#ifndef TERRAINRAYWALKER_H
#define TERRAINRAYWALKER_H

#include "software_global.h"

#include "Vector3.h"

namespace paysages {
namespace software {

/**
 * Ray walker to find intersections with terrain.
 *
 * This walker can be used to find a hard intersection between
 * a ray and the terrain (e.g. for raytracing), or a soft intersection
 * (e.g. for shadows).
 */
class SOFTWARESHARED_EXPORT TerrainRayWalker {
  public:
    typedef struct {
        Vector3 hit_location; // Location of the hit
        double escape_angle;  // Angle used to shift the ray to escape the terrain (0.0 if no escape was possible)
    } TerrainHitResult;

  public:
    TerrainRayWalker(SoftwareRenderer *renderer);

    /**
     * Set the walker quality.
     *
     * displacement_safety - Safety factor (around 1.0) to detect when displacement textures need to be applied
     * minimal_step - Minimal length of a walking step
     * maximal_step - Maximal length of a walking step
     * step_factor - Precision factor of steps, depending on terrain proximity
     * max_distance - Maximal distance allowed to travel before considering an escape
     * escape_step - Angle step when allowing an escape angle
     */
    void setQuality(double displacement_safety, double minimal_step, double maximal_step, double step_factor,
                    double max_distance, double escape_step);
    void setQuality(double factor);

    /**
     * Update the walker internal data, from the renderer and scenery.
     */
    void update();

    /**
     * Start the walking process to find intersection
     *
     * start - Point of origin of the ray
     * direction - Ray direction (normalized vector)
     * escape_angle - Maximal angle allowed to escape the terrain on hit (mainly for shadows computing)
     * result - Object to store the results info
     *
     * Returns true if there was a hit.
     */
    bool startWalking(const Vector3 &start, Vector3 direction, double escape_angle, TerrainHitResult &result);

  private:
    SoftwareRenderer *renderer;
    double ymin;
    double ymax;
    double displacement_base;

    // Quality control
    double displacement_safety;
    double minimal_step;
    double maximal_step;
    double step_factor;
    double max_distance;
    double escape_step;
};
}
}

#endif // TERRAINRAYWALKER_H