LÖVE

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-- TLECS v0.1b, an extensible Entity-Component System implementation in Lua
-- by Taehl (email.Taehl@gmail.com)

-- TODO: content pack system
	-- it'll have to be able to add/override nodes and systems
		-- when adding a node, also add components[node] = {}!

local TLECS = {}		-- namespace
TLECS.nodes = {}	-- nodes are prototypes for components, representing default state
TLECS.ents = {}		-- entities are numerical indices that link components
-- later, the ent itself may do more than isDead. Ideally, I'd like to be able to add tags to ents for better cross-content support
TLECS.components = {}	-- components are instanced per-ent, holding their state
-- each TLECS.components lists all ents possessing that component (much faster to iterate with rather than all ents!) (may possibly be replaced by the tag system?)
TLECS.systems = {}	-- systems are functions which iterate on components
TLECS.contents = {}	-- content populates nodes/components with data and systems with code

for node, v in pairs( TLECS.nodes ) do TLECS.components[node] = {} end


-- import contents into ECS
-- if fresh is true, all existing TLECS data will be replaced by ONLY contents (good when starting a new game)
-- otherwise, all content will be overlaid (best for adding new content, expanding others' content, etc.)
function TLECS.importContents( contents, fresh )
	contents = contents or TLECS.contents
	if fresh then
		TLECS.nodes = {}
		TLECS.ents = {}
		TLECS.components = {}
		TLECS.systems = {}
		for node, v in pairs( TLECS.nodes ) do TLECS.components[node] = {} end
	end
	for kind, adds in pairs( contents ) do
		for new, data in pairs( adds ) do
			TLECS[kind][new] = data
		end
	end
end


-- spawn an entity with given parameters
-- example: spawnEnt( { pos={ x=2, y=5 }, draw{ img=robot.png, scale= 2} } )
function TLECS.spawnEnt( comps )
	if not comps then error"Can't spawnEnt with no components!" end
	local ent = {}
	for component,data in pairs( comps ) do
		TLECS.addComponent( ent, component, data )
	end
	table.insert( TLECS.ents, {} )		-- ent, if ents are to list their components...
	return ent
end


--  adds a component to an existing object
--	returns the new component
function TLECS.addComponent( ent, component, data )
	if not (ent and component) then error"Can't addComponent without ent and component!" end
	-- instance the components from their nodes
	local comp = { parent = ent }
	for k,v in pairs( TLECS.nodes[component] ) do
		v = data[k] or v		-- if data was specified then add it, else use default
		comp[k] = v
	end
	ent[component] = comp
	table.insert( TLECS.components[component], comp )
	return comp
end


--	removes a component from an existing ent
--	returns true if it was removed, false if ent didn't have it
function TLECS.removeComponent( ent, component )
	if not (ent and component) then error"Can't removeComponent without ent and component!" end
	ent[component] = nil
	for k,v in TLECS.components do
		if v == ent then
			table.remove( TLECS.components[component], v )
			return true
		end
	end
end


-- systems execution and ent clean-up
function TLECS.update(dt)
	-- run each system on TLECS.ents with the requisite component
	for k,system in pairs( TLECS.systems ) do
		for k, comp in ipairs( TLECS.components[system.requires] or {} ) do
			system.run( comp, dt )		-- todo: support return values? (where would they be sent? callbacks?)
		end
	end	
	
	-- remove dead TLECS.ents
	for k = #TLECS.ents,1, -1 do
		local ent = TLECS.ents[k]
		if ent.isDead then
			table.remove(TLECS.ents, k)
			-- remove ent from all components' lists
			for component, entlist in pairs( TLECS.components ) do
				for k, v in pairs( entlist ) do
					if v == ent then
						table.remove( component, k )
						break
					end
				end
			end
		end
	end
end


return TLECS

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content = {
	nodes = {
		-- engine nodes
		draw = { img = whatever, m=0, color={255,255,255} },
		pos = { x=0, y=0, },
		move = { vx=0, vy=0, g=.98, airf=.001, groundf=2.99, },
		
		-- character nodes
		stats = { topSpeed=200, accel=50, },
		state = { is = "standing", running = false, dreaming = true },
		
		-- level nodes
		wall = { x1=0, y1=0, x2=0, y2=0 }
	}

	systems = {
		draw = {
			requires = nil,	-- don't run in TLECS.update(), since we'd probably want this in love.draw()
			run = function( draw )
				local ent = draw.parent
				local lg = love.graphics
				if not ( ent.draw and ent.pos ) then return end
				
				if ent.move then draw.m = math.sign( ent.move.vx ) end	-- if it moves left, flip it
				lg.setColor( draw.color )
				lg.draw( draw.img, ent.pos.x, ent.pos.y, 0, 1*draw.m, 1, 16, 16 )
			end
		},
		
		lamePhysics = {
			requires = "move",
			run = function( move, dt )
				local ent = move.parent
				local pos = ent.pos
				pos.x, pos.y = pos.x + move.vx*dt, pos.y + (move.vy + move.g)*dt 
			end
		},
	}
}

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function myModule:enter()
  local world = Game:getModule("PublicWorld")
  world:add(self:new(100, 100)) -- adds your module as an entity to another module
end

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      turret = Game:getModule("turret")
      hit = turret:hit(self.x, self.y, self.radius)