#pragma region CPL License
/*
Nuclex Native Framework
Copyright (C) 2002-2013 Nuclex Development Labs

This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 of the
License, or (at your option) any later version.

This library 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
IBM Common Public License for more details.

You should have received a copy of the IBM Common Public
License along with this library
*/
#pragma endregion // CPL License

#ifndef NUCLEX_INPUT_DEVICES_VIRTUALKEYBOARD_H
#define NUCLEX_INPUT_DEVICES_VIRTUALKEYBOARD_H

#include "Nuclex/Input/Devices/Keyboard.h"

namespace Nuclex { namespace Input { namespace Devices {

  /// <summary>Forwards keyboard input from an exchangeable backing device</summary>
  /// <remarks>
  ///   <para>
  ///     If this library directly dealt out instances of the input device implementations,
  ///     disconnecting a device and connecting another one, for example, would mean that
  ///     any pointers the user has to the disconnected device become either invalid.
  ///   </para>
  ///   <para>
  ///     So the design choice was to either let the library's user in on when devices are
  ///     replaced, forcing him to unsubscribe from events, resubscribe, replace pointers
  ///     he has stored to the old device and so on, or to use a forwarder device that
  ///     allows the underlying real input device to be replaced at will without anyone
  ///     outside of the library noticing.
  ///   </para>
  ///   <para>
  ///     Without a forwarding device assigned, this class can also be used as a dummy
  ///     device to fill slots for devices not available or not supported by the current
  ///     system (think keyboard on iPhone, etc.)
  ///   </para>
  /// </remarks>
  class VirtualKeyboard : public Keyboard, public sigslot::has_slots<> {

    /// <summary>Initializes a new virtual keyboard</summary>
    public: VirtualKeyboard() :
      forwardingKeyboard(nullptr) {
      this->neutralState.Reset();
    }

    /// <summary>Destroys the virtual keyboard</summary>
    public: virtual ~VirtualKeyboard() {
      if(this->forwardingKeyboard != nullptr) {
        unsubscribe(this->forwardingKeyboard);
      }
    }

    /// <summary>Assigns the keyboard for which this instance forwards input</summary>
    /// <param name="forwardingKeyboard">Keyboard for which input will be forwarded</param>
    public: void SetForwardingKeyboard(Keyboard *forwardingKeyboard) {
      if(this->forwardingKeyboard != nullptr) {
        unsubscribe(this->forwardingKeyboard);
      }
      
      this->forwardingKeyboard = forwardingKeyboard;

      if(this->forwardingKeyboard != nullptr) {
        subscribe(this->forwardingKeyboard);
      }
    }

    /// <summary>Whether the input device is currently attached</summary>
    /// <returns>True if the input device is attached, otherwise false</returns>
    public: virtual bool IsAttached() const {
      if(this->forwardingKeyboard == nullptr) {
        return false;
      } else {
        return this->forwardingKeyboard->IsAttached();
      }
    }

    /// <summary>Retrieves the human-readable name of the input device</summary>
    /// <returns>The human-readable name of the input device</returns>
    public: virtual const std::string &GetName() const {
      static std::string notConnected("No keyboard connected");

      if(this->forwardingKeyboard == nullptr) {
        return notConnected;
      } else {
        return this->forwardingKeyboard->GetName();
      }
    }

    /// <summary>Retrieves the current state of the input device</summary>
    /// <returns>The input device's current state</returns>
    public: virtual const KeyboardState &GetState() const {
      if(this->forwardingKeyboard == nullptr) {
        return this->neutralState;
      } else {
        return this->forwardingKeyboard->GetState();
      }
    }

    /// <summary>Updates the state of the input device</summary>
    protected: virtual void Update() {
      if(this->forwardingKeyboard != nullptr) {
        this->forwardingKeyboard->Update();
      }
    }

    /// <summary>Takes a snapshot of the input device's current state</summary>
    protected: virtual void TakeSnapshot() {
      if(this->forwardingKeyboard != nullptr) {
        this->forwardingKeyboard->TakeSnapshot();
      }
    }

    /// <summary>Removes all snapshots the device has taken</summary>
    protected: virtual void ClearSnapshots() {
      if(this->forwardingKeyboard != nullptr) {
        this->forwardingKeyboard->ClearSnapshots();
      }
    }

    /// <summary>Subscribes to the events of the forwarding keyboard</summary>
    /// <param name="keyboard">Keyboard to whose events to subscribe</param>
    private: void subscribe(Keyboard *keyboard) {
      keyboard->KeyPressed.connect(this, &VirtualKeyboard::onKeyPressed);
      keyboard->KeyReleased.connect(this, &VirtualKeyboard::onKeyReleased);
      keyboard->CharacterEntered.connect(this, &VirtualKeyboard::onCharacterEntered);
    }

    /// <summary>Unsubscribes from the events of the forwarding keyboard</summary>
    /// <param name="keyboard">Keyboard from whose events to unsubscribe</param>
    private: void unsubscribe(Keyboard *keyboard) {
      keyboard->CharacterEntered.disconnect(this);
      keyboard->KeyReleased.disconnect(this);
      keyboard->KeyPressed.disconnect(this);
    }

    /// <summary>Forwards a key press notification to the library user</summary>
    /// <param name="key">Key that has been pressed</param>
    private: void onKeyPressed(Key::Enum key) {
      KeyPressed(key);
    }

    /// <summary>Forwards a key release notification to the library user</summary>
    /// <param name="key">Key that has been released</param>
    private: void onKeyReleased(Key::Enum key) {
      KeyReleased(key);
    }

    /// <summary>Forwards a character entry notification to the library user</summary>
    /// <param name="character">Character that has been entered</param>
    private: void onCharacterEntered(wchar_t character) {
      CharacterEntered(character);
    }

    /// <summary>Disabled copy constructor for the virtual keyboard</summary>
    private: VirtualKeyboard(const VirtualKeyboard &);
    /// <summary>Disabled assignment operator for the virtual keyboard</summary>
    private: void operator =(const VirtualKeyboard &);

    /// <summary>Keyboard that is forwarded by this instance</summary>
    private: Keyboard *forwardingKeyboard;
    /// <summary>Neutral state that is returned when no keyboard is connected</summary>
    private: KeyboardState neutralState;

  };

}}} // namespace Nuclex::Input::Devices

#endif // NUCLEX_INPUT_DEVICES_VIRTUALKEYBOARD_H