Lua lib to send SMS with Telstra's SMS API

sendsms.lua

local telstra_sms_api = require "telstra_sms_api".new
local sleep = require "cqueues".sleep

if #arg < 2 then
	io.stderr:write("Expected number and body\n")
	os.exit(1)
end

local to = arg[1]
local message = table.concat(arg, " ", 2)

local api = telstra_sms_api {
	client_id = "MyID";
	client_secret = "MySecret";
}
local id = api:send_msg(to, message)
print("Sent message, id=", id)
repeat
	local status = api:message_status(id)
	sleep(2)
until status.status == "DELIVRD"
print("SMS Delivered.")

telstra_sms_api.lua

local cjson = require "cjson"
local monotime = require "cqueues".monotime
local request = require "http.request"
local http_util = require "http.util"

local wiggle_room = 5

local methods = {}
local mt = { __index = methods; }
local function telstra_sms_api(options)
	return setmetatable({
		client_id = assert(options.client_id, "missing client_secret ('Consumer Key')");
		client_secret = assert(options.client_secret, "missing client_id ('Consumer Secret')");
		token = nil;
		expires = nil;
	}, mt)
end

local function json_go(r)
	local headers, stream = assert(r:go())
	local body = assert(stream:get_body_as_string())
	stream:shutdown()
	local decoded
	if (headers:get("content-type") or ""):match("^%s*[^;]+") == "application/json" then
		decoded = cjson.decode(body)
	end
	if headers:get(":status"):sub(1,1) ~= "2" then
		error(decoded and decoded.error or body, 2)
	end
	if decoded == nil then
		error("not a json response", 2)
	end
	return decoded
end

function methods:get_token()
	local r = request.new_from_uri("https://api.telstra.com/v1/oauth/token")
	r.headers:upsert(":method", "POST")
	r.headers:upsert("accept", "application/json")
	r.headers:upsert("content-type", "application/x-www-form-urlencoded")
	r:set_body(http_util.dict_to_query {
		grant_type = "client_credentials";
		scope = "SMS";
		client_id = self.client_id;
		client_secret = self.client_secret;
	})
	local start = monotime()
	local decoded = json_go(r)
	self.token = assert(decoded and decoded.access_token, "missing access_token")
	self.expires = start + tonumber(decoded.expires_in) - wiggle_room
end

function methods:check_token()
	if not self.token or self.expires < monotime() then
		self:get_token()
	end
end

function methods:send_msg(to, body)
	assert(type(to) == "string")
	assert(type(body) == "string")
	self:check_token()
	local r = request.new_from_uri("https://api.telstra.com/v1/sms/messages")
	r.headers:upsert(":method", "POST")
	r.headers:upsert("accept", "application/json")
	r.headers:upsert("authorization", "Bearer "..self.token)
	r.headers:upsert("content-type", "application/json")
	r:set_body(cjson.encode {
		to = to;
		body = body;
	})
	local decoded = json_go(r)
	local message_id = assert(decoded and decoded.messageId, "missing messageId")
	return message_id
end

function methods:message_status(message_id)
	self:check_token()
	local r = request.new_from_uri("https://api.telstra.com/v1/sms/messages/"..message_id)
	r.headers:upsert("accept", "application/json")
	r.headers:upsert("authorization", "Bearer "..self.token)
	local decoded = json_go(r)
	return decoded
end

return {
	new = telstra_sms_api;
}