local p = {}



local function getListItem( data )

    if not type( data ) == 'string' then

        return ''

    end

    return mw.ustring.format( '<li style="line-height: inherit; margin: 0">%s</li>', data )

end



-- Returns an array containing the keys of all positional arguments

-- that contain data (i.e. non-whitespace values).

local function getArgNums( args )

    local nums = {}

    for k, v in pairs( args ) do

        if type( k ) == 'number' and

            k >= 1 and

            math.floor( k ) == k and

            type( v ) == 'string' and

            mw.ustring.match( v, '%S' ) then

                table.insert( nums, k )

        end

    end

    table.sort( nums )

    return nums

end



-- Formats a list of classes, styles or other attributes.

local function formatAttributes( attrType, ... )

    local attributes = { ... }

    local nums = getArgNums( attributes )

    local t = {}

    for i, num in ipairs( nums ) do

        table.insert( t, attributes num  )

    end

    if #t == 0 then

        return '' -- Return the blank string so concatenation will work.

    end

    return mw.ustring.format( ' %s="%s"', attrType, table.concat( t, ' ' ) )

end



-- TODO: use Module:List. Since the update for this comment is routine,

-- this is blocked without a consensus discussion by

-- [[MediaWiki_talk:Common.css/Archive_15#plainlist_+_hlist_indentation]]

-- if we decide hlist in plainlist in this template isn't an issue, we can use

-- module:list directly

-- [https://en.wikipedia.org/?title=Module:Collapsible_list/sandbox&oldid=1130172480]

-- is an implementation (that will code rot slightly I expect)

local function buildList( args )

    -- Get the list items.

    local listItems = {}

    local argNums = getArgNums( args )

    for i, num in ipairs( argNums ) do

        table.insert( listItems, getListItem( args num  ) )

    end

    if #listItems == 0 then

        return ''

    end

    listItems = table.concat( listItems )



	-- hack around mw-collapsible show/hide jumpiness by looking for text-alignment

	-- by setting a margin if centered

	local textAlignmentCentered = 'text%-align%s*:%s*center'

	local centeredTitle = (args.title_style and args.title_style:lower():match(textAlignmentCentered)

		or args.titlestyle and args.titlestyle:lower():match(textAlignmentCentered))

	local centeredTitleSpacing

	if centeredTitle then

		centeredTitleSpacing = 'margin: 0 4em'

	else

		centeredTitleSpacing = ''

	end



    -- Get class, style and title data.

    local collapsibleContainerClass = formatAttributes(

    	'class',

    	'collapsible-list',

    	'mw-collapsible',

    	not args.expand and 'mw-collapsed'

    )

    local collapsibleContainerStyle = formatAttributes(

        'style',

         -- mostly work around .infobox-full-data defaulting to centered

        'text-align: left;',

        args.frame_style,

        args.framestyle

    )

    local collapsibleTitleStyle = formatAttributes(

        'style',

        'line-height: 1.6em; font-weight: bold;',

        args.title_style,

        args.titlestyle

    )

    local jumpyTitleStyle = formatAttributes(

        'style',

        centeredTitleSpacing

    )

    local title = args.title or 'List'

    local ulclass = formatAttributes( 'class', 'mw-collapsible-content', args.hlist and 'hlist' )

    local ulstyle = formatAttributes( 

        'style',

        'margin-top: 0; margin-bottom: 0; line-height: inherit;',

        not args.bullets and 'list-style: none; margin-left: 0;',

        args.list_style,

        args.liststyle

    )

    

    local hlist_templatestyles = ''

    if args.hlist then

    	hlist_templatestyles = mw.getCurrentFrame():extensionTag{

    		name = 'templatestyles', args = { src = 'Hlist/styles.css' }

    	}

    end

    

    -- Build the list.

    return mw.ustring.format( 

        '%s<div%s%s>\n<div%s><div%s>%s</div></div>\n<ul%s%s>%s</ul>\n</div>',

        hlist_templatestyles, collapsibleContainerClass, collapsibleContainerStyle,

        collapsibleTitleStyle, jumpyTitleStyle, title, ulclass, ulstyle, listItems

    )

end



function p.main( frame )

    local origArgs

    if frame == mw.getCurrentFrame() then

        origArgs = frame:getParent().args

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

            origArgs = frame.args

            break

        end

    else

        origArgs = frame

    end

    

    local args = {}

    for k, v in pairs( origArgs ) do

        if type( k ) == 'number' or v ~= '' then

            args k  = v

        end

    end

    return buildList( args )

end



return p