Editing Module:Documentation

-- This module implements {{documentation}}.

-- Get required modules.
local getArgs = require('Module:Arguments').getArgs
local htmlBuilder = require('Module:HtmlBuilder')
local messageBox = require('Module:Message box')

-- Get the config table.
local cfg = mw.loadData('Module:Documentation/config')

local p = {}

-- Often-used functions.
local ugsub = mw.ustring.gsub

----------------------------------------------------------------------------
-- Helper functions
--
-- These are defined as local functions, but are made available in the p
-- table for testing purposes.
----------------------------------------------------------------------------

local function message(cfgKey, valArray, expectType)
	--[[
	-- Gets a message from the cfg table and formats it if appropriate.
	-- The function raises an error if the value from the cfg table is not
	-- of the type expectType. The default type for expectType is 'string'.
	-- If the table valArray is present, strings such as $1, $2 etc. in the
	-- message are substituted with values from the table keys [1], [2] etc.
	-- For example, if the message "foo-message" had the value 'Foo $2 bar $1.',
	-- message('foo-message', {'baz', 'qux'}) would return "Foo qux bar baz."
	--]]
	local msg = cfg[cfgKey]
	expectType = expectType or 'string'
	if type(msg) ~= expectType then
		error('message: type error in message cfg.' .. cfgKey .. ' (' .. expectType .. ' expected, got ' .. type(msg) .. ')', 2)
	end
	if not valArray then
		return msg
	end

	local function getMessageVal(match)
		match = tonumber(match)
		return valArray[match] or error('message: no value found for key $' .. match .. ' in message cfg.' .. cfgKey, 4)
	end

	local ret = ugsub(msg, '$([1-9][0-9]*)', getMessageVal)
	return ret
end

p.message = message

local function makeWikilink(page, display)
	if display then
		return mw.ustring.format('[[%s|%s]]', page, display)
	else
		return mw.ustring.format('[[%s]]', page)
	end
end

p.makeWikilink = makeWikilink

local function makeCategoryLink(cat, sort)
	local catns = mw.site.namespaces[14].name
	return makeWikilink(catns .. ':' .. cat, sort)
end

p.makeCategoryLink = makeCategoryLink

local function makeUrlLink(url, display)
	return mw.ustring.format('[%s %s]', url, display)
end

p.makeUrlLink = makeUrlLink

local function makeToolbar(...)
	local ret = {}
	local lim = select('#', ...)
	if lim < 1 then
		return nil
	end
	for i = 1, lim do
		ret[#ret + 1] = select(i, ...)
	end
	return '<small style="font-style: normal;">(' .. table.concat(ret, ' &#124; ') .. ')</small>'
end	

p.makeToolbar = makeToolbar

----------------------------------------------------------------------------
-- Argument processing
----------------------------------------------------------------------------

local function makeInvokeFunc(funcName)
	return function (frame)
		local args = getArgs(frame, {
			valueFunc = function (key, value)
				if type(value) == 'string' then
					value = value:match('^%s*(.-)%s*$') -- Remove whitespace.
					if key == 'heading' or value ~= '' then
						return value
					else
						return nil
					end
				else
					return value
				end
			end
		})
		return p[funcName](args)
	end
end

----------------------------------------------------------------------------
-- Main function
----------------------------------------------------------------------------

p.main = makeInvokeFunc('_main')

function p._main(args)
	--[[
	-- This function defines logic flow for the module.
	-- @args - table of arguments passed by the user
	-- 
	-- Messages:
	-- 'main-div-id' --> 'template-documentation'
	-- 'main-div-classes' --> 'template-documentation iezoomfix'
	--]]
	local env = p.getEnvironment(args)
	local root = htmlBuilder.create()
	root
		.wikitext(p.protectionTemplate(env))
		.wikitext(p.sandboxNotice(args, env))
		 -- This div tag is from {{documentation/start box}}, but moving it here
		 -- so that we don't have to worry about unclosed tags.
		.tag('div')
			.attr('id', message('main-div-id'))
			.addClass(message('main-div-classes'))
			.newline()
			.wikitext(p._startBox(args, env))
			.wikitext(p._content(args, env))
			.tag('div')
				.css('clear', 'both') -- So right or left floating items don't stick out of the doc box.
				.newline()
				.done()
			.done()
		.wikitext(p._endBox(args, env))
		.newline()
		.wikitext(p.addTrackingCategories(env))
	return tostring(root)
end

