local U = require "scriptbank\\utillib"
local Q = require "scriptbank\\quatlib"

local lights = {}

attachLightToMe = attachLightToMe or {}

local rad = math.rad

function light_npc_init( e )
	Include( "utillib.lua" )
	Include( "quatlib.lua" )
	
	lights[ e ] = { 
					lightNum = GetEntityLightNumber( e ),
					attachTo = nil
				  }
end

local function sqrd( x1, z1, x2, z2 )
	return  ( x1 - x2 )^2 + ( z1 - z2 )^2
end

local function getOffset( p1, q1, p2, q2 )
	local cq = Q.Conjugate( q1 )
	local xa, ya, za = Q.ToEuler( cq )
	local xo, yo, zo = U.Rotate3D( p2.x - p1.x, p2.y - p1.y, p2.z - p1.z, xa, ya, za )
	
	return { xo = xo, yo = yo, zo = zo}, Q.Mul( cq, q2 )
end

function light_npc_main( e )
	local light = lights[ e ]
	
	if light == nil then return end
	
	if light.attachTo == nil then 
		local x1, y1, z1 = GetLightPosition( light.lightNum )
		
		local dist1 = math.huge
		local closest = nil
		
		for _, v in pairs( attachLightToMe ) do
			if v ~= nil then
				local x2, y2, z2 = GetEntityPosAng( v )
				local dist2 = sqrd( x1, z1, x2, z2 )
				if dist2 < dist1 then 
					closest = v 
					dist1 = dist2
				end
			end
		end
		
		if closest == nil then
			light.attachTo = -1
			return 
		end

		attachLightToMe[ closest ] = nil
		light.attachTo = closest

 		--get the entity pos & angles values we are attaching too
		local ex, ey, ez, eax, eay, eaz = GetEntityPosAng( closest )
		--get our own (light) values 
		local lx, ly, lz, lax, lay, laz = GetEntityPosAng( e )
		
		-- convert euler angles to quats
		local eq, lq = Q.FromEuler( rad( eax ), rad( eay ), rad( eaz ) ),
		               Q.FromEuler( rad( lax ), rad( lay ), rad( laz ) )
		
		light.posOffs, light.angOff = getOffset( { x = eax, y = eay, z = eaz }, eq,
		                                         { x = lax, y = lay, z = laz }, lq )
		
	elseif 
	   light.attachTo ~= -1 then 
		--this part is run during the update
		
		--get the new values for our attached entity
		local x, y, z, Ax, Ay, Az = GetEntityPosAng( light.attachTo )
		
		Ax, Ay, Az = rad( Ax ), rad( Ay ), rad( Az )
		
		local quat = Q.FromEuler( Ax, Ay, Az )
		
		--place the light based on the new position + our offset
		local xo, yo, zo = U.Rotate3D( light.posOffs.xo, light.posOffs.yo, light.posOffs.zo, 
		                               Ax, Ay, Az )
		
		SetLightPosition ( light.lightNum, x + xo, y + yo, z + zo )
		
		--work out the light angle
		quat = Q.Mul( quat, light.angOff )
		
		-- !! Do any rotation here !! 
		
		Ax, Ay, Az = Q.ToEuler( quat )
		
		local xv, yv, zv = U.Rotate3D( 0, 0, 1, Ax, Ay, Az )
		
		SetLightAngle( light.lightNum, xv, yv, zv )
	end 
end