Module:Lang

--[=[

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

]=]

require('strict');

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_data =  mw.loadData ('Module:Lang/data');       -- language name override and transliteration tool-tip tables
local lang_name_table = lang_data.lang_name_table;        -- language codes, names, regions, scripts, suppressed scripts
local lang_table = lang_data.lang_name_table.lang;
local lang_dep_table = lang_data.lang_name_table.lang_dep;
local script_table = lang_data.lang_name_table.script;
local region_table = lang_data.lang_name_table.region;
local variant_table = lang_data.lang_name_table.variant;
local suppressed_table = lang_data.lang_name_table.suppressed;
local override_table = lang_data.override;

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

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

local content_lang = mw.language.getContentLanguage();
local this_wiki_lang_tag = content_lang.code;         -- get this wiki's language tag
local this_wiki_lang_dir = content_lang:getDir();        -- get this wiki's language direction

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

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 {{transliteration}}) 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 |italic=, |italics=, or |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
 private: lower case prefixed with -x-
 
]]

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

 if is_set (private) then
  return table.concat ({code:lower(), 'x', private:lower()}, '-');  -- if private, all other tags ignored
 end
 
 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; only one variant subtag supported
 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 (override_table[code] or lang_table[code] or synonym_table[code] or lang_dep_table[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 script_table[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 suppressed_table[script] then           -- ensure that code-script does not use a suppressed script
  if in_array (code, suppressed_table[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 region_table[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 variant_table[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}), variant_table[variant]['prefixes']) then
    return code, script, region, nil, nil, table.concat ({'unrecognized variant: ', variant, ' for code-script pair: ', code, '-', script});
   end
  elseif is_set (region) then            -- if region set, there are some prefixes that require lang code and region (en-CA-newfound)
   if not in_array (code, variant_table[variant]['prefixes']) then  -- first see if lang code is all that's required (en-oxendict though en-GB-oxendict is preferred)
    if not in_array (table.concat ({code, '-', region}), variant_table[variant]['prefixes']) then  -- now try for lang code and region (en-CA-newfound)
     return code, script, region, nil, nil, table.concat ({'unrecognized variant: ', variant, ' for code-region pair: ', code, '-', region});
    end
   end
  else                 -- cheap way to determine if there are prefixes; fonipa and others don't have prefixes; # operator always returns 0
   if variant_table[variant]['prefixes'][1] and not in_array (code, variant_table[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 override_table[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 'Transliteration' == template then
  category = 'Transliteration';
 else
  category = 'Lang and lang-xx'
 end
 
 table.insert (out, table.concat ({'[', args.text or 'undefined', '] '})); -- for error messages output args.text if available
 table.insert (out, table.concat ({'<span style=\"color:#d33\">Error: {{', template, '}}: '}));
 table.insert (out, msg);
 table.insert (out, table.concat ({' ([[:Category:', category, ' template errors|help]])'}));
 table.insert (out, '</span>');
 
 if (0 == namespace or 10 == namespace) and not args.nocat then    -- categorize in article space (and template space to take care of broken usages)
  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 text:gsub ('(\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


--[[--------------------------< T I T L E _ W R A P P E R _ M A K E >------------------------------------------

makes a <span title="<title text>"><content_text></span> or <div title="<title text>"><content_text></div> where
<title text> is in the tool-tip in the wiki's local language and <content_text> is non-local-language text in
html markup.  This because the lang= attibute applies to the content of its enclosing tag.

<tag> holds a string 'div' or 'span' used to choose the correct wrapping tag
]]

local function title_wrapper_make (title_text, content_text, tag)
 local wrapper_t = {};
 
 table.insert (wrapper_t, table.concat ({'<', tag}));      -- open opening wrapper tag
 table.insert (wrapper_t, ' title=\"');          -- begin title attribute
 table.insert (wrapper_t, title_text);          -- add <title_text>
 table.insert (wrapper_t, '\">');           -- end title attribute and close opening wrapper tag
 table.insert (wrapper_t, content_text);          -- add <content_text>
 table.insert (wrapper_t, table.concat ({'</', tag, '>'}));     -- add closing wrapper tag

 return table.concat (wrapper_t);           -- make a big string and done
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

