module MasterView

  # this hash is designed to track modified times of its values
  # this behaviour is only supported through using []= and store 
  # mechanisms and thus default semantics have been excluded
  # other update methods such as merge! have been excluded from 
  # this implementation and will raise errors
  class MTimeTrackingHash < Hash

    # MTimeTrackingHash does not support defaults and thus does
    # not take default object or block
    def initialize
      super
      @mtimes = {}
    end
    
    def []=(key, value)
      update_mtime(key)
      super
    end

    def store(key, value)
      update_mtime(key)
      super
    end

    # returns the Time object for this key
    def mtime(key)
      @mtimes[key]
    end

    private

    def update_mtime(key)
      @mtimes[key] = Time.now
    end

    def default=(obj); raise "Not implemented"; end
    def merge!(obj,&block); raise "Not implemented"; end
    def reject!(obj,&block); raise "Not implemented"; end
    def replace(obj); raise "Not implemented"; end

  end
end