import git
from git.exc import InvalidGitRepositoryError
from git.config import GitConfigParser
from StringIO import StringIO
import weakref

__all__ = (	'sm_section', 'sm_name', 'mkhead', 'unbare_repo', 'find_first_remote_branch', 
			'SubmoduleConfigParser')

#{ Utilities

def sm_section(name):
	""":return: section title used in .gitmodules configuration file"""
	return 'submodule "%s"' % name

def sm_name(section):
	""":return: name of the submodule as parsed from the section name"""
	section = section.strip()
	return section[11:-1]
	
def mkhead(repo, path):
	""":return: New branch/head instance"""
	return git.Head(repo, git.Head.to_full_path(path))
	
def unbare_repo(func):
	"""Methods with this decorator raise InvalidGitRepositoryError if they 
	encounter a bare repository"""
	def wrapper(self, *args, **kwargs):
		if self.repo.bare:
			raise InvalidGitRepositoryError("Method '%s' cannot operate on bare repositories" % func.__name__)
		#END bare method
		return func(self, *args, **kwargs)
	# END wrapper
	wrapper.__name__ = func.__name__
	return wrapper
	
def find_first_remote_branch(remotes, branch_name):
	"""Find the remote branch matching the name of the given branch or raise InvalidGitRepositoryError"""
	for remote in remotes:
		try:
			return remote.refs[branch_name]
		except IndexError:
			continue
		# END exception handling
	#END for remote
	raise InvalidGitRepositoryError("Didn't find remote branch %r in any of the given remotes", branch_name)
	
#} END utilities


#{ Classes

class SubmoduleConfigParser(GitConfigParser):
	"""
	Catches calls to _write, and updates the .gitmodules blob in the index
	with the new data, if we have written into a stream. Otherwise it will 
	add the local file to the index to make it correspond with the working tree.
	Additionally, the cache must be cleared
	
	Please note that no mutating method will work in bare mode
	"""
	
	def __init__(self, *args, **kwargs):
		self._smref = None
		self._index = None
		self._auto_write = True
		super(SubmoduleConfigParser, self).__init__(*args, **kwargs)
	
	#{ Interface
	def set_submodule(self, submodule):
		"""Set this instance's submodule. It must be called before 
		the first write operation begins"""
		self._smref = weakref.ref(submodule)

	def flush_to_index(self):
		"""Flush changes in our configuration file to the index"""
		assert self._smref is not None
		# should always have a file here
		assert not isinstance(self._file_or_files, StringIO)
		
		sm = self._smref()
		if sm is not None:
			index = self._index
			if index is None:
				index = sm.repo.index
			# END handle index
			index.add([sm.k_modules_file], write=self._auto_write)
			sm._clear_cache()
		# END handle weakref

	#} END interface
	
	#{ Overridden Methods
	def write(self):
		rval = super(SubmoduleConfigParser, self).write()
		self.flush_to_index()
		return rval
	# END overridden methods


#} END classes
