[kupfer] Introduce qfurl: kupfer URIs and URI resolution

[Ulrik Sverdrup <usverdrup src gnome org>]

commit 1ff73b621987b735882d5f557edd894758e78e05
Author: Ulrik Sverdrup <ulrik sverdrup gmail com>
Date:   Thu Sep 10 02:39:07 2009 +0200

    Introduce qfurl: kupfer URIs and URI resolution
    
    A qfurl is a URI to locate unique objects in kupfer's catalog
    
    The qfurl is built up as follows:
    ``qpfer://mother/qfid#module_and_type_hint``
    
    The mother part is a mother source identifier and is optional.
    The module_and_type_hint is optional.
    
    A short url looks like the following:
    ``qpfer:identifier``
    
    This class provides methods to get the qfurl for an object,
    and resolve the object in a catalog.

 kupfer/qfurl.py |   88 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 88 insertions(+), 0 deletions(-)
---
diff --git a/kupfer/qfurl.py b/kupfer/qfurl.py
new file mode 100644
index 0000000..24ea5e3
--- /dev/null
+++ b/kupfer/qfurl.py
@@ -0,0 +1,88 @@
+from urlparse import urlparse, urlunparse
+
+from kupfer import pretty
+
+QFURL_SCHEME = "qpfer"
+
+class QfurlError (Exception):
+	pass
+
+class qfurl (object):
+	"""A qfurl is a URI to locate unique objects in kupfer's catalog.
+
+	The qfurl is built up as follows:
+	``qpfer://mother/qfid#module_and_type_hint``
+
+	The mother part is a mother source identifier and is optional.
+	The module_and_type_hint is optional.
+
+	A short url looks like the following:
+	``qpfer:identifier``
+
+	This class provides methods to get the qfurl for an object,
+	and resolve the object in a catalog.
+	"""
+
+	def __init__(self, obj=None, url=None):
+		"""Create a new qfurl for object @obj"""
+		if obj:
+			typname = "%s.%s" % (type(obj).__module__, type(obj).__name__)
+			try:
+				qfid = obj.qf_id
+			except AttributeError, err:
+				raise QfurlError("%s has no qfurl" % obj)
+			self.url = urlunparse((QFURL_SCHEME, "", qfid, "", "", typname))
+		else:
+			self.url = url
+
+	def __str__(self):
+		return self.url
+
+	def __hash__(self):
+		return hash(self.url)
+
+	def __eq__(self, other):
+		return self.reduce_url(self.url) == self.reduce_url(other.url)
+
+	@classmethod
+	def reduce_url(cls, url):
+		split = url.rsplit("#", 1)
+		if len(split) == 2:
+			qfid, typname = split
+			return qfid
+		else:
+			return url
+
+	@classmethod
+	def _parts_mother_id_typename(cls, url):
+		scheme, mother, qfid, ignored, ignored2, typname = urlparse(url)
+		if "#" in qfid:
+			qfid, typname = qfid.rsplit("#", 1)
+		else:
+			typname = None
+		if scheme != QFURL_SCHEME:
+			raise QfurlError("Wrong scheme: %s" % scheme)
+		return mother, qfid, typname
+
+	def resolve_in_catalog(self, catalog):
+		"""Resolve self in a catalog of sources"""
+		mother, qfid, typname = self._parts_mother_id_typename(self.url)
+		module, name = typname.rsplit(".", 1) if typname else (None, None)
+		matches = []
+		for src in catalog:
+			if name:
+				if name not in (t.__name__
+						for pt in src.provides()
+						for t in pt.__subclasses__()):
+					continue
+			for obj in src.get_leaves():
+				if not hasattr(obj, "qf_id"):
+					continue
+				try:
+					if self == qfurl(obj):
+						matches.append(obj)
+				except QfurlError:
+					pass
+		pretty.print_debug(__name__, "Found matches:", matches)
+		pretty.print_debug(__name__, "For", self)
+		return matches[0] if matches else None