Ezlo Linux Firmware Lua Script: parse openweather output

openweather_cloud_all_extract.ezlo.scenes.lua

-- Oleksii.Kirdin@ezlo.com, 2023-06-12, fixed 2023-06-22
-- Anonymous Plugin (aka Lua script) for Ezlogic.

-- Get a stringified json from one variable, parse it to a Lua table, extract some value by path, save it to another variable with value type respect.
-- Meshbots/Scenes/Global Variables/HTTP Request Parsing.
-- The script can be used as an action in a meshbot after the sendHttpRequest/cloudAPI calls with SaveResult attribute
-- to post-process JSON value: extract a value to another expressions variable with type information.
-- After that, the variable with type can be used as a trigger in meshbots.

-- OpenWeather - a variable of type "string";
-- OpenWeatherCloudCover - a variable of type "float" or "int";
-- path_to_extract - path inside of the JSON stored in OpenWeather variable to fetch data by.
-- Result: saves extracted numeric value to the target variable.

local logging = require "logging"
local json = assert(require "json", "Could not load json library")
local scenes = require "scenes"

local variables = {
    source = "OpenWeather",
    target = "OpenWeatherCloudCover"
}

local path_to_extract = {"clouds", "all"}

local function extract_by_path(data, path)
    local value = data
    for _, key in ipairs(path) do
        logging.debug("key: " .. tostring(key))
        value = value[key]
        logging.trace(value)
    end
    return value
end

local function extract_and_save(variable_from, variable_to, path)
    logging.debug("HTTP Response variable: " .. variables.source)

    local http_response_variable = scenes.get_expression_value(variable_from)

    if http_response_variable.value ~= nil then
        logging.debug("Source variable has value: " .. tostring(http_response_variable.value))

        local data = http_response_variable.value

        local res = json.decode(data)
        logging.debug("After json.decode")
        logging.trace(res)

        local found_value = tonumber(extract_by_path(res, path))

        local success, saved_value = pcall(scenes.get_expression_value, variable_to, {compact = false})
        logging.trace("pcall.success: " .. tostring(success))
        logging.trace("pcall.saved_value: " .. json.encode(saved_value))

        local target_value = {
            value = found_value,
            value_type = saved_value.value_type or "float",
            metadata = saved_value.metadata or {}
        }

        logging.debug("Save to target variable: " .. variable_to)
        scenes.set_variable(variable_to, target_value)
        return true
    else
        logging.error("Source variable has no value")
        if http_response_variable.error ~= nil then
            logging.error("Variable.error: " .. tostring(http_response_variable.error))
        end
        return false
    end
end

return extract_and_save(variables.source, variables.target, path_to_extract)