Module:Template parameter value

 local p = {}
 local PrepareText = require("Module:Wikitext Parsing").PrepareText

 local function getTitle(title)
	local success, titleObj = pcall(mw.title.new, title)
	if success then return titleObj
	else return nil end
 end

 --string.gmatch will check the largest block it can without re-scanning whats inside, but we need whats inside
 local function matchAllTemplates(str)
	local matches = {}
	for template in string.gmatch(str, "{%b{}}") do
		table.insert(matches, template)
		local innerContent = string.sub(template, 3, -3)
		for _,subtemplate in next,matchAllTemplates(innerContent) do
			table.insert(matches, subtemplate)
		end
	end
	return matches
 end

 --Forked version of getParameters from [[Module:Transcluder]] with extra features removed
 local function escapeString(str)
	return string.gsub(str, '[%^%$%(%)%.%[%]%*%+%-%?%%]', '%%%0')
 end
 local function getParameters(template)
	local parameters, parameterOrder = {}, {}
	local params = string.match(template, '{{[^|}]-|(.*)}}')
	if params then
		local count = 0
		-- Temporarily replace pipes in subtemplates and wikilinks to avoid chaos
		for subtemplate in string.gmatch(params, '{%b{}}') do
			params = string.gsub(params, escapeString(subtemplate), string.gsub(subtemplate, ".", {["%"]="%%", ["|"]="@@:@@", ["="]="@@_@@"}) )
		end
		for wikilink in string.gmatch(params, '%[%b[]%]') do
			params = string.gsub(params, escapeString(wikilink), string.gsub(wikilink, ".", {["%"]="%%", ["|"]="@@:@@", ["="]="@@_@@"}) )
		end
		for parameter in mw.text.gsplit(params, '|') do
			local parts = mw.text.split(parameter, '=')
			local key = mw.text.trim(parts[1])
			local value
			if #parts == 1 then
				value = key
				count = count + 1
				key = tostring(count)
			else
				value = mw.text.trim(table.concat(parts, '=', 2))
			end
			value = string.gsub(string.gsub(value, '@@:@@', '|'), '@@_@@', '=')
			key = string.gsub(string.gsub(key, '@@:@@', '|'), '@@_@@', '=')
			table.insert(parameterOrder, key)
			parameters[key] = value
		end
	end
	return parameters, parameterOrder
 end

 -- Returns a table containing parameters and a table with the order in which each of their values were found.
 -- Since this considers all subtemplates, a single parameter is expected to have multiple values.
 -- E.g. {{ABC|X={{DEF|X=Value|Y=Other value}}{{ABC|X=Yes}}|Y=P}}
 -- Would return {X={"{{DEF|X=Value|Y=Other value}}", "Value", "Yes"}, Y={"Other value", "P"}}
 local function getAllParameters(template, ignore_blank, only_subtemplates)
	local parameterTree = setmetatable({}, {
		__index = function(self,key)
			rawset(self,key,{})
			return rawget(self,key)
		end
	})
	local params, paramOrder = getParameters(template)
	for _,key in ipairs(paramOrder) do
		local value = params[key]
		if not ignore_blank or value ~= "" then
			if not only_subtemplates then
				table.insert(parameterTree[key], value) --Insert the initial value into the tree
			end
			for subtemplate in string.gmatch(value, "{%b{}}") do --And now check for subvalues
				local subparams = getAllParameters(subtemplate, ignore_blank)
				for subkey,subset in next,subparams do
					for _,subvalue in ipairs(subset) do
						table.insert(parameterTree[subkey], subvalue) --And add any we find to our tree
					end
				end
			end
		end
	end
	return parameterTree
 end

