module Bencoding
  module Parser
    
    DICTIONARY_TOKEN = 100 # d # :nodoc:
    LIST_TOKEN       = 108 # l # :nodoc:
    INTEGER_TOKEN    = 105 # i # :nodoc:
    TERMINATOR_TOKEN = 101 # e # :nodoc:
    SEPERATOR_TOKEN  = 58  # : # :nodoc:
    
    def load(io)
      parse_anytype(io)
    end
    
    def parse_anytype(io, typechar=nil) # :nodoc:
      typechar ||= io.getc
      case typechar
      when DICTIONARY_TOKEN then parse_dictionary(io)
      when LIST_TOKEN       then parse_list(io)
      when INTEGER_TOKEN    then parse_integer(io)
      else
        io.ungetc typechar
        parse_string(io)
      end
    end
    
    def parse_dictionary(io) # :nodoc:
      dictionary = ::Hash.new
      until (c = io.getc) == TERMINATOR_TOKEN
        io.ungetc c
        key = parse_string(io)
        val = parse_anytype(io)
        dictionary[key] = val
      end
      dictionary
    end
    
    def parse_list(io) # :nodoc:
      list = ::Array.new
      until (c = io.getc) == TERMINATOR_TOKEN
        val = parse_anytype(io, c)
        list << val
      end
      list
    end
    
    def parse_integer(io, terminator=TERMINATOR_TOKEN) # :nodoc:
      integer_string = ""
      until (c = io.getc) == terminator
        integer_string << c.chr
      end
      integer_string.to_i
    end
    
    def parse_string(io) # :nodoc:
      length = parse_integer(io, SEPERATOR_TOKEN)
      io.read(length)
    end
    
    extend self
    
  end
end