Extract specific info from json-list - json

Question

In my system from json-call http://192.168.1.6:8080/json.htm?type=devices&rid=89 I get the output below.
{
"ActTime" : 1501360852,
"ServerTime" : "2017-07-29 22:40:52",
"Sunrise" : "05:50",
"Sunset" : "21:28",
"result" : [
{
"AddjMulti" : 1.0,
"AddjMulti2" : 1.0,
"AddjValue" : 0.0,
"AddjValue2" : 0.0,
"BatteryLevel" : 255,
"CustomImage" : 0,
"Data" : "73 Lux",
"Description" : "",
"Favorite" : 1,
"HardwareID" : 4,
"HardwareName" : "Dummies",
"HardwareType" : "Dummy (Does nothing, use for virtual switches only)",
"HardwareTypeVal" : 15,
"HaveTimeout" : true,
"ID" : "82089",
"LastUpdate" : "2017-07-29 21:16:22",
"Name" : "ESP8266C_Licht1",
"Notifications" : "false",
"PlanID" : "0",
"PlanIDs" : [ 0 ],
"Protected" : false,
"ShowNotifications" : true,
"SignalLevel" : "-",
"SubType" : "Lux",
"Timers" : "false",
"Type" : "Lux",
"TypeImg" : "lux",
"Unit" : 1,
"Used" : 1,
"XOffset" : "0",
"YOffset" : "0",
"idx" : "89"
}
],
"status" : "OK",
"title" : "Devices"
}
'Automating' such call by the below scripttime lua-script is aimed at extraction of specific information, to be further used in applications.
The first 11 lines run without problems, but further extraction of the information is a problem.
I have tried various scriptlines to get a solution for A), B), C), D) and E), but either they generate error-report, or they don't give results: see further below for the 'best' trial-scriptlines and related results.
To avoid misunderstanding: those dashed commentlines in the script just below this question with A), B), C), D) and E) are only describing the desired actions/functions and are in no way meant as scriptlines!
Question:
Help requested in the form of better applicable scriptlines for A) till E) in the trialscript at the end of this message, or hints where to find applicable example scriptlines.
-- Lua-script to determine staleness, time-out and value for data from Json-call
print('Start of Timeout-script')
commandArray = {}
TimeOutLimit = 10 -- Allowed timeout in seconds
json = (loadfile "/home/pi/domoticz/scripts/lua/JSON.lua")() -- For Linux
-- json = (loadfile "D:\\Domoticz\\scripts\\lua\\json.lua")() -- For Windows
-- Line 07
local content=assert(io.popen('curl "http://192.168.1.6:8080/json.htm?type=devices&rid=89"')) -- notice double quotes
local list = content:read('*all')
content:close()
local jsonList = json:decode(list)
-- Line 12 Next scriptlines describe desired actions
-- A) Extract ServerTime as numeric value (not as string)
-- B) Extract LastUpdate as numeric value (not as string)
-- Staleness = ServerTime - LastUpdate
-- C) Extract HaveTimeout as boolean (not as string)
-- If HaveTimeout and (Staleness > TimeOutlimit) then
-- Print('TimeOutLimit exceeded by ' .. (Staleness - TimeOutLimit) .. 'seconds')
-- End
-- D) Extract textstring from Type or Data
-- E) Extract numeric value from Data
print('End of Timeout-script')
return commandArray
For lines 11 etc, the following trial-scriptlines gave 'best' results (= no errors):
-- Line 11
-- local Servertime = json:decode(ServerTime)
-- print('Servertime : '..Servertime)
-- Line 14
-- CheckTimeOut =jsonValue.result[1].HaveTimeout -- value from "HaveTimeout", inside "result" bloc number 1 (even if it's the only one)
CurrentServerTime =jsonValue.Servertime -- value from "ServerTime"
CurrentLastUpdate = jsonValue.result[1].LastUpdate
CurrentData = jsonValue.result[1].Data
-- Line 19
print('TimeOut : '..CheckTimeOut)
print('Servertime : '..CurrentServerTime)
print('LastUpdate : '..CurrentLastUpdate)
print('Data-content : '..CurrentData)
print('End of Timeout-script')
return commandArray
Results:
Without dashes before the lines 12 and 13, respectively 15, then the following error reports:
660: nil passed to JSON:decode()
lua:15: attempt to index global 'jsonValue' (a nil value)
With dashes before lines 12, 13 and 15 for the trial-scriptlines shown above, according to the log no errors exist (as demonstrated by the 2 prints)
2017-07-31 16:30:02.520 LUA: Start of Timeout-script
2017-07-31 16:30:02.563 LUA: End of Timeout-script
But why no print-results in the log from Lines 20 till 23?
Not having those print-results makes it difficult to determine next steps in data-extraction, to achieve the objectives described under A) till E).
;-) Error reports generally are more useful information than "no errors, but no results"

Answer 1

Without downloading content over the network, the working script looks like this:
local json = require("json")
local jj = [[
{
"ActTime" : 1501360852,
"ServerTime" : "2017-07-29 22:40:52",
"Sunrise" : "05:50",
"Sunset" : "21:28",
"result" : [
{
"AddjMulti" : 1.0,
"AddjMulti2" : 1.0,
"AddjValue" : 0.0,
"AddjValue2" : 0.0,
"BatteryLevel" : 255,
"CustomImage" : 0,
"Data" : "73 Lux",
"Description" : "",
"Favorite" : 1,
"HardwareID" : 4,
"HardwareName" : "Dummies",
"HardwareType" : "Dummy (Does nothing, use for virtual switches only)",
"HardwareTypeVal" : 15,
"HaveTimeout" : true,
"ID" : "82089",
"LastUpdate" : "2017-07-29 21:16:22",
"Name" : "ESP8266C_Licht1",
"Notifications" : "false",
"PlanID" : "0",
"PlanIDs" : [ 0 ],
"Protected" : false,
"ShowNotifications" : true,
"SignalLevel" : "-",
"SubType" : "Lux",
"Timers" : "false",
"Type" : "Lux",
"TypeImg" : "lux",
"Unit" : 1,
"Used" : 1,
"XOffset" : "0",
"YOffset" : "0",
"idx" : "89"
}
],
"status" : "OK",
"title" : "Devices"
}
]]
print('Start of Timeout-script')
local jsonValue = json.decode(jj)
CheckTimeOut =jsonValue.result[1].HaveTimeout
CurrentServerTime =jsonValue.Servertime
CurrentLastUpdate = jsonValue.result[1].LastUpdate
CurrentData = jsonValue.result[1].Data
print('TimeOut : '.. (CheckTimeOut and "true" or "false") )
print('Servertime : '.. (CurrentServerTime or "nil") )
print('LastUpdate : '.. (CurrentLastUpdate or "nil") )
print('Data-content : '.. (CurrentData or "nil") )
print('End of Timeout-script')
result:
Start of Timeout-script
TimeOut : true
Servertime : nil
LastUpdate : 2017-07-29 21:16:22
Data-content : 73 Lux
End of Timeout-script