-- Prosody IM

-- Copyright (C) 2008-2010 Matthew Wild

-- Copyright (C) 2008-2010 Waqas Hussain

--

-- This project is MIT/X11 licensed. Please see the

-- COPYING file in the source package for more information.

--

local type = type;

local t_insert, t_concat, t_remove = table.insert, table.concat, table.remove;

local s_char = string.char;

local tostring, tonumber = tostring, tonumber;

local pairs, ipairs, spairs = pairs, ipairs, require "util.iterators".sorted_pairs;

local next = next;

local getmetatable, setmetatable = getmetatable, setmetatable;

local print = print;

local has_array, array = pcall(require, "util.array");

local array_mt = has_array and getmetatable(array()) or {};

--module("json")

local module = {};

local null = setmetatable({}, { __tostring = function() return "null"; end; });

module.null = null;

local escapes = {

	["\""] = "\\\"", ["\\"] = "\\\\", ["\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 function codepoint_to_utf8(code)

	if code < 0x80 then return s_char(code); end

	local bits0_6 = code % 64;

	if code < 0x800 then

		local bits6_5 = (code - bits0_6) / 64;

		return s_char(0x80 + 0x40 + bits6_5, 0x80 + bits0_6);

	end

	local bits0_12 = code % 4096;

	local bits6_6 = (bits0_12 - bits0_6) / 64;

	local bits12_4 = (code - bits0_12) / 4096;

	return s_char(0x80 + 0x40 + 0x20 + bits12_4, 0x80 + bits6_6, 0x80 + bits0_6);

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 _, 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;

		local _pairs = buffer.ordered and spairs or pairs;

		for k,v in _pairs(hash) do

			stringsave(k, buffer);

			t_insert(buffer, ":");

			simplesave(v, buffer);

			t_insert(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 o == null then

		t_insert(buffer, "null");

	elseif t == "number" then

		t_insert(buffer, tostring(o));

	elseif t == "string" then

		stringsave(o, buffer);

	elseif t == "table" then

		local mt = getmetatable(o);

		if mt == array_mt then

			arraysave(o, buffer);

		else

			tablesave(o, buffer);

		end

	elseif t == "boolean" then

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

	else

		t_insert(buffer, "null");

	end

end

function module.encode(obj)

	local t = {};

	simplesave(obj, t);

	return t_concat(t);

end

function module.encode_ordered(obj)

	local t = { ordered = true };

	simplesave(obj, t);

	return t_concat(t);

end

function module.encode_array(obj)

	local t = {};

	arraysave(obj, t);

	return t_concat(t);

end

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

local function _skip_whitespace(json, index)

	return json:find("[^ \t\r\n]", index) or index; -- no need to check \r\n, we converted those to \t

end

local function _fixobject(obj)

	local __array = obj.__array;

	if __array then

		obj.__array = nil;

		for _, v in ipairs(__array) do

			t_insert(obj, v);

		end

	end

	local __hash = obj.__hash;

	if __hash then

		obj.__hash = nil;

		local k;

		for _, v in ipairs(__hash) do

			if k ~= nil then

				obj[k] = v; k = nil;

			else

				k = v;

			end

		end

	end

	return obj;

end

local _readvalue, _readstring;

local function _readobject(json, index)

	local o = {};

	while true do

		local key, val;

		index = _skip_whitespace(json, index + 1);

		if json:byte(index) ~= 0x22 then -- "\""

			if json:byte(index) == 0x7d then return o, index + 1; end -- "}"

			return nil, "key expected";

		end

		key, index = _readstring(json, index);

		if key == nil then return nil, index; end

		index = _skip_whitespace(json, index);

		if json:byte(index) ~= 0x3a then return nil, "colon expected"; end -- ":"

		val, index = _readvalue(json, index + 1);

		if val == nil then return nil, index; end

		o[key] = val;

		index = _skip_whitespace(json, index);

		local b = json:byte(index);

		if b == 0x7d then return _fixobject(o), index + 1; end -- "}"

		if b ~= 0x2c then return nil, "object eof"; end -- ","

	end

end

local function _readarray(json, index)

	local a = {};

	local oindex = index;

	while true do

		local val;

		val, index = _readvalue(json, index + 1);

		if val == nil then

			if json:byte(oindex + 1) == 0x5d then return setmetatable(a, array_mt), oindex + 2; end -- "]"

			return val, index;

		end

		t_insert(a, val);

		index = _skip_whitespace(json, index);

		local b = json:byte(index);

		if b == 0x5d then return setmetatable(a, array_mt), index + 1; end -- "]"

		if b ~= 0x2c then return nil, "array eof"; end -- ","

