local table_remove = table.remove
local unpack = unpack

local function table_keys(t, is_array)
	local a = {}
	if is_array then
		for i = 1, #t do
			a[i] = i
		end
	else
		for k,v in pairs(t) do
			a[#a+1] = k
		end
	end
	return a
end

-- Queue to span processing on each game tick
-- Arguments:
--	  queue_name - name of queue
--    queue_table - table to process
--    func - function for processing, must have at least first 3 arguments: key of queue_table, value by that key, the number of key in processing order
--	  returning true will remove element from queue, returning false or nil will leave it in queue for next process cycle
--	  on_end_func - function at the end of queue processing, you can use this for chaining queue processing one after another
--	  step - amount of items in queue to process at a time
--    ... - additional arguments for "func"
-- active_queues table contains names of queues that are active.

-- Example usage, get an object by id one at a time per game update
--[[

local ids = {1, 2, 3, 4, 5, 6, 7, 8}
process_queue("my_queue", ids, function(k, id, i)
		local obj = level.object_by_id(id)
		if obj then
			printf("object %s, section %s, time_global %s", id, obj:section(), time_global())
		end
		return true
	end, function()
		printf("queue processed, final time %s", time_global())
	end
)

]]

active_queues = {}
function process_queue(queue_name, queue_table, func, on_end_func, step, ...)
	-- queue_table must be a table
	if not queue_table or type(queue_table) ~= "table" then
		printf("%s is not table, abort", queue_table)
		return
	end

	if active_queues[queue_name] then
		printf("queue %s is already active, abort", queue_name)
		return
	end

	-- Collect table keys and initialize the table index
	local i = 1
	local keys = table_keys(queue_table)
	local step = clamp(step or 1, 1, #keys)

	local args = {...}
	local update_func
	update_func = function()
		for s = 1, step do
			local j = keys[i]
			if func(j, queue_table[j], i, unpack(args)) == true then
				queue_table[j] = nil
				table_remove(keys, i)
				i = i - 1
				step = clamp(step, 1, #keys)
			end
			if not keys[1] then
				if on_end_func then on_end_func() end
				UnregisterScriptCallback("actor_on_update", update_func)
				active_queues[queue_name] = nil
				return
			end
			i = i == #keys and 1 or i + 1
		end
	end
	active_queues[queue_name] = {
		queue_table = queue_table,
		func = update_func,
		on_end_func = on_end_func,
		step = step,
	}
	RegisterScriptCallback("actor_on_update", update_func)
end

function remove_queue(queue_name, on_end)
	if active_queues[queue_name] then
		if on_end and active_queues[queue_name].on_end_func then
			active_queues[queue_name].on_end_func()
		end
		UnregisterScriptCallback("actor_on_update", active_queues[queue_name].func)
		active_queues[queue_name] = nil
	end
end