from reference import Reference

__all__ = ["TagReference", "Tag"]

class TagReference(Reference):
	"""Class representing a lightweight tag reference which either points to a commit 
	,a tag object or any other object. In the latter case additional information, 
	like the signature or the tag-creator, is available.
	
	This tag object will always point to a commit object, but may carray additional
	information in a tag object::
	
	 tagref = TagReference.list_items(repo)[0]
	 print tagref.commit.message
	 if tagref.tag is not None:
		print tagref.tag.message"""
	__slots__ = tuple()
	_common_path_default = "refs/tags"
	
	@property
	def commit(self):
		""":return: Commit object the tag ref points to"""
		obj = self.object
		if obj.type == "commit":
			return obj
		elif obj.type == "tag":
			# it is a tag object which carries the commit as an object - we can point to anything
			return obj.object
		else:
			raise ValueError( "Tag %s points to a Blob or Tree - have never seen that before" % self )	

	@property
	def tag(self):
		"""
		:return: Tag object this tag ref points to or None in case 
			we are a light weight tag"""
		obj = self.object
		if obj.type == "tag":
			return obj
		return None
		
	# make object read-only
	# It should be reasonably hard to adjust an existing tag
	object = property(Reference._get_object)
	
	@classmethod
	def create(cls, repo, path, ref='HEAD', message=None, force=False, **kwargs):
		"""Create a new tag reference.
		
		:param path:
			The name of the tag, i.e. 1.0 or releases/1.0. 
			The prefix refs/tags is implied
			
		:param ref:
			A reference to the object you want to tag. It can be a commit, tree or 
			blob.
			
		:param message:
			If not None, the message will be used in your tag object. This will also 
			create an additional tag object that allows to obtain that information, i.e.::
			
				tagref.tag.message
			
		:param force:
			If True, to force creation of a tag even though that tag already exists.
			
		:param kwargs:
			Additional keyword arguments to be passed to git-tag
			
		:return: A new TagReference"""
		args = ( path, ref )
		if message:
			kwargs['m'] =  message
		if force:
			kwargs['f'] = True
		
		repo.git.tag(*args, **kwargs)
		return TagReference(repo, "%s/%s" % (cls._common_path_default, path))
		
	@classmethod
	def delete(cls, repo, *tags):
		"""Delete the given existing tag or tags"""
		repo.git.tag("-d", *tags)
		
# provide an alias
Tag = TagReference
