class Chronic::Scalar

def self.scan(tokens)
  # for each token
  tokens.each_index do |i|
    if t = self.scan_for_scalars(tokens[i], tokens[i + 1]) then tokens[i].tag(t) end
    if t = self.scan_for_days(tokens[i], tokens[i + 1]) then tokens[i].tag(t) end
    if t = self.scan_for_months(tokens[i], tokens[i + 1]) then tokens[i].tag(t) end
    if t = self.scan_for_years(tokens[i], tokens[i + 1]) then tokens[i].tag(t) end
  end
  tokens
end

def self.scan_for_days(token, post_token)
  if token.word =~ /^\d\d?$/
    toi = token.word.to_i
    unless toi > 31 || toi < 1 || (post_token && %w{am pm morning afternoon evening night}.include?(post_token.word))
      return ScalarDay.new(toi)
    end
  end
  return nil
end

def self.scan_for_months(token, post_token)
  if token.word =~ /^\d\d?$/
    toi = token.word.to_i
    unless toi > 12 || toi < 1 || (post_token && %w{am pm morning afternoon evening night}.include?(post_token.word))
      return ScalarMonth.new(toi)
    end
  end
  return nil
end

def self.scan_for_scalars(token, post_token)
  if token.word =~ /^\d*$/
    unless post_token && %w{am pm morning afternoon evening night}.include?(post_token)
      return Scalar.new(token.word.to_i)
    end
  end
  return nil
end

def self.scan_for_years(token, post_token)
  if token.word =~ /^([1-9]\d)?\d\d?$/
    unless post_token && %w{am pm morning afternoon evening night}.include?(post_token.word)
      return ScalarYear.new(token.word.to_i)
    end
  end
  return nil
end

def to_s
  'scalar'
end