require 'gem_plugin'
require 'mongrel'
require 'digest/sha1'

class CryptedDownload < GemPlugin::Plugin "/handlers"
	include Mongrel::HttpHandlerPlugin	
  
  def process(request, response)
    query = Mongrel::HttpRequest.query_parse(request.params['QUERY_STRING'])	
		cookies  = Mongrel::HttpRequest.query_parse(request.params['HTTP_COOKIE'])
		secret_string  = cookies.keys.first
		
		query['path'] = CGI::unescape(query['path'])
		
		if secret_string.nil? or query['token'].nil? or query['timestamp'].nil? or query['path'].nil?
			response.start(500){}
		elsif query['timestamp'].to_i < Time.now.to_i
			response.start(408){}
		elsif query['token'] == Digest::SHA1.hexdigest("#{secret_string}#{query['path']}#{query['timestamp']}").to_s
			send_file(File.expand_path("." + query['path'].decrypt(:symmetric, :key => secret_string) + query['file-name']), response)
		else
			response.start(403){}
		end
  end
	
	def self.generate(file_name, path, uri_prefix, request)
	   secret_string  = request.cookies.keys.first
	   
	   path = path.encrypt(:symmetric, :key => secret_string)
     timestamp = 1.minute.from_now.to_i.to_s
     token = Digest::SHA1.hexdigest(secret_string + path + timestamp)
     path = CGI::escape(path)
     
     return "#{uri_prefix}/?token=#{token}&path=#{path}&file-name=#{file_name}&timestamp=#{timestamp}"
      
  end

  
		
	private
	  
		# Sends the contents of a file back to the user.
		def send_file(path, response)
			# first we setup the headers and status then we do a very fast send on the socket directly
			file_status = File.stat(path)
	
			response.status = 200
			# Set the last modified times as well and etag for all files
			response.header[Mongrel::Const::LAST_MODIFIED] = file_status.mtime.httpdate
			# Calculated the same as apache, not sure how well the works on win32
			response.header[Mongrel::Const::ETAG] = Mongrel::Const::ETAG_FORMAT % [file_status.mtime.to_i, file_status.size, file_status.ino]
			#set the content type to something generic for now
			response.header[Mongrel::Const::CONTENT_TYPE] = @default_content_type
			#set the content disposition and filename
			response.header['Content-Disposition'] = "attachment; filename=\"#{File.basename(path)}\""
	
			# send a status with out content length
			response.send_status(file_status.size)
			response.send_header
	    response.send_file(path)
	 end
end