from symbolic import SymbolicReference
from git.exc import GitCommandError

__all__ = ["HEAD"]


class HEAD(SymbolicReference):

    """Provides additional functionality using the git command"""
    __slots__ = tuple()

    _HEAD_NAME = 'HEAD'
    _ORIG_HEAD_NAME = 'ORIG_HEAD'
    __slots__ = tuple()

    def __init__(self, repo, path=_HEAD_NAME):
        if path != self._HEAD_NAME:
            raise ValueError("HEAD instance must point to %r, got %r" % (self._HEAD_NAME, path))
        super(HEAD, self).__init__(repo, path)

    def orig_head(self):
        """
        :return: SymbolicReference pointing at the ORIG_HEAD, which is maintained 
            to contain the previous value of HEAD"""
        return SymbolicReference(self.repo, self._ORIG_HEAD_NAME)

    def reset(self, commit='HEAD', index=True, working_tree=False,
              paths=None, **kwargs):
        """Reset our HEAD to the given commit optionally synchronizing 
        the index and working tree. The reference we refer to will be set to 
        commit as well.

        :param commit:
            Commit object, Reference Object or string identifying a revision we 
            should reset HEAD to.

        :param index:
            If True, the index will be set to match the given commit. Otherwise
            it will not be touched.

        :param working_tree:
            If True, the working tree will be forcefully adjusted to match the given
            commit, possibly overwriting uncommitted changes without warning.
            If working_tree is True, index must be true as well

        :param paths:
            Single path or list of paths relative to the git root directory
            that are to be reset. This allows to partially reset individual files.

        :param kwargs:
            Additional arguments passed to git-reset. 

        :return: self"""
        mode = "--soft"
        add_arg = None
        if index:
            mode = "--mixed"

            # it appears, some git-versions declare mixed and paths deprecated
            # see http://github.com/Byron/GitPython/issues#issue/2
            if paths:
                mode = None
            # END special case
        # END handle index

        if working_tree:
            mode = "--hard"
            if not index:
                raise ValueError("Cannot reset the working tree if the index is not reset as well")

        # END working tree handling

        if paths:
            add_arg = "--"
        # END nicely separate paths from rest

        try:
            self.repo.git.reset(mode, commit, add_arg, paths, **kwargs)
        except GitCommandError, e:
            # git nowadays may use 1 as status to indicate there are still unstaged
            # modifications after the reset
            if e.status != 1:
                raise
        # END handle exception

        return self