local p = {}

local isarticle = function(class)
	local nonarticleclasses = {'Template', 'File', 'Category', 'Disambig', 'Redirect', 'Portal', 'Project', 'Draft', 'Book', 'FM'} -- these classes will not be identified as conflicting with NA-class
	local article = true
	for _,v in ipairs(nonarticleclasses) do
		if class==v then -- class matches one of the non-article classes
			article = false
			break
		end
	end
	return article
end

local ucfirst = function(s)
	-- Returns the given string with the first character in upper case.
	-- Should not be used with non-ascii strings.
	return s:sub(1, 1):upper() .. s:sub(2, -1)
end

local resolveFQSgrade = function(grade, args)
	if (args[grade] or args.FQS)=='yes' then
		return ucfirst(grade)
	else
		return 'NA'
	end
end

p._main = function(args, title)
	title = title or mw.title.getCurrentTitle()
	local out = ''
	local grade = args[1]
	if not grade or grade=='¬' then -- undefined
		out = '¬'
	else
		local ns = title.namespace
		grade = grade:match('^%s*(.-)%s*$'):lower()
		if title.subjectPageTitle.isRedirect then
			out = resolveFQSgrade('redirect',args)
		elseif ns==1 then -- Talk
			if require('Module:Disambiguation').isDisambiguation(title.subjectPageTitle:getContent()) then
				out = resolveFQSgrade('disambig',args)
			else
				if grade=='start' or grade=='stub' then -- Ucfirst
					if args[grade]~='no' then
						out = ucfirst(grade)
					end
				elseif grade=='b' or grade=='c' or grade=='fa' or grade=='fl' or grade=='a' or grade=='ga' then -- Upper-case
					if args[grade]~='no' then
						out = grade:upper()
					end
				elseif args[grade:upper()] then -- Upper-case syntax
					out = args[grade:upper()]
				elseif args[grade:lower()]=='yes' then -- Lower-case syntax
					out = mw.language.getContentLanguage():ucfirst(grade:lower())
				elseif grade=='list' or grade=='sia' or grade=='si' or grade=='sl' then-- List
					if args['list']~='no' then
						out = 'List'
					end
				elseif grade=='dab' or grade=='disambig' or grade=='disambiguation' or grade=='disamb' then
					out = resolveFQSgrade('disambig', args)
				end
			end
		elseif ns==7 or ns==711 then -- File talk
			if grade=='fm' and (args.fm or args.FQS)=='yes' then
				out = 'FM'
			else
				out = resolveFQSgrade('file', args)
			end
		elseif ns==15 then -- Category talk
			out = resolveFQSgrade('category', args)
		elseif ns==101 then -- Portal talk
			out = resolveFQSgrade('portal', args)
		elseif ns==11 or ns==829 then -- Template talk
			out = resolveFQSgrade('template', args)
		elseif ns==5 then -- Wikipedia talk
			out = resolveFQSgrade('project', args)
		elseif ns==119 then -- Draft talk
			out = resolveFQSgrade('draft', args)
		elseif ns==13 and args['help']=='yes' then -- Help talk
			out = 'Help'
		elseif ns==3 and args['user']=='yes' then -- User talk
			out = 'User'
		else
			out = 'NA'
		end
	end
	return out
end

p.main = function(frame)
	local getArgs = require('Module:Arguments').getArgs
	local args = getArgs(frame, {
		removeBlanks = false,
		wrappers = 'Template:Class mask'
	})
	return p._main(args)
end

local getclass = function(args, title)
	local class = '¬'
	if args.QUALITY_SCALE == 'inline' then
		class = args.class
	elseif args.QUALITY_SCALE == 'subpage' then
		if mw.title.new(args.BANNER_NAME..'/class').exists then
			local frame = mw.getCurrentFrame()
			class = frame:expandTemplate{title = args.BANNER_NAME..'/class', args = args}
		end
	else
		args.FQS = (args.QUALITY_SCALE == 'extended') and 'yes' or 'no'
		args[1] = args.class
		class = p._main(args, title)
	end
	return class
end

p.readarticleclass = function(options, page) -- used by p._quality and Module:Banner shell
	page = page or mw.title.getCurrentTitle().prefixedText
	local get_parameter_value = require("Module:Template parameter value").getValue
	local WPBSredirects = {'WikiProject banner shell','WikiProject banner shell/sandbox','Bannershell','Multiple wikiprojects','Project shell','Scope shell','WPB','WPBS','WPBannerShell','WP Banner Shell','WP banner shell','WikiProjectBannerShell','WikiProjectBanner Shell','WikiProjectBanners','WikiProject BannerShell','WikiProject Banner Shell','WikiProject Banners','WikiProject Banners Shell','WikiProject Shell','WikiProject banner','WikiProject banner shell/redirect','WikiProject shell','WikiprojectBannerShell','Wikiproject banner holder','Wikiproject banner shell','Wikiprojectbanners','Wikiprojectbannershell','Wpb','Wpbannershell','Wpbsgclass'}
	local success, result = get_parameter_value(page, WPBSredirects, "class", options)
	return success and result
	-- returns FALSE if banner shell template does not exist on page
	-- returns BLANK if class parameter is not defined or is defined blank
	-- otherwise returns class parameter
end

p._quality = function(args)
	local title = args.page and mw.title.new(args.page) or mw.title.getCurrentTitle()
	local local_class = getclass(args, title)
	local prefix, class = 'Y', local_class
	if local_class=='¬' then
		class = '¬'
	elseif args.QUALITY_CRITERIA ~= 'custom' then -- project uses standard scale and will inherit article class if needed
		local article_class = p.readarticleclass({ignore_subtemplates=true},title.prefixedText)
		article_class = article_class and p._main({article_class}, title)
		if article_class then -- banner shell exists
			if article_class == '' then -- no article class defined
				if local_class == '' then -- local class also does not exist, check whether any other class parameters are defined inside the shell
					local classparam = p.readarticleclass({ignore_blank=true, only_subtemplates=true},title.prefixedText)
					if classparam == '' then -- no class parameters defined, display as globally unassessed
						prefix = 'H' -- hide quality class in project banner
					end
				end
			elseif local_class == '' or local_class == article_class then -- local class matches article class or is blank
				prefix = 'H' -- hide quality class in project banner
				class = article_class
			elseif (article_class == 'NA') and not isarticle(local_class) then -- article class and local class are both non-article classes
				prefix = 'H'
			else -- article class exists and differs from local class
				prefix = 'X' -- X will indicate to meta banner that classes are different, so trigger a tracking category
			end
		end
	end
	return (args.noprefix and '' or prefix) .. class
end

p.quality = function(frame) -- used by WPBM to check global quality and compare with local parameter
	return p._quality(frame.args)
end

return p