Mô đun:Random

-- This module contains a number of functions that make use of random numbers.

local cfg = {}

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-- Configuration
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-- Set this to true if your wiki has a traffic rate of less than one edit every two minutes or so.
-- This will prevent the same "random" number being generated many times in a row until a new edit is made
-- to the wiki. This setting is only relevant if the |same= parameter is set.
cfg.lowTraffic = false

-- If cfg.lowTraffic is set to true, and the |same= parameter is set, this value is used for the refresh rate of the random seed.
-- This is the number of seconds until the seed is changed. Getting this right is tricky. If you set it too high, the same number
-- will be returned many times in a row. If you set it too low, you may get different random numbers appearing on the same page,
-- particularly for pages that take many seconds to process.
cfg.seedRefreshRate = 60

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-- End configuration
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local p = {} -- For functions available from other Lua modules.
local l = {} -- For functions not available from other Lua modules, but that need to be accessed using table keys.

local yesno = require('Mô đun:Yesno')
local makeList = require('Mô đun:List').makeList

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-- Helper functions
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local function raiseError(msg)
	-- This helps to generate a wikitext error. It is the calling function's responsibility as to how to include it in the output.
	return mw.ustring.format('<b class="error">Lỗi [[Mô đun:Random]]: %s.</b>', msg)
end

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-- random number function
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local function getBigRandom(l, u)
	-- Gets a random integer between l and u, and is not limited to RAND_MAX.
	local r = 0
	local n = 2^math.random(30) -- Any power of 2.
	local limit = math.ceil(53 / (math.log(n) / math.log(2)))
	for i = 1, limit do
		r = r + math.random(0, n - 1) / (n^i)
	end
	return math.floor(r * (u - l + 1)) + l
end

function l.number(args)
	-- Gets a random number.
	first = tonumber(args[1])
	second = tonumber(args[2])
	-- This needs to use if statements as math.random won't accept explicit nil values as arguments.
	if first then
		if second then
			if first > second then -- Second number cannot be less than the first, or it causes an error.
				first, second = second, first
			end
			return getBigRandom(first, second)
		else
			return getBigRandom(1, first)
		end
	else
		return math.random()
	end
end

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-- Date function
--------------------------------------------------------------------------------------

function l.date(args)
	-- This function gets random dates, and takes timestamps as positional arguments.
	-- With no arguments specified, it outputs a random date in the current year.
	-- With two arguments specified, it outputs a random date between the timestamps.
	-- With one argument specified, the date is a random date between the unix epoch (1 Jan 1970) and the timestamp.
	-- The output can be formatted using the "format" argument, which works in the same way as the #time parser function.
	-- The default format is the standard Wikipedia timestamp.
	local lang = mw.language.getContentLanguage()

	local function getDate(format, ts)
		local success, date = pcall(lang.formatDate, lang, format, ts)
		if success then
			return date
		end
	end

	local function getUnixTimestamp(ts)
		local unixts = getDate('U', ts)
		if unixts then
			return tonumber(unixts)
		end
	end

	local t1 = args[1]
	local t2 = args[2]
	
	-- Find the start timestamp and the end timestamp.
	local startTimestamp, endTimestamp
	if not t1 then
		-- Find the first and last second in the current year.
		local currentYear = tonumber(getDate('Y'))
		local currentYearStartUnix = tonumber(getUnixTimestamp('1 Jan ' .. tostring(currentYear)))
		local currentYearEndUnix = tonumber(getUnixTimestamp('1 Jan ' .. tostring(currentYear + 1))) - 1
		startTimestamp = '@' .. tostring(currentYearStartUnix) -- @ is used to denote Unix timestamps with lang:formatDate.
		endTimestamp = '@' .. tostring(currentYearEndUnix)
	elseif t1 and not t2 then
		startTimestamp = '@0' -- the Unix epoch, 1 January 1970
		endTimestamp = t1
	elseif t1 and t2 then
		startTimestamp = t1
		endTimestamp = t2
	end