----------------------------------------------------------------------------
-- Environment settings
----------------------------------------------------------------------------

function p.getEnvironment(args)
	--[[
	-- Returns a table with information about the environment, including title objects and other namespace- or
	-- path-related data.
	-- @args - table of arguments passed by the user
	--
	-- Title objects include:
	-- env.title - the page we are making documentation for (usually the current title)
	-- env.templateTitle - the template (or module, file, etc.)
	-- env.docTitle - the /doc subpage.
	-- env.sandboxTitle - the /sandbox subpage.
	-- env.testcasesTitle - the /testcases subpage.
	-- env.printTitle - the print version of the template, located at the /Print subpage.
	--
	-- Data includes:
	-- env.subjectSpace - the number of the title's subject namespace.
	-- env.docSpace - the number of the namespace the title puts its documentation in.
	-- env.docpageBase - the text of the base page of the /doc, /sandbox and /testcases pages, with namespace.
	-- env.compareUrl - URL of the Special:ComparePages page comparing the sandbox with the template.
	-- 
	-- All table lookups are passed through pcall so that errors are caught. If an error occurs, the value
	-- returned will be nil.
	--]]
	
	local env, envFuncs = {}, {}

	-- Set up the metatable. If triggered we call the corresponding function in the envFuncs table. The value
	-- returned by that function is memoized in the env table so that we don't call any of the functions
	-- more than once. (Nils won't be memoized.)
	setmetatable(env, {
		__index = function (t, key)
			local envFunc = envFuncs[key]
			if envFunc then
				local success, val = pcall(envFunc)
				if success then
					env[key] = val -- Memoise the value.
					return val
				end
			end
			return nil
		end
	})	

	function envFuncs.title()
		-- The title object for the current page, or a test page passed with args.page.
		local title
		local titleArg = args.page
		if titleArg then
			title = mw.title.new(titleArg)
		else
			title = mw.title.getCurrentTitle()
		end
		return title
	end

	function envFuncs.templateTitle()
		--[[
		-- The template (or module, etc.) title object.
		-- Messages:
		-- 'sandbox-subpage' --> 'sandbox'
		-- 'testcases-subpage' --> 'testcases'
		--]]
		local subjectSpace = env.subjectSpace
		local title = env.title
		local subpage = title.subpageText
		if subpage == message('sandbox-subpage') or subpage == message('testcases-subpage') then
			return mw.title.makeTitle(subjectSpace, title.baseText)
		else
			return mw.title.makeTitle(subjectSpace, title.text)
		end
	end

	function envFuncs.docTitle()
		--[[
		-- Title object of the /doc subpage.
		-- Messages:
		-- 'doc-subpage' --> 'doc'
		--]]
		local title = env.title
		local docname = args[1] -- User-specified doc page.
		local docpage
		if docname then
			docpage = docname
		else
			docpage = env.docpageBase .. '/' .. message('doc-subpage')
		end
		return mw.title.new(docpage)
	end
	
	function envFuncs.sandboxTitle()
		--[[
		-- Title object for the /sandbox subpage.
		-- Messages:
		-- 'sandbox-subpage' --> 'sandbox'
		--]]
		return mw.title.new(env.docpageBase .. '/' .. message('sandbox-subpage'))
	end
	
	function envFuncs.testcasesTitle()
		--[[
		-- Title object for the /testcases subpage.
		-- Messages:
		-- 'testcases-subpage' --> 'testcases'
		--]]
		return mw.title.new(env.docpageBase .. '/' .. message('testcases-subpage'))
	end
	
	function envFuncs.printTitle()
		--[[
		-- Title object for the /Print subpage.
		-- Messages:
		-- 'print-subpage' --> 'Print'
		--]]
		return env.templateTitle:subPageTitle(message('print-subpage'))
	end

	function envFuncs.subjectSpace()
		-- The subject namespace number.
		return mw.site.namespaces[env.title.namespace].subject.id
	end

	function envFuncs.docSpace()
		-- The documentation namespace number. For most namespaces this is the same as the
		-- subject namespace. However, pages in the Article, File, MediaWiki or Category
		-- namespaces must have their /doc, /sandbox and /testcases pages in talk space.
		local subjectSpace = env.subjectSpace
		if subjectSpace == 0 or subjectSpace == 6 or subjectSpace == 8 or subjectSpace == 14 then
			return subjectSpace + 1
		else
			return subjectSpace
		end
	end

