मोड्युल:Highest archive number

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This module finds the highest archive number for a given set of numbered archive pages. The only input required is the prefix of the archive set. For example, for Talk:France/Archive 1, Talk:France/Archive 2, etc., the prefix would be "Talk:France/Archive ".

The module uses a binary search algorithm, so it will make relatively few expensive function calls even for large numbers of archives. (The expensive function call is necessary to determine whether an individual archive exists.) For 1-10 archive pages, the module typically uses 4-6 expensive function calls; for 20-100 archives, it uses 6-12 calls; and for hundreds of archives, it uses 12-20 calls. Because the module uses a binary search, a prerequisite of its use is that all archive pages below the highest number exist; if there are any red-linked pages below the highest number, then the module may return the number of any archive page that exists where the following archive page does not exist.

Usage

From wikitext

From wikitext this module is usually used via the {{highest archive number}} template. However, it is also possible to use it directly from invoke with the syntax {{#invoke:highest archive number|main|prefix}}.

From Lua

Load the module with the following code:

local mHAN = require('Module:Highest archive number')

You can then use it like this:

mHAN._main(prefix)

The prefix variable is the prefix of the archive set.

Examples

#invoke code	Lua code	Result
{{#invoke:highest archive number|main|Wikipedia:Administrators' noticeboard/IncidentArchive}}	mHAN._main("Wikipedia:Administrators' noticeboard/IncidentArchive")
{{#invoke:highest archive number|main|Talk:Byzantine Empire/Archive }}	mHAN._main("Talk:Byzantine Empire/Archive ")

-- This module finds the highest existing archive number for a set of talk
-- archive pages.

local p = {}

local function pageExists(page)
	local success, exists = pcall(function()
		return mw.title.new(page).exists
	end)
	return success and exists
end

local function midPoint(lower, upper)
	return math.floor(lower + (upper - lower) / 2)
end

local function findHighestArchive(prefix, i, lower, upper)
	if i < 1 then
		return nil
	elseif pageExists(prefix .. tostring(i)) then
		lower = i
		if upper and i + 1 == upper then
			return i
		elseif upper then
			i = midPoint(lower, upper)
		else
			i = i * 2
		end
		return findHighestArchive(prefix, i, lower, upper)
	else
		upper = i
		lower = lower or 0
		i = midPoint(lower, upper)
		return findHighestArchive(prefix, i, lower, upper)
	end
end

function p._main(prefix)
	if type(prefix) ~= 'string' or not prefix:find('%S') then
		error('no prefix supplied to [[Module:Highest archive number]]', 2)
	end
	return findHighestArchive(prefix, 10)
end

function p.main(frame)
	local args = require('Module:Arguments').getArgs(frame, {
		trim = false,
		removeBlanks = false,
		wrappers = 'Template:Highest archive number'
	})
	local prefix = args[1]
	return p._main(prefix)
end

return p