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-- 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 = 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

-- 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:Lista').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)

-- 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)
    return math.floor(r * (u - l + 1)) + l

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
            return getBigRandom(first, second)
            return getBigRandom(1, first)
        return math.random()

-- 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

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

    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

    -- 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 .. '")')

    -- 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
        return raiseError('"' .. dateFormat .. '" is not a valid date format')

-- 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]
    if limit and limit < len then
        local ret = {}
        for i, v in ipairs(t) do
            if i > limit then
            ret[i] = v
        return ret
        return t

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)
    for i, v in ipairs(ret) do
        ret[i] = t[v]
    return ret

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()
        return sep

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

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)]

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)

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)

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

-- 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
    return makeList(listType, listArgs)

-- 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))
        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()
            -- 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))
    if type(args) ~= 'table' then
        error('the second argument to p.main must be a table')
    return l[funcName](args, listType)
-- 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
            origArgs = frame
        -- 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)
            if v ~= '' then
                args[k] = v
        return p.main(funcName, args, listType)

-- 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)

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

return p