View source for Module:Lang

--[=[

Lua support for the {{lang}}, {{lang-xx}}, and {{transl}} templates and replacement of various supporting templates. 

]=]

require('Module:No globals');

local initial_style_state;														-- set by lang_xx_normal() and lang_xx_italic()

local getArgs = require ('Module:Arguments').getArgs;
local unicode = require ("Module:Unicode data");								-- for is_latin() and is_rtl()
local yesno = require ('Module:Yesno');

local lang_name_table = mw.loadData ('Module:Language/name/data');

local synonym_table = mw.loadData ('Module:Lang/ISO 639 synonyms');				-- ISO 639-2/639-2T code translation to 639-1 code

local lang_data =  mw.loadData ('Module:Lang/data');							-- language name override and transliteration tool-tip tables

local namespace = mw.title.getCurrentTitle().namespace;							-- used for categorization

local this_wiki_lang = mw.language.getContentLanguage().code;					-- get this wiki's language

local maint_cats = {};															-- maintenance categories go here
local maint_msgs = {};															-- and their messages go here


--[[--------------------------< I S _ S E T >------------------------------------------------------------------

Returns true if argument is set; false otherwise. Argument is 'set' when it exists (not nil) or when it is not an empty string.

]]

local function is_set( var )
	return not (var == nil or var == '');
end


--[[--------------------------< I N V E R T  _ I T A L I C S >-------------------------------------------------

This function attempts to invert the italic markup a args.text by adding/removing leading/trailing italic markup
in args.text.  Like |italic=unset, |italic=invert disables automatic italic markup.  Individual leading/trailing
apostrophes are converted to their html numeric entity equivalent so that the new italic markup doesn't become
bold markup inadvertently.

Leading and trailing wiki markup is extracted from args.text into separate table elements.  Addition, removal,
replacement of wiki markup is handled by a string.gsub() replacement table operating only on these separate elements.
In the string.gsub() matching pattern, '.*' matches empty string as well as the three expected wiki markup patterns.

This function expects that markup in args.text is complete and correct; if it is not, oddness may result.

]]

local function invert_italics (source)
	local invert_pattern_table = {												-- leading/trailing markup add/remove/replace patterns
		[""]="\'\'",															-- empty string becomes italic markup
		["\'\'"]="",															-- italic markup becomes empty string
		["\'\'\'"]="\'\'\'\'\'",												-- bold becomes bold italic
		["\'\'\'\'\'"]="\'\'\'",												-- bold italic become bold
		};
	local seg = {};

	source = source:gsub ("%f[\']\'%f[^\']", '&#39;');							-- protect single quote marks from being interpreted as bold markup

	seg[1] = source:match ('^(\'\'+%f[^\']).+') or '';							-- get leading markup, if any; ignore single quote
	seg[3] = source:match ('.+(%f[\']\'\'+)$') or '';							-- get trailing markup, if any; ignore single quote

	if '' ~= seg[1] and '' ~= seg[3] then										-- extract the 'text' 
		seg[2] = source:match ('^\'\'+%f[^\'](.+)%f[\']\'\'+$')					-- from between leading and trailing markup
	elseif '' ~= seg[1] then
		seg[2] = source:match ('^\'\'+%f[^\'](.+)')								-- following leading markup
	elseif '' ~= seg[3] then
		seg[2] = source:match ('(.+)%f[\']\'\'+$')								-- preceding trailing markup
	else
		seg[2] = source															-- when there is no markup
	end

	seg[1] = invert_pattern_table[seg[1]] or seg[1];							-- replace leading markup according to pattern table
	seg[3] = invert_pattern_table[seg[3]] or seg[3];							-- replace leading markup according to pattern table

	return table.concat (seg);													-- put it all back together and done
end


--[[--------------------------< V A L I D A T E _ I T A L I C >------------------------------------------------

validates |italic= or |italics= assigned values.

When |italic= is set and has an acceptible assigned value, return the matching css font-style property value or,
for the special case 'default', return nil.

When |italic= is not set, or has an unacceptible assigned value, return nil and a nil error message.

When both |italic= and |italics= are set, returns nil and a 'conflicting' error message.

The return value nil causes the calling lang, lang_xx, or transl function to set args.italic according to the template's
defined default ('inherit' for {{lang}}, 'inherit' or 'italic' for {{lang-xx}} depending on
the individual template's requirements, 'italic' for {{transl}}) or to the value appropriate to |script=, if set ({{lang}}
and {{lang-xx}} only).

Accepted values and the values that this function returns are are:
	nil		-	when |italic= absent or not set; returns nil
	default	-	for completeness, should rarely if ever be used; returns nil
	yes		-	force args.text to be rendered in italic font; returns 'italic'
	no		-	force args.text to be rendered in normal font; returns 'normal'
	unset	-	disables font control so that font-style applied to text is dictated by markup inside or outside the template; returns 'inherit'
	invert	-	disables font control so that font-style applied to text is dictated by markup outside or inverted inside the template; returns 'invert'

]]

local function validate_italic (args)
	local properties = {['yes'] = 'italic', ['no'] = 'normal', ['unset'] = 'inherit', ['invert'] = 'invert', ['default'] = nil};
	
	local count = 0
	for _, arg in pairs {'italic', 'italics', 'i'} do
		if args[arg] then
			count = count + 1
		end
	end

	if count > 1 then															-- return nil and an error message if more than one is set 
		return nil, 'only one of &#124;italic=, &#124;italics=, or &#124;i= can be specified';
	end
	
	return properties[args.italic or args.italics or args.i], nil;				-- return an appropriate value and a nil error message
end


--[=[--------------------------< V A L I D A T E _ C A T _ A R G S >----------------------------------------------------------

Default behavior of the {{lang}} and {{lang-xx}} templates is to add categorization when the templates are used in mainspace.
This default functionality may be suppressed by setting |nocat=yes or |cat=no.  This function selects one of these two parameters
to control categorization.

Because having two parameters with 'opposite' names and 'opposite' values is confusing, this function accepts only affirmative
values for |nocat= and only negative values for |cat=; in both cases the 'other' sense (and non-sense) is not accepted and the
parameter is treated as if it were not set in the template.

Sets args.nocat to true if categorization is to be turned off; to nil if the default behavior should apply.

Accepted values for |nocat= are the text strings:
	'yes', 'y', 'true', 't', on, '1'		-- [[Module:Yesno]] returns logical true for all of these; false or nil else
for |cat=
	'no', 'n', 'false', 'f', 'off', '0'		-- [[Module:Yesno]] returns logical false for all of these; true or nil else

]=]

local function validate_cat_args (args)
	if not (args.nocat or args.cat) then										-- both are nil, so categorize
		return;
	end
	
	if false == yesno (args.cat) or true == yesno (args.nocat) then
		args.nocat = true;														-- set to true when args.nocat is affirmative; nil else (as if the parameter were not set in the template)
	else																		-- args.nocat is the parameter actually used.
		args.nocat = nil;
	end
end


--[[--------------------------< I N _ A R R A Y >--------------------------------------------------------------

Whether needle is in haystack

]]

local function in_array ( needle, haystack )
	if needle == nil then
		return false;
	end
	for n,v in ipairs( haystack ) do
		if v == needle then
			return n;
		end
	end
	return false;
end


--[[--------------------------< F O R M A T _ I E T F _ T A G >------------------------------------------------

prettify ietf tags to use recommended subtag formats:
	code: lower case
	script: sentence case
	region: upper case
	variant: lower case

