module Eymiha
  
  # The MethodicHash is some method_missing magic that uses method names as hash
  # keys, so hash assignment and lookup appear to be attribute writing and
  # reading. For instance, if
  #
  #   mh = MethodicHash.new
  #   mh['four']  = 'iv'
  #   mh[:seven]  = 'vii'
  #   mh.eighteen = 'xviii'
  #
  # then
  #
  #   mh['four']     ---> 'iv'
  #   mh[:four]      ---> 'iv'
  #   mh.four        ---> 'iv'
  #   mh['seven']    ---> 'vii'
  #   mh[:seven]     ---> 'vii'
  #   mh.seven       ---> 'vii'
  #   mh['eighteen'] ---> 'xviii'
  #   mh[:eighteen]  ---> 'xviii'
  #   mh.eighteen    ---> 'xviii'
  #
  # This allows access to simply declared facts to be embedded in Ruby code and
  # leverages the possibility of hashing procs.
  #
  # Note that if the hash uses anything but strings or symbols as keys, the
  # magic stands a good chance of failing, raising an error or acting in a
  # bizarre manner. Note also that methods of the Hash cannot be used as
  # 'attribute' names.
  class MethodicHash < Hash
    
    # Try to look up using a key directly, or if that fails as a string, or as
    # a symbol as last resort. If a symbol conversion doesn't exists, rescue
    # with a nil.
    def [](key)
      begin
        super(key) || super(key.to_s) || super(key.to_sym)
      rescue
        nil
      end
    end
    
    # Deletes and returns the key-value pairs from hash whose keys are equal to
    # key.to_s or key.to_sym. If both key.to_s and key.to_sym are in the hash,
    # then both values are returned in an Array, respectively. If neither key is
    # found, the delete is deferred to the Hash.
    def delete(key,&block)
      values = [key.to_s, key.to_sym].collect {|k| super(k){ nil } }.compact
      case values.size
      when 0 then super(key,&block)
      when 1 then values[0]
      when 2 then values
      end
    end
    
    # A missing method is assummed to be the assignment of a value of a key, or
    # the lookup of a value with a key.
    def method_missing(method,*args)
      string = method.to_s
      if string[string.length-1,1] == '='
        self[string[0,string.length-1].to_sym] = args[0]
      else
        self[method]
      end
    end
    
  end
  
end