The lang= attribute also applies to the content of the tag where it is placed so this is wrong because 'Spanish
language text' is English:
 <i lang="es" title="Spanish language text">casa</i>
should be:
 <span title="Spanish language text"><i lang="es">casa</i></span>
or for <div>...</div>:
 <div title="Spanish language text"><div lang="es"><spanish-language-text></div></div>

]]

local function make_text_html (code, text, tag, rtl, style, size, language)
 local html_t = {};
 local style_added = '';
 local wrapper_tag = tag;             -- <tag> gets modified so save a copy for use when/if we create a wrapper span or div

 if text:match ('^%*') then
  table.insert (html_t, '&#42;');           -- move proto language text prefix outside of italic markup if any; use numeric entity because plain 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_t, table.concat ({'<', tag}));       -- open the <i>, <span>, or <div> html tag
 code = code:gsub ('%-x%-.*', '');           -- strip private use subtag from code tag because meaningless outside of wikipedia
 table.insert (html_t, table.concat ({' lang="', code, '\"'}));    -- add language attribute

 if (rtl or unicode.is_rtl(text)) and ('ltr' == this_wiki_lang_dir) then  -- text is right-to-left on a left-to-right wiki
  table.insert (html_t, ' dir="rtl"');         -- add direction attribute for right-to-left languages
 elseif not (rtl or unicode.is_rtl(text)) and ('rtl' == this_wiki_lang_dir) then -- text is left-to-right on a right-to-left wiki
  table.insert (html_t, ' dir="ltr"');         -- add direction attribute for left-to-right languages
 end

 if 'normal' == style then             -- when |italic=no
  table.insert (html_t, ' 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_t, table.concat ({' font-size: ', size, ';'})); -- add when style attribute already inserted
  else
   table.insert (html_t, table.concat ({' style=\"font-size: ', size, ';'})); -- create style attribute
   style_added = '\"';             -- remember that style attribute added and is not yet closed
  end
 end

 table.insert (html_t, table.concat ({style_added, '>'}));     -- close the opening html tag
 table.insert (html_t, text);            -- insert the text

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

 if is_set (language) then             -- create a <title_text> string for the title= attribute in a wrapper span or div
  local title_text;
   if 'zxx' == code then            -- special case for this tag 'no linguistic content'
    title_text = table.concat ({language, ' text'});    -- not a language so don't use 'language' in title text
   elseif mw.ustring.find (language, 'languages', 1, true) then
    title_text = table.concat ({language, ' collective text'});  -- for collective languages
   else
    title_text = table.concat ({language, '-language text'});  -- for individual languages
   end

  return title_wrapper_make (title_text, table.concat (html_t), wrapper_tag);
 else
  return table.concat (html_t);
 end
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 ISO 639-2 collective languages (and for 639-1 bh):
 [[Category:Articles with text in <language> languages]]

]=]

local function make_category (code, language_name, nocat, name_get)
 local cat = {};
 local retval;

 if ((0 ~= namespace) or nocat) and not name_get then      -- only categorize in article space
  return '';                -- return empty string for concatenation
 end

 if mw.ustring.find (language_name, 'languages', 1, true) then
  return table.concat ({'[[Category:Articles with text in ', language_name, ']]'});
 end
  
 table.insert (cat, '[[Category:Articles containing ');

 if this_wiki_lang_tag == code then
  table.insert (cat, 'explicitly cited ' .. language_name);    -- unique category name for the local language
 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 {{transliteration}} for this purpose; instead it uses |code.  Because language scripts
are listed in the {{transliteration}} 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 {{transliteration}}, style only applies when a language code is provided
]]

local function make_translit (code, language_name, translit, std, tscript, style)
 local title;
 local out_t = {};
 local title_t = lang_data.translit_title_table;        -- table of transliteration standards and the language codes and scripts that apply to those standards
 local title_text = '';              -- tool tip text for title= attribute
 