]]

local function format_ietf_tag (code, script, region, variant)
	local out = {};

	table.insert (out, code:lower());
	if is_set (script) then
		script = script:lower():gsub ('^%a', string.upper);
		table.insert (out, script);
	end

	if is_set (region) then
		table.insert (out, region:upper());
	end
	
	if is_set (variant) then
		table.insert (out, variant:lower());
	end
	
	return table.concat (out, '-');
end


--[[--------------------------< G E T _ I E T F _ P A R T S >--------------------------------------------------

extracts and returns IETF language tag parts:
	primary language subtag (required) - 2 or 3 character IANA language code
	script subtag - four character IANA script code
	region subtag - two-letter or three digit IANA region code
	variant subtag - four digit or 5-8 alnum variant code
	private subtag - x- followed by 1-8 alnum private code; only supported with the primary language tag

in any one of these forms
	lang					lang-variant
	lang-script				lang-script-variant
	lang-region				lang-region-variant
	lang-script-region		lang-script-region-variant
	lang-x-private	
	
each of lang, script, region, variant, and private, when used, must be valid

Languages with both two- and three-character code synonyms are promoted to the two-character synonym because
the IANA registry file omits the synonymous three-character code; we cannot depend on browsers understanding
the synonymous three-character codes in the lang= attribute.

For {{lang-xx}} templates, the parameters |script=, |region=, and |variant= are supported (not supported in {{lang}}
because those parameters are superfluous to the IETF subtags in |code=)

returns six  values; all lower case.  Valid parts are returned as themselves; omitted parts are returned as empty strings, invalid
parts are returned as nil; the sixth returned item is an error message (if an error detected) or nil.

see http://www.rfc-editor.org/rfc/bcp/bcp47.txt section 2.1

]]

local function get_ietf_parts (source, args_script, args_region, args_variant)
	local code, script, region, variant, private;								-- ietf tag parts

	if not is_set (source) then
		return nil, nil, nil, nil, nil, 'missing language tag';
	end

	local pattern = {															-- table of tables holding acceptibe ietf tag patterns and short names of the ietf part captured by the pattern
		{'^(%a%a%a?)%-(%a%a%a%a)%-(%a%a)%-(%d%d%d%d)$', 's', 'r', 'v'}, 				-- 1 -  ll-Ssss-RR-variant (where variant is 4 digits)
		{'^(%a%a%a?)%-(%a%a%a%a)%-(%d%d%d)%-(%d%d%d%d)$', 's', 'r', 'v'},				-- 2 -  ll-Ssss-DDD-variant (where region is 3 digits; variant is 4 digits)
		{'^(%a%a%a?)%-(%a%a%a%a)%-(%a%a)%-(%w%w%w%w%w%w?%w?%w?)$', 's', 'r', 'v'},		-- 3 -  ll-Ssss-RR-variant (where variant is 5-8 alnum characters)
		{'^(%a%a%a?)%-(%a%a%a%a)%-(%d%d%d)%-(%w%w%w%w%w%w?%w?%w?)$', 's', 'r', 'v'},	-- 4 -  ll-Ssss-DDD-variant (where region is 3 digits; variant is 5-8 alnum characters)
		
		{'^(%a%a%a?)%-(%a%a%a%a)%-(%d%d%d%d)$', 's', 'v'},						-- 5 -  ll-Ssss-variant (where variant is 4 digits)
		{'^(%a%a%a?)%-(%a%a%a%a)%-(%w%w%w%w%w%w?%w?%w?)$', 's', 'v'},			-- 6 -  ll-Ssss-variant (where variant is 5-8 alnum characters)
		
		{'^(%a%a%a?)%-(%a%a)%-(%d%d%d%d)$', 'r', 'v'},							-- 7 -  ll-RR-variant (where variant is 4 digits)
		{'^(%a%a%a?)%-(%d%d%d)%-(%d%d%d%d)$', 'r', 'v'},						-- 8 -  ll-DDD-variant (where region is 3 digits; variant is 4 digits)
		{'^(%a%a%a?)%-(%a%a)%-(%w%w%w%w%w%w?%w?%w?)$', 'r', 'v'},				-- 9 -  ll-RR-variant (where variant is 5-8 alnum characters)
		{'^(%a%a%a?)%-(%d%d%d)%-(%w%w%w%w%w%w?%w?%w?)$', 'r', 'v'},				-- 10 - ll-DDD-variant (where region is 3 digits; variant is 5-8 alnum characters)
		
		{'^(%a%a%a?)%-(%d%d%d%d)$', 'v'},										-- 11 - ll-variant (where variant is 4 digits)
		{'^(%a%a%a?)%-(%w%w%w%w%w%w?%w?%w?)$', 'v'},							-- 12 - ll-variant (where variant is 5-8 alnum characters)
		
		{'^(%a%a%a?)%-(%a%a%a%a)%-(%a%a)$', 's', 'r'},							-- 13 - ll-Ssss-RR
		{'^(%a%a%a?)%-(%a%a%a%a)%-(%d%d%d)$', 's', 'r'},						-- 14 - ll-Ssss-DDD (region is 3 digits)
		
		{'^(%a%a%a?)%-(%a%a%a%a)$', 's'},										-- 15 - ll-Ssss
		
		{'^(%a%a%a?)%-(%a%a)$', 'r'},											-- 16 - ll-RR
		{'^(%a%a%a?)%-(%d%d%d)$', 'r'},											-- 17 - ll-DDD (region is 3 digits)
		
		{'^(%a%a%a?)$'},														-- 18 - ll
		
		{'^(%a%a%a?)%-x%-(%w%w?%w?%w?%w?%w?%w?%w?)$', 'p'},						-- 19 - ll-x-pppppppp (private is 1-8 alnum characters)
		}

	local t = {};																-- table of captures; serves as a translator between captured ietf tag parts and named variables

	for i, v in ipairs (pattern) do												-- spin through the pattern table looking for a match
		local c1, c2, c3, c4;													-- captures in the 'pattern' from the pattern table go here
	
		c1, c2, c3, c4 = source:match (pattern[i][1]);							-- one or more captures set if source matches pattern[i])
			if c1 then															-- c1 always set on match
				code = c1;														-- first capture is always code
				t = {
					[pattern[i][2] or 'x'] = c2,								-- fill the table of captures with the rest of the captures
					[pattern[i][3] or 'x'] = c3,								-- take index names from pattern table and assign sequential captures
					[pattern[i][4] or 'x'] = c4,								-- index name may be nil in pattern[i] table so "or 'x'" spoofs a name for this index in this table
					};
				script = t.s or '';												-- translate table contents to named variables;
				region = t.r or '';												-- absent table entries are nil so set named ietf parts to empty string for concatenation
				variant= t.v or '';
				private = t.p or '';
				break;															-- and done
			end
	end

	if not code then
		return nil, nil, nil, nil, nil, table.concat ({'unrecognized language tag: ', source});		-- don't know what we got but it is malformed
	end

	code = code:lower();														-- ensure that we use and return lower case version of this
	
	if not (lang_data.override[code] or lang_name_table.lang[code]) then
		return nil, nil, nil, nil, nil, table.concat ({'unrecognized language code: ', code});		-- invalid language code, don't know about the others (don't care?)
	end
	
	if synonym_table[code] then													-- if 639-2/639-2T code has a 639-1 synonym
		table.insert (maint_cats, table.concat ({'Lang and lang-xx code promoted to ISO 639-1|', code}));
		table.insert (maint_msgs, table.concat ({'code: ', code, ' promoted to code: ', synonym_table[code]}));
		code = synonym_table[code];												-- use the synonym
	end

