-- LUA Script - precede every function and global member with lowercase name of script + '_main'
local U = require "scriptbank\\utillib"
local P = require "scriptbank\\physlib"

local hingeChain = {}
local linkSpacing = { w = 0.0, h = -1.2, l = 0.0 }
local endSpacing  = { w = 0.0, h = -1.0, l = 0.0 }

local topConstraint = 0
local lastLink      = nil
local dropChain     = false
local breakable     = true

function hinge_chain_alternating_init_name( e, name )
	
	hingeChain[ e ] = { name = name, linkUsed = false }
	
	if name == "ChainStart" then
	    topConstraint = P.AddEntitySingleHinge( e, "TopCentreW" )
	end
end

local function buildChain( chainHead )
	for k, v in pairs( hingeChain ) do
		if not v.linkUsed and v.name == "ChainLink" then
			P.AddEntityDoubleHinge( chainHead, k, 
			                        "BottomCentreW", 
									"TopCentreL", 
									linkSpacing, 1 )
			hingeChain[ k ].linkUsed = true
			lastLink = k
			buildChain( k )
			break
		end
	end
end

local function addEndEntity( e )
	P.AddEntityDoubleHinge( lastLink, e, "BottomCentreW", "TopCentreW", endSpacing, 1 )
	P.SetObjectDamping( lastLink, 0.5, 0.5 )
end

local timer1, timer2 = math.huge, math.huge
local chainMade = false

function hinge_chain_alternating_main( e )

	local hc = hingeChain[ e ]

	if chainMade then
		if hc ~= nil then
			if lastLink ~= nil and hc.name == "ChainEnd"  then
				addEndEntity( e )
				lastLink = nil
				return
			end
		end
		
		if dropChain and hc.name == "ChainStart" then
			if timer2 == math.huge then
				timer2 = g_Time + 10000
			end
		
			if g_Time > timer2 then
				RemoveConstraint( topConstraint )
				hingeChain[ e ] = nil
			end
		end
		
		if breakable and hc.name == "ChainLink" then 
			P.RemoveEntityConstraintsIfDead( e )
		end
		
		return
	end
	
	if hc ~= nil and hc.name == "ChainStart" then

		if g_Time > timer1 then
			hc.linkUsed = true
			buildChain( e )
			
			chainMade = true
			
		elseif timer1 == math.huge then
			-- allow time for all entities to be initialised
			timer1 = g_Time + 100  -- 1/10 second should be enough
		end
	end
end