	-- Get Unix timestamps and return errors for bad input (or for bugs in the underlying PHP library, of which there are unfortunately a few)
	local startTimestampUnix = getUnixTimestamp(startTimestamp)
	local endTimestampUnix = getUnixTimestamp(endTimestamp)
	if not startTimestampUnix then
		return raiseError('"' .. tostring(startTimestamp) .. '" không được công nhận là dấu thời gian hợp lệ')
	elseif not endTimestampUnix then
		return raiseError('"' .. tostring(endTimestamp) .. '" không được công nhận là dấu thời gian hợp lệ')
	elseif startTimestampUnix > endTimestampUnix then
		return raiseError('ngày bắt đầu phải không được muộn hơn ngày kết thúc (ngày bắt đầu: "' .. startTimestamp .. '", ngày kết thúc: "' .. endTimestamp .. '")')
	end

	-- Get a random number between the two Unix timestamps and return it using the specified format.
	local randomTimestamp = getBigRandom(startTimestampUnix, endTimestampUnix)
	local dateFormat = args.format or 'H:i, "ngày" d F "năm" Y (T)'
	local result = getDate(dateFormat, '@' .. tostring(randomTimestamp))
	if result then
		return result
	else
		return raiseError('"' .. dateFormat .. '" không phải là một định dạng ngày hợp lệ')
	end
end

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-- List functions
--------------------------------------------------------------------------------------

local function randomizeArray(t, limit)
	-- Randomizes an array. It works by iterating through the list backwards, each time swapping the entry
	-- "i" with a random entry. Courtesy of Xinhuan at http://forums.wowace.com/showthread.php?p=279756
	-- If the limit parameter is set, the array is shortened to that many elements after being randomized.
	-- The lowest possible value is 0, and the highest possible is the length of the array.
	local len = #t
	for i = len, 2, -1 do
		local r = math.random(i)
		t[i], t[r] = t[r], t[i]
	end
	if limit and limit < len then
		local ret = {}
		for i, v in ipairs(t) do
			if i > limit then
				break
			end
			ret[i] = v
		end
		return ret
	else
		return t
	end
end

local function removeBlanks(t)
	-- Removes blank entries from an array so that it can be used with ipairs.
	local ret = {}
	for k, v in pairs(t) do
		if type(k) == 'number' then
			table.insert(ret, k)
		end
	end
	table.sort(ret)
	for i, v in ipairs(ret) do
		ret[i] = t[v]
	end
	return ret
end

local function makeSeparator(sep)
	if sep == 'space' then
		-- Include an easy way to use spaces as separators.
		return ' '
	elseif sep == 'newline' then
		-- Ditto for newlines
		return '\n'
	elseif type(sep) == 'string' then
		-- If the separator is a recognised MediaWiki separator, use that. Otherwise use the value of sep if it is a string.
		local mwseparators = {'dot', 'pipe', 'comma', 'tpt-languages'}
		for _, mwsep in ipairs(mwseparators) do
			if sep == mwsep then
				return mw.message.new( sep .. '-separator' ):plain()
			end
		end
		return sep
	end
end

local function makeRandomList(args)
	local list = removeBlanks(args)
	list = randomizeArray(list, tonumber(args.limit))
	return list
end

function l.item(args)
	-- Returns a random item from a numbered list.
	local list = removeBlanks(args)
	local len = #list
	if len >= 1 then
		return list[math.random(len)]
	end
end

function l.list(args)
	-- Randomizes a list and concatenates the result with a separator.
	local list = makeRandomList(args)
	local sep = makeSeparator(args.sep or args.separator)
	return table.concat(list, sep)
end

function l.text_list(args)
	-- Randomizes a list and concatenates the result, text-style. Accepts separator and conjunction arguments.
	local list = makeRandomList(args)
	local sep = makeSeparator(args.sep or args.separator)
	local conj = makeSeparator(args.conj or args.conjunction)
	return mw.text.listToText(list, sep, conj)
end

function l.array(args)
	-- Returns a Lua array, randomized. For use from other Lua modules.
	return randomizeArray(args.t, args.limit)
end

