class FDB::KeySelector

def self.first_greater_or_equal(key)
  self.new(key, 0, 1)
end

def self.first_greater_than(key)
  self.new(key, 1, 1)
end

def self.last_less_or_equal(key)
  self.new(key, 1, 0)
end

def self.last_less_than(key)
  self.new(key, 0, 0)
end

def +(offset)
  KeySelector.new(@key, @or_equal, @offset + offset)
end

def -(offset)
  KeySelector.new(@key, @or_equal, @offset - offset)
end

def initialize(key, or_equal, offset)
  @key = key
  @or_equal = or_equal
  @offset = offset
end