

#ifndef QGLVIEWER_CONSTRAINT_H
#define QGLVIEWER_CONSTRAINT_H

#include "vec.h"
#include "quaternion.h"

namespace qglviewer {
  class Frame;
  class Camera;

  /*! \brief An interface class for Frame constraints.
  \class Constraint constraint.h QGLViewer/constraint.h

  This class defines the interface for the Constraints that can be applied to a Frame to limit its
  motion. Use Frame::setConstraint() to associate a Constraint to a Frame (default is a \c NULL
  Frame::constraint()).

  <h3>How does it work ?</h3>

  The Constraint acts as a filter on the translation and rotation Frame increments.
  constrainTranslation() and constrainRotation() should be overloaded to specify the constraint
  behavior: the desired displacement is given as a parameter that can optionally be modified.

  Here is how the Frame::translate() and Frame::rotate() methods use the Constraint:
  \code
  Frame::translate(Vec& T)
  {
    if (constraint())
      constraint()->constrainTranslation(T, this);
    t += T;
  }

  Frame::rotate(Quaternion& Q)
  {
    if (constraint())
      constraint()->constrainRotation(Q, this);
    q *= Q;
  }
  \endcode

  The default behavior of constrainTranslation() and constrainRotation() is empty (meaning no
  filtering).

  The Frame which uses the Constraint is passed as a parameter to the constrainTranslation() and
  constrainRotation() methods, so that they can have access to its current state (mainly
  Frame::position() and Frame::orientation()). It is not \c const for versatility reasons, but
  directly modifying it should be avoided.

  \attention Frame::setTranslation(), Frame::setRotation() and similar methods will actually indeed
  set the frame position and orientation, without taking the constraint into account. Use the \e
  WithConstraint versions of these methods to enforce the Constraint.

  <h3>Implemented Constraints</h3>

  Classical axial and plane Constraints are provided for convenience: see the LocalConstraint,
  WorldConstraint and CameraConstraint classes' documentations.

  Try the <a href="../examples/constrainedFrame.html">constrainedFrame</a> and <a
  href="../examples/constrainedCamera.html">constrainedCamera</a> examples for an illustration.

  <h3>Creating new Constraints</h3>

  The implementation of a new Constraint class simply consists in overloading the filtering methods:
  \code
  // This Constraint enforces that the Frame cannot have a negative z world coordinate.
  class myConstraint : public Constraint
  {
  public:
    virtual void constrainTranslation(Vec& t, Frame * const fr)
      {
        // Express t in the world coordinate system.
        const Vec tWorld = fr->inverseTransformOf(t);
	if (fr->position().z + tWorld.z < 0.0) // check the new fr z coordinate
	  t.z = fr->transformOf(-fr->position().z); // t.z is clamped so that next z position is 0.0
      }
  };
  \endcode

  Note that the translation (resp. rotation) parameter passed to constrainTranslation() (resp.
  constrainRotation()) is expressed in the \e local Frame coordinate system. Here, we use the
  Frame::transformOf() and Frame::inverseTransformOf() method to convert it to and from the world
  coordinate system.

  Combined constraints can easily be achieved by creating a new class that applies the different
  constraint filters:
  \code
  myConstraint::constrainTranslation(Vec& v, Frame* const fr)
  {
    constraint1->constrainTranslation(v, fr);
    constraint2->constrainTranslation(v, fr);
    // and so on, with possible branches, tests, loops...
  }
  \endcode
  */
  class QGLVIEWER_EXPORT Constraint
  {
  public:
    /*! Virtual destructor. Empty. */
    virtual ~Constraint() {};

    /*! Filters the translation applied to the \p frame. This default implementation is empty (no
      filtering).

    Overload this method in your own Constraint class to define a new translation constraint. \p
    frame is the Frame to which is applied the translation. It is not defined \c const, but you
    should refrain from directly changing its value in the constraint. Use its Frame::position() and
    update the \p translation accordingly instead.

    \p translation is expressed in local frame coordinate system. Use Frame::inverseTransformOf() to
    express it in the world coordinate system if needed. */
    virtual void constrainTranslation(Vec& translation, Frame* const frame) { Q_UNUSED(translation); Q_UNUSED(frame); };
    /*! Filters the rotation applied to the \p frame. This default implementation is empty (no
      filtering).

    Overload this method in your own Constraint class to define a new rotation constraint. See
    constrainTranslation() for details.

