Module:Extract short description

require('Module:No globals');

--[[--------------------------< E X T R A C T _ F R O M _ A R T I C L E >--------------------------------------

no direct template access

extracts short description text from a named template in the named article when that template is found in article
wiki source

requires three arguments:
	frame: frame object required for expandTemplate
	article_title: the name of the article to inspect - correct spelling and captialization is required
	template: the name of the template to inspect - name modified to make upper or lower first character agnostic

on success, returns the short description text; error message else

]]

local function extract_from_template (frame, article_title, template_name)
	local content = mw.title.new (article_title):getContent();
	local template_name_pattern = template_name:gsub ('^%a', string.lower):gsub ('^%a', '%[%1%1%]'):gsub ('%[%a', string.upper);	-- make lua pattern for initial letter upper or lower case: A -> [Aa]
	
	local start = string.find (content, '{{%s*' .. template_name_pattern);		-- find the start of {{template name ...;
	if not start then
		return '<span style="font-size:100%;" class="error">error: no template: ' .. template_name .. ' in: ' .. article_title .. '</span>';
	end

	local template_text = string.match (content, '%b{}', start);				-- start points to first { of the infobox template_name
	if not template_text then
		return '<span style="font-size:100%;" class="error">error: failed to extract template: ' .. template_name .. '</span>';
	end

	local text = frame:preprocess (template_text)
	text = text:match ('<div[^>]-class="shortdescription.->([^<]+)');			-- extract shortdescription text

	if not text then
		return '<span style="font-size:100%;" class="error">error: no short description text in: ' .. template_name .. ' in '.. article_title .. '</span>';
	end

	return text and mw.text.trim (text);										-- trim whitespace and done
																				-- preprocess the template then apply syntax highlighting
																				-- this will display the expanded template; not usable here because
																				-- syntaxhighlight returns a stripmarker
--	return frame:callParserFunction ('#tag:syntaxhighlight', frame:preprocess (template_text));
end


--[[--------------------------< E X T R A C T _ F R O M _ A R T I C L E >--------------------------------------

no direct template access

extracts short description text from {{short description}} template when that template is found in article wiki
source; searches for both the long name (short description) and the short-name redirect (SHD); if both are present
long name controls; if multiples of the same name are present, the first-found controls.

requires one argument: article_title is the name to the article to inspect

on success, returns the short description text; error message else

]]

local function extract_from_article (article_title)
	local content = mw.title.new (article_title):getContent();					-- read the unparsed article source
	local text, start;
	
	start = string.find (content, '{{%s*[Ss]hort description') or				-- find the start of {{Short description}} template
		string.find (content, '{{%s*SHD');										-- not full name, try the {{SHD}} redirect

	if not start then
		return '<span style="font-size:100%;" class="error">error: no short description in: ' .. article_title .. '</span>';
	end

	text = content:match ('%b{}', start);										-- get the short description template; start points to first { of the template
	text = text:match ('^[^|}]+|%s*(.+)%s*}}$');								-- strip '{{template name| and }}; trim leading and trailing whitespace
	
	return text and text or '<span style="font-size:100%;" class="error">error: no short description text in: ' .. article_title .. '</span>';
end


--[[--------------------------< E X T R A C T _ S H O R T _ D E S C R I P T I O N >----------------------------

template entry point:
	{{#invoke:extract short description|extract_short_description}}

search for and return text that is used by the {{short description}} template.  {{Short description}}, also {{SHD}}
may be located in article wikisource or embedded in a template (commonly an infobox template).  When neither of
|template= and {{{2|}}} are set, this code will look in the article wiki source; when set, this code look inside the
named template.

This template entry take two parameter:
	{{{1}}} or |article=: required; name of wiki article from which to extract the short description
	{{{2}}} or |template=; optional; name of template that holds the {{short description}} template

on success, returns the short description text; error message else

]]

local function extract_short_description (frame)
	local getArgs = require('Module:Arguments').getArgs;
	local args = getArgs(frame);
	
	local article_title = args[1] or args.article;								-- the required parameter
	
	if not article_title then													-- not supplied, fail with an error message
		return '<span style="font-size:100%;" class="error">error: article title required</span>';
	end
	
	local template_name = args[2] or args.template;								-- optional
	
	if template_name then
		return extract_from_template (frame, article_title, template_name);
	else
		return extract_from_article (article_title);
	end
end


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

return {
	extract_short_description = extract_short_description,
	extract_from_template = extract_from_template,
	extract_from_article = extract_from_article
	}
Usage