 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
  title_text = language_name;            -- write a generic tool tip
  if not mw.ustring.find (language_name, 'languages', 1, true) then  -- collective language names (plural 'languages' is part of the name)
   title_text = title_text .. '-language';        -- skip this text (individual and macro languages only)
  end
  title_text = title_text .. ' 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_t[std] then             -- and if standard is legitimate
   if title_t[std][tscript] then          -- and if script for that standard is legitimate
    if script_table[tscript] then
     title_text = title_text .. table.concat ({title_t[std][tscript:lower()], ' (', script_table[tscript], ' script) transliteration'}); -- add the appropriate text to the tool tip
    else
     title_text = title_text .. title_t[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
    title_text = title_text .. title_t[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_t[std] then return ''; end         -- invalid standard, setup for error message
  
  if title_t[std][code] then            -- if language code is in the table (transl may not provide a language code)
   title_text = title_text .. table.concat ({title_t[std][code:lower()], ' (', language_name, ' language) transliteration'}); -- add the appropriate text to the tool tip
  else                 -- code doesn't match
   title_text = title_text .. title_t[std]['default'];     -- so use the standard's default
  end

 else                  -- here if translit-script set but translit-std not set
  if title_t['no_std'][tscript] then
   title_text = title_text .. title_t['no_std'][tscript];    -- use translit-script if set
  elseif title_t['no_std'][code] then
   title_text = title_text .. title_t['no_std'][code];     -- use language code
  else
   if is_set (tscript) then
    title_text = title_text .. table.concat ({language_name, '-script transliteration'}); -- write a script tool tip
   elseif is_set (code) then
    if not mw.ustring.find (language_name, 'languages', 1, true) then -- collective language names (plural 'languages' is part of the name)
     title_text = title_text .. '-language';      -- skip this text (individual and macro languages only)
    end
    title_text = title_text .. ' transliteration';     -- finish the tool tip
   else
    title_text = title_text .. ' transliteration';     -- generic tool tip (can we ever get here?)
   end
  end
 end

 local close_tag;
 if is_set (code) then              -- when a language code is provided (always with {{lang-xx}} templates, not always with {{transliteration}})
  code = code:match ('^(%a%a%a?)');          -- strip all subtags leaving only the language subtag

  if not style then              -- nil for the default italic style
   table.insert (out_t, "<i lang=\"");         -- so use <i> tag
   close_tag = '</i>';             -- tag to be used when closing
  else
   table.insert (out_t, table.concat ({'<span style=\"font-style: ', style, '\" lang=\"'})); -- non-standard style, construct a span tag for it
   close_tag = '</span>';            -- tag to be used when closing
  end
  table.insert (out_t, code);
  table.insert (out_t, "-Latn\">");          -- transliterations are always Latin script
 else
  table.insert (out_t, "<span>");           -- when no language code: no lang= attribute, not italic ({{transliteration}} only)
  close_tag = '</span>';
 end

 table.insert (out_t, translit);            -- add the translit text
 table.insert (out_t, close_tag);           -- and add the appropriate </i> or </span>

 if '' == title_text then             -- when there is no need for a tool-tip
  return table.concat (out_t);           -- make a string and done
 else
  return title_wrapper_make (title_text, table.concat (out_t), 'span'); -- wrap with a tool-tip span and don
 end
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

proto_param is boolean or nil; true adds splat prefix regardless of language name; false removes and / or inhibits
regardless of language name; nil does nothing; presumes that the value in text is correct but removes extra splac

]]

local function proto_prefix (text, language_name, proto_param)
 if false == proto_param then            -- when forced by |proto=no
  return text:gsub ('^%**', '');           -- return text without splat prefix regardless of language name or existing splat prefix in text
 elseif (language_name:find ('^Proto%-') or (true == proto_param)) then  -- language is a proto or forced by |proto=yes
  return text:gsub ('^%**', '*');           -- prefix proto-language text with a splat; also removes duplicate prefixing splats
 end
 
 return text:gsub ('^%*+', '*');            -- return text unmolested except multiple splats reduced to one splat
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.

If the text contains any actual <div>...</div> tags, then it's again returned unmodified and <div>...</div>
tags are used to wrap it, to prevent div/span inversion.

