Generate a report by month for the amount of payment received in Blinksale

blinksale_report.rb

require 'open-uri'
require 'nokogiri'
require 'filecache'
require 'logger'
require 'date'
require 'pry'

# When do you want to grab invoices? Default is 90 days ago.
@since    = ENV.include?('SINCE') ? Date.parse(ENV['SINCE']) : Date.today - 90
# Blinksale username
@username = ENV['USERNAME']
# Blinksale password
@password = ENV['PASSWORD']
# Display status on this process.
@logger   = Logger.new($stdout)

# Read responses from website and memoize to file sytem.
def memoize(key, &block)
  if value = cache.get(key)
    value
  else
    value = block.call
    cache.set(key, value)
    value 
  end
end

# Initalize file cache to speed up invoice processing with multiple runs.
def cache
  @cache ||= FileCache.new('blinksale', '.cache')
end

# Execute and caches HTTP requests.
def get(url)
  memoize url do
    @logger.info "HTTP GET #{url.inspect}"
    open(url,
      :http_basic_authentication => [@username, @password],
      'Accept' => 'application/vnd.blinksale+xml'
    ).read
  end
end

# Read XML from website (and cache)
invoices_xml = get("https://polleverywhere.blinksale.com/invoices/closed/date/#{@since.strftime('%Y-%m-%d')}")
invoices = Nokogiri::XML(invoices_xml).css('invoice[uri]')

@logger.info "Analysis of #{invoices.count} invoice(s)"

# Parse invoices XML
invoice_payments_xml = invoices.map do |invoice|
  Nokogiri::XML(get(File.join(invoice[:uri], '/payments')))
end

# Group payments by month.
grouped = invoice_payments_xml.group_by do |payment|
  created_at = Time.parse(payment.css('payment').first[:created_at])
  Time.utc(created_at.year, created_at.month)
end

# Now lets sum up all of the payments per month
totals = grouped.reduce Hash.new do |hash, (month, payments)|
  hash[month] = payments.map{ |i| i.css('amount').map(&:content) }.flatten.map(&:to_i).reduce(&:+)
  hash
end

# And finally, we should print it out!
puts "Month\t\tTotal"
totals.each do |month, total|
  puts "#{month.strftime('%B, %Y')}\t#{total}"
end