function map(list, func)
	local new_list = {}
	for key, value in pairs(list) do
		new_list[key] = func(key, value)
	end
	return new_list
end
function join(list)
	local string = ""
	for key, value in pairs(list) do
		string = string .. value
	end
	return string
end

function render(element)
	if type(element) == "string" then
		-- TODO: escape
		return element
	end
	if element[1] then
		return join(map(element, function(key, value)
			return render(value)
		end))
	end

	local close_tag = "</"..element.type..">"
	local self_closing = element.type == "meta"
	if self_closing then
		close_tag = ""
	end

	return "<"..element.type
		..join(map(element.parameters, function(key, value)
			-- TODO: escape
			return " "..key.."='"..value.."'"
		end))
		..">"
		..join(map(element.children, function(key, value)
			return render(value)
		end))
		..close_tag
end

local function basic_element(name)
	return function(params, children)
		return { type = name, parameters = params, children = children }
	end
end

function a(params, children)
	if not params.href then
		print("WARNING: Link `"..join(children).."` doesn't have a href.")
	end
	return basic_element("a")(params, children)
end

head = basic_element("head")
body = basic_element("body")
title = basic_element("title")
h1 = basic_element("h1")
h2 = basic_element("h2")
h3 = basic_element("h3")
h4 = basic_element("h4")
h5 = basic_element("h5")
h6 = basic_element("h6")
ul = basic_element("ul")
ol = basic_element("ol")
li = basic_element("li")
p = basic_element("p")
meta = basic_element("meta")

local link = a({ href = "https://nulo.in" }, {"Hola, soy html.lua"})

local head_block = head({}, {
	meta({charset = "utf-8"}, {}),
	title({}, {"Hello world"}),
})
local body_block = body({}, {
	link
})

--print(render(head_block)..render(body_block))