]]

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 text:find ('<div') then            -- reductive; if the text contains a div tag, we must use div tags
  tag = 'div';
 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


--[[--------------------------< V A L I D A T E _ P R O T O >--------------------------------------------------

validates value assigned to |proto=; permitted values are yes and no; yes returns as true, no returns as false,
empty string (or parameter omitted) returns as nil; any other value returns as nil with a second return value of
true indicating that some other value has been assigned to |proto=

]]

local function validate_proto (proto_param)
 if 'yes' == proto_param then
  return true;
 elseif 'no' == proto_param then
  return false;
 elseif is_set (proto_param) then
  return nil, true;              -- |proto= something other than 'yes' or 'no'
 else
  return nil;                -- missing or empty
 end
end


--[[--------------------------< L A N G U A G E _ N A M E _ G E T >--------------------------------------------

common function to return language name from the data set according to IETF tag

returns language name if found in data tables; nil else

]]

local function language_name_get (ietf, code, cat)
 ietf = ietf:lower();              -- ietf:lower() because format_ietf_tag() returns mixed case
 
 local name;                 -- remains nil if not found
 
 if override_table[ietf] then            -- look for whole IETF tag in override table
  name = override_table[ietf];
 elseif override_table[code] then           -- not there so try basic language tag
  name = override_table[code];
 elseif lang_table[code] then            -- shift to iana active tag/name table
  name = lang_table[code];
 elseif lang_dep_table[code] then           -- try the iana deprecated tag/name table
  name = lang_dep_table[code];
 end

 if lang_dep_table[code] and cat then          -- because deprecated code may have been overridden to en.wiki preferred name
  table.insert (maint_cats, table.concat ({'Lang and lang-xx using deprecated ISO 639 codes|', code}));
  table.insert (maint_msgs, table.concat ({'code: ', code, ' is deprecated'}));
 end

 return name;                -- name from data tables or nil
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 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, 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';

 maint_cats = {};               -- initialize because when this module required into another module, these only declared once so only initialzed once
 maint_msgs = {};
 
 validate_cat_args (args);             -- determine if categorization should be suppressed

 if args[1] and args.code then
  return make_error_msg ('conflicting: {{{1}}} and |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 |text=', args, template);
 else
  args.text = args[2] or args.text;          -- prefer args.text
 end
 
 msg = validate_text (template, 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

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

 args.proto, msg = validate_proto (args.proto);        -- return boolean, or nil, or nil and error message flag
 if msg then
  return make_error_msg (table.concat ({'invalid |proto=: ', args.proto}), args, template);
 end

 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_tag ~= 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, subtags.private); -- format to recommended subtag styles
 language_name = language_name_get (args.code, code, true);     -- get language name; try ietf tag first, then code w/o variant then code w/ variant

 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, args.proto);   -- 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


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

stand-alone function to create literal translation of main text

Also used by {{lang-x2}}

]]

local function translation_make (args_t)
 local translation_t = {', '};            -- initialize output

 if 'none' ~= args_t.label then            -- if we want a label
  table.insert (translation_t, '<small>');        -- open the <small> html tag
  if 'no' == args_t.link then
   table.insert (translation_t, '<abbr title="literal translation">lit.</abbr>'); -- unlinked form
  else
   table.insert (translation_t, make_wikilink ('Literal translation', 'lit.')); -- linked form
  end
  table.insert (translation_t, "&thinsp;</small>");      -- close the <small> html tag
 end
 table.insert (translation_t, table.concat ({'&#39;', args_t.translation, '&#39;'})); -- use html entities to avoid wiki markup confusion
 return table.concat (translation_t);          -- make a big string and done
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()
 local template = args.template or 'Lang-xx';

 maint_cats = {};               -- initialize because when this module required into another module, these only declared once so only initialzed once
 maint_msgs = {};
 
 if args[1] and args.text then
  return make_error_msg ('conflicting: {{{1}}} and |text=', args, template);
 else
  args.text = args[1] or args.text;          -- prefer args.text
 end
 
 msg = validate_text (template, 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 |translit=', args, template);
 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 |lit= or |translation=', args, template);
 elseif args.translation and args.lit then
  return make_error_msg ('conflicting: |lit= and |translation=', args, template);
 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: |links= and |link=', args, template);
 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, template);
 end
 
 args.italic, msg = validate_italic (args);
 if msg then
  return make_error_msg (msg, args, template);
 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.proto, msg = validate_proto (args.proto);        -- return boolean, or nil, or nil and error message flag
 if msg then
  return make_error_msg (table.concat ({'invalid |proto=: ', args.proto}), args, template);
 end

 args.code = format_ietf_tag (code, subtags.script, subtags.region, subtags.variant, subtags.private); -- format to recommended subtag styles
 language_name = language_name_get (args.code, code, true);     -- get language name; try ietf tag first, then code w/o variant then code w/ variant

