module S33r
  module S3Logging
    
    # For manipulating logging directives on resources
    # (see http://docs.amazonwebservices.com/AmazonS3/2006-03-01/LoggingHowTo.html).
    # 
    # Creating a LoggingResource instance using new and no arguments will generate a "blank" instance;
    # this can be put to the ?logging URL for a resource to remove logging from it.
    # 
    # To set a Bucket up for logging, create a LoggingResource with the correct log_target and 
    # log_prefix settings and put that to the ?logging URL for a bucket.
    class LoggingResource
      attr_accessor :log_target, :log_prefix
    
      # +log_target+ is the bucket to put logs into.
      # +log_prefix+ is the prefix for log files put into the +log_target+ bucket.
      def initialize(log_target=nil, log_prefix=nil)
        @log_target = log_target
        @log_prefix = log_prefix
      end
      
      # Generate a BucketLoggingStatus XML document for putting to the ?logging
      # URL for a resource.
      def to_xml
        xml_str = ""
        xml = Builder::XmlMarkup.new(:target => xml_str, :indent => 0)
        
        xml.instruct!
        
        # BucketLoggingStatus XML.
        xml.BucketLoggingStatus({"xmlns" => RESPONSE_NAMESPACE_URI}) {
          unless @log_target.nil? and @log_prefix.nil?
            xml.LoggingEnabled {
              xml.TargetBucket @log_target
              xml.TargetPrefix @log_prefix
            }
          end
        }
        
        xml_str
      end
      
      # Convert XML from S3 response into a LoggingResource
      # 
      #-- TODO: tests
      def self.from_xml(logging_xml)
        return nil if logging_xml.nil?
        
        logging_xml = S33r.remove_namespace(logging_xml)
        doc = XML.get_xml_doc(logging_xml)
        
        log_target = doc.xget('//TargetBucket')
        log_prefix = doc.xget('//TargetPrefix')
        
        self.new(log_target, log_prefix)
      end
      
    end
  end
  
  # Extensions to the S3ACL module to cover logging.
  module S3ACL
    class Policy
    # Does the ACL make the associated resource available as a log target?
      def log_targetable?
        log_target_grants = Grant.log_target_grants
        log_target_grants.each { |g| return false if !grants.include?(g) }
        return true
      end
      
      # Add permissions to an instances which give READ_ACL
      # and WRITE permissions to the LogDelivery group. Used
      # to enable a bucket as a logging destination.
      # 
      # Returns true if grants added, false otherwise
      # (if already a log target).
      def add_log_target_grants
        if log_targetable?
          return false
        else
          Grant.log_target_grants.each { |g| add_grant(g) }
          return true
        end
      end
      
      # Remove log target ACLs from the document.
      # 
      # Returns true if all log target grants were removed;
      # false otherwise.
      # 
      # NB even if this method returns false, that doesn't mean
      # the bucket is still a log target. Use log_targetable? to check
      # whether a bucket can be used as a log target.
      def remove_log_target_grants
        ok = true
        Grant.log_target_grants.each { |g| ok = ok and remove_grant(g) }
        ok
      end
    end
    
    class Grant
      # Generator for a grant which gives the LogDelivery group
      # write and read_acl permissions on a bucket.
      # 
      # Returns an array with the two required Grant instances.
      def Grant.log_target_grants
        log_delivery_group = Group.new(:log_delivery)
        [Grant.new(log_delivery_group, :read_acl), Grant.new(log_delivery_group, :write)]
      end
    end
  end
end