Module:Random

*Documentation for this module may be created at Module:Random/doc*

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

local cfg = {}

## -- Configuration

-- 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 = true

-- 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 = 2

## -- End configuration

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('Module:Yesno')
local makeList = require('Module:List').makeList

## -- Helper functions

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">[[Module:Random]] error: %s.</b>', msg)
end

## -- random number function

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

## -- 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) .. '" was not recognised as a valid timestamp')
 elseif not endTimestampUnix then
 return raiseError('"' .. tostring(endTimestamp) .. '" was not recognised as a valid timestamp')
 elseif startTimestampUnix > endTimestampUnix then
 return raiseError('the start date must not be later than the end date (start date: "' .. startTimestamp .. '", end date: "' .. 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, d F Y (T)'
 local result = getDate(dateFormat, '@' .. tostring(randomTimestamp))
 if result then
 return result
 else
 return raiseError('"' .. dateFormat .. '" is not a valid date format')
 end
end

## -- 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 [[Module:List]].
 listType = listType or 'bulleted'
 local listArgs = makeRandomList(args) -- Arguments for [[Module: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('the second argument to p.main must be a table')
 end
 return l[funcName](args, listType)
end

## -- 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

```