--------------------------------------------------------------------------------------
-- HTML list function
--------------------------------------------------------------------------------------

function l.html_list(args, listType)
	-- Randomizes a list and turns it into an HTML list. Uses [[Mô đun:List]].
	listType = listType or 'bulleted'
	local listArgs = makeRandomList(args) -- Arguments for [[Mô đun:List]].
	for k, v in pairs(args) do
		if type(k) == 'string' then
			listArgs[k] = v
		end
	end
	return makeList(listType, listArgs)
end

--------------------------------------------------------------------------------------
-- The main function. Called from other Lua modules.
--------------------------------------------------------------------------------------

function p.main(funcName, args, listType)
	-- Sets the seed for the random number generator and passes control over to the other functions.
	local same = yesno(args.same)
	if not same then
		-- Generates a different number every time the module is called, even from the same page.
		-- This is because of the variability of os.clock (the time in seconds that the Lua script has been running for).
		math.randomseed(mw.site.stats.edits + mw.site.stats.pages + os.time() + math.floor(os.clock() * 1000000000))
	else
		if not cfg.lowTraffic then
			-- Make the seed as random as possible without using anything time-based. This means that the same random number
			-- will be generated for the same input from the same page - necessary behaviour for some wikicode templates that
			-- assume bad pseudo-random-number generation.
			local stats = mw.site.stats
			local views = stats.views or 0 -- This is not always available, so we need a backup.
			local seed = views + stats.pages + stats.articles + stats.files + stats.edits + stats.users + stats.activeUsers + stats.admins -- Make this as random as possible without using os.time() or os.clock()
			math.randomseed(seed)
		else
			-- Make the random seed change every n seconds, where n is set by cfg.seedRefreshRate.
			-- This is useful for low-traffic wikis where new edits may not happen very often.
			math.randomseed(math.floor(os.time() / cfg.seedRefreshRate))
		end
	end
	if type(args) ~= 'table' then
		error('đối số thứ hai với p.main phải là một bảng')
	end
	return l[funcName](args, listType)
end
	
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-- Process arguments from #invoke
--------------------------------------------------------------------------------------

local function makeWrapper(funcName, listType)
	-- This function provides a wrapper for argument-processing from #invoke.
	-- listType is only used with p.html_list, and is nil the rest of the time.
	return function (frame)
		-- If called via #invoke, use the args passed into the invoking template, or the args passed to #invoke if any exist.
		-- Otherwise assume args are being passed directly in from the debug console or from another Lua module.
		local origArgs
		if frame == mw.getCurrentFrame() then
			origArgs = frame:getParent().args
			for k, v in pairs(frame.args) do
				origArgs = frame.args
				break
			end
		else
			origArgs = frame
		end
		-- Trim whitespace and remove blank arguments.
		local args = {}
		for k, v in pairs(origArgs) do
			if type(v) == 'string' then
				v = mw.text.trim(v)
			end
			if v ~= '' then
				args[k] = v
			end
		end
		return p.main(funcName, args, listType)
	end
end

-- Process arguments for HTML list functions.
local htmlListFuncs = {
	bulleted_list           = 'bulleted',
	unbulleted_list         = 'unbulleted',
	horizontal_list         = 'horizontal',
	ordered_list            = 'ordered',
	horizontal_ordered_list = 'horizontal_ordered'
}
for funcName, listType in pairs(htmlListFuncs) do
	p[funcName] = makeWrapper('html_list', listType)
end

-- Process arguments for other functions.
local otherFuncs = {'number', 'date', 'item', 'list', 'text_list'}
for _, funcName in ipairs(otherFuncs) do
	p[funcName] = makeWrapper(funcName)
end

return p