#include "externals.hh"
#include "camera.hh"
#include "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_;
	distance_ = glm::length( dir_ );
	if ( distance_ == 0 ) {
		angles_ = glm::vec3( 0 );
		return;
	}

	const glm::vec3 nDir{ - dir_ / distance_ };
	const glm::vec3 side{ normalize( cross( normalize( up_ ) , 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 );
}

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

void T_Camera::handleDND(
		ImVec2 const& move ,
		const bool hasCtrl ,
		const bool hasShift ,
		const bool lmb ) noexcept
{
	if ( move.x == 0 || move.y == 0 ) {
		return;
	}

	const float fdx( move.x * .1f * ( hasCtrl ? 1.f : .1f ) );
	const float fdy( move.y * .1f * ( hasCtrl ? 1.f : .1f ) );

	if ( lmb && hasShift ) {
		// Left mouse button, shift - move camera
		const auto side( glm::normalize( glm::cross( up_ , dir_ ) ) );
		lookAt_ += .1f * ( side * fdx + up_ * fdy );
	} else if ( lmb ) {
		// Left mouse button, no shift - change yaw/pitch
		updateAngle( angles_.y , fdx );
		updateAngle( angles_.x , fdy );
	} else {
		// Right mouse button - change roll
		updateAngle( angles_.z , fdx );
	}
	cvtAnglesToVectors( );
}

void T_Camera::handleWheel(
		const float wheel ,
		const bool hasCtrl ,
		const bool hasShift ) noexcept
{
	const float delta( wheel * ( hasCtrl ? 1.f : .1f) );
	if ( hasShift ) {
		fov_ = std::max( 1.f , std::min( 179.f , fov_ + delta ) );
		cvtFov2Np( );
	} else {
		distance_ = std::max( .01f , distance_ - delta );
		cvtAnglesToVectors( );
	}
}

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

T_Camera::T_Changes T_Camera::makeUI( ) noexcept
{
	using namespace ImGui;

	// What gets changed
	static const T_Changes changeFlags[] = {
		E_Changes::MATRIX ,
		{} ,
		E_Changes::MATRIX ,
		E_Changes::MATRIX ,
		{} ,
		E_Changes::MATRIX ,
		E_Changes::MATRIX ,
		{} ,
		E_Changes::FOV ,
		E_Changes::FOV ,
	};

	// Which update gets called.
	enum E_ChangeCall_ {
		CC_NONE ,
		CC_FROM_VECTORS ,
		CC_FROM_ANGLES ,
		CC_FROM_FOV ,
		CC_FROM_NP ,
	};
	static const E_ChangeCall_ changeCalls[] = {
		CC_FROM_ANGLES ,
		CC_NONE ,
		CC_FROM_ANGLES ,
		CC_FROM_ANGLES ,
		CC_NONE ,
		CC_FROM_VECTORS ,
		CC_FROM_VECTORS ,
		CC_NONE ,
		CC_FROM_FOV ,
		CC_FROM_NP ,
	};

	static_assert( sizeof( changeFlags ) / sizeof( T_Changes ) == sizeof( changeCalls ) / sizeof( E_ChangeCall_ ) ,
			"invalid configuration" );

	// Changes (also draws the fields)
	const bool changed[] = {
		DragFloat3( "Target" , &lookAt_.x ) ,
		( Separator( ) , false ) ,
		DragFloat( "Distance" , &distance_ , .1f , .1f , 1e8 , "%.1f" ) ,
		DragFloat3( "Angles" , &angles_.x , .01f , -180 , 180 ) ,
		( Separator( ) , false ) ,
		DragFloat3( "Position" , &pos_.x ) ,
		DragFloat3( "Up vector" , &up_.x ) ,
		( Separator( ) , false ) ,
		DragFloat( "FoV" , &fov_ , .01f , .01f , 179.9f ) ,
		DragFloat( "Near plane" , &np_ , .00001f , .001f , 1e6f ) ,
	};

	static_assert( sizeof( changeFlags ) / sizeof( T_Changes ) == sizeof( changed ) / sizeof( bool ) ,
			"invalid configuration" );

	T_Changes changes;
	for ( unsigned i = 0 ; i < sizeof( changed ) / sizeof( bool ) ; i ++ ) {
		if ( changed[ i ] ) {
			switch ( changeCalls[ i ] ) {
			    case CC_NONE: break;
			    case CC_FROM_VECTORS: cvtVectorsToAngles( ); break;
			    case CC_FROM_ANGLES: cvtAnglesToVectors( ); break;
			    case CC_FROM_FOV: cvtFov2Np( ); break;
			    case CC_FROM_NP: cvtNp2Fov( ); break;
			}
			changes = changes | changeFlags[ i ];
		}
	}
	return changes;
}