	function envFuncs.docpageBase()
		-- The base page of the /doc, /sandbox, and /testcases subpages.
		-- For some namespaces this is the talk page, rather than the template page.
		local templateTitle = env.templateTitle
		local docSpace = env.docSpace
		local docSpaceText = mw.site.namespaces[docSpace].name
		-- Assemble the link. docSpace is never the main namespace, so we can hardcode the colon.
		return docSpaceText .. ':' .. templateTitle.text
	end
	
	function envFuncs.compareUrl()
		-- Diff link between the sandbox and the main template using [[Special:ComparePages]].
		local templateTitle = env.templateTitle
		local sandboxTitle = env.sandboxTitle
		if templateTitle.exists and sandboxTitle.exists then
			local compareUrl = mw.uri.fullUrl(
				'Special:ComparePages',
				{page1 = templateTitle.prefixedText, page2 = sandboxTitle.prefixedText}
			)
			return tostring(compareUrl)
		else
			return nil
		end
	end		

	return env
end	

----------------------------------------------------------------------------
-- Auxiliary templates
----------------------------------------------------------------------------

function p.sandboxNotice(args, env)
	--[=[
	-- Generates a sandbox notice for display above sandbox pages.
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	-- 
	-- Messages:
	-- 'sandbox-notice-image' --> '[[Image:Sandbox.png|50px|alt=|link=]]'
	-- 'sandbox-notice-blurb' --> 'This is the $1 for $2.'
	-- 'sandbox-notice-diff-blurb' --> 'This is the $1 for $2 ($3).'
	-- 'sandbox-notice-pagetype-template' --> '[[Wikipedia:Template test cases|template sandbox]] page'
	-- 'sandbox-notice-pagetype-module' --> '[[Wikipedia:Template test cases|module sandbox]] page'
	-- 'sandbox-notice-pagetype-other' --> 'sandbox page'
	-- 'sandbox-notice-compare-link-display' --> 'diff'
	-- 'sandbox-notice-testcases-blurb' --> 'See also the companion subpage for $1.'
	-- 'sandbox-notice-testcases-link-display' --> 'test cases'
	-- 'sandbox-category' --> 'Template sandboxes'
	--]=]
	local title = env.title
	local sandboxTitle = env.sandboxTitle
	local templateTitle = env.templateTitle
	local subjectSpace = env.subjectSpace
	if not (subjectSpace and title and sandboxTitle and templateTitle and mw.title.equals(title, sandboxTitle)) then
		return nil
	end
	-- Build the table of arguments to pass to {{ombox}}. We need just two fields, "image" and "text".
	local omargs = {}
	omargs.image = message('sandbox-notice-image')
	-- Get the text. We start with the opening blurb, which is something like
	-- "This is the template sandbox for [[Template:Foo]] (diff)."
	local text = ''
	local frame = mw.getCurrentFrame()
	local isPreviewing = frame:preprocess('{{REVISIONID}}') == '' -- True if the page is being previewed.
	local pagetype
	if subjectSpace == 10 then
		pagetype = message('sandbox-notice-pagetype-template')
	elseif subjectSpace == 828 then
		pagetype = message('sandbox-notice-pagetype-module')
	else
		pagetype = message('sandbox-notice-pagetype-other')
	end
	local templateLink = makeWikilink(templateTitle.prefixedText)
	local compareUrl = env.compareUrl
	if isPreviewing or not compareUrl then
		text = text .. message('sandbox-notice-blurb', {pagetype, templateLink})
	else
		local compareDisplay = message('sandbox-notice-compare-link-display')
		local compareLink = makeUrlLink(compareUrl, compareDisplay)
		text = text .. message('sandbox-notice-diff-blurb', {pagetype, templateLink, compareLink})
	end
	-- Get the test cases page blurb if the page exists. This is something like
	-- "See also the companion subpage for [[Template:Foo/testcases|test cases]]."
	local testcasesTitle = env.testcasesTitle
	if testcasesTitle and testcasesTitle.exists then
		local testcasesLinkDisplay = message('sandbox-notice-testcases-link-display')
		local testcasesLink = makeWikilink(testcasesTitle.prefixedText, testcasesLinkDisplay)
		text = text .. '<br />' .. message('sandbox-notice-testcases-blurb', {testcasesLink})
	end
	-- Add the sandbox to the sandbox category.
	text = text .. makeCategoryLink(message('sandbox-category'))
	omargs.text = text
	return messageBox.main('ombox', omargs)
end

