Probably a really bad implementation of word wrapping

wrap.rb

class Wrap < Struct.new(:string, :max_length)
  def self.wrap(s, max_length)
    raise ArgumentError.new("Maximum wrap length can't be 0") if max_length == 0
    new(s, max_length).wrap
  end
  
  def wrap
    return [""] if blank?
    string.scan(regexp)
  end
  
  private

  def blank?
    !string.match /\S/
  end
  
  def regexp
    Regexp.new(matchers.join('|'))
  end
  
  def matchers
    [beginning_of_line, without_whitespace, with_whitespace]
  end
  
  def beginning_of_line
    "^.{0,#{max_length - 1}}\\S(?=\\b)"
  end
  
  def without_whitespace
    "\\S{#{max_length}}"
  end
  
  def with_whitespace
    "\\S.{0,#{max_length - 2}}\\S(?=\\b)"
  end
end

wrap_spec.rb

require_relative "../wrap"

describe Wrap do
  it "wraps at word boundaries" do
    Wrap.wrap("foo bar", 3).should == ["foo", "bar"]
    Wrap.wrap("foo bar", 4).should == ["foo", "bar"]
    Wrap.wrap("foo bar baz", 9).should == ["foo bar", "baz"]
  end

  it "errors when the wrap width is 0" do
    expect { Wrap.wrap("foo", 0) }.to raise_error(ArgumentError)
  end

  it "doesn't wrap when it's not needed" do
    Wrap.wrap("foo", 3).should == ["foo"]
    Wrap.wrap("foo", 4).should == ["foo"]
    Wrap.wrap("", 1).should == [""]
    Wrap.wrap("", 2).should == [""]
    Wrap.wrap(" ", 1).should == [""]
    Wrap.wrap(" ", 2).should == [""]
    Wrap.wrap("foo bar", 7).should == ["foo bar"]
  end

  it "doesn't left-strip lines" do
    Wrap.wrap(" foo", 4).should == [" foo"]
    Wrap.wrap(" foo bar", 4).should == [" foo", "bar"]
  end

  it "breaks words if necessary" do
    Wrap.wrap("foobar", 3).should == ["foo", "bar"]
    Wrap.wrap("foobar", 2).should == ["fo", "ob", "ar"]
    Wrap.wrap("foobar ", 3).should == ["foo", "bar"]
    Wrap.wrap("   foo", 3).should == ["foo"]
  end
end