Resolve a (possible) redirect

resolve.rb

require 'net/http'

def resolve(uri_str,limit=5)
  $stderr.puts("Resolving #{uri_str}")
  limit.times do |i|
    uri = URI.parse(uri_str)
    raise "No host given #{uri_str}" unless uri.host 
    http = Net::HTTP.new(uri.host, uri.port)
    request = Net::HTTP::Head.new(uri.request_uri)
    response = http.request(request)
    # $stderr.puts("response: #{response.inspect}")
    case response
      when Net::HTTPSuccess then
        return uri_str
      when Net::HTTPRedirection then
        uri_str = response['location']
        raise "No redirection location given for #{uri_str}" if (not uri_str)
      else
        raise "Non-success/redirect response: " + response.inspect
    end
  end
  raise "Too many retries; latest resolution was #{uri_str}"
end

#while (line=gets)
#    url = line.strip
#    begin
#      x = resolve(url)
#      puts [true,url,x].join("\t")
#    rescue Exception => e
#      puts [false, url, e].join("\t")
#    end
#  $stdout.flush
#end