class SemVer

def <=> other
  maj = major.to_i <=> other.major.to_i
  return maj unless maj == 0
  min = minor.to_i <=> other.minor.to_i
  return min unless min == 0
  pat = patch.to_i <=> other.patch.to_i
  return pat unless pat == 0
  spe = special <=> other.special
  return spec unless spe == 0
  0
end

def format fmt
  fmt.gsub! '%M', @major.to_s
  fmt.gsub! '%m', @minor.to_s
  fmt.gsub! '%p', @patch.to_s
  fmt.gsub! '%s', @special.to_s
  fmt
end

def initialize major=0, minor=0, patch=0, special=''
  major.kind_of? Integer or raise "invalid major: #{major}"
  minor.kind_of? Integer or raise "invalid minor: #{minor}"
  patch.kind_of? Integer or raise "invalid patch: #{patch}"
  unless special.empty?
    special =~ /[A-Za-z][0-9A-Za-z-]+/ or raise "invalid special: #{special}"
  end
  @major, @minor, @patch, @special = major, minor, patch, special
end

def load file
  @file = file
  hash = YAML.load_file(file) || {}
  @major = hash[:major] or raise "invalid semver file: #{file}"
  @minor = hash[:minor] or raise "invalid semver file: #{file}"
  @patch = hash[:patch] or raise "invalid semver file: #{file}"
  @special = hash[:special]  or raise "invalid semver file: #{file}"
end

def save file=nil
  file ||= @file
  hash = {
    :major => @major,
    :minor => @minor,
    :patch => @patch,
    :special => @special
  }
  yaml = YAML.dump hash
  open(file, 'w') { |io| io.write yaml }
end

def to_s
  format TAG_FORMAT
end