--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_json_streams/mod_json_streams.lua	Sat Apr 02 00:04:26 2011 +0500
@@ -0,0 +1,123 @@
+--
+-- XEP-0295: JSON Encodings for XMPP
+--
+
+module.host = "*"
+
+local filters = require "util.filters"
+local json = require "util.json"
+
+local json_escapes = {
+	["\""] = "\\\"", ["\\"] = "\\\\", ["\b"] = "\\b", ["\f"] = "\\f",
+	["\n"] = "\\n", ["\r"] = "\\r", ["\t"] = "\\t"};
+
+local s_char = string.char;
+for i=0,31 do
+	local ch = s_char(i);
+	if not json_escapes[ch] then json_escapes[ch] = ("\\u%.4X"):format(i); end
+end
+
+local state_out = 0;
+local state_key_before = 1;
+local state_key_in = 2;
+local state_key_escape = 3;
+local state_key_after = 4;
+local state_val_before = 5;
+local state_val_in = 6;
+local state_val_escape = 7;
+local state_val_after = 8;
+
+local whitespace = { [" "] = true, ["\n"] = true, ["\r"] = true, ["\t"] = true };
+function json_decoder()
+	local state = state_out;
+	local quote;
+	local output = "";
+	local buffer = "";
+	return function(input)
+		for ch in input:gmatch(".") do
+			module:log("debug", "%s | %d", ch, state)
+			local final = false;
+			if state == state_out then
+				if whitespace[ch] then
+				elseif ch ~= "{" then return nil, "{ expected";
+				else state = state_key_before end
+			elseif state == state_key_before then
+				if whitespace[ch] then
+				elseif ch ~= "'" and ch ~= "\"" then return nil, "\" expected";
+				else quote = ch; state = state_key_in; end
+			elseif state == state_key_in then
+				if ch == quote then state = state_key_after;
+				elseif ch ~= "s" then return nil, "invalid key, 's' expected"; -- only s as key allowed
+				else end -- ignore key
+			elseif state == state_key_after then
+				if whitespace[ch] then
+				elseif ch ~= ":" then return nil, ": expected";
+				else state = state_val_before; end
+			elseif state == state_val_before then
+				if whitespace[ch] then
+				elseif ch ~= "'" and ch ~= "\"" then return nil, "\" expected";
+				else quote = ch; state = state_val_in; end
+			elseif state == state_val_in then
+				if ch == quote then state = state_val_after;
+				elseif ch == "\\" then state = state_val_escape;
+				else end
+			elseif state == state_val_after then
+				if whitespace[ch] then
+				elseif ch ~= "}" then return nil, "} expected";
+				else state = state_out;
+					final = true;
+				end
+			elseif state == state_val_escape then
+				state = state_val_in;
+			else
+				module:log("error", "Unhandled state: "..state);
+				return nil, "Unhandled state in parser"
+			end
+			buffer = buffer..ch;
+			if final then
+				module:log("debug", "%s", buffer)
+				local tmp;
+				pcall(function() tmp = json.decode(buffer); end);
+				if not tmp then return nil, "Invalid JSON"; end
+				output, buffer = output..tmp.s, "";
+			end
+		end
+		local _ = output; output = "";
+		return _;
+	end;
+end
+
+function filter_hook(session)
+	local determined = false;
+	local is_json = false;
+	local function in_filter(t)
+		if not determined then
+			is_json = (t:sub(1,1) == "{") and json_decoder();
+			determined = true;
+		end
+		if is_json then
+			local s, err = is_json(t);
+			if not err then return s; end
+			session:close("not-well-formed");
+			return;
+		end
+		return t;
+	end
+	local function out_filter(t)
+		if is_json then
+			return '{"s":"' .. t:gsub(".", json_escapes) .. '"}'; -- encode
+		end
+		return t;
+	end
+	filters.add_filter(session, "bytes/in", in_filter,   100);
+	filters.add_filter(session, "bytes/out", out_filter, 100);
+end
+
+function module.load()
+	filters.add_filter_hook(filter_hook);
+end
+function module.unload()
+	filters.remove_filter_hook(filter_hook);
+end
+
+