	if is_set (script) then
		if is_set (args_script) then
			return code, nil, nil, nil, nil, 'redundant script tag';			-- both code with script and |script= not allowed
		end
	else
		script = args_script or '';												-- use args.script if provided
	end 

	if is_set (script) then
		script = script:lower();												-- ensure that we use and return lower case version of this
		if not lang_name_table.script[script] then
			return code, nil, nil, nil, nil, table.concat ({'unrecognized script: ', script, ' for code: ', code});	-- language code ok, invalid script, don't know about the others (don't care?)
		end
	end
	if lang_name_table.suppressed[script] then									-- ensure that code-script does not use a suppressed script
		if in_array (code, lang_name_table.suppressed[script]) then
			return code, nil, nil, nil, nil, table.concat ({'script: ', script, ' not supported for code: ', code});	-- language code ok, script is suppressed for this code
		end
	end

	if is_set (region) then
		if is_set (args_region) then
			return code, nil, nil, nil, nil, 'redundant region tag';			-- both code with region and |region= not allowed
		end
	else
		region = args_region or '';												-- use args.region if provided
	end 

	if is_set (region) then
		region = region:lower();												-- ensure that we use and return lower case version of this
		if not lang_name_table.region[region] then
			return code, script, nil, nil, nil, table.concat ({'unrecognized region: ', region, ' for code: ', code});
		end
	end
	
	if is_set (variant) then
		if is_set (args_variant) then
			return code, nil, nil, nil, nil, 'redundant variant tag';			-- both code with variant and |variant= not allowed
		end
	else
		variant = args_variant or '';											-- use args.variant if provided
	end 

	if is_set (variant) then
		variant = variant:lower();												-- ensure that we use and return lower case version of this
		if not lang_name_table.variant[variant] then							-- make sure variant is valid
			return code, script, region, nil, nil, table.concat ({'unrecognized variant: ', variant});
		end																		-- does this duplicate/replace tests in lang() and lang_xx()?
		if is_set (script) then													-- if script set it must be part of the 'prefix'
			if not in_array (table.concat ({code, '-', script}), lang_name_table.variant[variant]['prefixes']) then
				return code, script, region, nil, nil, table.concat ({'unrecognized variant: ', variant, ' for code-script pair: ', code, '-', script});
			end
		else
			if not in_array (code, lang_name_table.variant[variant]['prefixes']) then
				return code, script, region, nil, nil, table.concat ({'unrecognized variant: ', variant, ' for code: ', code});
			end				
		end
	end
	
	if is_set (private) then
		private = private:lower();												-- ensure that we use and return lower case version of this
		if not lang_data.override[table.concat ({code, '-x-', private})] then	-- make sure private tag is valid; note that index 
			return code, script, region, nil, nil, table.concat ({'unrecognized private tag: ', private});
		end
	end
	return code, script, region, variant, private, nil;							-- return the good bits; make sure that msg is nil
end


--[[--------------------------< M A K E _ E R R O R _ M S G >--------------------------------------------------

assembles an error message from template name, message text, help link, and error category.

]]

local function make_error_msg (msg, args, template)
	local out = {};
	local category;
	
	if 'transl' == template then
		category = 'transl';
	else
		category = 'lang and lang-xx'
	end
	
	table.insert (out, table.concat ({'&#x5B;', args.text or 'undefined', '&#x5D; '}));	-- for error messages output args.text if available
	table.insert (out, table.concat ({'<span style=\"font-size:100%; font-style:normal;\" class=\"error\">error: {{', template, '}}: '}));
	table.insert (out, msg);
	table.insert (out, table.concat ({' ([[:Category:', category, ' template errors|help]])'}));
	table.insert (out, '</span>');
	
	if (0 == namespace) and not args.nocat then						-- only categorize in article space
		table.insert (out, table.concat ({'[[Category:', category, ' template errors]]'}));
	end

	return table.concat (out);
end
	

--[=[-------------------------< M A K E _ W I K I L I N K >----------------------------------------------------

Makes a wikilink; when both link and display text is provided, returns a wikilink in the form [[L|D]]; if only
link is provided, returns a wikilink in the form [[L]]; if neither are provided or link is omitted, returns an
empty string.

]=]

local function make_wikilink (link, display)
	if is_set (link) then
		if is_set (display) then
			return table.concat ({'[[', link, '|', display, ']]'});
		else
			return table.concat ({'[[', link, ']]'});
		end
	else
		return '';
	end
end


--[[--------------------------< D I V _ M A R K U P _ A D D >--------------------------------------------------

adds <i> and </i> tags to list-item text or to implied <p>..</p> text.  mixed not supported

]]

local function div_markup_add (text, style)
local implied_p = {};

	if text:find ('^\n[%*:;#]') then											-- look for list markup; list markup must begin at start of text
		if 'italic' == style then
			return mw.ustring.gsub (text, '(\n[%*:;#]+)([^\n]+)', '%1<i>%2</i>');	-- insert italic markup at each list item
		else
			return text;
		end
	end

	if text:find ('\n+') then													-- look for any number of \n characters in text
		text = text:gsub ('([^\n])\n([^\n])', '%1 %2');							-- replace single newline characters with a space character which mimics mediawiki

		if 'italic' == style then
			text = text:gsub('[^\n]+', '<p><i>%1</i></p>');						-- insert p and italic markup tags at each impled p (two or more consecutive '\n\n' sequences)
		else
			text = text:gsub ('[^\n]+', '<p>%1</p>');							-- insert p markup at each impled p
			text = text:gsub ('\n', '');										-- strip newline characters
		end
	end

	return text;
end


--[[--------------------------< M A K E _ T E X T _ H T M L >--------------------------------------------------

Add the html markup to text according to the type of content that it is: <span> or <i> tags for inline content or
<div> tags for block content

]]

local function make_text_html (code, text, tag, rtl, style, size, language)
	local html = {};
	local style_added = '';

	if text:match ('^%*') then
		table.insert (html, '&#42;');											-- move proto language text prefix outside of italic markup if any; use numeric entity because plane splat confuses MediaWiki
		text = text:gsub ('^%*', '');											-- remove the splat from the text
	end

	if 'span' == tag then														-- default html tag for inline content
		if 'italic' == style then												-- but if italic
			tag = 'i';															-- change to <i> tags
		end
	else																		-- must be div so go
		text = div_markup_add (text, style);									-- handle implied <p>, implied <p> with <i>, and list markup (*;:#) with <i>
	end

	table.insert (html, table.concat ({'<', tag}));								-- open the <i>, <span>, or <div> html tag
	table.insert (html, table.concat ({' lang="', code, '\"'}));				-- add language attribute

	if rtl or unicode.is_rtl(text) then
		table.insert (html, ' dir="rtl"');										-- add direction attribute for right to left languages
	end

	if 'normal' == style then													-- when |italic=no
		table.insert (html, ' style=\"font-style:normal;');						-- override external markup, if any
		style_added = '\"';														-- remember that style attribute added and is not yet closed
	end

	if is_set (size) then														-- when |size=<something>
		if is_set (style_added) then
			table.insert (html, table.concat ({' font-size:', size, ';'}));		-- add when style attribute already inserted
		else
			table.insert (html, table.concat ({' style=\"font-size:', size, ';'}));	-- create style attribute
			style_added = '\"';													-- remember that style attribute added and is not yet closed
		end
	end

	if is_set (language) then
		table.insert (html, table.concat ({style_added, ' title=\"', language}));	--start the title text
		if language:find ('languages') then
			table.insert (html, ' collective text\"');							-- for collective languages
		else
			table.insert (html, ' language text\"');							-- for individual languages
		end
		table.insert (html, '>');												-- close the opening html tag
	else
		table.insert (html, table.concat ({style_added, '>'}));					-- close the style attribute and close opening html tag
	end
	table.insert (html, text);													-- insert the text

	table.insert (html, table.concat ({'</', tag, '>'}));						-- close the <i>, <span>, or <div> html tag

	if rtl then																	-- legacy; shouldn't be necessary because all of the rtl text is wrapped inside an html tag with dir="rtl" attribute 
		table.insert (html, '&lrm;');											-- make sure the browser knows that we're at the end of the rtl
	end
	
	return table.concat (html);													-- put it all together and done
end


--[=[-------------------------< M A K E _ C A T E G O R Y >----------------------------------------------------

For individual language, <language>, returns:
	[[Category:Articles containing <language>-language text]]

for English:
	[[Category:Articles containing explicitly cited English-language text]]
	
for artificial languages (code: art)
	[[Category:Articles containing constructed-language text]]

for ISO 639-2 collective languages (and for 639-1 bh):
	[[Category:Articles with text from the <language> languages collective]]

