# 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 __future__ import absolute_import

from .i18n import _

from . import (

    bookmarks,

    error,

    obsolete,

)

def _destupdatevalidate(repo, rev, clean, check):

    """validate that the destination comply to various rules

    This exists as its own function to help wrapping from extensions."""

    wc = repo[None]

    p1 = wc.p1()

    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")

                    raise error.UpdateAbort(msg, hint=hint)

                elif not check:  # destination is not a descendant.

                    msg = _("not a linear update")

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

                    raise error.UpdateAbort(msg, hint=hint)

def _destupdateobs(repo, clean, check):

    """decide of an update destination from obsolescence markers"""

    node = None

    wc = repo[None]

    p1 = wc.p1()

    movemark = None

    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()

            if bookmarks.isactivewdirparent(repo):

                movemark = repo['.'].node()

    return node, movemark, None

def _destupdatebook(repo, clean, check):

    """decide on an update destination from active bookmark"""

    # we also move the active bookmark, if any

    activemark = None

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

    if node is not None:

        activemark = node

    return node, movemark, activemark

def _destupdatebranch(repo, clean, check):

    """decide on an update destination from current branch"""

    wc = repo[None]

    movemark = node = None

    try:

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

        if bookmarks.isactivewdirparent(repo):

            movemark = repo['.'].node()

    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())

    return node, movemark, None

# order in which each step should be evalutated

# steps are run until one finds a destination

destupdatesteps = ['evolution', 'bookmark', 'branch']

# mapping to ease extension overriding steps.

destupdatestepmap = {'evolution': _destupdateobs,

                     'bookmark': _destupdatebook,

                     'branch': _destupdatebranch,

                     }

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 = movemark = activemark = None

    for step in destupdatesteps:

        node, movemark, activemark = destupdatestepmap[step](repo, clean, check)

        if node is not None:

            break

    rev = repo[node].rev()

    _destupdatevalidate(repo, rev, clean, check)

    return rev, movemark, activemark

def _destmergebook(repo):

    """find merge destination in the active bookmark case"""

    node = None

    bmheads = repo.bookmarkheads(repo._activebookmark)

    curhead = repo[repo._activebookmark].node()

    if len(bmheads) == 2:

        if curhead == bmheads[0]:

            node = bmheads[1]

        else:

            node = bmheads[0]

    elif len(bmheads) > 2:

        raise error.Abort(_("multiple matching bookmarks to merge - "

            "please merge with an explicit rev or bookmark"),

            hint=_("run 'hg heads' to see all heads"))

    elif len(bmheads) <= 1:

        raise error.Abort(_("no matching bookmark to merge - "

            "please merge with an explicit rev or bookmark"),

            hint=_("run 'hg heads' to see all heads"))

    assert node is not None

    return node

def _destmergebranch(repo):

    """find merge destination based on branch heads"""

    node = None

    branch = repo[None].branch()

    bheads = repo.branchheads(branch)

    nbhs = [bh for bh in bheads if not repo[bh].bookmarks()]

    if len(nbhs) > 2:

        raise error.Abort(_("branch '%s' has %d heads - "

                           "please merge with an explicit rev")

                         % (branch, len(bheads)),

                         hint=_("run 'hg heads .' to see heads"))

    parent = repo.dirstate.p1()

    if len(nbhs) <= 1:

        if len(bheads) > 1:

            raise error.Abort(_("heads are bookmarked - "

                               "please merge with an explicit rev"),

                             hint=_("run 'hg heads' to see all heads"))

        if len(repo.heads()) > 1:

            raise error.Abort(_("branch '%s' has one head - "

                               "please merge with an explicit rev")

                             % branch,

                             hint=_("run 'hg heads' to see all heads"))

        msg, hint = _('nothing to merge'), None

        if parent != repo.lookup(branch):

            hint = _("use 'hg update' instead")

        raise error.Abort(msg, hint=hint)

    if parent not in bheads:

        raise error.Abort(_('working directory not at a head revision'),

                         hint=_("use 'hg update' or merge with an "

                                "explicit revision"))

    if parent == nbhs[0]:

        node = nbhs[-1]

    else:

        node = nbhs[0]

    assert node is not None

    return node

def destmerge(repo):

    if repo._activebookmark:

        node = _destmergebook(repo)

    else:

        node = _destmergebranch(repo)

    return repo[node].rev()

histeditdefaultrevset = 'reverse(only(.) and not public() and not ::merge())'

def desthistedit(ui, repo):

    """Default base revision to edit for `hg histedit`."""

    # Avoid cycle: scmutil -> revset -> destutil

    from . import scmutil

    default = ui.config('histedit', 'defaultrev', histeditdefaultrevset)

    if default:

        revs = scmutil.revrange(repo, [default])

        if revs:

            # The revset supplied by the user may not be in ascending order nor

            # take the first revision. So do this manually.

            revs.sort()

            return revs.first()

    return None