require "engine.class"
local Map = require "engine.Map"
require "engine.Generator"

--- Tower Defence creep spawner
module(..., package.seeall, class.inherit(engine.Generator))

function _M:init(zone, map, level, spots)
	engine.Generator.init(self, zone, map, level, spots)
	self.data = level.data.generator.actor

	self.rate = self.data.rate

	self.turn_scale = game.energy_per_tick / game.energy_to_act
end

function _M:generate()
	self.max_rate = self.data.max_rate or #level.spawnsource
	self.count = 0
end

function _M:factorial(n)
	if n == 0 then
		return 1
	else
		return n * factorial(n - 1)
	end
end

function _P:poissonProcess(k)
	return math.exp(-self.rate*self.turn_scale)*((self.rate*self.turn_scale)^k)/self:factorial(k)
end

function _M:tick()
	local val = rng.float(0,1)
	for i = 0,self.max_rate - 1 do
		if self:poissonProcess(k) < val then
			self:generateOne()
		else
			break
		end
	end
end

function _M:generateOne()
	local f = nil
	if self.filters then f = self.filters[rng.range(1, #self.filters)] end
	local m = self.zone:makeEntity(self.level, "actor", f)
	if m then
		local pos = rng.table(self.level.spawnsource)
		local x = pos.x
		local y = pos.y
		local tries = 0
		while (not m:canMove(x, y)) and tries < 100 do
			pos = rng.table(self.level.spawnsource)
			x = pos.x
			y = pos.y
			tries = tries + 1
		end
		if tries < 100 then
			self.zone:addEntity(self.level, m, "actor", x, y)
			if self.post_generation then self.post_generation(m) end
		end
	end
end