    Use Frame::inverseTransformOf() on the \p rotation Quaternion::axis() to express \p rotation in
    the world coordinate system if needed. */
    virtual void constrainRotation(Quaternion& rotation, Frame* const frame) { Q_UNUSED(rotation); Q_UNUSED(frame); };
  };

  /*!
   \brief An abstract class for Frame Constraints defined by an axis or a plane.
   \class AxisPlaneConstraint constraint.h QGLViewer/constraint.h

   AxisPlaneConstraint is an interface for (translation and/or rotation) Constraint that are defined
   by a direction. translationConstraintType() and rotationConstraintType() define how this
   direction should be interpreted: as an axis (AxisPlaneConstraint::AXIS) or as a plane normal
   (AxisPlaneConstraint::PLANE). See the Type() documentation for details.

   The three implementations of this class: LocalConstraint, WorldConstraint and CameraConstraint
   differ by the coordinate system in which this direction is expressed.

   Different implementations of this class are illustrated in the
   <a href="../examples/constrainedCamera.html">contrainedCamera</a> and
   <a href="../examples/constrainedFrame.html">constrainedFrame</a> examples.

   \attention When applied, the rotational Constraint may not intuitively follow the mouse
   displacement. A solution would be to directly measure the rotation angle in screen coordinates,
   but that would imply to know the QGLViewer::camera(), so that we can compute the projected
   coordinates of the rotation center (as is done with the QGLViewer::SCREEN_ROTATE binding).
   However, adding an extra pointer to the QGLViewer::camera() in all the AxisPlaneConstraint
   derived classes (which the user would have to update in a multi-viewer application) was judged as
   an overkill. */
  class QGLVIEWER_EXPORT AxisPlaneConstraint : public Constraint
  {
  public:
    AxisPlaneConstraint();
    /*! Virtual destructor. Empty. */
    virtual ~AxisPlaneConstraint() {};

    /*! Type lists the different types of translation and rotation constraints that are available.

    It specifies the meaning of the constraint direction (see translationConstraintDirection() and
    rotationConstraintDirection()): as an axis direction (AxisPlaneConstraint::AXIS) or a plane
    normal (AxisPlaneConstraint::PLANE). AxisPlaneConstraint::FREE means no constraint while
    AxisPlaneConstraint::FORBIDDEN completely forbids the translation and/or the rotation.

    See translationConstraintType() and rotationConstraintType().

    \attention The AxisPlaneConstraint::PLANE Type is not valid for rotational constraint.

    New derived classes can use their own extended enum for specific constraints:
    \code
    class MyAxisPlaneConstraint : public AxisPlaneConstraint
    {
    public:
      enum MyType { FREE, AXIS, PLANE, FORBIDDEN, CUSTOM };
      virtual void constrainTranslation(Vec &translation, Frame *const frame)
      {
        // translationConstraintType() is simply an int. CUSTOM Type is handled seamlessly.
        switch (translationConstraintType())
	{
	case MyAxisPlaneConstraint::FREE: ... break;
	case MyAxisPlaneConstraint::CUSTOM: ... break;
	}
      };

      MyAxisPlaneConstraint* c = new MyAxisPlaneConstraint();
      // Note the Type conversion
      c->setTranslationConstraintType(AxisPlaneConstraint::Type(MyAxisPlaneConstraint::CUSTOM));
    };
    \endcode */
    enum Type { FREE, AXIS, PLANE, FORBIDDEN };

    /*! @name Translation constraint */
    //@{
    /*! Overloading of Constraint::constrainTranslation(). Empty */
    virtual void constrainTranslation(Vec& translation, Frame* const frame) { Q_UNUSED(translation); Q_UNUSED(frame); };

    void setTranslationConstraint(Type type, const Vec& direction);
    /*! Sets the Type() of the translationConstraintType(). Default is AxisPlaneConstraint::FREE. */
    void setTranslationConstraintType(Type type) { translationConstraintType_ = type; };
    void setTranslationConstraintDirection(const Vec& direction);

    /*! Returns the translation constraint Type().

    Depending on this value, the Frame will freely translate (AxisPlaneConstraint::FREE), will only
    be able to translate along an axis direction (AxisPlaneConstraint::AXIS), will be forced to stay
    into a plane (AxisPlaneConstraint::PLANE) or will not able to translate at all
    (AxisPlaneConstraint::FORBIDDEN).

    Use Frame::setPosition() to define the position of the constrained Frame before it gets
    constrained. */
    Type translationConstraintType() const { return translationConstraintType_; };
    /*! Returns the direction used by the translation constraint.

