Poll for Tesla chargers in stock and emails when found

.gitignore

/poller.log
/.env
/last_run

tesla_poller.rb

# Scrapes for chargers in the canadian Tesla store and notifies when found.
#
# Set it up in the cron to run every few minutes:
#   */2 * * * * /bin/bash -l -c 'cd /home/example/tesla_poller && ruby tesla_poller.rb' >/dev/null 2>&1
#
# The `.env` file should have entries that look kinda like this:
#   SMTP_ADDRESS=smtp.example.com
#   SMTP_DOMAIN=example.com
#   [email protected]
#   SMTP_PASSWORD=password
#   [email protected]
#   SMTP_FROM="Tesla Scraper Bot" <[email protected]>
#   SMTP_PORT=587
#   NOTIFIER_TYPE=email
#
# You should be able to use gmail app passwords, or whatever service you use. You can notify with something else if you write a different Notifier class.

require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  gem "pry", "0.13.1"
  gem "httparty", "0.18.1"
  gem "dotenv", "2.7.6"
  gem "mail", "2.7.1"
end

require "dotenv/load"

require "logger"
Log = Logger.new(File.join(File.dirname(__FILE__), 'poller.log'))

class ConsoleNotifier
  attr_reader :logger

  def initialize
    @logger = Log
  end

  def notify(title:, message:)
    puts "[ConsoleNotifier] title:#{ title } message:#{ message }"
    @logger.info("[ConsoleNotifier] title:#{ title } message:#{ message }")
  end
end

Mail.defaults do
  delivery_method :smtp, {
    address: ENV["SMTP_ADDRESS"],
    port: ENV["SMTP_PORT"],
    domain: ENV["SMTP_DOMAIN"],
    user_name: ENV["SMTP_USERNAME"],
    password: ENV["SMTP_PASSWORD"],
    authentication: 'plain',
    enable_starttls_auto: true
  }
end

class EmailNotifier
  attr_reader :logger

  def initialize
    @logger = Log
  end

  def notify(title:, message:)
    @logger.info("[EmailNotifier] title:#{ title } message:#{ message }")

    mail = Mail.new(
      to: ENV["EMAIL_NOTIFIER_RECIPIENT"],
      from: ENV["SMTP_FROM"],
      subject: title,
      body: message,
      charset: 'UTF-8',
    )
    mail.deliver
  end
end

class Response
  attr_reader :result

  def initialize
    @result = nil
    @path = "https://shop.tesla.com/en_ca/inventory.json"
    @headers = {
      "Accept" => "application/json, text/javascript, */*; q=0.01",
      "Accept-Language" => "en-CA,en;q=0.8,en-US;q=0.6,fr-CA;q=0.4,nl;q=0.2",
      "Connection" => "keep-alive",
      "Content-Type" => "application/json",
      "Host" => "shop.tesla.com",
      "Origin" => "https://shop.tesla.com",
      "Referer" => "https://shop.tesla.com/en_ca/product/wall-connector",
      "TE" => "Trailers",
      "User-Agent" => "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:80.0) Gecko/20100101 Firefox/80.0",
      "X-Requested-With" => "XMLHttpRequest",
    }
    @request_body = "[\"1457768-01-F\",\"1457768-00-F\"]"
  end

  def fetch
    @result = HTTParty.post(@path, headers: @headers, body: @request_body)
    success?
  end

  def success?
    @result && @result.success?
  end

  def code
    @result && @result.code
  end

  def in_stock?
    node = @result.find { |r| r["skuCode"] == "1457768-00-F" } # 00 is the 8.5, 01 is the longer one
    raise "Cannot find item in response" unless node
    node["purchasable"] # also "error"=>"Out of stock"
  end
end

class LastRun
  def initialize
    @file_path = File.join(File.dirname(__FILE__), 'last_run')
  end

  def read
    begin
      File.open(@file_path, "r") { |f| f.read }
    rescue Errno::ENOENT => e
      nil
    end
  end

  def write(str)
    File.open(@file_path, "w") { |f| f.write(str.to_s) } != 0
  end

  def change?(incoming)
    previous = read
    write(incoming)
    previous != incoming.to_s
  end
end

class Runner
  attr_reader :logger, :notifier, :response

  def initialize
    @notifier = case ENV["NOTIFIER_TYPE"]
      when "console" then ConsoleNotifier.new
      when "email" then EmailNotifier.new
      else
        raise "Unknown NOTIFIER_TYPE=#{ ENV['NOTIFIER_TYPE'] }"
    end
    @response = Response.new
    @last_run = LastRun.new
    @logger = Log
  end

  def run
    begin
      response.fetch

      if response.success?
        logger.info("success response")

        if response.in_stock?
          logger.info("found in stock")

          if @last_run.change?("in_stock")
            notifier.notify(
              title: "Tesla wall charger in stock!",
              message: "https://shop.tesla.com/en_ca/product/wall-connector",
            )
          end
        else
          @last_run.write("out_of_stock")
          logger.info("out of stock")
        end

        0
      else
        logger.error("response error")
        logger.error(response.result.body)

        if @last_run.change?("error")
          notifier.notify(
            title: "Tesla scraper error",
            message: "code: #{ response.code }\n\n#{ response.result.body }",
          )
        end

        1
      end
    rescue => e
      if @last_run.change?("error")
        notifier.notify(
          title: "Tesla scraper error",
          message: e.inspect,
        )
      end

      1
    end
  end
end

exit Runner.new.run