local type = type;

local s_char = string.char;

local tostring, tonumber = tostring, tonumber;

local pairs, ipairs = pairs, ipairs;

local next = next;

local error = error;

local newproxy, getmetatable = newproxy, getmetatable;

local print = print;

--module("json")

local json = {};

local null = newproxy and newproxy(true) or {};

if getmetatable and getmetatable(null) then

	getmetatable(null).__tostring = function() return "null"; end;

end

json.null = null;

local escapes = {

	["\""] = "\\\"", ["\\"] = "\\\\", ["\b"] = "\\b",

	["\f"] = "\\f", ["\n"] = "\\n", ["\r"] = "\\r", ["\t"] = "\\t"};

local unescapes = {

	["\""] = "\"", ["\\"] = "\\", ["/"] = "/",

	b = "\b", f = "\f", n = "\n", r = "\r", t = "\t"};

for i=0,31 do

	local ch = s_char(i);

	if not escapes[ch] then escapes[ch] = ("\\u%.4X"):format(i); end

end

local valid_types = {

	number  = true,

	string  = true,

	table   = true,

	boolean = true

};

local special_keys = {

	__array = true;

	__hash  = true;

};

local simplesave, tablesave, arraysave, stringsave;

function stringsave(o, buffer)

	-- FIXME do proper utf-8 and binary data detection

	t_insert(buffer, "\""..(o:gsub(".", escapes)).."\"");

end

function arraysave(o, buffer)

	t_insert(buffer, "[");

	if next(o) then

		for i,v in ipairs(o) do

			simplesave(v, buffer);

			t_insert(buffer, ",");

		end

		t_remove(buffer);

	end

	t_insert(buffer, "]");

end

function tablesave(o, buffer)

	local __array = {};

	local __hash = {};

	local hash = {};

	for i,v in ipairs(o) do

		__array[i] = v;

	end

	for k,v in pairs(o) do

		local ktype, vtype = type(k), type(v);

		if valid_types[vtype] or v == null then

			if ktype == "string" and not special_keys[k] then

				hash[k] = v;

			elseif (valid_types[ktype] or k == null) and __array[k] == nil then

				__hash[k] = v;

			end

		end

	end

	if next(__hash) ~= nil or next(hash) ~= nil or next(__array) == nil then

		t_insert(buffer, "{");

		local mark = #buffer;

		end

		if next(__hash) ~= nil then

			t_insert(buffer, "\"__hash\":[");

			for k,v in pairs(__hash) do

				simplesave(k, buffer);

				t_insert(buffer, ",");

				simplesave(v, buffer);

				t_insert(buffer, ",");

			end

			t_remove(buffer);

			t_insert(buffer, "]");

			t_insert(buffer, ",");

		end

		if next(__array) then

			t_insert(buffer, "\"__array\":");

			arraysave(__array, buffer);

			t_insert(buffer, ",");

		end

		if mark ~= #buffer then t_remove(buffer); end

		t_insert(buffer, "}");

	else

		arraysave(__array, buffer);

	end

end

function simplesave(o, buffer)

	local t = type(o);

	if t == "number" then

		t_insert(buffer, tostring(o));

	elseif t == "string" then

		stringsave(o, buffer);

	elseif t == "table" then

		tablesave(o, buffer);

	elseif t == "boolean" then

		t_insert(buffer, (o and "true" or "false"));

	else

		t_insert(buffer, "null");

	end

end

function json.encode(obj)

	local t = {};

	simplesave(obj, t);

	return t_concat(t);

end

-----------------------------------

function json.decode(json)

	json = json.." "; -- appending a space ensures valid json wouldn't touch EOF

	local pos = 1;

	local current = {};

	local stack = {};

	local ch, peek;

	local function next()

		ch = json:sub(pos, pos);

		if ch == "" then error("Unexpected EOF"); end

		pos = pos+1;

		peek = json:sub(pos, pos);

		return ch;

	end

	local function skipwhitespace()

		while ch and (ch == "\r" or ch == "\n" or ch == "\t" or ch == " ") do

			next();

		end

	end

	local function skiplinecomment()

		repeat next(); until not(ch) or ch == "\r" or ch == "\n";

		skipwhitespace();

	end

	local function skipstarcomment()

		next(); next(); -- skip '/', '*'

		while peek and ch ~= "*" and peek ~= "/" do next(); end

		if not peek then error("eof in star comment") end

		next(); next(); -- skip '*', '/'

		skipwhitespace();

	end

	local function skipstuff()

		while true do

			skipwhitespace();

			if ch == "/" and peek == "*" then

				skipstarcomment();

