-- This module implements the ((Track gauge)) template.
-- Data is in Module:Track gauge/data
local p = {}
local gaugeDataAll = nil
local dataPageName = 'Module:Track gauge/data' -- set /data/sandbox here to test data/sandbox
-----------------------------------------------------------------------------------
-- prepareArgs -- Normalise Arguments coming from an #invoke or from a module
-----------------------------------------------------------------------------------
local function prepareArgs(frame)
	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
	local args = {}
	-- searchAlias is the cleaned value of args[1]. args[1] is kept as rawInput for error message
	local searchAlias = ''
	local rawDisp
	for k, v in pairs(origArgs) do
		if tonumber(k) == nil then -- Named argment
			if k == 'disp' then
				rawDisp = v -- Keep raw disp input to pass through plain (wiki)text
				args[k] = mw.ustring.lower(v)
			elseif k == 'first' then
				v = mw.ustring.lower(v)
				if v == 'met' or v == 'metric' then
					v = 'met'
				elseif v == 'imp' or v == 'imperial' then
					v = 'imp'
				else k = 'trashparam_first' end
				args[k] = v
			elseif k == 'nowrap' or k == 'wrap' then -- wrap=y deprecated; reading: nowrap=off
				v = mw.ustring.lower(v)
				if v == '' or v == 'off' or v == 'on' or v == 'all' then
				elseif v == 'inline' or (k == 'wrap' and v == 'y') then
					v = 'off'
				else v = '' end
				args['nowrap'] = v
			else
				args[k] = mw.ustring.lower(v)
			end
		else
			args[k] = v -- Keep rawInput in [1] for error message
			if k == 1 then
			-- Unnamed argument, the alias to be searched
			-- Cleanup
				searchAlias = p.normaliseAliasInput(v)
			end
		end
	end
	args['searchAlias'] = searchAlias
	if rawDisp then args['rawDisp'] = rawDisp end
	return args
end
-----------------------------------------------------------------------------------
-- normaliseAliasInput
-----------------------------------------------------------------------------------
function p.normaliseAliasInput(aliasIn)
	local a
	a = mw.ustring.lower(mw.ustring.gsub(aliasIn, '[%s%,]', ''))
	a = mw.ustring.gsub(a, ' ', '')
	a = mw.ustring.gsub(a, 'gauge$', '')
	a = mw.ustring.gsub(a, "'", "ft")
	a = mw.ustring.gsub(a, '"', 'in')
	a = mw.ustring.gsub(a, '⁄', '/')
	a = mw.ustring.gsub(a, '⁄', '/')
	return a	
end
-----------------------------------------------------------------------------------
-- debugReturnArgs -- Debug function.
-----------------------------------------------------------------------------------
function p.debugReturnArgs(frame)
	local args = prepareArgs(frame)
	local retArgs = {}
	for k, a in pairs(args) do
		table.insert(retArgs, k .. '=' .. a)
	end
	return 'Args: ' .. table.concat(retArgs, '; ')
end
-----------------------------------------------------------------------------------
-- getTrackGaugeEntry -- Find entry data for a single gauge (alias)
-----------------------------------------------------------------------------------
function p.getTrackGaugeEntry(searchAlias)
	gaugeDataAll = mw.loadData(dataPageName)
	if searchAlias == '' then
		return nil
	end
	local tgEntry = nil
	for i, tgEntry in ipairs(gaugeDataAll) do
		for j, alias in ipairs(tgEntry.aliases) do
			if alias == searchAlias then
				return tgEntry
			end
		end
	end
end
-----------------------------------------------------------------------------------
-- noWrap -- Add span tags to prevent a string from wrapping.
-----------------------------------------------------------------------------------
local function noWrap(s)
	return mw.ustring.format('<span class="nowrap">%s</span>', s)
end
-----------------------------------------------------------------------------------
-- frac -- A slimmed-down version of the ((frac)) template (a nowrap is to be added with the unit)
-----------------------------------------------------------------------------------
local function frac(whole, num, den)
	-- normally would do the TemplateStyles expansion here, but instead we do
	-- it at the callsite because of [[:phab:T200704]]
	return mw.ustring.format(
		'<span class="frac">%s<span class="num">%s</span>&frasl;<span class="den">%s</span></span>',
		whole and (whole .. '<span class="sr-only">+</span>') or '',
		num,
		den
	)
end
-----------------------------------------------------------------------------------
-- catMentions -- Wikicode for "article mentions gauge" categories
-----------------------------------------------------------------------------------
function p.catMentions(tgEntry, sortlabel, doReturn)
	local ns = 'Category:'
	local cat

