# destutil.py - Mercurial utility function for command destination

#

#  Copyright Matt Mackall <mpm@selenic.com> and other

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

from .i18n import _

from . import (

    bookmarks,

    error,

    obsolete,

)

def destupdate(repo, clean=False, check=False):

    """destination for bare update operation

    return (rev, movemark, activemark)

    - rev: the revision to update to,

    - movemark: node to move the active bookmark from

                (cf bookmark.calculate update),

    - activemark: a bookmark to activate at the end of the update.

    """

    node = None

    wc = repo[None]

    p1 = wc.p1()

    activemark = None

    # we also move the active bookmark, if any

    node, movemark = bookmarks.calculateupdate(repo.ui, repo, None)

    if node is not None:

        activemark = node

    if node is None:

        try:

            node = repo.branchtip(wc.branch())

        except error.RepoLookupError:

            if wc.branch() == 'default': # no default branch!

                node = repo.lookup('tip') # update to tip

            else:

                raise error.Abort(_("branch %s not found") % wc.branch())

    if p1.obsolete() and not p1.children():

        # allow updating to successors

        successors = obsolete.successorssets(repo, p1.node())

        # behavior of certain cases is as follows,

        #

        # divergent changesets: update to highest rev, similar to what

        #     is currently done when there are more than one head

        #     (i.e. 'tip')

        #

        # replaced changesets: same as divergent except we know there

        # is no conflict

        #

        # pruned changeset: no update is done; though, we could

        #     consider updating to the first non-obsolete parent,

        #     similar to what is current done for 'hg prune'

        if successors:

            # flatten the list here handles both divergent (len > 1)

            # and the usual case (len = 1)

            successors = [n for sub in successors for n in sub]

            # get the max revision for the given successors set,

            # i.e. the 'tip' of a set

            node = repo.revs('max(%ln)', successors).first()

    rev = repo[node].rev()

    if not clean:

        # Check that the update is linear.

        #

        # Mercurial do not allow update-merge for non linear pattern

        # (that would be technically possible but was considered too confusing

        # for user a long time ago)

        #

        # See mercurial.merge.update for details

        if p1.rev() not in repo.changelog.ancestors([rev], inclusive=True):

            dirty = wc.dirty(missing=True)

            foreground = obsolete.foreground(repo, [p1.node()])

            if not repo[rev].node() in foreground:

                if dirty:

                    msg = _("uncommitted changes")

                    hint = _("commit and merge, or update --clean to"

                             " discard changes")

                elif not check:  # destination is not a descendant.

                    msg = _("not a linear update")

                    hint = _("merge or update --check to force update")

    return rev, movemark, activemark