Julian's challenge, solution 1

sms_chunker.rb

#! env ruby

require "rspec/autorun"
require "byebug"

class SMScarrier
  def self.deliver(text, to, from)
    puts "From: #{from}"
    puts "To: #{to}"
    puts "Message: #{text}"
    puts "Message length: #{text.length}"
    puts "---"
  end
end

class SMSsplitter
  MAXLEN = 160

  def initialize(text)
    @text = text.chomp
  end

  def call
    if @text.length <= 160
      return [@text]
    end

    words = @text.split(" ")
    break_up_text(words)
  end

  def break_up_text(words)
    parts = []
    chunk = ""
    chunk_counter = 1

    words.each do |word|
      new_chunk = "#{chunk} #{word}"
      if number_chunk(new_chunk, chunk_counter).length < MAXLEN - 3
        chunk = new_chunk
      else
        parts << number_chunk(new_chunk, chunk_counter)
        chunk_counter = chunk_counter + 1
        chunk = word # FIXME: Huge words break things
      end
    end
    parts << number_chunk(chunk, chunk_counter)

    parts.map { |chunk| "#{chunk} #{chunk_counter}" }
  end

  def number_chunk(chunk, counter)
    format("%s - message %d of", chunk, counter)
  end
end

def send_sms_message(text, to, from)
   deliver_message_via_carrier(text, to, from)
end

def deliver_message_via_carrier(text, to, from)
  SMSsplitter.new(text).call.each do |message|
    SMScarrier.deliver(message, to, from)
  end
end

RSpec.describe SMSsplitter do
  it "does not split a short message" do
    msg = <<-EOMSG
This is just a short message.
EOMSG

    chunks = SMSsplitter.new(msg).call

    expect(chunks.length).to eq 1
    expect(chunks[0]).to eq "This is just a short message."
  end

  it "does split a medium-length message" do
    msg = <<-EOMSG
This is a message that will have to be split because it slightly exceeds the 160 character limit imposed by the SMS system. It will result in two messages with a counter.
    EOMSG

    chunks = SMSsplitter.new(msg).call

    expect(chunks.length).to eq 2
    expect(chunks[0].length).to be <= 160
    expect(chunks[0]).to match(/message 1 of 2$/)
    expect(chunks[1].length).to be <= 160
    expect(chunks[1]).to match(/message 2 of 2$/)
  end

  it "does split a long message" do
    msg = <<-EOMSG
"True happiness is to enjoy the present, without anxious dependence upon the future, not to amuse ourselves with either hopes or fears but to rest satisfied with what we have, which is sufficient, for he that is so wants nothing. The greatest blessings of mankind are within us and within our reach. A wise man is content with his lot, whatever it may be, without wishing for what he has not." -- Seneca
    EOMSG

    chunks = SMSsplitter.new(msg).call

    expect(chunks.length).to eq 3
    expect(chunks[0].length).to be <= 160
    expect(chunks[0]).to match(/message 1 of 3$/)
    expect(chunks[1].length).to be <= 160
    expect(chunks[1]).to match(/message 2 of 3$/)
    expect(chunks[2].length).to be <= 160
    expect(chunks[2]).to match(/message 3 of 3$/)
  end
end