string combination diff for Diff::LCS

gistfile1.txt

require 'diff/lcs'

class Comparison
  attr_reader :sequences

  def initialize
    @state = ' '
    @buffer = ''
    @sequences = []
  end

  def match(element)
    append_state(' ', element.old_element)
  end

  def discard_a(element)
    append_state('-', element.old_element)
  end

  def discard_b(element)
    append_state('+', element.new_element)
  end
  
  def finalize
    dump_buffer('e')
  end
  
  private
  
  def append_state(new_state, character)
    if (@state == new_state)
    else
      dump_buffer(new_state)
    end
    @buffer += character
  end
  
  def dump_buffer(new_state)
    return if @buffer.empty?
    @sequences << [@state, @buffer]
    @state = new_state
    @buffer = ''
  end
end

seq1 = 'This is a test of the emergency broadcast system.'
seq2 = 'This is only a TEST of the broadcast system.'

diff = Diff::LCS.diff(seq1, seq2)

comp = Comparison.new
Diff::LCS.traverse_sequences(seq1, seq2, comp)
comp.finalize

puts comp.sequences.inspect