class BEncoder

# File lib/bencoder.rb, line 25
def decode(string)    
  parse string
end

# File lib/bencoder.rb, line 8
def encode(object)
  case object
  when Symbol
    encode object.to_s
  when String
    encode_string object
  when Integer
    encode_int object
  when Array
    encode_array object
  when Hash
    encode_hash object
  else
    raise UnencodableTypeError, "Cannot encode instance of type #{object.class}"
  end
end

# File lib/bencoder.rb, line 124
def encode_array(array)
  array.inject("l") { |result, el| result += encode(el) } + "e"
end

# File lib/bencoder.rb, line 128
def encode_hash(hash)
  hash.inject("d") { |result, (k,v)| result += "#{ encode(k.to_s) }#{ encode(v) }" } + 'e'
end

# File lib/bencoder.rb, line 120
def encode_int(int)
  "i#{ int }e"
end

# File lib/bencoder.rb, line 116
def encode_string(string)
  "#{ string.length }:#{ string }"
end

# File lib/bencoder.rb, line 91
def make_hash_from_array(list)
  hash = {}
  list.each_slice(2) do |k,v|
    hash[k] = v
  end
  hash
end

# File lib/bencoder.rb, line 33
def parse(string)
  case string[0]
  when 'i'
    parse_int string
  when 'l'
    parse_list string
  when 'd'
    parse_dict string
  else
    parse_string string
  end
end

# File lib/bencoder.rb, line 58
def parse_dict(string)
  if string.is_a? StringIO
    string.getc if peek(string) == 'd'
    list_of_keys_and_values = parse_list(string)
  elsif string[0] == 'd' && string[-1] == 'e'
    list_of_keys_and_values = parse_list("l#{ string[1..-2] }e")
  else
    raise InvalidEncodingError, 'Dict does not have a closing e'
  end
  make_hash_from_array list_of_keys_and_values
end

# File lib/bencoder.rb, line 99
def parse_int(string)
  if string[0] == 'i' && string[-1] == 'e'
    string[1..-2].to_i
  else
    raise InvalidEncodingError, 'Integer does not have closing e'
  end
end

# File lib/bencoder.rb, line 70
def parse_io_list(io)
  list = []
  until peek(io) == 'e' || io.eof?
    case peek(io)
    when 'i'
      list << parse_int(io.gets sep='e')
    when 'l'
      list << parse_list(io)
    when 'd'
      list << parse_dict(io)
    when ->(e) { e =~ /\d/ }
      length = io.gets(sep=':').to_i
      list << io.gets(length)
    else
      raise InvalidEncodingError, "Encountered unexpected identifier #{ peek io }"
    end
  end
  io.getc
  list
end

# File lib/bencoder.rb, line 46
def parse_list(string)
  if string.is_a? StringIO
    str = string
    str.getc if peek(str) == 'l'
  elsif string[0] == 'l' && string[-1] == 'e'
    str = StringIO.new string[1..-2]
  else 
    raise InvalidEncodingError, 'List does not have a closing e'
  end
  parse_io_list str
end

# File lib/bencoder.rb, line 107
def parse_string(string)
  length, content = string.split ':'
  if content.length == length.to_i
    content
  else
    raise InvalidEncodingError, "String length declared as #{length.to_i}, but was #{content.length} " 
  end
end

# File lib/bencoder.rb, line 132
def peek(io)
  char = io.getc
  io.ungetc char
  char
end