# We proxy cover images from foreign sources through Umlaut sometimes, in order
# to switch their access from http to https to avoid browser warnings on an
# https page.  This controller does that.
#
# It does NOT take URL in request parameters, but instead takes a response ID.
# it will only proxy urls already stored in umlaut responses, so this is not
# an open proxy with the security problems that would cause. 
class ResourceController < UmlautController
  require 'open-uri'

  # We really ought to _stream_ the remote response to our client, but I
  # couldn't get that to work how I wanted in Rails2. Even using
  # render :text=>proc, problem is we needed to know the content-type before
  # we read any of the response, which we didn't. This implementation holds
  # the whole image in memory for a second while it delivers it, oh well.
  # doesn't seem to effect speed much, even though it's not optimal. 
  def proxy
    svc_resp = ServiceResponse.find(params[:id])      
    url_str =  svc_resp.view_data[:url]
    uri = nil
    begin
      uri = URI(url_str)
    rescue
      raise Exception.new("resource#proxy can only handle String urls, not '#{url.inspect}'")
    end

    proxied_headers = proxy_headers( request, uri.host )
    remote_response = open(uri, 'rb', proxied_headers)

    # copy certain headers to our proxied response    
    ["Content-Type", "Cache-Control", "Expires", "Content-Length", "Last-Modified", "Etag", "Date"].each do |key|
      value = remote_response.meta[key.downcase] # for some reason open-uri lowercases em
      # rack doens't like it if we set a nil value here. 
      response.headers[key] = value unless value.blank?
    end
    response.headers["X-Original-Url"] = url_str
    
    # And send the actual result out
    render(:text => remote_response.read)
    
  end

  protected

  # Generate headers as if we are a proxy server, to be more or less honest
  # and to maybe keep Google et al from rate throttling us.
  # This is kind of copy and paste of UmlautHttp#proxy_like_headers, but that
  # method was written to require an UmlautRequest, which we don't have here.
  # TODO should refactor to DRY.
  # Argument here is a Rails Request
  def proxy_headers( request, host  )
    orig_env = request.headers  
  
    header = {}
    
  
    header["User-Agent"] = orig_env['HTTP_USER_AGENT'] || 'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9) Gecko/2008061015 Firefox/3.0'
    header['Accept'] = orig_env['HTTP_ACCEPT'] || 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'
    header['Accept-Language'] = orig_env['HTTP_ACCEPT_LANGUAGE'] || 'en-us,en;q=0.5'
    header['Accept-Encoding'] = orig_env['HTTP_ACCEPT_ENCODING'] || ''
    header["Accept-Charset"] = orig_env['HTTP_ACCEPT_CHARSET'] || 'UTF-8,*'

    # Set referrer to be, well, an Umlaut page, like the one we are
    # currently generating would be best. That is, the resolve link. 
    
    header["Referer"] = "http://#{orig_env['HTTP_HOST']}#{orig_env['REQUEST_URI']}"

    # Proxy X-Forwarded headers. 

    # The original Client's ip, most important and honest. Look for
    # and add on to any existing x-forwarded-for, if neccesary, as per
    # x-forwarded-for convention. 
    header['X-Forwarded-For'] =  (orig_env['HTTP_X_FORWARDED_FOR']) ?
       (orig_env['HTTP_X_FORWARDED_FOR'].to_s + ', ' + request.remote_ip.to_s) :
       request.remote_ip.to_s
       
    #Theoretically the original host requested by the client in the Host HTTP request header. We're disembling a bit.  
    header['X-Forwarded-Host'] = host if host
    # The proxy server: That is, Umlaut, us. 
    header['X-Forwarded-Server'] = orig_env['SERVER_NAME'] || ''

    return header
  end
  
end