function p.protectionTemplate(env)
	-- Generates the padlock icon in the top right.
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	-- Messages:
	-- 'protection-template' --> 'pp-template'
	-- 'protection-template-args' --> {docusage = 'yes'}
	local title = env.title
	local protectionTemplate = message('protection-template')
	local namespace = title.namespace
	if not (protectionTemplate and (namespace == 10 or namespace == 828)) then
		-- Don't display the protection template if we are not in the template or module namespaces.
		return nil
	end
	local frame = mw.getCurrentFrame()
	local function getProtectionLevel(protectionType, page)
		-- Gets the protection level for page, or for the current page if page is not specified.
		local level = frame:callParserFunction('PROTECTIONLEVEL', protectionType, page)
		if level ~= '' then
			return level
		else
			return nil -- The parser function returns the blank string if there is no match.
		end
	end
	local prefixedTitle = title.prefixedText
	if getProtectionLevel('move', prefixedTitle) == 'sysop' or getProtectionLevel('edit', prefixedTitle) then
		-- The page is full-move protected, or full, template, or semi-protected.
		return frame:expandTemplate{title = protectionTemplate, args = message('protection-template-args', nil, 'table')}
	end
	return nil
end

----------------------------------------------------------------------------
-- Start box
----------------------------------------------------------------------------

p.startBox = makeInvokeFunc('_startBox')

function p._startBox(args, env)
	--[[
	-- This function generates the start box.
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	-- 
	-- The actual work is done by p.makeStartBoxLinksData and p.renderStartBoxLinks which make
	-- the [view] [edit] [history] [purge] links, and by p.makeStartBoxData and p.renderStartBox
	-- which generate the box HTML.
	--]]
	env = env or p.getEnvironment(args)
	local links
	local content = args.content
	if not content then
		-- No need to include the links if the documentation is on the template page itself.
		local linksData = p.makeStartBoxLinksData(args, env)
		if linksData then
			links = p.renderStartBoxLinks(linksData)
		end
	end
	-- Generate the start box html.
	local data = p.makeStartBoxData(args, env, links)
	if data then
		return p.renderStartBox(data)
	else
		-- User specified no heading.
		return nil
	end
end

function p.makeStartBoxLinksData(args, env)
	--[[
	-- Does initial processing of data to make the [view] [edit] [history] [purge] links.
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	-- 
	-- Messages:
	-- 'view-link-display' --> 'view'
	-- 'edit-link-display' --> 'edit'
	-- 'history-link-display' --> 'history'
	-- 'purge-link-display' --> 'purge'
	-- 'file-docpage-preload' --> 'Template:Documentation/preload-filespace'
	-- 'module-preload' --> 'Template:Documentation/preload-module-doc'
	-- 'docpage-preload' --> 'Template:Documentation/preload'
	-- 'create-link-display' --> 'create'
	--]]
	local subjectSpace = env.subjectSpace
	local title = env.title
	local docTitle = env.docTitle
	if not title or not docTitle then
		return nil
	end

	local data = {}
	data.title = title
	data.docTitle = docTitle
	-- View, display, edit, and purge links if /doc exists.
	data.viewLinkDisplay = message('view-link-display')
	data.editLinkDisplay = message('edit-link-display')
	data.historyLinkDisplay = message('history-link-display')
	data.purgeLinkDisplay = message('purge-link-display')
	-- Create link if /doc doesn't exist.
	local preload = args.preload
	if not preload then
		if subjectSpace == 6 then -- File namespace
			preload = message('file-docpage-preload')
		elseif subjectSpace == 828 then -- Module namespace
			preload = message('module-preload')
		else
			preload = message('docpage-preload')
		end
	end
	data.preload = preload
	data.createLinkDisplay = message('create-link-display')
	return data
end

function p.renderStartBoxLinks(data)
	--[[
	-- Generates the [view][edit][history][purge] or [create] links from the data table.
	-- @data - a table of data generated by p.makeStartBoxLinksData
	--]]
	local ret
	local docTitle = data.docTitle
	local title = data.title
	if docTitle.exists then
		local viewLink = makeWikilink(docTitle.prefixedText, data.viewLinkDisplay)
		local editLink = makeUrlLink(docTitle:fullUrl{action = 'edit'}, data.editLinkDisplay)
		local historyLink = makeUrlLink(docTitle:fullUrl{action = 'history'}, data.historyLinkDisplay)
		local purgeLink = makeUrlLink(title:fullUrl{action = 'purge'}, data.purgeLinkDisplay)
		ret = '[%s] [%s] [%s] [%s]'
		ret = ret:gsub('%[', '&#91;') -- Replace square brackets with HTML entities.
		ret = ret:gsub('%]', '&#93;')
		ret = mw.ustring.format(ret, viewLink, editLink, historyLink, purgeLink)
	else
		ret = makeUrlLink(docTitle:fullUrl{action = 'edit', preload = data.preload}, data.createLinkDisplay)
	end
	return ret
end

