local posix = require 'posix'

_G.core = {}
_G.dump = dump
dofile("../../../tests/lib/misc_helpers.lua")
local mod_paths = {
	vl_scheduler = "./",
}

local on_mods_loaded
local globalsteps = 0
local last_fake_globalstep_dtime
local time_offset = 0

local function fastforward(amount)
	time_offset = time_offset + amount
end

local function init_core()
	return {
		registered_globalsteps = {
			function(dtime)
				globalsteps = globalsteps + 1
				last_fake_globalstep_dtime = dtime
			end,
		},
		get_current_modname = function() return "vl_scheduler" end,
		get_modpath = function(modname) return mod_paths[modname] end,
		register_on_mods_loaded = function(func) on_mods_loaded = func end,
		get_us_time = function()
			local sec, nsec = posix.clock_gettime(0)
			return sec * 1e6 + nsec // 1000 + time_offset
		end,
	}
end

local function call_globalstep(dtime)
	local callbacks = _G.core.registered_globalsteps
	for i =1,#callbacks do
		callbacks[i](0.0532432)
	end
end

describe('vl_scheduler',function()
	-- Setup a mock environment like Luanti has
	local core_mock = init_core()
	_G.minetest = core_mock
	_G.core = core_mock
	_G.bit = require('bitop.funcs')
	_G.loadstring = loadstring or load
	_G.unpack = table.unpack
	_G.dump = dump
	_G.math.round = function(x) return math.floor(x + 0.5) end

	it('loads',function()
		local vl_scheduler = dofile("./init.lua")
	end)
	it('intercepts the globalstep handlers',function()
		on_mods_loaded()
		call_globalstep(0.0532432)
		assert.is_same(last_fake_globalstep_dtime, 0.0532432)
	end)
	it('schedules tasks',function()
		local called = false
		_G.core.after(0,function()
			called = true
		end)
		call_globalstep(0.05)
		assert.is_same(true, called)
	end)
	it('schedules 44 correctly',function()
		local after = _G.core.after
		local failed = false

		for i=40,50 do
			after((i-1)*0.05, function(expected_timestep)
				if expected_timestep ~= globalsteps then
					failed = true
					print("expected="..expected_timestep..",actual="..globalsteps)
				end
			end, i)
		end
		--_G.vl_scheduler.print_debug_dump()
		globalsteps = 0
		for i=1,3005 do
			call_globalstep(0.05)
		end
		assert.is_same(false, failed)
	end)
	it('schedules tasks correctly',function()
		local after = _G.core.after
		local failed = false

		for i = 5,3000,1 do
			after((i-1)*0.05, function(expected_timestep)
				if expected_timestep ~= globalsteps then
					failed = true
					print("expected="..expected_timestep..",actual="..globalsteps)
				end
			end, i)
		end
		globalsteps = 0
		for i=1,3005 do
			call_globalstep(0.05)
		end
		assert.is_same(false, failed)
	end)
	it('can schedule multiple tasks for the same timestep',function()
		local after = _G.core.after
		local num_run = 0
		local vl_scheduler = _G.vl_scheduler

		for i=1,10 do
			after(1, function()
				num_run = num_run + 1
			end)
		end
		for i=1,10 do
			after(5/0.05, function()
				num_run = num_run + 1
			end,10+i)
		end

		globalsteps = 0
		for i=1,2000 do
			call_globalstep(0.05)
		end
		call_globalstep(0.05)
		assert.is_same(20, num_run)
	end)
	it('will not run background tasks if over budget with priority = 3',function()
		local num_run = 0
		local vl_scheduler = _G.vl_scheduler
		vl_scheduler.after(0, 2, function()
			fastforward(40000)
		end)
		for i = 1,50 do
			vl_scheduler.after(0, 3, function()
				fastforward(1000)
				num_run = num_run + 1
			end)
		end
		call_globalstep(0.05)
		assert.is_same(10, num_run)
		while(num_run < 50) do
			call_globalstep(0.05)
		end
	end)
	it('will not run background tasks if over budget with priority = 4',function()
		local num_run = 0
		local vl_scheduler = _G.vl_scheduler
		vl_scheduler.after(0, 2, function()
			fastforward(40000)
		end)
		for i = 1,50 do
			vl_scheduler.after(0, 4, function()
				fastforward(1000)
				num_run = num_run + 1
			end)
		end
		call_globalstep(0.05)
		assert.is_same(10, num_run)
		while(num_run < 50) do
			call_globalstep(0.05)
		end
	end)
	it('will not run background tasks if over budget with mixed priority',function()
		local num_3_run = 0
		local num_4_run = 0
		local vl_scheduler = _G.vl_scheduler
		vl_scheduler.after(0, 2, function()
			fastforward(40000)
		end)
		for i = 1,10 do
			vl_scheduler.after(0, 3, function()
				fastforward(500)
				num_3_run = num_3_run + 1
			end)
		end
		for i = 1,20 do
			vl_scheduler.after(0, 4, function()
				fastforward(500)
				num_4_run = num_4_run + 1
			end)
		end
		call_globalstep(0.05)
		assert.is_same(10, num_3_run)
		assert.is_same(10, num_4_run)
		while(num_4_run < 20) do
			call_globalstep(0.05)
		end
	end)
	it('can schedule new tasks recursively and they run on the next timestep',function()
		local vl_scheduler = _G.vl_scheduler
		vl_scheduler.after(0, 2, function() end)
		vl_scheduler.after(0, 2, function()
			vl_scheduler.after(0, 2, function() end)
			vl_scheduler.after(0, 2, function() end)
		end)
		assert.no_error(function()
			call_globalstep(0.05)
		end)
	end)
	it('can provide cancellable jobs from core.after()',function()
		local after = _G.core.after
		local ran = false
		local job = after(1,function()
			ran = true
		end)
		call_globalstep(0.5)
		assert.no_error(function()
			job:cancel()
		end)
		for i = 1,10 do call_globalstep(0.5) end
		assert.is_false(ran)
	end)
end)