    It represents the axis direction (AxisPlaneConstraint::AXIS) or the plane normal
    (AxisPlaneConstraint::PLANE) depending on the translationConstraintType(). It is undefined for
    AxisPlaneConstraint::FREE or AxisPlaneConstraint::FORBIDDEN.

    The AxisPlaneConstraint derived classes express this direction in different coordinate system
    (camera for CameraConstraint, local for LocalConstraint, and world for WorldConstraint). This
    value can be modified with setTranslationConstraintDirection(). */
    Vec translationConstraintDirection() const { return translationConstraintDir_; };
    //@}

    /*! @name Rotation constraint */
    //@{
    /*! Overloading of Constraint::constrainRotation(). Empty. */
    virtual void constrainRotation(Quaternion& rotation, Frame* const frame) { Q_UNUSED(rotation); Q_UNUSED(frame); };

    void setRotationConstraint(Type type, const Vec& direction);
    void setRotationConstraintType(Type type);
    void setRotationConstraintDirection(const Vec& direction);

    /*! Returns the rotation constraint Type(). */
    Type rotationConstraintType() const { return rotationConstraintType_; };
    /*! Returns the axis direction used by the rotation constraint.

    This direction is defined only when rotationConstraintType() is AxisPlaneConstraint::AXIS.

    The AxisPlaneConstraint derived classes express this direction in different coordinate system
    (camera for CameraConstraint, local for LocalConstraint, and world for WorldConstraint). This
    value can be modified with setRotationConstraintDirection(). */
    Vec rotationConstraintDirection() const { return rotationConstraintDir_; };
    //@}

  private:
    // int and not Type to allow for overloading and new types definition.
    Type translationConstraintType_;
    Type rotationConstraintType_;

    Vec translationConstraintDir_;
    Vec rotationConstraintDir_;
  };


  /*! \brief An AxisPlaneConstraint defined in the Frame local coordinate system.
  \class LocalConstraint constraint.h QGLViewer/constraint.h

  The translationConstraintDirection() and rotationConstraintDirection() are expressed in the Frame
  local coordinate system (see Frame::referenceFrame()).

  See the <a href="../examples/constrainedFrame.html">constrainedFrame</a> example for an illustration. */
  class QGLVIEWER_EXPORT LocalConstraint : public AxisPlaneConstraint
  {
  public:
    /*! Virtual destructor. Empty. */
    virtual ~LocalConstraint() {};

    virtual void constrainTranslation(Vec&     translation, Frame* const frame);
    virtual void constrainRotation   (Quaternion& rotation, Frame* const frame);
  };



  /*! \brief An AxisPlaneConstraint defined in the world coordinate system.
    \class WorldConstraint constraint.h QGLViewer/constraint.h

  The translationConstraintDirection() and rotationConstraintDirection() are expressed in world
  coordinate system.

  See the <a href="../examples/constrainedFrame.html">constrainedFrame</a> and <a
  href="../examples/multiView.html">multiView</a> examples for an illustration. */
  class QGLVIEWER_EXPORT WorldConstraint : public AxisPlaneConstraint
  {
  public:
    /*! Virtual destructor. Empty. */
    virtual ~WorldConstraint() {};

    virtual void constrainTranslation(Vec&     translation, Frame* const frame);
    virtual void constrainRotation   (Quaternion& rotation, Frame* const frame);
  };



  /*! \brief An AxisPlaneConstraint defined in the camera coordinate system.
  \class CameraConstraint constraint.h QGLViewer/constraint.h

  The translationConstraintDirection() and rotationConstraintDirection() are expressed in the
  associated camera() coordinate system.

  See the <a href="../examples/constrainedFrame.html">constrainedFrame</a> and <a
  href="../examples/constrainedCamera.html">constrainedCamera</a> examples for an illustration. */
  class QGLVIEWER_EXPORT CameraConstraint : public AxisPlaneConstraint
  {
  public:
    explicit CameraConstraint(const Camera* const camera);
    /*! Virtual destructor. Empty. */
    virtual ~CameraConstraint() {};

    virtual void constrainTranslation(Vec&     translation, Frame* const frame);
    virtual void constrainRotation   (Quaternion& rotation, Frame* const frame);

    /*! Returns the associated Camera. Set using the CameraConstraint constructor. */
    const Camera* camera() const { return camera_; };

  private:
    const Camera* const camera_;
  };

} // namespace qglviewer

#endif // QGLVIEWER_CONSTRAINT_H
