class Differ::Diff

def ==(other)
  @raw == other.raw_array
end

def delete(*str)
  return if str.empty?
  if @raw.last.is_a? Change
    change = @raw.pop
    if change.insert? && @raw.last
      @raw.last << sep if change.insert.sub!(/^#{Regexp.quote(sep)}/, '')
    end
    change.delete << sep if change.delete?
  else
    change = Change.new(:delete => @raw.empty? ? '' : sep)
  end
  @raw << change
  @raw.last.delete << str.join(sep)
end

def format_as(f)
  f = Differ.format_for(f)
  @raw.inject('') do |sum, part|
    part = case part
    when String then part
    when Change then f.format(part)
    end
    sum << part
  end
end

def initialize
  @raw = []
end

def insert(*str)
  return if str.empty?
  if @raw.last.is_a? Change
    change = @raw.pop
    if change.delete? && @raw.last
      @raw.last << sep if change.delete.sub!(/^#{Regexp.quote(sep)}/, '')
    end
    change.insert << sep if change.insert?
  else
    change = Change.new(:insert => @raw.empty? ? '' : sep)
  end
  @raw << change
  @raw.last.insert << str.join(sep)
end

def raw_array
  @raw
end

def same(*str)
  return if str.empty?
  if @raw.last.is_a? String
    @raw.last << sep
  elsif @raw.last.is_a? Change
    if @raw.last.change?
      @raw << sep
    else
      change = @raw.pop
      if change.insert? && @raw.last
        @raw.last << sep if change.insert.sub!(/^#{Regexp.quote(sep)}/, '')
      end
      if change.delete? && @raw.last
        @raw.last << sep if change.delete.sub!(/^#{Regexp.quote(sep)}/, '')
      end
      @raw << change
      @raw.last.insert << sep if @raw.last.insert?
      @raw.last.delete << sep if @raw.last.delete?
      @raw << ''
    end
  else
    @raw << ''
  end
  @raw.last << str.join(sep)
end

def sep
  "#{$;}"
end

def to_s
  @raw.join()
end