///@file
/// Interface for 2D Canvas elements
//
// Copyright (C) 2012  Thomas Geymayer <tomgey@gmail.com>
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public
// License as published by the Free Software Foundation; either
// version 2 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 GNU
// Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA

#ifndef CANVAS_ELEMENT_HXX_
#define CANVAS_ELEMENT_HXX_

#include <simgear/canvas/canvas_fwd.hxx>
#include <simgear/canvas/CanvasEvent.hxx>
#include <simgear/props/PropertyBasedElement.hxx>
#include <simgear/misc/stdint.hxx> // for uint32_t
#include <simgear/std/type_traits.hxx>

#include <osg/BoundingBox>
#include <osg/MatrixTransform>

namespace osg
{
  class Drawable;
}

namespace simgear
{
namespace canvas
{

  /**
   * Base class for Elements displayed inside a Canvas.
   */
  class Element:
    public PropertyBasedElement
  {
    public:
      using SceneGroupWeakPtr = osg::observer_ptr<osg::MatrixTransform>;

      /**
       * Store pointer to window as user data
       */
      class OSGUserData:
        public osg::Referenced
      {
        public:
          ElementPtr element;
          OSGUserData(ElementPtr element);
      };

      typedef std::function<bool(Element&, const SGPropertyNode*)>
              StyleSetterFunc;
      typedef std::function<void(Element&, const SGPropertyNode*)>
              StyleSetterFuncUnchecked;
      struct StyleSetter:
        public SGReferenced
      {
        StyleSetterFunc func;
        SGSharedPtr<StyleSetter> next;
      };
      struct StyleInfo
      {
        StyleSetter setter; ///< Function(s) for setting this style
        std::string type;   ///< Interpolation type
        bool inheritable;   ///< Whether children can inherit this style from
                            ///  their parents
      };

      /**
       * Coordinate reference frame (eg. "clip" property)
       */
      enum ReferenceFrame
      {
        GLOBAL, ///< Global coordinates
        PARENT, ///< Coordinates relative to parent coordinate frame
        LOCAL   ///< Coordinates relative to local coordinates (parent
                ///  coordinates with local transformations applied)
      };

      /**
       *
       */
      virtual ~Element() = 0;
      void onDestroy() override;

      ElementPtr getParent() const;
      CanvasWeakPtr getCanvas() const;

      /**
       * Called every frame to update internal state
       *
       * @param dt  Frame time in seconds
       */
      void update(double dt) override;

      bool addEventListener(const std::string& type, const EventListener& cb);
      virtual void clearEventListener();

      /// Get (keyboard) input focus.
      void setFocus();

      bool hasFocus() const;

      virtual bool accept(EventVisitor& visitor);
      virtual bool ascend(EventVisitor& visitor);
      virtual bool traverse(EventVisitor& visitor);

      /// Get the number of event handlers for the given type
      size_t numEventHandler(int type) const;

      virtual bool handleEvent(const EventPtr& event);
      bool dispatchEvent(const EventPtr& event);

      /**
       *
       * @param global_pos Position in global (canvas) coordinate frame
       * @param parent_pos Position in parent coordinate frame
       * @param local_pos  Position in local (element) coordinate frame
       */
      virtual bool hitBound( const osg::Vec2f& global_pos,
                             const osg::Vec2f& parent_pos,
                             const osg::Vec2f& local_pos ) const;

      /**
       * Set visibility of the element.
       */
      virtual void setVisible(bool visible);

      /**
       * Get whether the element is visible or hidden.
       */
      virtual bool isVisible() const;

      /**
       * Get the according group in the OSG scene graph
       */
      // TODO ref_ptr
      osg::MatrixTransform* getSceneGroup() const;

      /**
       * Transform position to local coordinates.
       */
      osg::Vec2f posToLocal(const osg::Vec2f& pos) const;

      /**
       * @brief transform position from local coordinates
       * 
       * @param pos - in coordinates of this element
       * @return osg::Vec2f  in coordinates of parent Group
       */
      osg::Vec2f posFromLocal(const osg::Vec2f& pos) const;