 --Module entry point. Returns a success boolean and either the target template or why it failed
 function p.getTemplate(page, templates, options)
	if not templates then --Required parameters
		return false, "Missing required parameter 'templates'"
	end
	options = options or {}
	
	local template_index = tonumber(options.template_index) or 1
	local treat_as_regex = options.treat_as_regex or false
	if type(templates) == "string" then
		-- TODO: Find a good way to allow specifying multiple templates via template invocation
		-- (Modules can just provide a table so no concerns there)
		-- Comma splitting is a bad idea (lots of templates have a comma in their name)
		templates = {templates}
	end
	
	local title = getTitle(page)
	if title == nil then
		return false, "Requested title doesn't exist"
	end
	local content = PrepareText(title:getContent() or "")
	
	local foundTemplates = 0
	for _,template in next,matchAllTemplates(content) do
		for _,wantedTemplate in pairs(templates) do
			if not treat_as_regex then
				wantedTemplate = escapeString(wantedTemplate)
			end
			local firstLetter = string.sub(wantedTemplate, 1, 1)
			local firstUpper, firstLower = firstLetter:upper(), firstLetter:lower()
			if firstUpper ~= firstLower then
				wantedTemplate = "[" .. firstUpper .. firstLower .. "]" .. string.sub(wantedTemplate, 2)
			end
			if string.match(template, "^{{%s*"..wantedTemplate.."%s*[|}]") then
				foundTemplates = foundTemplates + 1
				if foundTemplates == template_index then --Found our wanted template
					return true, template
				end
			end
		end
	end
	return false, "No valid template found"
 end

 --Module entry point. Returns a success boolean and either the target parameter's value or why it failed
 function p.getParameter(page, templates, parameter, options)
	if not (templates and parameter) then --Required parameters
		return false, "Missing required parameters 'templates' and 'parameter'"
	end
	parameter = tostring(parameter) --Force consistency
	options = options or {}
	
	local success, text = p.getTemplate(page, templates, options)
	if not success then
		return success, text
	else
		local parameter_index = tonumber(options.parameter_index) or 1
		local ignore_subtemplates = options.ignore_subtemplates or false
		local only_subtemplates = options.only_subtemplates or false
		local ignore_blank = options.ignore_blank or false

		local value
		if ignore_subtemplates then
			value = getParameters(text)[parameter] or ""
		else
			local params = getAllParameters(text, ignore_blank, only_subtemplates)
			value = params[parameter][parameter_index] or ""
		end

		value = string.gsub(value, "</?%a*include%a*>", "")
		value = mw.text.trim(value) --technically wrong in some cases but not a big issue
		return true, mw.text.decode(value) --decode due to PrepareText
	end
 end

 --Template entry point. Returns either "yes" or nothing depending on if the wanted template is found
 --Will return error text if no template is provided
 function p.hasTemplate(frame)
	local args = require('Module:Arguments').getArgs(frame)
	local yesno = require("Module:Yesno")
	local page = args[1] or args.page
	local template = args[2] or args.template
	local template_index = tonumber(args[3] or args.N) or 1
	if not template or template == "" then
		return '<span class="error">No template provided for hasTemplate</span>'
	end
	local follow = yesno(args.follow) or false
	if follow then
		page = require("Module:Redirect").luaMain(page)
	end
	local options = {
		template_index = template_index,
		treat_as_regex = yesno(args.treat_as_regex) or false,
	}

	local success, _ = p.getTemplate(page, template, options)
	return success and "yes" or ""
 end

 --Template entry point for getParameter. Returns an empty string upon failure
 function p.main(frame)
	local args = require('Module:Arguments').getArgs(frame, {
		wrappers = 'Template:Template parameter value'
	})
	local yesno = require("Module:Yesno")
	local options = {
		template_index = args[3] or args.template_index,
		parameter_index = args[5] or args.parameter_index,
		ignore_subtemplates = yesno(args.ignore_subtemplates or args.ist) or false,
		only_subtemplates = yesno(args.only_subtemplates) or false,
		ignore_blank = yesno(args.ignore_blank) or false,
		treat_as_regex = yesno(args.treat_as_regex) or false,
	}
	local page = args[1] or args.page
	local template = args[2] or args.template
	local parameter = args[4] or args.parameter
	local success, result = p.getParameter(page, template, parameter, options)
	if not success then
		return ""
	else
		if args.dontprocess then
			return result
		else
			return frame:preprocess(result)
		end
	end
 end

 --Backwards compatability
 p.getValue = p.getParameter
 --Potentially useful module entry points
 p.matchAllTemplates = matchAllTemplates
 p.getParameters = getParameters
 p.getAllParameters = getAllParameters

 return p