Ruby, code you enjoy coming back to

# Ruby almost reads like a sentence
invoices = []

5.times do |number|
  invoices << "Invoice #{number + 1}"
end

puts invoices
# Invoice 1, Invoice 2, ... Invoice 5
# Each name appears on its own line.

amounts = [20, 35, 45]
puts amounts.sum
# 100 euros, without maintaining a counter yourself.

# Time in everyday words
require "active_support/all"

# Active Support adds these time expressions.
cutoff = 3.days.ago
issued_at = 5.days.ago

if issued_at < cutoff
  puts "This invoice is over three days old."
end

# A point in the future reads naturally too.
next_review = 2.weeks.from_now
puts next_review.to_date
# The date two weeks from now.

# No bare numbers with units you have to guess.
# 3.days is a duration; 3.days.ago is a point in time.

# Our own language for reminders
class ReminderPlan
  attr_reader :steps

  def initialize(&rules)
    @steps = []
    instance_eval(&rules)
  end

  def after(delay, via:)
    @steps << { delay: delay, via: via }
  end
end

# This is our own DSL, written in ordinary Ruby.
plan = ReminderPlan.new do
  after 3.days, via: :email
  after 7.days, via: :phone
end

# Inspect the rules we have recorded.
plan.steps.each do |step|
  days = step[:delay].in_days.to_i
  puts "After #{days} days: #{step[:via]}"
end
# After 3 days: email
# After 7 days: phone

# The delays are relative to the start of the plan.
# Sending messages and scheduling jobs belong elsewhere.