cli-confirm.rb

# Get reasonable CLI confirmation before continuing.
#
# @param text [String] - the descriptive text
# @param options [Hash{Symbol=>Object}]
# @option options [Boolean] :default - the default action (false)
# @option options [#puts] :out - the IO on which to puts output ($stderr)
# @option options [#readline] :in - the IO on which to readline input ($stdin)
# @option options [String] :prompt - the prompt string ("ok?")
#
# @example
# ~~~ ruby
# if confirm?('This action is destructive', default: true, prompt: 'do it anyway?')
#   dangerous_thing!
# else
#   return false
# end
# ~~~
def confirm?(text, options={})
  default = options.fetch(:default, false)
  output = options.fetch(:out, $stderr)
  input = options.fetch(:in, $stdin)
  prompt = options.fetch(:prompt, 'ok?')

  output.puts text

  loop do
    output.puts "#{prompt} #{default ? '(Y/n)' : '(y/N)'}:"
    received = input.readline
    
    case
    when received.chomp.empty?
      return default
    when received =~ /^y(es)?$/i
      return true
    when received =~ /^n(o)?$/i
      return false
    else
      output.puts('input not understood. Please type "yes" or "no".')
      next
    end
  end
end