require('strict')
local p = {}
local getArgs = require('Module:Arguments').getArgs
local yesno = require("Module:Yesno")

local function converttolinearrgb(c)
	c = tonumber(c, 16)
	c = c / 255.0
	if c <= 0.03928 then
		c = c/12.92321  -- Correct constant from sRGB standard
	else
		c = ((c+0.055)/1.055) ^ 2.4
	end
	
	return c
end

local function luminance(color)
	-- The text color in the header is automatically chosen based on the best contrast
	-- https://stackoverflow.com/questions/3942878/how-to-decide-font-color-in-white-or-black-depending-on-background-color
	
	local rgb = string.gsub(color, '#', '')
	rgb = mw.text.split(rgb, '')
	local r, g, b
	if #rgb == 6 then
		r = rgb[1] .. rgb[2]
		g = rgb[3] .. rgb[4]
		b = rgb[5] .. rgb[6]
	elseif #rgb == 3 then
		r = rgb[1] .. rgb[1]
		g = rgb[2] .. rgb[2]
		b = rgb[3] .. rgb[3]
	end
	r = converttolinearrgb(r)
	g = converttolinearrgb(g)
	b = converttolinearrgb(b)
	
	return 0.2126 * r + 0.7152 * g + 0.0722 * b
end

local function generate_header(root, args)
	local header = root:tag('div')
	header:css('font-size','1.6875em')
	header:css('border-radius','2px')
	header:css('font-weight','bold')
	header:css('padding','0.25em')
	header:css('background',args.themecolor)
	header:css('color',luminance(args.themecolor) > 0.1791 and '#000' or '#fff')
	header:cssText(args.headerstyle)
	header:wikitext(args.portalname)
	if args.portalicon then
		local span = header:tag('span')
		span:css('padding','0.3em')
		span:css('display','inline-block')
		span:css('margin-right','0.5em')
		span:wikitext(portalicon)
	end
	return header
end

local function generate_tab(body, index, args)
	local container = body:tag('li')
	container:css('display','inline-block')
	container:css('position','relative')
	container:css('vertical-align','top')
	container:css('margin','0')
			
	-- Create the tab itself
			
	local entry = container:tag('span')
	entry:css('display','inline-block')
	entry:css('margin','1em')
	entry:css('padding-bottom','0.5em')
	entry:css('font-weight','bold')
	if index == args.active then
		if not args.subtabs[index] or args.hidesubnav then
			entry:css('border-bottom','0.3em solid '..args.themecolor)
		else
			entry:css('margin-bottom','0')
		end
	else
		entry:css('border-bottom','0.3em solid #c8ccd1')
	end
			
	if args.tabsicons[index] then
		local icon = entry:tag('span')
		icon:css('margin-right','0.75em')
		icon:wikitext(args.tabsicons[index])
	end
	entry:wikitext(args.tabs[index])
	
	-- If the tab is active, show the subnav if there is any
			
	if index == args.active and args.subtabs[index] and not args.hidesubnav then
		local subnav = container:tag('ul')
		subnav:css('font-size','95%')
		subnav:css('margin','0 1em')
		subnav:css('padding','1.125em 0')
		local borderColor = '0.35em solid '..args.themecolor
		subnav:css('border-top',borderColor)
		subnav:css('border-bottom',borderColor)
		subnav:css('list-style','none')
		for _, subpagelink in ipairs(args.subtabs[index]) do
			local link = subnav:tag('li')
			link:css('margin','0')
			link:wikitext(subpagelink)
		end
	end
	return container
end

function p._render(args)
	local tabs = {}
	local subtabs = {}
	local tabsicons = {}
    -- Default values
	args.portalname = args.portalname or 'Portal'
	args.themecolor = args.themecolor or '#54595d'
	for _, key in ipairs({'wrc','hidenav','hidesubnav'}) do
		args[key] = yesno(args[key])
	end
	args.active = tonumber(args.active)
	for key, value in pairs(args) do
		local id = tonumber(mw.ustring.match(key,'^tab(%d+)$'))
		if id then
			tabs[id] = value
		else
			id = tonumber(mw.ustring.match(key,'^icon(%d+)$'))
			if id then
				tabsicons[id] = value
			else
				local primetab, subtab = mw.ustring.match(key,'^subtab(%d+)-(%d+)$')
				if primetab and subtab then
					primetab = tonumber(primetab)
					subtab = tonumber(subtab)
					if not subtabs[primetab] then
						subtabs[primetab] = {}
					end
					subtabs[primetab][subtab] = value
				end
			end
		end
	end
	args.tabs = tabs
	args.subtabs = subtabs
	args.tabsicons = tabsicons
		
	-- Constructing header
	
	local root = mw.html.create('div')
	if args.wrc then
		local badgeargs = {}
		if wrcadditional then
			badgeargs['additional'] = args.wrcadditional
		end

		root:wikitext(frame:expandTemplate{
			title = 'Wikimedia Resource Center badge',
			args = badgeargs })
	end
	generate_header(root, args)
	
	-- Constructing the rest
	
	if not args.hidenav then
		local body = root:tag('ul')
		body:css('font-size','1.125em')
		body:css('list-style','none')
		body:css('margin','0 0 1.125em 0')
		
		local tabindex = {}
		for index, _ in pairs(tabs) do
			table.insert(tabindex,index)
		end
		table.sort(tabindex)
		
		for _, index in ipairs(tabindex) do
			generate_tab(body, index, args)
		end
	end
	local clear = root:tag('div')
	clear:css('clear','both')
	return tostring(root)
end

function p.render(frame)
	local args = getArgs(frame)
	return p._render(args)
end

return p