function p.makeStartBoxData(args, env, links)
	--[=[
	-- Does initial processing of data to pass to the start-box render function, p.renderStartBox.
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	-- @links - a string containing the [view][edit][history][purge] links - could be nil if there's an error.
	--
	-- Messages:
	-- 'documentation-icon-wikitext' --> '[[File:Template-info.png|50px|link=|alt=Documentation icon]]'
	-- 'template-namespace-heading' --> 'Template documentation'
	-- 'module-namespace-heading' --> 'Module documentation'
	-- 'file-namespace-heading' --> 'Summary'
	-- 'other-namespaces-heading' --> 'Documentation'
	-- 'start-box-linkclasses' --> 'mw-editsection plainlinks'
	-- 'start-box-link-id' --> 'doc_editlinks'
	-- 'testcases-create-link-display' --> 'create'
	--]=]
	local subjectSpace = env.subjectSpace
	if not subjectSpace then
		-- Default to an "other namespaces" namespace, so that we get at least some output
		-- if an error occurs.
		subjectSpace = 2
	end
	local data = {}
	
	-- Heading
	local heading = args.heading -- Blank values are not removed.
	if heading == '' then
		-- Don't display the start box if the heading arg is defined but blank.
		return nil
	end
	if heading then
		data.heading = heading
	elseif subjectSpace == 10 then -- Template namespace
		data.heading = message('documentation-icon-wikitext') .. ' ' .. message('template-namespace-heading')
	elseif subjectSpace == 828 then -- Module namespace
		data.heading = message('documentation-icon-wikitext') .. ' ' .. message('module-namespace-heading')
	elseif subjectSpace == 6 then -- File namespace
		data.heading = message('file-namespace-heading')
	else
		data.heading = message('other-namespaces-heading')
	end
	
	-- Heading CSS
	local headingStyle = args['heading-style']
	if headingStyle then
		data.headingStyleText = headingStyle
	elseif subjectSpace == 10 then
		-- We are in the template or template talk namespaces.
		data.headingFontWeight = 'bold'
		data.headingFontSize = '125%'
	else
		data.headingFontSize = '150%'
	end
	
	-- Data for the [view][edit][history][purge] or [create] links.
	if links then
		data.linksClass = message('start-box-linkclasses')
		data.linksId = message('start-box-link-id')
		data.links = links
	end
	
	return data
end

function p.renderStartBox(data)
	-- Renders the start box html.
	-- @data - a table of data generated by p.makeStartBoxData.
	local sbox = htmlBuilder.create('div')
	sbox
		.css('padding-bottom', '3px')
		.css('border-bottom', '1px solid #aaa')
		.css('margin-bottom', '1ex')
		.newline()
		.tag('span')
			.cssText(data.headingStyleText)
			.css('font-weight', data.headingFontWeight)
			.css('font-size', data.headingFontSize)
			.wikitext(data.heading)
	local links = data.links
	if links then
		sbox.tag('span')
			.addClass(data.linksClass)
			.attr('id', data.linksId)
			.wikitext(links)
	end
	return tostring(sbox)
end

----------------------------------------------------------------------------
-- Documentation content
----------------------------------------------------------------------------

p.content = makeInvokeFunc('_content')

function p._content(args, env)
	-- Displays the documentation contents
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	env = env or p.getEnvironment(args)
	local docTitle = env.docTitle
	local content = args.content
	if not content and docTitle and docTitle.exists then
		local frame = mw.getCurrentFrame()
		content = frame:preprocess('{{ ' .. docTitle.prefixedText .. ' }}')
	end
	-- The line breaks below are necessary so that "=== Headings ===" at the start and end
	-- of docs are interpreted correctly.
	return '\n' .. (content or '') .. '\n' 
end

----------------------------------------------------------------------------
-- End box
----------------------------------------------------------------------------

p.endBox = makeInvokeFunc('_endBox')

function p._endBox(args, env)
	--[=[
	-- This function generates the end box (also known as the link box).
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	-- 
	-- Messages:
	-- 'fmbox-id' --> 'documentation-meta-data'
	-- 'fmbox-style' --> 'background-color: #ecfcf4'
	-- 'fmbox-textstyle' --> 'font-style: italic'
	-- 
	-- The HTML is generated by the {{fmbox}} template, courtesy of [[Module:Message box]].
	--]=]
	