]=]

local function make_category (code, language_name, nocat)
	local cat = {};
	
	if (0 ~= namespace) or nocat then											-- only categorize in article space
		return '';																-- return empty string for concatenation
	end
	
	if language_name:find ('languages') then
		return table.concat ({'[[Category:Articles with text from the ', language_name, ' collective]]'});
	end
		
	table.insert (cat, '[[Category:Articles containing ');
	
	if 'en' == code then
		table.insert (cat, 'explicitly cited English');
	elseif 'art' == code then
		table.insert (cat, 'constructed')
	else
		table.insert (cat, language_name);
	end
	
	table.insert (cat, '-language text]]');

	return table.concat (cat);	
end


--[[--------------------------< M A K E _ T R A N S L I T >----------------------------------------------------

return translit <i lang=xx-Latn>...</i> where xx is the language code; else return empty string

The value |script= is not used in {{transl}} for this purpose; instead it uses |code.  Because language scripts
are listed in the {{transl}} switches they are included in the data tables.  The script parameter is introduced
at {{Language with name and transliteration}}.  If |script= is set, this function uses it in preference to code.

To avoid confusion, in this module and the templates that use it, the transliteration script parameter is renamed
to be |translit-script= (in this function, tscript)

This function is used by both lang_xx() and transl()
	lang_xx() always provides code, language_name, and translit; may provide tscript; never provides style
	transl() always provides language_name, translit, and one of code or tscript, never both; always provides style

For {{transl}}, style only applies when a language code is provided
]]

local function make_translit (code, language_name, translit, std, tscript, style)
	local title;
	local tout = {};
	local title_table = lang_data.translit_title_table;							-- table of transliteration standards and the language codes and scripts that apply to those standards
	
	if is_set (code) then														-- when a language code is provided (always with {{lang-xx}} templates, not always with {{transl}})
		if not style then														-- nil for the default italic style
			table.insert (tout, "<i lang=\"");									-- so use <i> tag
		else
			table.insert (tout, table.concat ({'<span style=\"font-style:', style, '\" lang=\"'}));	-- non-standard style, construct a span tag for it
		end
		table.insert (tout, code);
		table.insert (tout, "-Latn\" title=\"");								-- transliterations are always Latin script
	else
		table.insert (tout, "<span title=\"");									-- when no language code: no lang= attribute, not italic ({{transl}} only)
	end
	
	std = std and std:lower();													-- lower case for table indexing
	
	if not is_set (std) and not is_set (tscript) then							-- when neither standard nor script specified
		table.insert (tout, language_name);										-- write a generic tool tip
		if not language_name:find ('languages') then							-- collective language names (plural 'languages' is part of the name)
			table.insert (tout, '-language')									-- skip this text (individual and macro languages only)
		end
		table.insert (tout, ' romanization');									-- finish the tool tip; use romanization when neither script nor standard supplied
	elseif is_set (std) and is_set (tscript) then								-- when both are specified
		if title_table[std] then												-- and if standard is legitimate
			if title_table[std][tscript] then									-- and if script for that standard is legitimate
				table.insert (tout, table.concat ({title_table[std][tscript:lower()], ' (', lang_name_table.script[tscript][1], ' script) transliteration'}));	-- add the appropriate text to the tool tip
			else
				table.insert (tout, title_table[std]['default']);				-- use the default if script not in std table; TODO: maint cat? error message because script not found for this standard?
			end
		else
			return '';															-- invalid standard, setup for error message
		end

	elseif is_set (std) then													-- translit-script not set, use language code
		if not title_table[std] then return ''; end								-- invalid standard, setup for error message
		
		if title_table[std][code] then											-- if language code is in the table (transl may not provide a language code)
			table.insert (tout, table.concat ({title_table[std][code:lower()], ' (', lang_name_table.lang[code][1], ' language) transliteration'}));	-- add the appropriate text to the tool tip
		else																	-- code doesn't match
			table.insert (tout, title_table[std]['default']);					-- so use the standard's default
		end
	else																		-- here if translit-script set but translit-std not set
		if title_table['no_std'][tscript] then
			table.insert (tout, title_table['no_std'][tscript]);				-- use translit-script if set
		elseif title_table['no_std'][code] then
			table.insert (tout, title_table['no_std'][code]);					-- use language code
		else
			if is_set (tscript) then
				table.insert (tout, table.concat ({language_name, '-script transliteration'}));	-- write a script tool tip
			elseif is_set (code) then
				if not language_name:find ('languages') then					-- collective language names (plural 'languages' is part of the name)
					table.insert (tout, '-language')							-- skip this text (individual and macro languages only)
				end
				table.insert (tout, ' transliteration');						-- finish the tool tip
			else
				table.insert (tout, ' transliteration');						-- generic tool tip (can we ever get here?)
			end
		end
	end

	table.insert (tout, '">');
	table.insert (tout, translit);
	if is_set (code) and not style then											-- when a language code is provided (always with {{lang-xx}} templates, not always with {{transl}})
		table.insert (tout, "</i>");											-- close the italic tag
	else
		table.insert (tout, "</span>");											-- no language code so close the span tag
	end
	return table.concat (tout);
end


--[[--------------------------< V A L I D A T E _ T E X T >----------------------------------------------------

This function checks the content of args.text and returns empty string if nothing is amiss else it returns an
error message.  The tests are for empty or missing text and for improper or disallowed use of apostrophe markup.

Italic rendering is controlled by the |italic= template parameter so italic markup should never appear in args.text
either as ''itself'' or as '''''bold italic''''' unless |italic=unset or |italic=invert.

