(Optionally) promote protocols to first-class entity

+ reflect that on the formats' level (also bring a convention for that)
+ make plugin_registry.probe fnc more tolerant towards non-classes
  as we want to differentiate between protocol on instance basis
  rather than based on dedicated classes (because we want to
  pragmatically maintain interchangeability with plain strings!)
+ make extra steps in protocol.py so the mentioned interchangeability
  actually works

Signed-off-by: Jan Pokorný <jpokorny@redhat.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/protocol.py b/protocol.py
new file mode 100644
index 0000000..54c81d4
--- /dev/null
+++ b/protocol.py
@@ -0,0 +1,41 @@
+# -*- coding: UTF-8 -*-
+# Copyright 2014 Red Hat, Inc.
+# Part of clufter project
+# Licensed under GPLv2+ (a copy included | http://gnu.org/licenses/gpl-2.0.txt)
+"""Base protocol stuff (metaclass, etc.)"""
+__author__ = "Jan Pokorný <jpokorny @at@ Red Hat .dot. com>"
+
+import logging
+
+from .plugin_registry import PluginRegistry
+from .utils import tuplist
+from .utils_prog import cli_undecor
+
+log = logging.getLogger(__name__)
+
+
+class protocols(PluginRegistry):
+    """Protocol registry (to be used as a metaclass for filters)
+
+    To be noted, this harness is solely optional, and only good to allow
+    early discovery of the typos in the protocols and to maintain some
+    in-code documentation of their usage as opposed to much further
+    in the processing with some files already successfully produced, etc.
+    """
+    @classmethod
+    def register(registry, pr):
+        # undecor to pass the checks in probe
+        return registry.probe(cli_undecor(pr),
+                              pr if isinstance(pr, Protocol) else Protocol(pr))
+
+
+class Protocol(str):
+    """Class intended to be (exceptionally) instantioned (enhanced string)"""
+    __metaclass__ = protocols
+
+    def __new__(cls, *args, **kwargs):
+        ret = super(Protocol, cls).__new__(cls, *args, **kwargs)
+        return protocols.register(ret)
+
+    def ensure_proto(self, value):
+        return value if tuplist(value) else (self, value)