      /**
       * Transform from coordinates of our Canvas, to this
       * Element's local coordinates
      */
      osg::Vec2f canvasToLocal(const osg::Vec2f& pos) const;

      /**
       * Transform from our local coordinates into those
       * of our Canvas
      */
      osg::Vec2f localToCanvas(const osg::Vec2f& pos) const;

      void childAdded(SGPropertyNode* parent, SGPropertyNode* child) override;
      void childRemoved(SGPropertyNode* parent, SGPropertyNode* child) override;
      void valueChanged(SGPropertyNode* child) override;

      virtual bool setStyle( const SGPropertyNode* child,
                             const StyleInfo* style_info = 0 );

      /**
       * Set clipping shape
       *
       * @note Only "rect(<top>, <right>, <bottom>, <left>)" is supported
       * @see http://www.w3.org/TR/CSS21/visufx.html#propdef-clip
       */
      void setClip(const std::string& clip);

      /**
       * Clipping coordinates reference frame
       */
      void setClipFrame(ReferenceFrame rf);

      /**
       *
       */
      void setRotation(unsigned int index, double r);

      /**
       *
       */
      void setTranslation(unsigned int index, double x, double y);

      /**
       *
       *
       */
      void setTransformEnabled(unsigned int index, bool enabled);

      /**
       * Get bounding box (may not be as tight as bounding box returned by
       * #getTightBoundingBox)
       */
      osg::BoundingBox getBoundingBox() const;

      /**
       * Get tight bounding box (child points are transformed to elements
       * coordinate space before calculating the bounding box).
       */
      osg::BoundingBox getTightBoundingBox() const;

      /**
       * Get bounding box with children/drawables transformed by passed matrix
       */
      virtual osg::BoundingBox getTransformedBounds(const osg::Matrix& m) const;

      /**
       * Get the transformation matrix (product of all transforms)
       */
      osg::Matrix getMatrix() const;

      /**
       * Create an canvas Element
       *
       * @tparam Derived    Type of element (needs to derive from Element)
       */
      template<typename Derived>
      static
      std::enable_if_t<
        std::is_base_of<Element, Derived>::value,
        ElementPtr
      >
      create( const CanvasWeakPtr& canvas,
              const SGPropertyNode_ptr& node,
              const Style& style = Style(),
              Element* parent = NULL )
      {
        return ElementPtr( new Derived(canvas, node, style, parent) );
      }

    protected:

      enum Attributes
      {
        TRANSFORM       = 1,
        BLEND_FUNC      = TRANSFORM << 1,
        LAST_ATTRIBUTE  = BLEND_FUNC << 1
      };

      enum TransformType
      {
        TT_NONE,
        TT_MATRIX,
        TT_TRANSLATE,
        TT_ROTATE,
        TT_SCALE
      };

      class RelativeScissor;

      CanvasWeakPtr   _canvas;
      ElementWeakPtr  _parent;

      mutable uint32_t _attributes_dirty = 0;

      SceneGroupWeakPtr             _scene_group;
      std::vector<TransformType>    _transform_types;

      Style             _style;
      RelativeScissor  *_scissor = nullptr;

      typedef std::vector<EventListener> Listener;
      typedef std::map<int, Listener> ListenerMap;

      ListenerMap _listener;

      typedef std::map<std::string, StyleInfo> StyleSetters;
      static StyleSetters _style_setters;

      static void staticInit();

      Element( const CanvasWeakPtr& canvas,
               const SGPropertyNode_ptr& node,
               const Style& parent_style,
               ElementWeakPtr parent );