]]

local function validate_text (template, args)
	if not is_set (args.text) then
		return make_error_msg ('no text', args, template);
	end

	if args.text:find ("%f[\']\'\'\'\'%f[^\']") or args.text:find ("\'\'\'\'\'[\']+") then	-- because we're looking, look for 4 appostrophes or 6+ appostrophes
		return make_error_msg ('text has malformed markup', args, template);
	end

	local style = args.italic;

	if ('unset' ~= style) and ('invert' ~=style) then
		if args.text:find ("%f[\']\'\'%f[^\']") or args.text:find ("%f[\']\'\'\'\'\'%f[^\']") then	-- italic but not bold, or bold italic
			return make_error_msg ('text has italic markup', args, template);
		end
	end
end


--[[--------------------------< R E N D E R _ M A I N T >------------------------------------------------------

render mainenance messages and categories

]]

local function render_maint(nocat)
	local maint = {};
	
	if 0 < #maint_msgs then														-- when there are maintenance messages
		table.insert (maint, table.concat ({'<span class="lang-comment" style="font-style:normal; display:none; color:#33aa33; margin-left:0.3em">'}));	-- opening <span> tag
		for _, msg in ipairs (maint_msgs) do
			table.insert (maint, table.concat ({msg, ' '}));					-- add message strings
		end
		table.insert (maint, '</span>');										-- close the span
	end
	
	if (0 < #maint_cats) and (0 == namespace) and not nocat then				-- when there are maintenance categories; article namespace only
		for _, cat in ipairs (maint_cats) do
			table.insert (maint, table.concat ({'[[Category:', cat, ']]'}));	-- format and add the categories
		end
	end
	
	return table.concat (maint);
end


--[[--------------------------< P R O T O _ P R E F I X >------------------------------------------------------

for proto languages, text is prefixed with a splat.  We do that here as a flag for make_text_html() so that a splat
will be rendered outside of italic markup (if used).  If the first character in text here is already a splat, we
do nothing

]]

local function proto_prefix (text, language_name)
	if language_name:find ('^Proto%-') and not text:find ('^*') then			-- language is a proto and text does not already have leading splat
		return table.concat ({'*', text});										-- prefix proto language text with a splat
	end
	
	return text;
end


--[[--------------------------< H A S _ P O E M _ T A G >------------------------------------------------------

looks for a poem strip marker in text; returns true when found; false else

auto-italic detection disabled when text has poem stripmarker because it is not possible for this code to know
the content that will replace the stripmarker.

]]

local function has_poem_tag (text)
	return text:find ('\127[^\127]*UNIQ%-%-poem%-[%a%d]+%-QINU[^\127]*\127') and true or false;
end


--[[--------------------------< H T M L _ T A G _ S E L E C T >------------------------------------------------

Inspects content of and selectively trims text.  Returns text and the name of an appropriate html tag for text.

If text contains:
	\n\n	text has implied <p>..</p> tags - trim leading and trailing whitespace and return 
If text begins with list markup:
	\n*		unordered
	\n;		definition
	\n:		definition
	\n#		ordered
trim all leading whitespace except  \n and trim all trailing whitespace

If text contains <poem>...</poem> stripmarker, return text unmodified and choose <div>..</div> tags because 
the stripmarker is replaced with text wrapped in <div>..</div> tags.

]]

local function html_tag_select (text)
	local tag;
	
	if has_poem_tag (text) then													-- contains poem stripmarker (we can't know the content of that)
		tag = 'div';															-- poem replacement is in div tags so lang must use div tags
	elseif mw.text.trim (text):find ('\n\n+') then								-- contains implied p tags
		text = mw.text.trim (text);												-- trim leading and trailing whitespace characters
		tag = 'div';															-- must be div because span may not contain p tags (added later by MediaWiki); poem replacement is in div tags
	elseif text:find ('\n[%*:;%#]') then										-- if text has list markup
		text = text:gsub ('^[\t\r\f ]*', ''):gsub ('%s*$', '');					-- trim all whitespace except leading newline character '\n'
		tag = 'div';															-- must be div because span may not contain ul, dd, dl, ol tags (added later by MediaWiki)
	else
		text = mw.text.trim (text);												-- plain text
		tag = 'span';															-- so span is fine
	end
	
	return text, tag;
end


--[[--------------------------< L A N G >----------------------------------------------------------------------

entry point for {{lang}}

there should be no reason to set parameters in the {{lang}} {{#invoke:}}
	<includeonly>{{#invoke:lang|lang}}</includeonly>

parameters are received from the template's frame (parent frame)

]]

local function _lang (args)
	local out = {};
	local language_name;														-- used to make category names
	local subtags = {};															-- IETF subtags script, region, variant, and private
	local code;																	-- the language code
	local msg;																	-- for error messages
	local tag = 'span';															-- initial value for make_text_html()
	local template = args.template or 'lang';

	if args[1] and args.code then
		return make_error_msg ('conflicting: {{{1}}} and &#124;code=', args, template);
	else
		args.code = args[1] or args.code;										-- prefer args.code
	end

	if args[2] and args.text then
		return make_error_msg ('conflicting: {{{2}}} and &#124;text=', args, template);
	else
		args.text = args[2] or args.text;										-- prefer args.text
	end
	
	msg = validate_text ('lang', args);											-- ensure that |text= is set
	if is_set (msg) then														-- msg is an already-formatted error message
		return msg;
	end
	
	args.text, tag = html_tag_select (args.text);								-- inspects text; returns appropriate html tag with text trimmed accordingly

	validate_cat_args (args);													-- determine if categorization should be suppressed

	args.rtl = args.rtl == 'yes';												-- convert to boolean: 'yes' -> true, other values -> false

	code, subtags.script, subtags.region, subtags.variant, subtags.private, msg = get_ietf_parts (args.code);	-- |script=, |region=, |variant= not supported because they should be part of args.code ({{{1}}} in {{lang}})

	if msg then
		return make_error_msg ( msg, args, template);
	end

	args.italic, msg = validate_italic (args);
	if msg then
		return make_error_msg (msg, args, template);
	end

	if nil == args.italic then													-- nil when |italic= absent or not set or |italic=default; args.italic controls
		if ('latn' == subtags.script) or								 		-- script is latn
			(this_wiki_lang ~= code and not is_set (subtags.script) and not has_poem_tag (args.text) and unicode.is_Latin (args.text)) then -- text not this wiki's language, no script specified and not in poem markup but is wholly latn script (auto-italics)
				args.italic = 'italic';											-- DEFAULT for {{lang}} templates is upright; but if latn script set for font-style:italic
		else
			args.italic = 'inherit';											-- italic not set; script not latn; inherit current style
		end
	end
	
	if is_set (subtags.script) then												-- if script set, override rtl setting
		if in_array (subtags.script, lang_data.rtl_scripts) then
			args.rtl = true;													-- script is an rtl script
		else
			args.rtl = false;													-- script is not an rtl script
		end
	end

	args.code = format_ietf_tag (code, subtags.script, subtags.region, subtags.variant);	-- format to recommended subtag styles; private omitted because private

	subtags.private = subtags.private and table.concat ({code, '-x-', subtags.private}) or nil;		-- assemble a complete private ietf subtag; args.code does not get private subtag

	if is_set (subtags.private) and lang_data.override[subtags.private] then	-- get the language name for categorization
		language_name = lang_data.override[subtags.private][1];					-- first look for private use tag language name
	elseif lang_data.override[code] then
		language_name = lang_data.override[code][1]								-- then language names taken from the override table
	elseif lang_name_table.lang[code] then
		language_name = lang_name_table.lang[code][1];							-- table entries sometimes have multiple names, always take the first one
	end

	if 'invert' == args.italic and 'span' == tag then							-- invert only supported for in-line content
		args.text = invert_italics (args.text)
	end
	
	args.text = proto_prefix (args.text, language_name);						-- prefix proto-language text with a splat

	table.insert (out, make_text_html (args.code, args.text, tag, args.rtl, args.italic, args.size, language_name));
	table.insert (out, make_category (code, language_name, args.nocat));
	table.insert (out, render_maint(args.nocat));								-- maintenance messages and categories

	return table.concat (out);													-- put it all together and done
end


--[[--------------------------< L A N G >----------------------------------------------------------------------

entry point for {{lang}}

there should be no reason to set parameters in the {{lang}} {{#invoke:}}
	<includeonly>{{#invoke:lang|lang}}</includeonly>

parameters are received from the template's frame (parent frame)

]]

local function lang (frame)
	local args = getArgs (frame, {												-- this code so that we can detect and handle wiki list markup in text
		valueFunc = function (key, value)
			if 2 == key or 'text' == key then									-- the 'text' parameter; do not trim wite space
				return value;													-- return untrimmed 'text'
			elseif value then													-- all other values: if the value is not nil
				value = mw.text.trim (value);									-- trim whitespace
				if '' ~= value then												-- empty string when value was only whitespace
					return value;
				end
			end
			return nil;															-- value was empty or contained only whitespace
		end																		-- end of valueFunc
		});

	return _lang (args);
end


--[[--------------------------< L A N G _ X X >----------------------------------------------------------------

For the {{lang-xx}} templates, the only parameter required to be set in the template is the language code.  All
other parameters can, usually should, be written in the template call.  For {{lang-xx}} templates for languages
that can have multiple writing systems, it may be appropriate to set |script= as well.

