Watch the price of Bitcoin on Coinbase, and alert me.

watch.rb

require 'logger'
require 'net/http'
require 'json'
require 'mail' # gem 'mail'

dir = File.dirname(__FILE__)

logger = Logger.new(STDOUT)
logger.level = Logger::INFO

# credentials.yml example:
# ---
# :user_name: some+user@gmail.com
# :password: muchdoge
#
credentials = YAML.load_file(File.join(dir, "credentials.yml"))

Mail.defaults do
  delivery_method :smtp, credentials.merge(
    address:              "smtp.gmail.com",
    port:                 "587",
    authentication:       :plain,
    enable_starttls_auto: true
  )
end

def send_notice(to, price)
  Mail.deliver do
    from    "BTC Communicator <#{to}>"
    to      to
    subject "BTC is TOO DAMN HIGH! ($#{price})"
    body    "Get out now, while you still can!"
  end
end

target = 990.0
seconds = 30 # seconds between API calls

loop do
  json  = Net::HTTP.get URI("https://coinbase.com/api/v1/prices/spot_rate")
  logger.debug "JSON Response: #{json}"
  data  = JSON.parse json
  price = data["amount"].to_f
  logger.debug "Price: $ #{price}"

  if price > target
    logger.info "Price ($#{price}) above target ($#{target}). Sending alert."
    send_notice credentials[:user_name], price
    break
  else
    logger.info "Price ($#{price}) below target ($#{target}). Doing nothing."
  end
  sleep seconds
end

Thanks!