	if tgEntry == nil then
		-- Parent, the container cat
		cat = 'Articles that mention a specific track gauge'
	else
		cat = 'Articles that mention track gauge ' .. tgEntry.id .. ' mm'
	end
	-- Argument 'label' can be used to add a catsort. Catsort is not used (as of 20 May 2014)
	if sortlabel ~= nil then
		sortlabel = '|' .. sortlabel
	else
		sortlabel = ''
	end
	if doReturn ~= nil then
		if doReturn == 'fullpagename' then
			return ns .. cat
		elseif doReturn == 'pagename' then -- plaintext, no namespace
			return cat
		elseif doReturn == 'show' then -- colontrick
			return '[[:' .. ns .. cat .. sortlabel .. ']]'
		else -- unknown arg value
			return ns .. cat
		end
	else -- Returns straight categorisation (wikitext)
		return '[[' .. ns .. cat .. sortlabel .. ']]'
	end
end
-----------------------------------------------------------------------------------
-- formatImp -- Formats imperial units size into a single text element
-----------------------------------------------------------------------------------
function p.formatImp(tgEntry, measurementToLink, setNowrap, addUnitlink)
	local ret = {}
	local ft = tgEntry.ft
	if ft then
		local ftlink = addUnitlink and measurementToLink ~= 'imp' and '[[Foot (unit)|ft]]' or 'ft'

		table.insert(ret, mw.ustring.format('%s&nbsp;%s', ft, ftlink))
	end
	local inches = tgEntry['in']
	local num = tgEntry.num
	local den = tgEntry.den
	local has_fraction = num and den
	if inches and not num and not den then

		table.insert(ret, inches)
	elseif has_fraction then
		table.insert(ret, frac(inches, num, den))
	end
	if inches or num and den then
		local incheslink = addUnitlink and measurementToLink ~= 'imp' and '[[inch|in]]' or 'in'
		table.insert(ret, incheslink)
	end
	local gaugeSize
	if setNowrap then
		gaugeSize = noWrap(table.concat(ret, '&nbsp;'))
	else
		gaugeSize = table.concat(ret, '&nbsp;')
	end
	 -- we have do this here to work around [[phab:T200704]]
	local templatestyles
	if has_fraction then
		templatestyles = mw.getCurrentFrame():extensionTag{
			name = 'templatestyles', args = { src = 'Fraction/styles.css' }
		}
	else
		templatestyles = ''
	end
			
	if measurementToLink == 'imp' and tgEntry.pagename ~= nil then
		return mw.ustring.format(
			'%s[[%s|%s]]',
			templatestyles,
			tgEntry.pagename,
			gaugeSize
		)
	else
		return templatestyles .. gaugeSize
	end
end
-----------------------------------------------------------------------------------
-- formatMet -- Formats metric measurements into a single formatted text element. Public for autodocument
-----------------------------------------------------------------------------------
function p.formatMet(tgEntry, measurementToLink, setNowrap, addUnitlink, removeComma)
	local m = tgEntry.m
	local gaugeSize
	if m then
		local mUnit = addUnitlink and measurementToLink ~= 'met' and '[[metre|m]]' or 'm'
		gaugeSize = mw.ustring.format('%s&nbsp;%s', m, mUnit)
	else
		local mm = tgEntry.mm
		mm = tonumber(mm)
		if mm then
			mm = mw.getContentLanguage():formatNum(mm)
			if removeComma then
				mm = string.gsub( mm, ",", "" )
			end
		end
		local mmUnit = addUnitlink and measurementToLink ~= 'met' and '[[millimetre|mm]]' or 'mm'
		gaugeSize = mw.ustring.format('%s&nbsp;%s', mm, mmUnit)
	end
	if setNowrap then
		gaugeSize = noWrap(gaugeSize)
	end
	if measurementToLink == 'met' and tgEntry.pagename ~= nil then
		return mw.ustring.format('[[%s|%s]]', tgEntry.pagename, gaugeSize)
	else
		return gaugeSize
	end
end
-----------------------------------------------------------------------------------
-- formatAltName
-----------------------------------------------------------------------------------
function formatAltName(tgEntry, addGaugeName, addGaugeNameLink, disp, setNowrap, engvar)
	-- Assumed: at least one to add is true.
	if tgEntry.name == nil then
		-- Not checked: link does exist alone
		return ''
	end
	local retAlt = {}
	if disp == 'br' then
		table.insert(retAlt, '<br />')
	else
		table.insert(retAlt, ' ')
	end
	if setNowrap then
		table.insert(retAlt, '<span class="nowrap">')
	end
	if addGaugeNameLink then
		if engvar == 'en-us' then
			-- Current implementations (2016): metER for metRE (1000-met, 1009-met)
			table.insert(retAlt, tgEntry.en_US_link or tgEntry.link or tgEntry.name)
		else
			table.insert(retAlt, tgEntry.link or tgEntry.name)
		end
	else -- so must be unlinked .name to add
			if engvar == 'en-us' then
			-- Current implementations (2016): metER for metRE (1000-met, 1009-met)
			table.insert(retAlt, tgEntry.en_US_name or tgEntry.name)
		else
			table.insert(retAlt, tgEntry.name)
		end
	end
	if setNowrap then --close tag
		table.insert(retAlt, '</span>')
	end
	return table.concat(retAlt, '')
end
-----------------------------------------------------------------------------------
-- main -- The basic module
-----------------------------------------------------------------------------------
function p.main(frame)
	-- In general: the tgEntry object (from TG/data) is passed to the functions, while arguments are processed here.
	local title = mw.title.getCurrentTitle()
	local args = prepareArgs(frame)
	local tgEntry = p.getTrackGaugeEntry(args.searchAlias)