For each {{lang-xx}} template choose the appropriate entry-point function so that this function knows the default
styling that should be applied to text.

For normal, upright style:
	<includeonly>{{#invoke:lang|lang_xx_inherit|code=xx}}</includeonly>
For italic style:
	<includeonly>{{#invoke:lang|lang_xx_italic|code=xx}}</includeonly>

All other parameters should be received from the template's frame (parent frame)

Supported parameters are:
	|code = (required) the IANA language code
	|script = IANA script code; especially for use with languages that use multiple writing systems
	|region = IANA region code
	|variant = IANA variant code
	|text = (required) the displayed text in language specified by code
	|link = boolean false ('no') does not link code-spcified language name to associated language article
	|rtl = boolean true ('yes') identifies the language specified by code as a right-to-left language
	|nocat = boolean true ('yes') inhibits normal categorization; error categories are not affected
	|cat = boolian false ('no') opposite form of |nocat=
	|italic = boolean true ('yes') renders displayed text in italic font; boolean false ('no') renders displayed text in normal font; not set renders according to initial_style_state
	|lit = text that is a literal translation of text
	|label = 'none' to suppress all labeling (language name, 'translit.', 'lit.')
				any other text replaces language-name label - automatic wikilinking disabled
	
	for those {{lang-xx}} templates that support transliteration (those templates where |text= is not entirely latn script):
	|translit = text that is a transliteration of text
	|translit-std = the standard that applies to the transliteration
	|translit-script = ISO 15924 script name; falls back to code

For {{lang-xx}}, the positional parameters are:
	{{{1}}}	text
	{{{2}}}	transliterated text
	{{{3}}}	literal translation text
no other positional parameters are allowed

]]

local function _lang_xx (args)
	local out = {};
	local language_name;														-- used to make display text, article links
	local category_name;														-- same as language_name except that it retains any parenthetical disambiguators (if any) from the data set
	local subtags = {};															-- IETF subtags script, region, and variant
	local code;																	-- the language code

	local translit_script_name;													-- name associated with IANA (ISO 15924) script code
	local translit;
	local translit_title;
	local msg;																	-- for error messages
	local tag = 'span';															-- initial value for make_text_html()

	if args[1] and args.text then
		return make_error_msg ('conflicting: {{{1}}} and &#124;text=', args, 'lang-xx');
	else
		args.text = args[1] or args.text;										-- prefer args.text
	end
	
	msg = validate_text ('lang-xx', args);										-- ensure that |text= is set, does not contain italic markup and is protected from improper bolding
	if is_set (msg) then
		return msg;
	end

	args.text, tag = html_tag_select (args.text);								-- inspects text; returns appropriate html tag with text trimmed accordingly

	if args[2] and args.translit then
		return make_error_msg ('conflicting: {{{2}}} and &#124;translit=', args, 'lang-xx');
	else
		args.translit = args[2] or args.translit								-- prefer args.translit
	end
	
	if args[3] and (args.translation or args.lit) then
		return make_error_msg ('conflicting: {{{3}}} and &#124;lit= or &#124;translation=', args, 'lang-xx');
	elseif args.translation and args.lit then
		return make_error_msg ('conflicting: &#124;lit= and &#124;translation=', args, 'lang-xx');
	else
		args.translation = args[3] or args.translation or args.lit;				-- prefer args.translation
	end

	if args.links and args.link then
		return make_error_msg ('conflicting: &#124;links= and &#124;link=', args, 'lang-xx');
	else
		args.link = args.link or args.links;									-- prefer args.link
	end

	validate_cat_args (args);													-- determine if categorization should be suppressed

	args.rtl = args.rtl == 'yes';												-- convert to boolean: 'yes' -> true, other values -> false

	code, subtags.script, subtags.region, subtags.variant, subtags.private, msg = get_ietf_parts (args.code, args.script, args.region, args.variant);	-- private omitted because private

	if msg then																	-- if an error detected then there is an error message
		return make_error_msg (msg, args, 'lang-xx');
	end
	
	args.italic, msg = validate_italic (args);
	if msg then
		return make_error_msg (msg, args, 'lang-xx');
	end

	if nil == args.italic then													-- args.italic controls
		if is_set (subtags.script) then
			if 'latn' == subtags.script then
				args.italic = 'italic';											-- |script=Latn; set for font-style:italic
			else
				args.italic = initial_style_state;								-- italic not set; script is not latn; set for font-style:<initial_style_state>
			end
		else
			args.italic = initial_style_state;									-- here when |italic= and |script= not set; set for font-style:<initial_style_state>
		end
	end
	
	if is_set (subtags.script) then												-- if script set override rtl setting
		if in_array (subtags.script, lang_data.rtl_scripts) then
			args.rtl = true;													-- script is an rtl script
		else
			args.rtl = false;													-- script is not an rtl script
		end
	end

	args.code = format_ietf_tag (code, subtags.script, subtags.region, subtags.variant);	-- format to recommended subtag styles
	
	subtags.private = subtags.private and table.concat ({code, '-x-', subtags.private}) or nil;		-- assemble a complete private ietf subtag; args.code does not get private subtag

	if is_set (subtags.private) and lang_data.override[subtags.private] then	-- get the language name for categorization
		language_name = lang_data.override[subtags.private][1];					-- first look for private use tag language name
	elseif lang_data.override[args.code:lower()] then							-- look for whole IETF tag in override table
		language_name = lang_data.override[args.code:lower()][1];				-- args.code:lower() because format_ietf_tag() returns mixed case
	elseif lang_data.override[code] then										-- not there so try basic language code
		language_name = lang_data.override[code][1];
	elseif not is_set (subtags.variant) then									
		if lang_name_table.lang[code] then
			language_name = lang_name_table.lang[code][1];						-- table entries sometimes have multiple names, always take the first one
		end
	else																		-- TODO: is this the right thing to do: take language display name from variants table?
		if lang_name_table.variant[subtags.variant] then						-- TODO: there is some discussion at Template talk:Lang about having a label parameter for use when variant name is not desired among other things
			language_name = lang_name_table.variant[subtags.variant]['descriptions'][1];	-- table entries sometimes have multiple names, always take the first one
		end
	end

	category_name = language_name;												-- category names retain IANA parenthetical diambiguators (if any)
	language_name = language_name:gsub ('%s+%b()', '');							-- remove IANA parenthetical disambiguators or qualifiers from names that have them

	if args.label then
		if 'none' ~= args.label then
			table.insert (out, table.concat ({args.label, ': '}));				-- custom label
		end
	else
		if 'no' == args.link then
			table.insert (out, language_name);									-- language name without wikilink
		else
			if language_name:find ('languages') then
				table.insert (out, make_wikilink (language_name));				-- collective language name uses simple wikilink
			elseif lang_data.article_name[code] then
				table.insert (out, make_wikilink (lang_data.article_name[code][1], language_name));	-- language name with wikilink from override data
			else
				table.insert (out, make_wikilink (language_name .. ' language', language_name));	-- language name with wikilink
			end
		end
		table.insert (out, ': ');												-- separator
	end

