#!/usr/local/bin/ruby
require 'resolv-replace'
require 'timeout'
require 'net/http'
require 'open-uri'
require 'cgi'

REMOTE_CONTENT_TIMEOUT = 10
REMOTE_CONTENT_MAX_LENGTH = 4 * 1024 * 1024

def get_remote_content(uri)
  meta = nil
  timeout(REMOTE_CONTENT_TIMEOUT) do
    size = file_size_by_uri(uri)
    if (size && size > REMOTE_CONTENT_MAX_LENGTH)
      raise RuntimeError
      end
    meta = uri.read
  end
  if (meta.length > REMOTE_CONTENT_MAX_LENGTH)
    raise RuntimeError
  end
  meta
end

def file_size_by_uri(uri)
  s = nil
  Net::HTTP.start( uri.host, uri.port ) do |http|
    file = uri.path
    if (uri.query)
      file += "?" + uri.query
    end
    response = http.head(file)
    s = response['content-length']
    end
  if (s)
    s.to_i
  else
    nil
  end
end

cgi = CGI.new
url = cgi['url']
if (url)
  c = get_remote_content(URI.parse(url))
  mime = c.content_type
  if (mime =~ /^image/)
    cgi.out(mime) do
      c
    end
  end
end