#include "externals.hh"
#include "c-camera.hh"
#include "c-utilities.hh"

#include <glm/gtc/matrix_access.hpp>


/*= T_Camera =================================================================*/

T_Camera::T_Camera( ) noexcept
{
	cvtFov2Np( );
	cvtAnglesToVectors( );
}

/*----------------------------------------------------------------------------*/

void T_Camera::camera(
		glm::vec3 const& lookAt ,
		glm::vec3 const& angles ,
		const float distance ) noexcept
{
	lookAt_ = lookAt;
	angles_ = angles;
	distance_ = distance;
	cvtAnglesToVectors( );
}

void T_Camera::camera(
		glm::vec3 const& lookAt ,
		glm::vec3 const& position ,
		glm::vec3 const& up ) noexcept
{
	pos_ = position;
	up_ = up;
	lookAt_ = lookAt;
	cvtVectorsToAngles( );
}

void T_Camera::cvtAnglesToVectors( ) noexcept
{
	anglesToMatrix( &angles_.x , &rotMat_[ 0 ].x );
	dir_ = glm::vec3( 0 , 0 , -distance_ ) * rotMat_;
	up_ = glm::vec3( 0 , 1 , 0 ) * rotMat_;
	pos_ = lookAt_ - dir_;
}

void T_Camera::cvtVectorsToAngles( ) noexcept
{
	dir_ = lookAt_ - pos_;
	const float distance{ length( dir_ ) };
	if ( distance == 0 || length( up_ ) == 0 ) {
		return;
	}
	distance_ = distance;

	const glm::vec3 nDir{ - dir_ / distance_ };
	const glm::vec3 nUp{ normalize( up_ ) };
	if ( abs( dot( nUp , nDir ) ) == 1 ) {
		return;
	}

	const glm::vec3 side{ normalize( cross( nUp , nDir ) ) };
	const glm::vec3 up{ normalize( cross( nDir , side ) ) };
	column( rotMat_ , 0 ) = side;
	column( rotMat_ , 1 ) = up;
	column( rotMat_ , 2 ) = nDir;

	glm::vec3 nAngles;
	nAngles.x = atan2f( nDir.y , nDir.z );

	const float c2{ sqrtf( side.x * side.x + side.y * side.y ) };
	nAngles.y = atan2f( -side.z , c2 );

	const float s1{ sinf( nAngles.x ) } , c1{ cosf( nAngles.x ) };
	nAngles.z = atan2f( s1 * nDir.x - c1 * up.x ,
			c1 * up.y - s1 * nDir.y );

	angles_ = nAngles * 180.f / float( M_PI );
}