	if 'invert' == args.italic then
		args.text = invert_italics (args.text)
	end
	
	args.text = proto_prefix (args.text, language_name);						-- prefix proto-language text with a splat

	table.insert (out, make_text_html (args.code, args.text, tag, args.rtl, args.italic, args.size))

	if is_set (args.translit) and not unicode.is_Latin (args.text) then			-- transliteration (not supported in {{lang}}); not supported when args.text is wholly latn text (this is an imperfect test)
		table.insert (out, ', ');												-- comma to separate text from translit
		if 'none' ~= args.label then
			table.insert (out, '<small>');
			if lang_name_table.script[args['translit-script']] then				-- when |translit-script= is set, try to use the script's name
				translit_script_name = lang_name_table.script[args['translit-script'][1]];
			else
				translit_script_name = language_name;							-- fall back on language name
			end
			translit_title = mw.title.makeTitle (0, table.concat ({'Romanization of ', translit_script_name}));		-- make a title object
			if translit_title.exists and ('no' ~= args.link) then
				table.insert (out, make_wikilink ('Romanization of ' .. translit_script_name or language_name, 'romanized') .. ':');	-- make a wikilink if there is an article to link to
			else
				table.insert (out, 'romanized:');								-- else plain text
			end
			table.insert (out, '&nbsp;</small>');								-- close the small tag
		end
		
		translit = make_translit (args.code, language_name, args.translit, args['translit-std'], args['translit-script'])
		if is_set (translit) then
			table.insert (out, translit);
		else
			return make_error_msg (table.concat ({'invalid translit-std: \'', args['translit-std'] or '[missing]'}), args, 'lang-xx');
		end
	end
	
	if is_set (args.translation) then											-- translation (not supported in {{lang}})
		table.insert (out, ', ');
		if 'none' ~= args.label then
			table.insert (out, '<small>');
			if 'no' == args.link then
				table.insert (out, '<abbr title="literal translation">lit.</abbr>');
			else
				table.insert (out, make_wikilink ('Literal translation', 'lit.'));
			end
			table.insert (out, "&nbsp;</small>");
		end
		table.insert (out, table.concat ({'&#39;', args.translation, '&#39;'}));	-- use html entities to avoid wiki markup confusion
	end
	
	table.insert (out, make_category (code, category_name, args.nocat));
	table.insert (out, render_maint(args.nocat));								-- maintenance messages and categories

	return table.concat (out);													-- put it all together and done
end


--[[--------------------------< L A N G _ X X _ A R G S _ G E T >----------------------------------------------

common function to get args table from {{lang-??}} templates

returns table of args

]]

local function lang_xx_args_get (frame)
	local args = getArgs(frame,
		{
		parentFirst= true,														-- parameters in the template override parameters set in the {{#invoke:}}
		valueFunc = function (key, value)
			if 1 == key then													-- the 'text' parameter; do not trim wite space
				return value;													-- return untrimmed 'text'
			elseif value then													-- all other values: if the value is not nil
				value = mw.text.trim (value);									-- trim whitespace
				if '' ~= value then												-- empty string when value was only whitespace
					return value;
				end
			end
			return nil;															-- value was empty or contained only whitespace
		end																		-- end of valueFunc
	});

	return args;
end


--[[--------------------------< L A N G _ X X _ I T A L I C >--------------------------------------------------

Entry point for those {{lang-xx}} templates that call lang_xx_italic().  Sets the initial style state to italic.

]]

local function lang_xx_italic (frame)
	local args = lang_xx_args_get (frame);
	
	initial_style_state = 'italic';
	return _lang_xx (args);
end


--[[--------------------------< _ L A N G _ X X _ I T A L I C >------------------------------------------------

Entry point ffrom another module.  Sets the initial style state to italic.

]]

local function _lang_xx_italic (args)
	initial_style_state = 'italic';
	return _lang_xx (args);
end


--[[--------------------------< L A N G _ X X _ I N H E R I T >------------------------------------------------

Entry point for those {{lang-xx}} templates that call lang_xx_inherit().  Sets the initial style state to inherit.

]]

local function lang_xx_inherit (frame)
	local args = lang_xx_args_get (frame);

	initial_style_state = 'inherit';
	return _lang_xx (args);
end


--[[--------------------------< _ L A N G _ X X _ I N H E R I T >----------------------------------------------

Entry point from another module.  Sets the initial style state to inherit.

]]

local function _lang_xx_inherit (args)
	initial_style_state = 'inherit';
	return _lang_xx (args);
end


--[[--------------------------< _ I S _ I E T F _ T A G >------------------------------------------------------

Returns true when a language name associated with IETF language tag exists; nil else.  IETF language tag must be valid.

All code combinations supported by {{lang}} and the {{lang-xx}} templates are supported by this function.

The purpose of this function is to replace {{#ifexist:Template:ISO 639 name xx|<exists>|<does not exist>}} in
templates that are better served by using {{#invoke:lang|name_from_tag|<code>}}

Module entry point from another module

]]

local function _is_ietf_tag (tag)												-- entry point when this module is require()d into another
	local c, s, r, v, p, err;													-- code, script, region, private, error message
	
	c, s, r, v, p, err = get_ietf_parts (tag);									-- disassemble tag into constituent part and validate
	return ((c and not err) and true) or nil;									-- return true when code portion has a value without error message; nil else
end


--[[--------------------------< I S _ I E T F _ T A G >--------------------------------------------------------

Module entry point from an {{#invoke:}}

]]

local function is_ietf_tag (frame)												-- entry point from an {{#invoke:Lang|is_ietf_tag|<ietf tag>}}
	return _is_ietf_tag (frame.args[1]);										-- frame.args[1] is the ietf language tag
end


--[[--------------------------< _ N A M E _ F R O M _ C O D E >------------------------------------------------

Returns language name associated with IETF language tag if valid; empty string else.

All code combinations supported by {{lang}} and the {{lang-xx}} templates are supported by this function.

Set invoke's |link= parameter to yes to get wikilinked version of the language name.

Module entry point from another module

]]

local function _name_from_tag (args)
	local subtags = {};															-- IETF subtags script, region, variant, and private
	local raw_code = args[1];													-- save a copy of the input IETF subtag
	local link = 'yes' == args['link'];											-- make a boolean
	local code;																	-- the language code
	local msg;																	-- gets an error message if IETF language tag is malformed or invalid
	local language_name = '';
	
	code, subtags.script, subtags.region, subtags.variant, subtags.private, msg = get_ietf_parts (raw_code);
	if msg then
		local template = (args['template'] and table.concat ({'{{', args['template'], '}}: '})) or '';	-- make template name (if provided by the template)
		return table.concat ({'<span style=\"font-size:100%; font-style:normal;\" class=\"error\">error: ', template, msg, '</span>'});
	end

	if lang_data.override[raw_code:lower()] then								-- look for whole IETF tag in override table (force lower case)
		language_name = lang_data.override[raw_code:lower()][1];
	elseif lang_data.override[code] then										-- not there so try basic language code in override table
		language_name = lang_data.override[code][1];
	elseif not is_set (subtags.variant) then									
		if lang_name_table.lang[code] then
			language_name = lang_name_table.lang[code][1];						-- table entries sometimes have multiple names, always take the first one
		end
	else																		-- TODO: is this the right thing to do: take language display name from variants table?
		if lang_name_table.variant[subtags.variant] then						-- TODO: there is some discussion at Template talk:Lang about having a label parameter for use when variant name is not desired among other things
			language_name = lang_name_table.variant[subtags.variant]['descriptions'][1];	-- table entries sometimes have multiple names, always take the first one
		end
	end

