--- Callback system
-- Allow to call callbacks defined in other systems in entity methods.
-- Example:
-- entity.callback:onMove(...) -- call onAdd(system, entitySystemTable, ...) on every system the entity belong to (which has this callback)
-- Can be also used for onAdd, etc.

--- Recursively get a list of systems with a certain method.
let recGetSystemsWithMethod = (method, systems, l={})
	for _, s in ipairs(systems) do
		if s[method] then
			table.insert(l, s)
		end
		recGetSystemsWithMethod(method, s.systems, l)
	end
	return l
end

return {
	name = "callback",
	filter = true,
	methods = {
		__index = :(c, k)
			let s = recGetSystemsWithMethod(k, {@world})
			@methods[k] = :(c, ...)
				let e = c.entity
				for _, sys in ipairs(s) do
					if sys._previous[e] then
						sys[k](sys, e[sys.name], ...)
					end
				end
			end
			return @_methods_mt[k]
		end
	}
}