	-- Get environment data.
	env = env or p.getEnvironment(args)
	local subjectSpace = env.subjectSpace
	local docTitle = env.docTitle
	if not subjectSpace or not docTitle then
		return nil
	end
		
	-- Check whether we should output the end box at all. Add the end
	-- box by default if the documentation exists or if we are in the
	-- user, module or template namespaces.
	local linkBox = args['link box']
	if linkBox == 'off'
		or not (
			docTitle.exists
			or subjectSpace == 2
			or subjectSpace == 828
			or subjectSpace == 10
		)
	then
		return nil
	end

	-- Assemble the arguments for {{fmbox}}.
	local fmargs = {}
	fmargs.id = message('fmbox-id') -- Sets 'documentation-meta-data'
	fmargs.image = 'none'
	fmargs.style = message('fmbox-style') -- Sets 'background-color: #ecfcf4'
	fmargs.textstyle = message('fmbox-textstyle') -- 'font-style: italic;'

	-- Assemble the fmbox text field.
	local text = ''
	if linkBox then
		text = text .. linkBox
	else
		text = text .. (p.makeDocPageBlurb(args, env) or '') -- "This documentation is transcluded from [[Foo]]." 
		if subjectSpace == 2 or subjectSpace == 10 or subjectSpace == 828 then
			-- We are in the user, template or module namespaces.
			-- Add sandbox and testcases links.
			-- "Editors can experiment in this template's sandbox and testcases pages."
			text = text .. p.makeExperimentBlurb(args, env)
			text = text .. '<br />'
			if not args.content and not args[1] then
				-- "Please add categories to the /doc subpage."
				-- Don't show this message with inline docs or with an explicitly specified doc page,
				-- as then it is unclear where to add the categories.
				text = text .. (p.makeCategoriesBlurb(args, env) or '')
			end
			text = text .. ' ' .. (p.makeSubpagesBlurb(args, env) or '') --"Subpages of this template"
			local printBlurb = p.makePrintBlurb(args, env) -- Two-line blurb about print versions of templates.
			if printBlurb then
				text = text .. '<br />' .. printBlurb
			end
		end
	end
	fmargs.text = text

	return messageBox.main('fmbox', fmargs)
end

function p.makeDocPageBlurb(args, env)
	--[=[
	-- Makes the blurb "This documentation is transcluded from [[Template:Foo]] (edit, history)".
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	-- 
	-- Messages:
	-- 'edit-link-display' --> 'edit'
	-- 'history-link-display' --> 'history'
	-- 'transcluded-from-blurb' --> 
	-- 'The above [[Wikipedia:Template documentation|documentation]] 
	-- is [[Wikipedia:Transclusion|transcluded]] from $1.'
	-- 'module-preload' --> 'Template:Documentation/preload-module-doc'
	-- 'create-link-display' --> 'create'
	-- 'create-module-doc-blurb' -->
	-- 'You might want to $1 a documentation page for this [[Wikipedia:Lua|Scribunto module]].'
	--]=]
	local docTitle = env.docTitle
	if not docTitle then
		return nil
	end
	local ret
	if docTitle.exists then
		-- /doc exists; link to it.
		local docLink = makeWikilink(docTitle.prefixedText)
		local editUrl = docTitle:fullUrl{action = 'edit'}
		local editDisplay = message('edit-link-display')
		local editLink = makeUrlLink(editUrl, editDisplay)
		local historyUrl = docTitle:fullUrl{action = 'history'}
		local historyDisplay = message('history-link-display')
		local historyLink = makeUrlLink(historyUrl, historyDisplay)
		ret = message('transcluded-from-blurb', {docLink})
			.. ' '
			.. makeToolbar(editLink, historyLink)
			.. '<br />'
	elseif env.subjectSpace == 828 then
		-- /doc does not exist; ask to create it.
		local createUrl = docTitle:fullUrl{action = 'edit', preload = message('module-preload')}
		local createDisplay = message('create-link-display')
		local createLink = makeUrlLink(createUrl, createDisplay)
		ret = message('create-module-doc-blurb', {createLink})
			.. '<br />'
	end
	return ret
end