	language_name = language_name:gsub ('%s+%b()', '');							-- remove IANA parenthetical disambiguators or qualifiers from names that have them

	if link then																-- when |link=yes, wikilink the language name
		if language_name:find ('languages') then
			return make_wikilink (language_name);								-- collective language name uses simple wikilink
		elseif lang_data.article_name[code] then
			return make_wikilink (lang_data.article_name[code][1], language_name);	-- language name with wikilink from override data
		else
			return make_wikilink (language_name .. ' language', language_name);	-- language name with wikilink
		end
	end

	return language_name;

end


--[[--------------------------< N A M E _ F R O M _ C O D E >--------------------------------------------------

Module entry point from an {{#invoke:}}

]]

local function name_from_tag (frame)											-- entry point from an {{#invoke:Lang|name_from_tag|<ietf tag>|link=<yes>|template=<template name>}}
	return _name_from_tag (frame.args);											-- pass-on the args table, nothing else
end


--[[--------------------------< _ T A G _ F R O M _ N A M E >--------------------------------------------------

Returns the ietf language tag associated with the language name.  Spelling of language name must be correct
according to the spelling in the source tables.  When a standard language name has a parenthetical disambiguator,
that disambiguator must be omitted (they are not present in the data name-to-tag tables).

Module entry point from another module

]]

local function _tag_from_name (args)											-- entry point from another module
	local msg;

	if args[1] and '' ~= args[1] then
		local data = mw.loadData ('Module:Lang/name to tag');					-- get the reversed data tables
		local lang = args[1]:lower();											-- allow any-case for the language name (speeling must till be correct)
		local tag = data.rev_lang_data[lang] or data.rev_lang_name_table[lang];-- get the code; look first in the override then in the standard

		if tag then
			return tag;															-- language name found so return tag and done
		else
			msg = 'language: ' .. args[1] .. ' not found'						-- language name not found, error message
		end
	else
		msg = 'missing language name'											-- language name not provided, error message
	end

	local template = '';
	if args.template and '' ~= args.template then
		template = table.concat ({'{{', args['template'], '}}: '});				-- make template name (if provided by the template)
	end
	return table.concat ({'<span style=\"font-size:100%; font-style:normal;\" class=\"error\">error: ', template, msg, '</span>'});
end


--[[--------------------------< T A G _ F R O M _ N A M E >----------------------------------------------------

Module entry point from an {{#invoke:}}

]]

local function tag_from_name (frame)											-- entry point from an {{#invoke:Lang|tag_from_name|<language name>|link=<yes>|template=<template name>}}
	return _tag_from_name (frame.args);											-- pass-on the args table, nothing else
end


--[[--------------------------< _ T R A N S L >----------------------------------------------------------------

Module entry point from another module

]]

local function _transl (args)
	local title_table = lang_data.translit_title_table;							-- table of transliteration standards and the language codes and scripts that apply to those standards
	local language_name;														-- language name that matches language code; used for tool tip
	local translit;																-- translitterated text to display
	local script;																-- IANA script
	local msg;																	-- for when called functions return an error message

	if is_set (args[3]) then													-- [3] set when {{transl|code|standard|text}}
		args.text = args[3];													-- get the transliterated text
		args.translit_std = args[2] and args[2]:lower();						-- get the standard; lower case for table indexing

		if not title_table[args.translit_std] then
			return make_error_msg (table.concat ({'unrecognized transliteration standard: ', args.translit_std}), args, 'transl');
		end
	else
		if is_set (args[2]) then												-- [2] set when {{transl|code|text}}
			args.text = args[2];												-- get the transliterated text
		else
			if args[1] and args[1]:match ('^%a%a%a?%a?$') then					-- args[2] missing; is args[1] a code or its it the transliterated text?
				return make_error_msg ('no text', args, 'transl');				-- args[1] is a code so we're missing text
			else
				args.text = args[1];											-- args[1] is not a code so we're missing that; assign args.text for error message
				return make_error_msg ('missing language / script code', args, 'transl');
			end
		end
	end

	if is_set (args[1]) then													-- IANA language code used for html lang= attribute; or ISO 15924 script code
		if args[1]:match ('^%a%a%a?%a?$') then									-- args[1] has correct form?
			args.code = args[1]:lower();										-- use the language/script code; only (2, 3, or 4 alpha characters); lower case because table indexes are lower case
		else
			return make_error_msg (table.concat ({'unrecognized language / script code: ', args[1]}), args, 'transl');	-- invalid language / script code
		end
	else
		return make_error_msg ('missing language / script code', args, 'transl');			-- missing language / script code so quit
	end

	args.italic, msg = validate_italic (args);
	if msg then
		return make_error_msg (msg, args, 'transl');
	end
	
	if 'italic' == args.italic then												-- 'italic' when |italic=yes; because that is same as absent or not set and |italic=default
		args.italic = nil;														-- set to nil; 
	end

	if lang_data.override[args.code] then										-- is code a language code defined in the override table?
		language_name = lang_data.override[args.code][1];
	elseif lang_name_table.lang[args.code] then									-- is code a language code defined in the standard language code tables?
		language_name = lang_name_table.lang[args.code][1];
	elseif lang_name_table.script[args.code] then								-- if here, code is not a language code; is it a script code?
		language_name = lang_name_table.script[args.code][1];
		script = args.code;														-- code was an ISO 15924 script so use that instead
		args.code = '';															-- unset because not a language code
	else
		return make_error_msg (table.concat ({'unrecognized language / script code: ', args.code}), args, 'transl');	-- invalid language / script code
	end
																				-- here only when all parameters passed to make_translit() are valid
	return make_translit (args.code, language_name, args.text, args.translit_std, script, args.italic);
end


--[[--------------------------< T R A N S L >------------------------------------------------------------------

Module entry point from an {{#invoke:}}

]]

local function transl (frame)
	local args = getArgs(frame);												-- no {{#invoke:}} parameters
	return _transl (args);
end


--[[--------------------------< E X P O R T E D   F U N C T I O N S >------------------------------------------
]]

return {
	lang = lang,																-- entry point for {{lang}}
	lang_xx_inherit = lang_xx_inherit,											-- entry points for {{lang-??}}
	lang_xx_italic = lang_xx_italic,
	is_ietf_tag = is_ietf_tag,
	tag_from_name = tag_from_name,												-- returns ietf tag associated with language name
	name_from_tag = name_from_tag,												-- used for template documentation; possible use in ISO 639 name from code templates
	transl = transl,															-- entry point for {{transl}}

	_lang = _lang,																-- entry points when this module is require()d into other modules
	_lang_xx_inherit = _lang_xx_inherit,
	_lang_xx_italic = _lang_xx_italic,
	_is_ietf_tag = _is_ietf_tag,
	_tag_from_name = _tag_from_name, 
	_name_from_tag = _name_from_tag,
	_transl = _transl,

--deprecated entry points:
	code_from_name = tag_from_name,												-- code is wrong; should be tag; these here to ease transition to the proper name
	is_ietf_code = is_ietf_tag,
	name_from_code = name_from_tag,

	_code_from_name = _tag_from_name,
	_is_ietf_code = _is_ietf_tag,
	_name_from_code = _name_from_tag,
	};
Description	What you type	What you get
Italic	''Italic text''	Italic text
Bold	'''Bold text'''	Bold text
Bold & italic	'''''Bold & italic text'''''	*Bold & italic text*