	end

end

local _unescape_error;

local function _unescape_surrogate_func(x)

	local lead, trail = tonumber(x:sub(3, 6), 16), tonumber(x:sub(9, 12), 16);

	local codepoint = lead * 0x400 + trail - 0x35FDC00;

	local a = codepoint % 64;

	codepoint = (codepoint - a) / 64;

	local b = codepoint % 64;

	codepoint = (codepoint - b) / 64;

	local c = codepoint % 64;

	codepoint = (codepoint - c) / 64;

	return s_char(0xF0 + codepoint, 0x80 + c, 0x80 + b, 0x80 + a);

end

local function _unescape_func(x)

	x = x:match("%x%x%x%x", 3);

	if x then

		local codepoint = tonumber(x, 16)

		if codepoint >= 0xD800 and codepoint <= 0xDFFF then _unescape_error = true; end -- bad surrogate pair

		return codepoint_to_utf8(codepoint);

	end

	_unescape_error = true;

end

function _readstring(json, index)

	index = index + 1;

	local endindex = json:find("\"", index, true);

	if endindex then

		local s = json:sub(index, endindex - 1);

		--if s:find("[%z-\31]") then return nil, "control char in string"; end

		-- FIXME handle control characters

		_unescape_error = nil;

		s = s:gsub("\\u[dD][89abAB]%x%x\\u[dD][cdefCDEF]%x%x", _unescape_surrogate_func);

		-- FIXME handle escapes beyond BMP

		s = s:gsub("\\u.?.?.?.?", _unescape_func);

		if _unescape_error then return nil, "invalid escape"; end

		return s, endindex + 1;

	end

	return nil, "string eof";

end

local function _readnumber(json, index)

	local m = json:match("[0-9%.%-eE%+]+", index); -- FIXME do strict checking

	return tonumber(m), index + #m;

end

local function _readnull(json, index)

	local a, b, c = json:byte(index + 1, index + 3);

	if a == 0x75 and b == 0x6c and c == 0x6c then

		return null, index + 4;

	end

	return nil, "null parse failed";

end

local function _readtrue(json, index)

	local a, b, c = json:byte(index + 1, index + 3);

	if a == 0x72 and b == 0x75 and c == 0x65 then

		return true, index + 4;

	end

	return nil, "true parse failed";

end

local function _readfalse(json, index)

	local a, b, c, d = json:byte(index + 1, index + 4);

	if a == 0x61 and b == 0x6c and c == 0x73 and d == 0x65 then

		return false, index + 5;

	end

	return nil, "false parse failed";

end

function _readvalue(json, index)

	index = _skip_whitespace(json, index);

	local b = json:byte(index);

	-- TODO try table lookup instead of if-else?

	if b == 0x7B then -- "{"

		return _readobject(json, index);

	elseif b == 0x5B then -- "["

		return _readarray(json, index);

	elseif b == 0x22 then -- "\""

		return _readstring(json, index);

	elseif b ~= nil and b >= 0x30 and b <= 0x39 or b == 0x2d then -- "0"-"9" or "-"

		return _readnumber(json, index);

	elseif b == 0x6e then -- "n"

		return _readnull(json, index);

	elseif b == 0x74 then -- "t"

		return _readtrue(json, index);

	elseif b == 0x66 then -- "f"

		return _readfalse(json, index);

	else

		return nil, "value expected";

	end

end

local first_escape = {

	["\\\""] = "\\u0022";

	["\\\\"] = "\\u005c";

	["\\/" ] = "\\u002f";

	["\\b" ] = "\\u0008";

	["\\f" ] = "\\u000C";

	["\\n" ] = "\\u000A";

	["\\r" ] = "\\u000D";

	["\\t" ] = "\\u0009";

	["\\u" ] = "\\u";

};

function module.decode(json)

	json = json:gsub("\\.", first_escape) -- get rid of all escapes except \uXXXX, making string parsing much simpler

		--:gsub("[\r\n]", "\t"); -- \r\n\t are equivalent, we care about none of them, and none of them can be in strings

	-- TODO do encoding verification

	local val, index = _readvalue(json, 1);

	if val == nil then return val, index; end

	if json:find("[^ \t\r\n]", index) then return nil, "garbage at eof"; end

	return val;

end

function module.test(object)

	local encoded = module.encode(object);

	local decoded = module.decode(encoded);

	local recoded = module.encode(decoded);

	if encoded ~= recoded then

		print("FAILED");

		print("encoded:", encoded);

		print("recoded:", recoded);

	else

		print(encoded);

	end

	return encoded == recoded;

end

return module;