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

#include <imgui_internal.h>


void ImGui::PushDisabled( ) noexcept
{
	PushItemFlag( ImGuiItemFlags_Disabled , true );
	PushStyleVar( ImGuiStyleVar_Alpha , GetStyle( ).Alpha * .5f );
}

void ImGui::PopDisabled( ) noexcept
{
	PopItemFlag( );
	PopStyleVar( );
}

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

bool ImGui::MenuItemCheckbox(
		char const* name ,
		bool* checked ) noexcept
{
	bool rv{ MenuItem( name , "" , *checked , true ) };
	if ( rv ) {
		*checked = !*checked;
	}
	return rv;
}

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

bool ImGui::ToolbarButton(
		char const* const string ,
		ImVec2 const& size ,
		char const* const tooltip ,
		bool enabled ) noexcept
{
	if ( !enabled ) {
		PushDisabled( );
	}
	const bool rv{ Button( string , size ) };
	if ( !enabled ) {
		PopDisabled( );
	} else if ( tooltip && IsItemHovered( ) ) {
		BeginTooltip( );
		Text( tooltip );
		EndTooltip( );
	}
	return rv;
}

void ImGui::ToolbarSeparator( ) noexcept
{
	SameLine( );
	VerticalSeparator( );
	SameLine( );
}


/*= T_CameraMouseControl =======================================================*/

void T_CameraMouseControl::handleDragAndDrop(
		ImVec2 const& move ,
		T_KeyboardModifiers modifiers ,
		T_MouseButtons buttons ) noexcept
{
	if ( move.x == 0 || move.y == 0 ) {
		return;
	}

	const float fdx( move.x * .1f * ( ( modifiers & E_KeyboardModifier::CTRL ) ? 1.f : .1f ) );
	const float fdy( move.y * .1f * ( ( modifiers & E_KeyboardModifier::CTRL ) ? 1.f : .1f ) );

	if ( ( buttons & E_MouseButton::LEFT ) && ( modifiers & E_KeyboardModifier::SHIFT ) ) {
		// Left mouse button, shift - move camera
		const auto side( normalize( cross( camera.upVector( ) , camera.direction( ) ) ) );
		camera.lookAt( ) += .1f * ( side * fdx + camera.upVector( ) * fdy );
	} else if ( buttons & E_MouseButton::LEFT ) {
		// Left mouse button, no shift - change yaw/pitch
		updateAngle( camera.angles( ).y , fdx );
		updateAngle( camera.angles( ).x , fdy );
	} else if ( buttons & E_MouseButton::RIGHT ) {
		// Right mouse button - change roll
		updateAngle( camera.angles( ).z , fdx );
	}
	camera.cvtAnglesToVectors( );
}

void T_CameraMouseControl::handleWheel(
		const float wheel ,
		T_KeyboardModifiers modifiers ,
		T_MouseButtons /* buttons */ ) noexcept
{
	const float delta( wheel * ( ( modifiers & E_KeyboardModifier::CTRL ) ? 1.f : .1f) );
	if ( modifiers & E_KeyboardModifier::SHIFT ) {
		camera.fieldOfView( ) = ImClamp( camera.fieldOfView( ) + delta , 1.f , 179.f );
		camera.cvtFov2Np( );
	} else {
		camera.distance( ) = std::max( .01f , camera.distance( ) - delta );
		camera.cvtAnglesToVectors( );
	}
}

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

T_CameraChanges CameraUI( T_Camera& camera ) noexcept
{
	using namespace ImGui;

	// What gets changed
	static const T_CameraChanges changeFlags[] = {
		E_CameraChange::MATRIX ,
		{} ,
		E_CameraChange::MATRIX ,
		E_CameraChange::MATRIX ,
		{} ,
		E_CameraChange::MATRIX ,
		E_CameraChange::MATRIX ,
		{} ,
		E_CameraChange::FOV ,
		E_CameraChange::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( IM_ARRAYSIZE( changeFlags ) == IM_ARRAYSIZE( changeCalls ) ,
			"invalid configuration" );

	// Changes (also draws the fields)
	const bool changed[] = {
		DragFloat3( "Target" , &camera.lookAt( ).x ) ,
		( Separator( ) , false ) ,
		DragFloat( "Distance" , &camera.distance( ) , .1f , .1f , 1e8 , "%.1f" ) ,
		DragFloat3( "Angles" , &camera.angles( ).x , .01f , -180 , 180 ) ,
		( Separator( ) , false ) ,
		DragFloat3( "Position" , &camera.position( ).x ) ,
		DragFloat3( "Up vector" , &camera.upVector( ).x ) ,
		( Separator( ) , false ) ,
		DragFloat( "FoV" , &camera.fieldOfView( ) , .01f , .01f , 179.9f ) ,
		DragFloat( "Near plane" , &camera.nearPlane( ) , .00001f , .001f , 1e6f ) ,
	};

	static_assert( IM_ARRAYSIZE( changeFlags ) == IM_ARRAYSIZE( changed ) ,
			"invalid configuration" );

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