--[[
Copyright (c) 2014, Robert 'Bobby' Zenz
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--- An implementation of the Fisher-Yates algorithm, which allows to access
-- an array in a random or pseudo-random order.
fisheryates = {}


--- Runs the Fisher-Yates algorithm on the given data.
--
-- The given action method is invoked on each item, which means that the action
-- method gets items in random order.
--
-- @param data The array on which to operate.
-- @param min The minimum index of the array (inclusive).
-- @param max The maximum index of the array (inclusive).
-- @param random The method that returns random numbers, assumed to accept two
--               parameters, a minimum and maximum value. Can also be a table
--               with an instance method like the one descriped above.
-- @param action The action to perform on each item. Assumed to accept two
--               parameters, the item and the current index.
function fisheryates.run(data, min, max, random, action)
	local random_is_object = type(random) == "userdata"
	
	for index = min, max, 1 do
		local swap_index = nil
		
		if random_is_object then
			swap_index = random:next(0, 32767)
		else
			swap_index = random(0, 32767)
		end
		
		swap_index = transform.linear(swap_index, 0, 32767, index, max)
		swap_index = mathutil.round(swap_index)
		
		local swap_value = data[swap_index]
		
		data[swap_index] = data[index]
		data[index] = swap_value
		
		action(data[index], index)
	end
end