class URI
  class InvalidURIError < StandardError; end

  def self.parse(str)
    x = /^([a-z]+):\/\/([a-z0-9-.]+)(:([0-9]+))?(\/([^?]*))?(\?(.*))?$/.match(str)
    raise InvalidURIError unless x
    scheme, host, _, port, path, _, _, query = x.captures
    self.new(scheme:, host:, port:, path:, query:)
  end

  def self.decode_www_form(query)
    query.split('&').map{
      k, v = it.split('=', 2)
      v = v.gsub(/%[0-9A-F][0-9A-F]/i){it[1,2].to_i(16).chr}
      [k, v]
    }
  end

  def self.encode_www_form(ary)
    ary.map{|k,v| "#{k}=#{v}"}.join('&')
  end

  attr_accessor :scheme, :host, :port, :path, :query

  def initialize(scheme: nil, host: nil, port: nil, path: nil, query: nil)
    @scheme = scheme
    @host = host
    @port = port
    @path = path.to_s
    @query = query
  end

  def to_s
    s = "#{scheme}://#{host}"
    s += ":#{port}" if port
    s += "/"
    s += path.sub(/^\/+/, '')
    s += "?#{query}" if query
    s
  end
end