function p.makeExperimentBlurb(args, env)
	--[[
	-- Renders the text "Editors can experiment in this template's sandbox (edit | diff) and testcases (edit) pages."
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	-- 
	-- Messages:
	-- 'sandbox-link-display' --> 'sandbox'
	-- 'sandbox-edit-link-display' --> 'edit'
	-- 'compare-link-display' --> 'diff'
	-- 'module-sandbox-preload' --> 'Template:Documentation/preload-module-sandbox'
	-- 'template-sandbox-preload' --> 'Template:Documentation/preload-sandbox'
	-- 'sandbox-create-link-display' --> 'create'
	-- 'mirror-edit-summary' --> 'Create sandbox version of $1'
	-- 'mirror-link-display' --> 'mirror'
	-- 'sandbox-link-display' --> 'sandbox'
	-- 'testcases-link-display' --> 'testcases'
	-- 'testcases-edit-link-display'--> 'edit'
	-- 'module-testcases-preload' --> 'Template:Documentation/preload-module-testcases'
	-- 'template-sandbox-preload' --> 'Template:Documentation/preload-sandbox'
	-- 'testcases-create-link-display' --> 'create'
	-- 'testcases-link-display' --> 'testcases'
	-- 'testcases-edit-link-display' --> 'edit'
	-- 'module-testcases-preload' --> 'Template:Documentation/preload-module-testcases'
	-- 'template-testcases-preload' --> 'Template:Documentation/preload-testcases'
	-- 'experiment-blurb-module' --> 'Editors can experiment in this module's $1 and $2 pages.'
	-- 'experiment-blurb-template' --> 'Editors can experiment in this template's $1 and $2 pages.'
	--]]
	local subjectSpace = env.subjectSpace
	local templateTitle = env.templateTitle
	local sandboxTitle = env.sandboxTitle
	local testcasesTitle = env.testcasesTitle
	local templatePage = templateTitle.prefixedText
	if not subjectSpace or not templateTitle or not sandboxTitle or not testcasesTitle then
		return nil
	end
	-- Make links.
	local sandboxLinks, testcasesLinks
	if sandboxTitle.exists then
		local sandboxPage = sandboxTitle.prefixedText
		local sandboxDisplay = message('sandbox-link-display')
		local sandboxLink = makeWikilink(sandboxPage, sandboxDisplay)
		local sandboxEditUrl = sandboxTitle:fullUrl{action = 'edit'}
		local sandboxEditDisplay = message('sandbox-edit-link-display')
		local sandboxEditLink = makeUrlLink(sandboxEditUrl, sandboxEditDisplay)
		local compareUrl = env.compareUrl
		local compareLink
		if compareUrl then
			local compareDisplay = message('compare-link-display')
			compareLink = makeUrlLink(compareUrl, compareDisplay)
		end
		sandboxLinks = sandboxLink .. ' ' .. makeToolbar(sandboxEditLink, compareLink)
	else
		local sandboxPreload
		if subjectSpace == 828 then
			sandboxPreload = message('module-sandbox-preload')
		else
			sandboxPreload = message('template-sandbox-preload')
		end
		local sandboxCreateUrl = sandboxTitle:fullUrl{action = 'edit', preload = sandboxPreload}
		local sandboxCreateDisplay = message('sandbox-create-link-display')
		local sandboxCreateLink = makeUrlLink(sandboxCreateUrl, sandboxCreateDisplay)
		local mirrorSummary = message('mirror-edit-summary', {makeWikilink(templatePage)})
		local mirrorUrl = sandboxTitle:fullUrl{action = 'edit', preload = templatePage, summary = mirrorSummary}
		local mirrorDisplay = message('mirror-link-display')
		local mirrorLink = makeUrlLink(mirrorUrl, mirrorDisplay)
		sandboxLinks = message('sandbox-link-display') .. ' ' .. makeToolbar(sandboxCreateLink, mirrorLink)
	end
	if testcasesTitle.exists then
		local testcasesPage = testcasesTitle.prefixedText
		local testcasesDisplay = message('testcases-link-display')
		local testcasesLink = makeWikilink(testcasesPage, testcasesDisplay)
		local testcasesEditUrl = testcasesTitle:fullUrl{action = 'edit'}
		local testcasesEditDisplay = message('testcases-edit-link-display')
		local testcasesEditLink = makeUrlLink(testcasesEditUrl, testcasesEditDisplay)
		testcasesLinks = testcasesLink .. ' ' .. makeToolbar(testcasesEditLink)
	else
		local testcasesPreload
		if subjectSpace == 828 then
			testcasesPreload = message('module-testcases-preload')
		else
			testcasesPreload = message('template-testcases-preload')
		end
		local testcasesCreateUrl = testcasesTitle:fullUrl{action = 'edit', preload = testcasesPreload}
		local testcasesCreateDisplay = message('testcases-create-link-display')
		local testcasesCreateLink = makeUrlLink(testcasesCreateUrl, testcasesCreateDisplay)
		testcasesLinks = message('testcases-link-display') .. ' ' .. makeToolbar(testcasesCreateLink)
	end
	local messageName
	if subjectSpace == 828 then
		messageName = 'experiment-blurb-module'
	else
		messageName = 'experiment-blurb-template'
	end
	return message(messageName, {sandboxLinks, testcasesLinks})
end

