-- This module implements ((gallery))

local p = {}

local templatestyles = 'Module:Gallery/styles.css'
local yesno = require('Module:Yesno')

local function trim(s)
	return mw.ustring.gsub(mw.ustring.gsub(s, '%s', ' '), '^%s*(.-)%s*$', '%1')
end

local tracking, preview

local function checkarg(k,v)
	if k and type(k) == 'string' then
		if k == 'align' or k == 'state' or k == 'style' or k == 'title' or
			k == 'width' or k == 'height' or k == 'whitebg' or
			k == 'mode' or k == 'footer' or k == 'perrow' or k == 'noborder' or
			k:match('^alt%d+$') or k:match('^%d+$') then
			-- valid
		elseif k == 'captionstyle' then
			if not v:match('^text%-align%s*:%s*center[;%s]*$') then
				table.insert(tracking, '[[Category:Pages using gallery with the captionstyle parameter]]')
			end
		else
			-- invalid
			local vlen = mw.ustring.len(k)
			k = mw.ustring.sub(k, 1, (vlen < 25) and vlen or 25) 
			k = mw.ustring.gsub(k, '[^%w%-_ ]', '?')
			table.insert(tracking, '[[Category:Pages using gallery with unknown parameters|' .. k .. ']]')
			table.insert(preview, '"' .. k .. '"')
		end
	end
end

function p.gallery(frame)
	-- If called via #invoke, use the args passed into the invoking template.
	-- Otherwise, for testing purposes, assume args are being passed directly in.
	local origArgs = (type(frame.getParent) == 'function') and frame:getParent().args or frame
    
    -- ParserFunctions considers the empty string to be false, so to preserve the previous 
    -- behavior of ((gallery)), change any empty arguments to nil, so Lua will consider
    -- them false too.
    local args = {}
    tracking, preview = {}, {}
    for k, v in pairs(origArgs) do
    	if v ~= '' then
    		args[k] = v
    		checkarg(k,v)
    	end
	end
	
	if (args.mode or '') == 'packed' and (args.align or '') == '' then
		args.align = 'center'
	end

	local tbl = mw.html.create('div')
	tbl:addClass('mod-gallery')
    
	if args.state then
		tbl
			:addClass('mod-gallery-collapsible')
			:addClass('collapsible')
			:addClass(args.state)
	end
	
	if args.style then
		tbl:cssText(args.style)
	else
		tbl:addClass('mod-gallery-default')
	end
	
	if args.align then
		tbl:addClass('mod-gallery-' .. args.align:lower())
	end

	if args.title then
		tbl:tag('div')
			:addClass('title')
				:tag('div')
					:wikitext(args.title)
	end
	
	local gargs = {}
	gargs['class'] = 'nochecker' .. (args.noborder and '' or ' bordered-images')
	gargs['widths'] = tonumber(args.width) or 180
	gargs['heights'] = tonumber(args.height) or 180
	gargs['style'] = args.captionstyle
	gargs['perrow'] = args.perrow
	gargs['mode'] = args.mode
	if yesno(args.whitebg or 'yes') then
		gargs['class'] = gargs['class'] .. ' whitebg'
	end
	
	local gallery = {}
	
	local imageCount = math.ceil(#args / 2)

    for i = 1, imageCount do
		local img = trim(args[i*2 - 1] or '')
		local caption = trim(args[i*2] or '')
		local alt = trim(args['alt' .. i] or '')
		if img ~= '' then
			table.insert(gallery, img .. (alt ~= '' and ('|alt=' .. alt) or '') .. '|' .. caption )
		end
	end
	
	tbl:tag('div')
		:addClass('main')
		:tag('div')
			:wikitext(
				frame:extensionTag{ name = 'gallery', content = '\n' .. table.concat(gallery,'\n'), args = gargs}
				)
    
	if args.footer then
		tbl:tag('div')
			:addClass('footer')
				:tag('div')
					:wikitext(args.footer)
	end

	local trackstr = (#tracking > 0) and table.concat(tracking, '') or ''
	if #preview > 0 then
		trackstr = require('Module:If preview')._warning({
			'Unknown parameters ' .. table.concat(preview, '; ') .. '.'
		}) .. trackstr
	end
	
	return frame:extensionTag{ name = 'templatestyles', args = { src = templatestyles} } .. tostring(tbl) .. trackstr
end

return p