local t_insert      =  table.insert;

local t_remove      =  table.remove;

local s_format      = string.format;

local tostring      =      tostring;

local setmetatable  =  setmetatable;

local pairs         =         pairs;

local ipairs        =        ipairs;

local type          =          type;

local unpack        =        unpack;

local s_gsub        =   string.gsub;

module "stanza"

stanza_mt = {};

stanza_mt.__index = stanza_mt;

function stanza(name, attr)

	local stanza = { name = name, attr = attr or {}, tags = {}, last_add = {}};

	return setmetatable(stanza, stanza_mt);

end

function stanza_mt:query(xmlns)

	return self:tag("query", { xmlns = xmlns });

end

function stanza_mt:tag(name, attrs)

	local s = stanza(name, attrs);

	(self.last_add[#self.last_add] or self):add_child(s);

	t_insert(self.last_add, s);

	return self;

end

function stanza_mt:text(text)

	(self.last_add[#self.last_add] or self):add_child(text);

	return self; 

end

function stanza_mt:up()

	t_remove(self.last_add);

	return self;

end

function stanza_mt:add_child(child)

	if type(child) == "table" then

		t_insert(self.tags, child);

	end

	t_insert(self, child);

end

function stanza_mt:child_with_name(name)

	for _, child in ipairs(self) do	

		if child.name == name then return child; end

	end

end

function stanza_mt:children()

	local i = 0;

	return function (a)

			i = i + 1

			local v = a[i]

			if v then return v; end

		end, self, i;

end

function stanza_mt:childtags()

	local i = 0;

	return function (a)

			i = i + 1

			local v = self.tags[i]

			if v then return v; end

		end, self.tags[1], i;

end

do

	local xml_entities = { ["'"] = "&apos;", ["\""] = "&quot;", ["<"] = "&lt;", [">"] = "&gt;", ["&"] = "&amp;" };

	function xml_escape(s) return s_gsub(s, "['&<>\"]", xml_entities); end

end

local xml_escape = xml_escape;

function stanza_mt.__tostring(t)

	local children_text = "";

	for n, child in ipairs(t) do

		if type(child) == "string" then	

			children_text = children_text .. xml_escape(child);

		else

			children_text = children_text .. tostring(child);

		end

	end

	local attr_string = "";

	if t.attr then

		for k, v in pairs(t.attr) do if type(k) == "string" then attr_string = attr_string .. s_format(" %s='%s'", k, tostring(v)); end end

	end

	return s_format("<%s%s>%s</%s>", t.name, attr_string, children_text, t.name);

end

function stanza_mt.__add(s1, s2)

	return s1:add_child(s2);

end

do

        local id = 0;

        function new_id()

                id = id + 1;

                return "lx"..id;

        end

end

function preserialize(stanza)

	local s = { name = stanza.name, attr = stanza.attr };

	for _, child in ipairs(stanza) do

		if type(child) == "table" then

			t_insert(s, preserialize(child));

		else

			t_insert(s, child);

		end

	end

	return s;

end

function deserialize(stanza)

	-- Set metatable

	if stanza then

		setmetatable(stanza, stanza_mt);

		for _, child in ipairs(stanza) do

			if type(child) == "table" then

				deserialize(child);

			end

		end

		if not stanza.tags then

			-- Rebuild tags

			local tags = {};

			for _, child in ipairs(stanza) do

				if type(child) == "table" then

					t_insert(tags, child);

				end

			end

			stanza.tags = tags;

		end

	end

	return stanza;

end

function message(attr, body)

	if not body then

		return stanza("message", attr);

	else

		return stanza("message", attr):tag("body"):text(body);

	end

end

function iq(attr)

	if attr and not attr.id then attr.id = new_id(); end

	return stanza("iq", attr or { id = new_id() });

end

function reply(orig)

	return stanza(orig.name, orig.attr and { to = orig.attr.from, from = orig.attr.to, id = orig.attr.id, type = ((orig.name == "iq" and "result") or nil) });

end

function error_reply(orig, type, condition, message, clone)

	local t = reply(orig);

	t.attr.type = "error";

	-- TODO use clone

	t:tag("error", {type = type})

		:tag(condition, {xmlns = "urn:ietf:params:xml:ns:xmpp-stanzas"}):up();

	if (message) then t:tag("text"):text(message):up(); end

	return t; -- stanza ready for adding app-specific errors

end

function presence(attr)

	return stanza("presence", attr);

end

return _M;