			elseif ch == "/" and peek == "/" then

				skiplinecomment();

			else

				return;

			end

		end

	end

	local readvalue;

	local function readarray()

		local t = {};

		next(); -- skip '['

		skipstuff();

		if ch == "]" then next(); return t; end

		t_insert(t, readvalue());

		while true do

			skipstuff();

			if ch == "]" then next(); return t; end

			if not ch then error("eof while reading array");

			elseif ch == "," then next();

			elseif ch then error("unexpected character in array, comma expected"); end

			if not ch then error("eof while reading array"); end

			t_insert(t, readvalue());

		end

	end

	local function checkandskip(c)

		local x = ch or "eof";

		if x ~= c then error("unexpected "..x..", '"..c.."' expected"); end

		next();

	end

	local function readliteral(lit, val)

		for c in lit:gmatch(".") do

			checkandskip(c);

		end

		return val;

	end

	local function readstring()

		local s = "";

		checkandskip("\"");

		while ch do

			while ch and ch ~= "\\" and ch ~= "\"" do

				s = s..ch; next();

			end

			if ch == "\\" then

				next();

				if unescapes[ch] then

					s = s..unescapes[ch];

					next();

				elseif ch == "u" then

					local seq = "";

					for i=1,4 do

						next();

						if not ch then error("unexpected eof in string"); end

						if not ch:match("[0-9a-fA-F]") then error("invalid unicode escape sequence in string"); end

						seq = seq..ch;

					end

					s = s..s.char(tonumber(seq, 16)); -- FIXME do proper utf-8

					next();

				else error("invalid escape sequence in string"); end

			end

			if ch == "\"" then

				next();

				return s;

			end

		end

		error("eof while reading string");

	end

	local function readnumber()

		local s = "";

		if ch == "-" then

			s = s..ch; next();

			if not ch:match("[0-9]") then error("number format error"); end

		end

		if ch == "0" then

			s = s..ch; next();

			if ch:match("[0-9]") then error("number format error"); end

		else

			while ch and ch:match("[0-9]") do

				s = s..ch; next();

			end

		end

		if ch == "." then

			s = s..ch; next();

			if not ch:match("[0-9]") then error("number format error"); end

			while ch and ch:match("[0-9]") do

				s = s..ch; next();

			end

			if ch == "e" or ch == "E" then

				s = s..ch; next();

				if ch == "+" or ch == "-" then

					s = s..ch; next();

					if not ch:match("[0-9]") then error("number format error"); end

					while ch and ch:match("[0-9]") do

						s = s..ch; next();

					end

				end

			end

		end

		return tonumber(s);

	end

	local function readmember(t)

		skipstuff();

		local k = readstring();

		skipstuff();

		checkandskip(":");

		t[k] = readvalue();

	end

	local function fixobject(obj)

		local __array = obj.__array;

		if __array then

			obj.__array = nil;

			for i,v in ipairs(__array) do

				t_insert(obj, v);

			end

		end

		local __hash = obj.__hash;

		if __hash then

			obj.__hash = nil;

			local k;

			for i,v in ipairs(__hash) do

				if k ~= nil then

					obj[k] = v; k = nil;

				else

					k = v;

				end

			end

		end

		return obj;

	end

	local function readobject()

		local t = {};

		next(); -- skip '{'

		skipstuff();

		if ch == "}" then next(); return t; end

		if not ch then error("eof while reading object"); end

		readmember(t);

		while true do

			skipstuff();

			if ch == "}" then next(); return fixobject(t); end

			if not ch then error("eof while reading object");

			elseif ch == "," then next();

			elseif ch then error("unexpected character in object, comma expected"); end

			if not ch then error("eof while reading object"); end

			readmember(t);

		end

	end

	function readvalue()

		skipstuff();

		while ch do

			if ch == "{" then

				return readobject();

			elseif ch == "[" then

				return readarray();

			elseif ch == "\"" then

				return readstring();

			elseif ch:match("[%-0-9%.]") then

				return readnumber();

			elseif ch == "n" then

				return readliteral("null", null);

			elseif ch == "t" then

				return readliteral("true", true);

			elseif ch == "f" then

				return readliteral("false", false);

			else

				error("invalid character at value start: "..ch);

			end

		end

		error("eof while reading value");

	end

	next();

	return readvalue();

end

function json.test(object)

	local encoded = json.encode(object);

	local decoded = json.decode(encoded);

	local recoded = json.encode(decoded);

	if encoded ~= recoded then

		print("FAILED");

		print("encoded:", encoded);

		print("recoded:", recoded);

	else

		print(encoded);

	end

	return encoded == recoded;

end

return json;