	-- Categorise & preview warning when no track gauge definition was found.
	if tgEntry == nil then
		local input = args[1] or ''
		local errorTail = require('Module:If preview')._warning({
			'Track gauge ' ..
			input ..
			' not in [[:Template:Track_gauge#List_of_defined_track_gauges|List of defined track gauges]] ([[Template talk:Track gauge|talk]]).'
		})

		if title:inNamespaces(0, 14) then -- mainspace and category space
			errorTail = errorTail .. "[[Category:Articles using Template:Track gauge with unrecognized input]]"
		end
		return input .. errorTail
	end

	-- Check and set args & tgEntry props: disp, first, nowrap, first
	local disp = args.disp or ''
	local first = args.first or tgEntry.def1
	local unitlink = args.unitlink or ''
	local comma = args.comma or ''
	local nowrap = args.nowrap or ''
	local setNowrapElement = (nowrap == '' or nowrap == 'off') -- To prevent nested nowrap tags
	local measurementToLink
	if args.lk == 'on' then
		if disp == '1' then
			measurementToLink = first -- Can make metric text links to the imp linked page
		else
			measurementToLink = tgEntry.def1 -- When first=swapped, this could link 2nd measure.
		end
	end
	-- String the text elements together (compose the return table)
	local ret = {}
	-- nowrap opening tag
	if nowrap == 'all' or nowrap == 'on' then
		table.insert(ret, '<span class="nowrap">')
	end
	-- First measure
	if first == 'met' then
		table.insert(ret,
			p.formatMet(tgEntry, measurementToLink, setNowrapElement, unitlink == 'on', comma == 'off'))
	else
		table.insert(ret,
			p.formatImp(tgEntry, measurementToLink, setNowrapElement, unitlink == 'on', comma == 'off'))
	end
	-- The joint and the second measure
	if disp == '1' then
	else
		local joinText = ''
		local closeDisp = ''
		if disp == 's' or disp == '/' then
			joinText = '&nbsp;/ ' --spaces
		elseif disp == 'br' then
			joinText = '<br />('
			closeDisp = ')'
		elseif disp == '[' or disp == '[]' then
			joinText = ' ['
			closeDisp = ']'
		elseif disp ~= '' then -- Is anytext
			joinText = ' ' .. args['rawDisp'] .. ' '
		else
			joinText = ' ('
			closeDisp = ')'
		end
		table.insert(ret, joinText)
		if first ~= 'met' then
			table.insert(ret,
				p.formatMet(tgEntry, measurementToLink, setNowrapElement, unitlink == 'on', comma == 'off'))
		else
			table.insert(ret,
				p.formatImp(tgEntry, measurementToLink, setNowrapElement, unitlink == 'on'))
		end
		table.insert(ret, closeDisp) -- Could be ''
	end
	if nowrap == 'on' then -- Closing tag
		table.insert(ret, '</span>')
	end
	-- Alternative name
	if args.al == 'on' or args.allk == 'on' then
		local setNowrapAltname = (nowrap == '' or nowrap == 'on') -- Logic applied to prevent nested nowrap tags
		table.insert(ret, formatAltName(tgEntry, args.al == 'on', args.allk == 'on', disp, setNowrapAltname, args.engvar))
	end
	-- Closing nowrap tag
	if nowrap == 'all' then
		table.insert(ret, '</span>')
	end
	
	-- Category mentionings (maintenance)
	if args.addcat or '' == 'no' then
		-- No categorization
	elseif title:inNamespaces(0) then
		-- switched off per [[Wikipedia:Categories_for_discussion/Log/2016_December_6#Category:Articles_that_mention_a_specific_track_gauge]]
		-- 2016-12-19
		-- table.insert(ret, p.catMentions(tgEntry))
	end

	-- Now sting the table together
	return table.concat(ret, '')
end

return p
--20161219: maintenance categorisation switched off per CfD
--20170602: fix bug, show name when al=on
--20180708: show preview warning when gauge is not in list
--20190124: with disp=/ (slash) value separator: surround by spaces
--20210304: add option comma=off (mm only)