      /**
       * Returns false on first call and true on any successive call. Use to
       * perform initialization tasks which are only required once per element
       * type.
       *
       * @tparam Derived    (Derived) class type
       */
      template<class Derived>
      static bool isInit()
      {
        static bool is_init = false;
        if( is_init )
          return true;

        is_init = true;
        return false;
      }

      /**
       * Register a function for setting a style specified by the given property
       *
       * @param name        Property name
       * @param type        Interpolation type
       * @param setter      Setter function
       * @param inheritable If this style propagates to child elements
       *
       * @tparam T1         Type of value used to retrieve value from property
       *                    node
       * @tparam T2         Type of value the setter function expects
       * @tparam Derived    Type of class the setter can be applied to
       *
       * @note T1 needs to be convertible to T2
       */
      template<
        typename T1,
        typename T2,
        class Derived
      >
      static
      StyleSetter
      addStyle( const std::string& name,
                const std::string& type,
                const std::function<void (Derived&, T2)>& setter,
                bool inheritable = true )
      {
        StyleInfo& style_info = _style_setters[ name ];
        if( !type.empty() )
        {
          if( !style_info.type.empty() && type != style_info.type )
            SG_LOG
            (
              SG_GENERAL,
              SG_WARN,
              "changing animation type for '" << name << "': "
                << style_info.type << " -> " << type
            );

          style_info.type = type;
        }
        // TODO check if changed?
        style_info.inheritable = inheritable;

        StyleSetter* style = &style_info.setter;
        while( style->next )
          style = style->next;
        if( style->func )
          style = style->next = new StyleSetter;

        style->func = std::bind(&type_match<Derived>::call,
                                std::placeholders::_1,
                                std::placeholders::_2,
                                bindStyleSetter<T1>(name, setter));
        return *style;
      }

      template<
        typename T,
        class Derived
      >
      static
      StyleSetter
      addStyle( const std::string& name,
                const std::string& type,
                const std::function<void (Derived&, T)>& setter,
                bool inheritable = true )
      {
        return addStyle<T, T>(name, type, setter, inheritable);
      }

      template<
        typename T,
        class Derived
      >
      static
      StyleSetter
      addStyle( const std::string& name,
                const std::string& type,
                void (Derived::*setter)(T),
                bool inheritable = true )
      {
        return addStyle<T, T>
        (
          name,
          type,
          std::function<void (Derived&, T)>(setter),
          inheritable
        );
      }

      template<
        typename T1,
        typename T2,
        class Derived
      >
      static
      StyleSetterFunc
      addStyle( const std::string& name,
                const std::string& type,
                void (Derived::*setter)(T2),
                bool inheritable = true )
      {
        return addStyle<T1>
        (
          name,
          type,
          std::function<void (Derived&, T2)>(setter),
          inheritable
        );
      }

      template<
        class Derived
      >
      static
      StyleSetter
      addStyle( const std::string& name,
                const std::string& type,
                void (Derived::*setter)(const std::string&),
                bool inheritable = true )
      {
        return addStyle<std::string, const std::string&>
        (
          name,
          type,
          std::function<void (Derived&, const std::string&)>(setter),
          inheritable
        );
      }

      template<
        typename T,
        class Derived,
        class Other,
        class OtherRef
      >
      static
      StyleSetter
      addStyle( const std::string& name,
                const std::string& type,
                void (Other::*setter)(T),
                OtherRef Derived::*instance_ref,
                bool inheritable = true )
      {
        return addStyle<T, T>
        (
          name,
          type,
          bindOther(setter, instance_ref),
          inheritable
        );
      }

      template<
        typename T1,
        typename T2,
        class Derived,
        class Other,
        class OtherRef
      >
      static
      StyleSetter
      addStyle( const std::string& name,
                const std::string& type,
                void (Other::*setter)(T2),
                OtherRef Derived::*instance_ref,
                bool inheritable = true )
      {
        return addStyle<T1>
        (
          name,
          type,
          bindOther(setter, instance_ref),
          inheritable
        );
      }

      template<
        typename T1,
        typename T2,
        class Derived,
        class Other,
        class OtherRef
      >
      static
      StyleSetter
      addStyle( const std::string& name,
                const std::string& type,
                const std::function<void (Other&, T2)>& setter,
                OtherRef Derived::*instance_ref,
                bool inheritable = true )
      {
        return addStyle<T1>
        (
          name,
          type,
          bindOther(setter, instance_ref),
          inheritable
        );
      }

