
    {
      auto const& target_name = active_sub_menu_->title ();

      if (MessageBox::Yes != MessageBox::query_message (main_window,
                                                        tr ("Reset Configuration"),
                                                        tr ("Confirm reset to default values for configuration \"%1\"?")
                                                        .arg (target_name)))
        {
          return;
        }

      if (target_name == current_)
        {
          // restart with default settings
          reposition_type_ = RepositionType::replace;
          new_settings_.clear ();
          exit_flag_ = false;
          main_window->close ();
        }
      else
        {
          SettingsGroup alternatives {&settings_, multi_settings_root_group};
          SettingsGroup target_group {&settings_, target_name};
          settings_.remove (""); // purge entire group
          // add a placeholder to stop alternative configuration name
          // being lost
          settings_.setValue (multi_settings_place_holder_key, QVariant {});
          settings_.sync ();
        }
    }
}

void MultiSettings::impl::rename_configuration (QMainWindow * main_window)
{
  if (active_sub_menu_)
    {
      auto const& target_name = active_sub_menu_->title ();

      // gather names we cannot use
      SettingsGroup alternatives {&settings_, multi_settings_root_group};
      auto invalid_names = settings_.childGroups ();
      invalid_names << settings_.value (multi_settings_current_name_key).toString ();

      // get the new name
      NameDialog dialog {target_name, invalid_names, main_window};
      if (QDialog::Accepted == dialog.exec ())
        {
          if (target_name == current_)
            {
              settings_.setValue (multi_settings_current_name_key, dialog.new_name ());
              settings_.sync ();
              current_ = dialog.new_name ();
            }
          else
            {
              // switch to the target group and fetch the configuration data
              Dictionary target_settings;
              {
                // grab the target configuration settings
                SettingsGroup target_group {&settings_, target_name};
                target_settings = get_settings ();
                // purge the old configuration data
                settings_.remove (""); // purge entire group
              }
              // load into new configuration group name
              SettingsGroup target_group {&settings_, dialog.new_name ()};
              load_from (target_settings);
            }
          // change the action text in the menu
          active_sub_menu_->setTitle (dialog.new_name ());
        }
    }
}

void MultiSettings::impl::delete_configuration (QMainWindow * main_window)
{
  if (active_sub_menu_)
    {
      auto const& target_name = active_sub_menu_->title ();

      if (target_name == current_)
        {
          return;               // suicide not allowed here
        }
      else
        {
          if (MessageBox::Yes != MessageBox::query_message (main_window,
                                                            tr ("Delete Configuration"),
                                                            tr ("Confirm deletion of configuration \"%1\"?")
                                                            .arg (target_name)))
            {
              return;
            }
          SettingsGroup alternatives {&settings_, multi_settings_root_group};
          SettingsGroup target_group {&settings_, target_name};
          // purge the configuration data
          settings_.remove (""); // purge entire group
          settings_.sync ();
        }
      // update the menu
      active_sub_menu_->deleteLater (), active_sub_menu_ = nullptr;
    }
}