json.lua

--
-- Licensed to the Apache Software Foundation (ASF) under one or more
-- contributor license agreements.  See the NOTICE file distributed with
-- this work for additional information regarding copyright ownership.
-- The ASF licenses this file to You under the Apache License, Version 2.0
-- (the "License"); you may not use this file except in compliance with
-- the License.  You may obtain a copy of the License at
--
--     http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
--

--- Wrapped serialization and deserialization modules for json and lua tables.
--
-- @module core.json

local cjson = require("cjson.safe")
local json_encode = cjson.encode
local clear_tab = require("table.clear")
local ngx = ngx
local tostring = tostring
local type = type
local pairs = pairs
local cached_tab = {}


cjson.encode_escape_forward_slash(false)
cjson.decode_array_with_array_mt(true)
local _M = {
    version = 0.1,
    array_mt = cjson.array_mt,
    decode = cjson.decode,
    -- This method produces the same encoded string when the input is not changed.
    -- Different calls with cjson.encode will produce different string because
    -- it doesn't maintain the object key order.
    stably_encode = require("dkjson").encode
}


local function serialise_obj(data)
    if type(data) == "function" or type(data) == "userdata"
       or type(data) == "cdata"
       or type(data) == "table" then
        return tostring(data)
    end

    return data
end


local function tab_clone_with_serialise(data)
    if type(data) ~= "table" then
        return serialise_obj(data)
    end

    local t = {}
    for k, v in pairs(data) do
        if type(v) == "table" then
            if cached_tab[v] then
                t[serialise_obj(k)] = tostring(v)
            else
                cached_tab[v] = true
                t[serialise_obj(k)] = tab_clone_with_serialise(v)
            end

        else
            t[serialise_obj(k)] = serialise_obj(v)
        end
    end

    return t
end


local function encode(data, force)
    if force then
        clear_tab(cached_tab)
        data = tab_clone_with_serialise(data)
    end

    return json_encode(data)
end
_M.encode = encode


local delay_tab = setmetatable({data = "", force = false}, {
    __tostring = function(self)
        local res, err = encode(self.data, self.force)
        if not res then
            ngx.log(ngx.WARN, "failed to encode: ", err,
                    " force: ", self.force)
        end

        return res
    end
})


---
-- Delayed encoding of input data, avoid unnecessary encode operations.
-- When really writing logs, if the given parameter is table, it will be converted to string in
-- OpenResty by checking if there is a metamethod registered for `__tostring`, and if so,
-- calling this method to convert it to string.
--
-- @function core.json.delay_encode
-- @tparam string|table data The data to be encoded.
-- @tparam boolean force encode data can't be encoded as JSON with tostring
-- @treturn table The table with the __tostring function overridden.
-- @usage
-- core.log.info("conf  : ", core.json.delay_encode(conf))
function _M.delay_encode(data, force)
    delay_tab.data = data
    delay_tab.force = force
    return delay_tab
end


return _M