util/template.lua

local st = require "util.stanza";

local lxp = require "lxp";

local setmetatable = setmetatable;

local pairs = pairs;

local ipairs = ipairs;

local error = error;

local loadstring = loadstring;

local debug = debug;

module("template")

local parse_xml = (function()

	local ns_prefixes = {

		["http://www.w3.org/XML/1998/namespace"] = "xml";

	};

	local ns_separator = "\1";

	local ns_pattern = "^([^"..ns_separator.."]*)"..ns_separator.."?(.*)$";

	return function(xml)

		local handler = {};

		local stanza = st.stanza("root");

		function handler:StartElement(tagname, attr)

			local curr_ns,name = tagname:match(ns_pattern);

			if name == "" then

				curr_ns, name = "", curr_ns;

			end

			if curr_ns ~= "" then

				attr.xmlns = curr_ns;

			end

			for i=1,#attr do

				local k = attr[i];

				attr[i] = nil;

				local ns, nm = k:match(ns_pattern);

				if nm ~= "" then

					ns = ns_prefixes[ns]; 

					if ns then 

						attr[ns..":"..nm] = attr[k];

						attr[k] = nil;

					end

				end

			end

			stanza:tag(name, attr);

		end

		function handler:CharacterData(data)

			data = data:gsub("^%s*", ""):gsub("%s*$", "");

			stanza:text(data);

		end

		function handler:EndElement(tagname)

			stanza:up();

		end

		local parser = lxp.new(handler, "\1");

		local ok, err, line, col = parser:parse(xml);

		if ok then ok, err, line, col = parser:parse(); end

		--parser:close();

		if ok then

			return stanza.tags[1];

		else

			return ok, err.." (line "..line..", col "..col..")";

		end

	end;

end)();

local function create_string_string(str)

	str = ("%q"):format(str);

	str = str:gsub("{([^}]*)}", function(s)

		return '"..(data["'..s..'"]or"").."';

	end);

	return str;

end

local function create_attr_string(attr, xmlns)

	local str = '{';

	for name,value in pairs(attr) do

		if name ~= "xmlns" or value ~= xmlns then

			str = str..("[%q]=%s;"):format(name, create_string_string(value));

		end

	end

	return str..'}';

end

local function create_clone_string(stanza, lookup, xmlns)

	if not lookup[stanza] then

		local s = ('setmetatable({name=%q,attr=%s,tags={'):format(stanza.name, create_attr_string(stanza.attr, xmlns));

		-- add tags

		for i,tag in ipairs(stanza.tags) do

			s = s..create_clone_string(tag, lookup, stanza.attr.xmlns)..";";

		end

		s = s..'};';

		-- add children

		for i,child in ipairs(stanza) do

			if child.name then

				s = s..create_clone_string(child, lookup, stanza.attr.xmlns)..";";

			else

				s = s..create_string_string(child)..";"

			end

		end

		s = s..'}, stanza_mt)';

		s = s:gsub('%.%.""', ""):gsub('([=;])""%.%.', "%1"):gsub(';"";', ";"); -- strip empty strings

		local n = #lookup + 1;

		lookup[n] = s;

		lookup[stanza] = "_"..n;

	end

	return lookup[stanza];

end

local stanza_mt = st.stanza_mt;

local function create_cloner(stanza, chunkname)

	local lookup = {};

	local name = create_clone_string(stanza, lookup, "");

	local f = "local setmetatable,stanza_mt=...;return function(data)";

	for i=1,#lookup do

		f = f.."local _"..i.."="..lookup[i]..";";

	end

	f = f.."return "..name..";end";

	local f,err = loadstring(f, chunkname);

	if not f then error(err); end

	return f(setmetatable, stanza_mt);

end

local template_mt = { __tostring = function(t) return t.name end };

local function create_template(templates, text)

	local stanza, err = parse_xml(text);

	if not stanza then error(err); end

	local info = debug.getinfo(3, "Sl");

	info = info and ("template(%s:%d)"):format(info.short_src:match("[^\\/]*$"), info.currentline) or "template(unknown)";

	local template = setmetatable({ apply = create_cloner(stanza, info), name = info, text = text }, template_mt);

	templates[text] = template;

	return template;

end

local templates = setmetatable({}, { __mode = 'k', __index = create_template });

return function(text)

	return templates[text];

end;