 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 mw.ustring.find (language_name, 'languages', 1, true) then
    table.insert (out, make_wikilink (language_name));    -- collective language name uses simple wikilink
   elseif lang_data.article_name[args.code:lower()] then    -- is ietf tag in article name over ride?
    table.insert (out, make_wikilink (lang_data.article_name[args.code:lower()], language_name)); -- language name with wikilink from override data
   elseif lang_data.article_name[code] then       -- is language tag in article override
    table.insert (out, make_wikilink (lang_data.article_name[code], 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, args.proto);   -- prefix proto-language text with a splat

 table.insert (out, make_text_html (args.code, args.text, tag, args.rtl, args.italic, args.size, ('none' == args.label) and language_name or nil))

 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 script_table[args['translit-script']] then      -- when |translit-script= is set, try to use the script's name
    translit_script_name = script_table[args['translit-script']];
   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, template);
  end
 end
 
 if is_set (args.translation) then           -- translation (not supported in {{lang}})
  table.insert (out, translation_make (args));
 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.

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, variant, 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)
 return _is_ietf_tag (getArgs (frame)[1]);         -- args[1] is the ietf language tag to be tested; also get parent frame
end


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

Module entry point from an {{#invoke:}}; same as is_ietf_tag() except does not get parameters from the parent
(template) frame.  This function not useful when called by {{lang|fn=is_ietf_tag_frame|<tag>}} because <tag>
is in the parent frame.

]]

local function is_ietf_tag_frame (frame)
 return _is_ietf_tag (getArgs (frame, {frameOnly = true,})[1]);    -- args[1] is the ietf language tag to be tested; do not get parent frame
end


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

Returns language name associated with IETF language tag if valid; error message 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 label = args.label;
 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=\"color:#d33\">Error: ', template, msg, '</span>'});
 end

 raw_code = format_ietf_tag (code, subtags.script, subtags.region, subtags.variant, subtags.private); -- format to recommended subtag styles; private omitted because private
 language_name = language_name_get (raw_code, code);       -- get language name; try ietf tag first, then code w/o variant then code w/ variant

 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 mw.ustring.find (language_name, 'languages', 1, true) then
   language_name = make_wikilink (language_name, label);    -- collective language name uses simple wikilink
  elseif lang_data.article_name[raw_code:lower()] then     -- is ietf tag in article name override?
   language_name = make_wikilink (lang_data.article_name[raw_code:lower()], label or language_name); -- language name with wikilink from override data
  elseif lang_data.article_name[code] then        -- is language tag in article name override?
   language_name = make_wikilink (lang_data.article_name[code], label or language_name); -- language name with wikilink from override data
  else
   language_name = make_wikilink (language_name .. ' language', label or language_name); -- language name with wikilink
  end
 end

 return language_name;
end


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

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 (getArgs(frame))          -- pass-on the args table, nothing else; getArgs() so we also get parent frame
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/tag from name');     -- get the reversed data tables TODO: change when going live
  local lang = args[1]:lower();           -- allow any-case for the language name (speeling must till be correct)
  local tag = data.rev_override_table[lang] or data.rev_lang_table[lang] or data.rev_lang_dep_table[lang]; -- get the code; look first in the override then in the standard

  if tag then
   return tag, true;             -- language name found so return tag and done; second return used by is_lang_name()
  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=\"color:#d33\">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>}}
 local result, _ = _tag_from_name (getArgs(frame))       -- pass-on the args table, nothing else; getArgs() so we also get parent frame; supress second return used by is_lang_name()
 return result;  
end


