local function xml_escape(str)
    return string.gsub(str, "&", "&")
end

local function process_comment(table, a)
    return "<!-- " .. a .. " -->"
end

local function process_tag(table, key, a)
    local middle, options, options_str, k, v, b
    
    middle = ""
    options = {}
    
    if type(a) == "table" then
        for k, v in ipairs(a) do
            middle = middle .. v
        end
        for k, v in pairs(a) do
            if (type(k) == "string") then
                options[k] = string.gsub(v, '"', '\\"')
            end
        end
    elseif type(a) == "string" then
        middle = xml_escape(a)
    end
    
    if middle ~= "" then
        options_str = ""
        for k, v in pairs(options) do
            if (v == "") then
                options_str = " " .. options_str .. k
            else
                options_str = " " .. options_str .. k .. '="' .. v .. '"'
            end
        end
        return "<" .. key .. options_str .. ">" .. middle .. "</" .. key .. ">"
    else
        return "<" .. key .. " />"
    end
end

local xmlmarkup_metatable = {
    __index = function(table, key)
        local k = key
        return function(t, a) return process_tag(t, k, a) end
    end
}

function NewXmlMarkup()
    local r = {
        comment = process_comment,
    }
    
    setmetatable(r, xmlmarkup_metatable)
    
    return r
end

--[[

xm = NewXmlMarkup()

s = xm:html {
    xm:head {
        xm:title "Test"
    },
    xm:body {
        bgcolor = "#ffeedd",
    
        "Normal test",
        xm:br(),
        xm:b "Bold test.",
        xm:comment "Hi there...",
    }
}

print(s)

]]--