function p.makeCategoriesBlurb(args, env)
	--[[
	-- Generates the text "Please add categories to the /doc subpage."
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	-- Messages:
	-- 'doc-link-display' --> '/doc'
	-- 'add-categories-blurb' --> 'Please add categories to the $1 subpage.'
	--]]
	local docTitle = env.docTitle
	if not docTitle then
		return nil
	end
	local docPathLink = makeWikilink(docTitle.prefixedText, message('doc-link-display'))
	return message('add-categories-blurb', {docPathLink})
end

function p.makeSubpagesBlurb(args, env)
	--[[
	-- Generates the "Subpages of this template" link.
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	
	-- Messages:
	-- 'template-pagetype' --> 'template'
	-- 'module-pagetype' --> 'module'
	-- 'default-pagetype' --> 'page'
	-- 'subpages-link-display' --> 'Subpages of this $1'
	--]]
	local subjectSpace = env.subjectSpace
	local templateTitle = env.templateTitle
	if not subjectSpace or not templateTitle then
		return nil
	end
	local pagetype
	if subjectSpace == 10 then
		pagetype = message('template-pagetype')
	elseif subjectSpace == 828 then
		pagetype = message('module-pagetype')
	else
		pagetype = message('default-pagetype')
	end
	local subpagesLink = makeWikilink(
		'Special:PrefixIndex/' .. templateTitle.prefixedText .. '/',
		message('subpages-link-display', {pagetype})
	)
	return message('subpages-blurb', {subpagesLink})
end

function p.makePrintBlurb(args, env)
	--[=[
	-- Generates the blurb displayed when there is a print version of the template available.
	-- @args - a table of arguments passed by the user
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	--
	-- Messages:
	-- 'print-link-display' --> '/Print'
	-- 'print-blurb' --> 'A [[Help:Books/for experts#Improving the book layout|print version]]'
	--		.. ' of this template exists at $1.'
	--		.. ' If you make a change to this template, please update the print version as well.'
	-- 'display-print-category' --> true
	-- 'print-category' --> 'Templates with print versions'
	--]=]
	local printTitle = env.printTitle
	if not printTitle then
		return nil
	end
	local ret
	if printTitle.exists then
		local printLink = makeWikilink(printTitle.prefixedText, message('print-link-display'))
		ret = message('print-blurb', {printLink})
		local displayPrintCategory = message('display-print-category', nil, 'boolean')
		if displayPrintCategory then
			ret = ret .. makeCategoryLink(message('print-category'))
		end
	end
	return ret
end

----------------------------------------------------------------------------
-- Tracking categories
----------------------------------------------------------------------------

function p.addTrackingCategories(env)
	--[[
	-- Check if {{documentation}} is transcluded on a /doc or /testcases page.
	-- @env - environment table containing title objects, etc., generated with p.getEnvironment
	
	-- Messages:
	-- 'display-strange-usage-category' --> true
	-- 'doc-subpage' --> 'doc'
	-- 'testcases-subpage' --> 'testcases'
	-- 'strange-usage-category' --> 'Wikipedia pages with strange ((documentation)) usage'
	-- 
	-- /testcases pages in the module namespace are not categorised, as they may have
	-- {{documentation}} transcluded automatically.
	--]]
	local title = env.title
	local subjectSpace = env.subjectSpace
	if not title or not subjectSpace then
		return nil
	end
	local subpage = title.subpageText
	local ret = ''
	if message('display-strange-usage-category', nil, 'boolean')
		and (
			subpage == message('doc-subpage')
			or subjectSpace ~= 828 and subpage == message('testcases-subpage')
		)
	then
		ret = ret .. makeCategoryLink(message('strange-usage-category'))
	end
	return ret
end

return p