class Diff::LCS::Change

def self.from_a(arr)
  arr = arr.flatten
  case arr.size
  when 5
    Diff::LCS::ContextChange.new(*(arr[0...5]))
  when 3
    Diff::LCS::Change.new(*(arr[0...3]))
  else
    raise "Invalid change array format provided."
  end
end

def self.valid_action?(action)
  VALID_ACTIONS.include? action
end

def <=>(other)
  r = self.action <=> other.action
  r = self.position <=> other.position if r.zero?
  r = self.element <=> other.element if r.zero?
  r
end

def ==(other)
  (self.action == other.action) and
  (self.position == other.position) and
  (self.element == other.element)
end

def adding?
  @action == '+'
end

def changed?
  @action == '!'
end

def deleting?
  @action == '-'
end

def finished_a?
  @action == '>'
end

def finished_b?
  @action == '<'
end

def initialize(*args)
  @action, @position, @element = *args
  unless Diff::LCS::Change.valid_action?(@action)
    raise "Invalid Change Action '#{@action}'"
  end
  raise "Invalid Position Type" unless @position.kind_of? Fixnum
end

def inspect
  to_a.inspect
end

def to_a
  [ @action, @position, @element ]
end

def unchanged?
  @action == '='
end