--[[--------------------------< I S _ L A N G _ N A M E >------------------------------------------------------

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

]]

local function is_lang_name (frame)
 local _, result = _tag_from_name (getArgs(frame))       -- pass-on the args table, nothing else; getArgs() so we also get parent frame; supress second return used by tag_from_name()
 return result and true or nil;  
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;                -- transliterated text to display
 local script;                -- IANA script
 local msg;                 -- for when called functions return an error message

 maint_cats = {};               -- initialize because when this module required into another module, these only declared once so only initialzed once
 maint_msgs = {};
 
 if is_set (args[3]) then             -- [3] set when {{transliteration|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, 'Transliteration');
  end
 else
  if is_set (args[2]) then            -- [2] set when {{transliteration|code|text}}
   args.text = args[2];            -- get the transliterated text
  else
   if args[1] and (args[1]:match ('^%a%a%a?%a?$') or     -- args[2] missing; is args[1] a language or script tag or is it the transliterated text?
    args[1]:match ('^%a%a%a?%-x%-')) then       -- or is args[1] a private-use tag
     return make_error_msg ('no text', args, 'Transliteration'); -- 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, 'Transliteration');
   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?$') or args[1]:match ('^%a%a%a?%-x%-') then -- args[1] has correct form?
   args.code = args[1]:lower();          -- use the language/script code; only (2, 3, or 4 alpha characters) or private-use; lower case because table indexes are lower case
  else
   return make_error_msg (table.concat ({'unrecognized language / script code: ', args[1]}), args, 'Transliteration'); -- invalid language / script code
  end
 else
  return make_error_msg ('missing language / script code', args, 'Transliteration'); -- missing language / script code so quit
 end

 args.italic, msg = validate_italic (args);
 if msg then
  return make_error_msg (msg, args, 'Transliteration');
 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 override_table[args.code] then           -- is code a language code defined in the override table?
  language_name = override_table[args.code];
  args.code = args.code:match ('^%a%a%a?');        -- if private use, strip all but language subtag
 elseif lang_table[args.code] then           -- is code a language code defined in the standard language code tables?
  language_name = lang_table[args.code];
 elseif lang_dep_table[args.code] then          -- is code a language code defined in the deprecated language code tables?
  language_name = lang_dep_table[args.code];
 elseif script_table[args.code] then           -- if here, code is not a language code; is it a script code?
  language_name = script_table[args.code];
  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, 'Transliteration'); -- 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)
 return _transl (getArgs(frame));
end


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

Returns category name associated with IETF language tag if valid; error message else

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

Module entry point from another module

]]

local function _category_from_tag (args_t)
 local subtags = {};               -- IETF subtags script, region, variant, and private
 local raw_code = args_t[1];             -- save a copy of the input IETF subtag
 local link = 'yes' == args_t.link;           -- make a boolean
 local label = args_t.label;
 local code;                 -- the language code
 local msg;                 -- gets an error message if IETF language tag is malformed or invalid
 local category_name = '';
 
 code, subtags.script, subtags.region, subtags.variant, subtags.private, msg = get_ietf_parts (raw_code);
 if msg then
  local template = (args_t.template and table.concat ({'{{', args_t.template, '}}: '})) or ''; -- make template name (if provided by the template)
  return table.concat ({'<span style=\"color:#d33\">Error: ', template, msg, '</span>'});
 end

 raw_code = format_ietf_tag (code, subtags.script, subtags.region, subtags.variant, subtags.private); -- format to recommended subtag styles; private omitted because private
 category_name = language_name_get (raw_code, code);       -- get language name; try ietf tag first, then code w/o variant then code w/ variant
 category_name = make_category (code, category_name, nil, true):gsub ('[%[%]]', '');

 if link then
  return table.concat ({'[[:', category_name, ']]'});
 else
  return category_name;
 end
end


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

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

]]

local function category_from_tag (frame)          -- entry point from an {{#invoke:Lang|category_from_tag|<ietf tag>|template=<template name>}}
 return _category_from_tag (getArgs (frame));        -- pass-on the args table, nothing else; getArgs() so we also get parent frame
end


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

return {
 category_from_tag = category_from_tag,
 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,
 is_ietf_tag_frame = is_ietf_tag_frame,
 is_lang_name = is_lang_name,
 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 {{transliteration}}
 
 _category_from_tag = _category_from_tag,         -- entry points when this module is require()d into other modules
 _lang = _lang,
 _lang_xx_inherit = _lang_xx_inherit,
 _lang_xx_italic = _lang_xx_italic,
 _is_ietf_tag = _is_ietf_tag,
 get_ietf_parts = get_ietf_parts,
 _tag_from_name = _tag_from_name, 
 _name_from_tag = _name_from_tag,
 _transl = _transl,
 _translation_make = translation_make,
 };