#include "trackballcamera.h"
#include <glm/ext.hpp>

#define DEFAULT_SCROLL_SPEED 0.998f
#define DEFAULT_ROTATION_SPEED 0.01f
#define DEFAULT_MOVE_SPEED 0.002f

TrackBallCamera::TrackBallCamera(float myFov, float myNear, float myFar) :
    BasicCamera(myFov, myNear, myFar)
{
    reset();
}

void TrackBallCamera::rotateCamera(float dx, float dy)
{
    m_rotation.x += dx*DEFAULT_ROTATION_SPEED;
    m_rotation.y += dy*DEFAULT_ROTATION_SPEED;
    if(m_rotation.y > 1.57f)
        m_rotation.y = 1.57f;
    if(m_rotation.y < -1.57f)
        m_rotation.y = -1.57f;
    computeView();
}

void TrackBallCamera::moveCamera(float dx, float dy)
{
        glm::mat4 inverseMVP = glm::inverse(m_projection * m_view);
        glm::vec4 diff = inverseMVP * glm::vec4(dx*m_dist*DEFAULT_MOVE_SPEED, dy*m_dist*DEFAULT_MOVE_SPEED, 0, 1);
        m_center += glm::vec3(diff);
        computeView();
}

void TrackBallCamera::reset()
{
    m_center = glm::vec3(0, 4, 0);
    m_rotation = glm::vec2(0, 1);
    m_dist = 20;
    computeView();
}

void TrackBallCamera::computeView()
{
    m_view = glm::translate(glm::mat4(), glm::vec3(0, 0, -m_dist));
    m_view = glm::rotate(m_view, m_rotation.y, glm::vec3(1, 0, 0));
    m_view = glm::rotate(m_view, m_rotation.x, glm::vec3(0, 1, 0));
    m_view = glm::translate(m_view, -m_center);
}

void TrackBallCamera::zoom(int nbUnits)
{
	while(nbUnits != 0)
	{
		if(nbUnits > 0)
		{
			m_dist *= DEFAULT_SCROLL_SPEED;
			--nbUnits;
		}
		else
		{
			m_dist /= DEFAULT_SCROLL_SPEED;
			++nbUnits;
		}
	}
	computeView();
}