local p = {}



-- Ripped from Module:Infobox. TODO: Make a utility module that can do this kind of thing

local function getArgNums(args, prefix)

    -- Returns a table containing the numbers of the arguments that exist

    -- for the specified prefix. For example, if the prefix were to be 'data', and

    -- 'data1', 'data2', and 'data5' were to exist, it would return {1, 2, 5}.

    local nums = {}

    for k, v in pairs(args) do

        local num = tostring(k):match('^' .. prefix .. '([1-9]%d*)$')

        if num then table.insert(nums, tonumber(num)) end

    end

    table.sort(nums)

    return nums

end



-- Forked from Module:Unsubst-infobox



local specialParams = {

	'$B' = 'template content'

}



p'' = function ( frame )

	if not frame.args'$B' then

		error( '{{#invoke:Singles|}} requires parameter $B (template content)' )

	end



	if mw.isSubsting() then

		---- substing

		-- Passed args

		local args = {}

		for k, v in pairs( frame:getParent().args ) do

			argsk = v

		end



		-- Build an equivalent template invocation

		-- First, find the title to use

		local titleobj = mw.title.new(frame:getParent():getTitle())

		local title

		if titleobj.namespace == 10 then -- NS_TEMPLATE

			title = titleobj.text

		elseif titleobj.namespace == 0 then -- NS_MAIN

			title = ':' .. titleobj.text

		else

			title = titleobj.prefixedText

		end



		-- Remove empty fields

		for k, v in pairs( args ) do

			if v == '' then argsk = nil end

		end



		-- Pull aliases

		local nums = getArgNums(args, '[Ss]ingle ?')

		for _, num in ipairs(nums) do

			args'single' .. num = args'single' .. num or args'single ' .. num or args'Single ' .. num

			args'single' .. num .. 'date' = args'single' .. num .. 'date' or args'single ' .. num .. ' date' or args'Single ' .. num .. ' date' or ''

			args'single ' .. num], args'Single ' .. num], args'single ' .. num .. ' date'], args'Single ' .. num .. ' date' = nil, nil, nil, nil

		end

		for k, v in pairs( {Type = 'type', Name = 'name'} ) do

			if argsk and not argsv then argsv], argsk = argsk], nil end

		end



		-- Build the invocation body

		local ret = '{{' .. title



		-- Make parameter list

		local params = {'name', 'type'}

		for _, num in ipairs( nums ) do table.insert( params, 'single' .. num ); table.insert( params, 'single' .. num .. 'date' ) end



		-- Align parameters correctly and remove extra ones

		local maxlength = 0

		for k, v in ipairs( params ) do

			local tmp = mw.ustring.len( v )

			if tmp > maxlength then maxlength = tmp end

		end



		for k, v in ipairs( params ) do

			ret = ret .. '\n | ' .. v .. string.rep(' ', (maxlength - mw.ustring.len( v ))) .. ' = ' .. (argsv or '')

		end



		ret = ret .. '\n}}'



		ret = mw.ustring.gsub(ret, '%s+\n', '\n')



		return ret

	else

		-- Not substing

		-- Just return the "body"

		return frame.args'$B'

	end

end



function p.main(frame)

	local args = require('Module:Arguments').getArgs(frame, {wrappers = 'Template:Singles'})

	local out = ''

	local nums = getArgNums(args, '[Ss]ingle ?')

	for _, num in ipairs(nums) do

		out = out .. '\n# <span class="item"><span class="fn">"' .. (args'single' .. num or args'single ' .. num or args'Single ' .. num]) .. '"</span>'

		local date = args'single' .. num .. 'date' or args'single ' .. num .. ' date' or args'Single ' .. num .. ' date'

		if date then

			out = out .. '<br />Released: ' .. date

		end

		out = out .. '</span>'

	end

	

	if out ~= '' then

		if mw.ustring.match(out, '</?t[drh][ >]') then out = out .. ' [[Category:Music infoboxes with malformed table placement|R]]' end

		return '<div style="text-align:left">' .. out .. '\n</div>'

	end

	

	return out

end



return p