Editing Module:Format link

--------------------------------------------------------------------------------
-- Format link
--
-- Makes a wikilink from the given link and display values. Links are escaped
-- with colons if necessary, and links to sections are detected and displayed
-- with " § " as a separator rather than the standard MediaWiki "#". Used in
-- the {{format link}} template.
--------------------------------------------------------------------------------
local libraryUtil = require('libraryUtil')
local checkType = libraryUtil.checkType
local checkTypeForNamedArg = libraryUtil.checkTypeForNamedArg
local mArguments -- lazily initialise [[Module:Arguments]]
local yesno -- lazily initialise [[Module:Yesno]]

local p = {}

--------------------------------------------------------------------------------
-- Helper functions
--------------------------------------------------------------------------------

local function getArgs(frame)
	-- Fetches the arguments from the parent frame. Whitespace is trimmed and
	-- blanks are removed.
	mArguments = require('Module:Arguments')
	return mArguments.getArgs(frame, {parentOnly = true})
end

local function removeInitialColon(s)
	-- Removes the initial colon from a string, if present.
	return s:match('^:?(.*)')
end

local function italicize(s)
	-- Italicize a string.
	return '<i>' .. s .. '</i>'
end

local function maybeItalicize(s, shouldItalicize)
	-- italicize s if s is a string and the shouldItalicize parameter is true.
	if s and shouldItalicize then
		return italicize(s)
	else
		return s
	end
end

local function parseLink(link)
	-- Parse a link and return a table with the link's components.
	-- These components are:
	-- - link: the link, stripped of any initial colon (always present)
	-- - page: the page name (always present)
	-- - section: the page name (may be nil)
	-- - display: the display text, if manually entered after a pipe (may be nil)
	link = removeInitialColon(link)

	-- Find whether a faux display value has been added with the {{!}} magic
	-- word.
	local prePipe, display = link:match('^(.-)|(.*)$')
	link = prePipe or link

	-- Find the page, if it exists.
	-- For links like [[#Bar]], the page will be nil.
	local preHash, postHash = link:match('^(.-)#(.*)$')
	local page
	if not preHash then
		-- We have a link like [[Foo]].
		page = link
	elseif preHash ~= '' then
		-- We have a link like [[Foo#Bar]].
		page = preHash
	end

	-- Find the section, if it exists.
	local section
	if postHash and postHash ~= '' then
		section = postHash
	end
	
	return {
		link = link,
		page = page,
		section = section,
		display = display,
	}
end

--------------------------------------------------------------------------------
-- Main functions
--------------------------------------------------------------------------------

function p.formatLink(frame)
	-- The formatLink export function, for use in templates.
	yesno = require('Module:Yesno')
	local args = getArgs(frame)
	local link = args[1]
	if not link then
		return p.makeWikitextError(
			'no link specified',
			'Template:Format link#Errors',
			args.category
		)
	end
	return p._formatLink{
		link = link,
		display = args[2],
		italicizePage = yesno(args.italicizepage),
		italicizeSection = yesno(args.italicizesection),
		categorizeMissing = args.categorizemissing
	}
end

function p._formatLink(options)
	-- The formatLink export function, for use in modules.
	checkType('_formatLink', 1, options, 'table')
	checkTypeForNamedArg('_formatLink', 'link', options.link, 'string', false)
	checkTypeForNamedArg(
		'_formatLink',
		'display',
		options.display,
		'string',
		true
	)
	checkTypeForNamedArg(
		'_formatLink',
		'italicizePage',
		options.italicizePage,
		'boolean',
		true
	)
	checkTypeForNamedArg(
		'_formatLink',
		'italicizeSection',
		options.italicizeSection,
		'boolean',
		true
	)
	checkTypeForNamedArg(
		'_formatLink',
		'categorizeMissing',
		options.categorizeMissing,
		'string',
		true
	)

	local parsed = parseLink(options.link)
	local display = options.display or parsed.display
	local catMissing = options.categorizeMissing
	local category = ''

	--Test if page exists if a diagnostic category is specified
	if catMissing and (mw.ustring.len(catMissing) > 0) then
		if not mw.title.new(parsed.page).exists then
			category = mw.ustring.format('[[Category:%s]]', catMissing)
		end
	end

	-- Deal with the case where we don't have to pipe the link
	if not display and not parsed.section and not options.italicizePage then
		return mw.ustring.format('[[:%s]]%s', parsed.link, category)
	end
	
	-- Find the display text for piped links
	if not display then
		local page = maybeItalicize(parsed.page, options.italicizePage)
		local section = maybeItalicize(parsed.section, options.italicizeSection)
		if not page then
			display = mw.ustring.format('§&nbsp;%s', section)
		elseif section then
			display = mw.ustring.format('%s §&nbsp;%s', page, section)
		else
			display = page
		end
	end
	
	return mw.ustring.format('[[:%s|%s]]%s', parsed.link, display, category)
end

--------------------------------------------------------------------------------
-- Derived convenience functions
--------------------------------------------------------------------------------

function p.formatPages(options, pages)
	-- Formats an array of pages using formatLink and the given options table,
	-- and returns it as an array. Nil values are not allowed.
	local ret = {}
	for i, page in ipairs(pages) do
		ret[i] = p._formatLink{
			link = page,
			categorizeMissing = options.categorizeMissing,
			italicizePage = options.italicizePage,
			italicizeSection = options.italicizeSection
		}
	end
	return ret
end

return p