/*
Open Asset Import Library (assimp)
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*/

/** @file Defines a helper class for the ASE and 3DS loaders to
 help them compute camera and spot light animation channels */
#ifndef AI_TARGET_ANIMATION_H_INC
#define AI_TARGET_ANIMATION_H_INC

#include <assimp/anim.h>
#include <vector>

namespace Assimp {

// ---------------------------------------------------------------------------
/** Helper class to iterate through all keys in an animation channel.
 *
 *  Missing tracks are interpolated. This is a helper class for
 *  TargetAnimationHelper, but it can be freely used for other purposes.
*/
class KeyIterator {
public:
    // ------------------------------------------------------------------
    /** Constructs a new key iterator
     *
     *  @param _objPos Object position track. May be nullptr.
     *  @param _targetObjPos Target object position track. May be nullptr.
     *  @param defaultObjectPos Default object position to be used if
     *    no animated track is available. May be nullptr.
     *  @param defaultTargetPos Default target position to be used if
     *    no animated track is available. May be nullptr.
     */
    KeyIterator(const std::vector<aiVectorKey> *_objPos,
            const std::vector<aiVectorKey> *_targetObjPos,
            const aiVector3D *defaultObjectPos = nullptr,
            const aiVector3D *defaultTargetPos = nullptr);

    // ------------------------------------------------------------------
    /** Returns true if all keys have been processed
     */
    bool Finished() const { return reachedEnd; }

    // ------------------------------------------------------------------
    /** Increment the iterator
     */
    void operator++();
    inline void operator++(int) { return ++(*this); }

    // ------------------------------------------------------------------
    /** Getters to retrieve the current state of the iterator
     */
    inline const aiVector3D &GetCurPosition() const { return curPosition; }

    inline const aiVector3D &GetCurTargetPosition() const { return curTargetPosition; }

    inline double GetCurTime() const { return curTime; }

private:
    //! Did we reach the end?
    bool reachedEnd;

    //! Represents the current position of the iterator
    aiVector3D curPosition, curTargetPosition;

    double curTime;

    //! Input tracks and the next key to process
    const std::vector<aiVectorKey> *objPos, *targetObjPos;

    unsigned int nextObjPos, nextTargetObjPos;
    std::vector<aiVectorKey> defaultObjPos, defaultTargetObjPos;
};

// ---------------------------------------------------------------------------
/** Helper class for the 3DS and ASE loaders to compute camera and spot light
 *  animations.
 *
 * 3DS and ASE store the differently to Assimp - there is an animation
 * channel for the camera/spot light itself and a separate position
 * animation channels specifying the position of the camera/spot light
 * look-at target */
class TargetAnimationHelper {
public:
    ///	@brief The class constructor.
    TargetAnimationHelper() :
            targetPositions(nullptr),
            objectPositions(nullptr) {
        // empty
    }

    ///	@brief The class destructor.
    ~TargetAnimationHelper() = default;

    // ------------------------------------------------------------------
    /** Sets the target animation channel
     *
     *  This channel specifies the position of the camera/spot light
     *  target at a specific position.
     *
     *  @param targetPositions Translation channel*/
    void SetTargetAnimationChannel(const std::vector<aiVectorKey> *targetPositions);

    // ------------------------------------------------------------------
    /** Sets the main animation channel
     *
     *  @param objectPositions Translation channel */
    void SetMainAnimationChannel(const std::vector<aiVectorKey> *objectPositions);

    // ------------------------------------------------------------------
    /** Sets the main animation channel to a fixed value
     *
     *  @param fixed Fixed value for the main animation channel*/
    void SetFixedMainAnimationChannel(const aiVector3D &fixed);

    // ------------------------------------------------------------------
    /** Computes final animation channels
     * @param distanceTrack Receive camera translation keys ... != nullptr. */
    void Process(std::vector<aiVectorKey> *distanceTrack);

private:
    const std::vector<aiVectorKey> *targetPositions, *objectPositions;
    aiVector3D fixedMain;
};

} // namespace Assimp

#endif // include guard