      template<
        class Derived,
        class Other,
        class OtherRef
      >
      static
      StyleSetter
      addStyle( const std::string& name,
                const std::string& type,
                void (Other::*setter)(const std::string&),
                OtherRef Derived::*instance_ref,
                bool inheritable = true )
      {
        return addStyle<std::string, const std::string&>
        (
          name,
          type,
          std::function<void (Other&, const std::string&)>(setter),
          instance_ref,
          inheritable
        );
      }

      template<typename T, class Derived, class Other, class OtherRef>
      static
      std::function<void (Derived&, T)>
      bindOther( void (Other::*setter)(T), OtherRef Derived::*instance_ref )
      {
        return std::bind(setter,
                         std::bind(instance_ref, std::placeholders::_1),
                         std::placeholders::_2);
      }

      template<typename T, class Derived, class Other, class OtherRef>
      static
      std::function<void (Derived&, T)>
      bindOther( const std::function<void (Other&, T)>& setter,
                 OtherRef Derived::*instance_ref )
      {
        return std::bind(setter,
                         std::bind(&reference_from_pointer<Other, OtherRef>,
                                   std::bind(instance_ref, std::placeholders::_1)),
                         std::placeholders::_2);
      }

      template<typename T1, typename T2, class Derived>
      static
      StyleSetterFuncUnchecked
      bindStyleSetter( const std::string& name,
                       const std::function<void (Derived&, T2)>& setter )
      {
        return std::bind(setter,
                         // We will only call setters with Derived instances, so we can safely
                         // cast here.
                         std::bind(&derived_cast<Derived>, std::placeholders::_1),
                         std::bind(&getValue<T1>, std::placeholders::_2));
      }

      bool isStyleEmpty(const SGPropertyNode* child) const;
      bool canApplyStyle(const SGPropertyNode* child) const;
      bool setStyleImpl( const SGPropertyNode* child,
                         const StyleInfo* style_info = 0 );

      const StyleInfo* getStyleInfo(const std::string& name) const;
      const StyleSetter* getStyleSetter(const std::string& name) const;
      const SGPropertyNode* getParentStyle(const SGPropertyNode* child) const;

      virtual void childAdded(SGPropertyNode * child)  {}
      virtual void childRemoved(SGPropertyNode * child){}
      virtual void childChanged(SGPropertyNode * child){}

      void setDrawable(osg::Drawable* drawable);

      /**
       * Get stateset of drawable if available or use transform otherwise
       */
      virtual osg::StateSet* getOrCreateStateSet();

      void setupStyle();

      void updateMatrix() const;

      virtual void updateImpl(double dt);

    private:

      osg::ref_ptr<osg::Drawable> _drawable;

      Element(const Element&) = delete;

      template<class Derived>
      static Derived& derived_cast(Element& el)
      {
        return static_cast<Derived&>(el);
      }

      template<class T, class SharedPtr>
      static T& reference_from_pointer(const SharedPtr& p)
      {
        return *get_pointer(p);
      }

      /**
       * Helper to call a function only of the element type can be converted to
       * the required type.
       *
       * @return Whether the function has been called
       */
      template<class Derived>
      struct type_match
      {
        static bool call( Element& el,
                          const SGPropertyNode* prop,
                          const StyleSetterFuncUnchecked& func )
        {
          Derived* d = dynamic_cast<Derived*>(&el);
          if( !d )
            return false;
          func(*d, prop);
          return true;
        }
      };
  };

} // namespace canvas

  template<>
  struct enum_traits<canvas::Element::ReferenceFrame>
  {
    static const char* name()
    {
      return "canvas::Element::ReferenceFrame";
    }

    static canvas::Element::ReferenceFrame defVal()
    {
      return canvas::Element::GLOBAL;
    }

    static bool validate(int frame)
    {
      return frame >= canvas::Element::GLOBAL
          && frame <= canvas::Element::LOCAL;
    }
  };

} // namespace simgear

#endif /* CANVAS_ELEMENT_HXX_ */
