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

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

'''This extension add a hacky command to drop changeset during review

This extension is intended as a temporary hack to allow Matt Mackall to use

evolve in the Mercurial review it self. You should probably not use it if your

name is not Matt Mackall.

'''

import os

import time

import contextlib

from mercurial.i18n import _

from mercurial import cmdutil

from mercurial import repair

from mercurial import scmutil

from mercurial import lock as lockmod

from mercurial import util

from mercurial import commands

cmdtable = {}

command = cmdutil.command(cmdtable)

@contextlib.contextmanager

def timed(ui, caption):

    ostart = os.times()

    cstart = time.time()

    yield

    cstop = time.time()

    ostop = os.times()

    wall = cstop - cstart

    user = ostop[0] - ostart[0]

    sys  = ostop[1] - ostart[1]

    comb = user + sys

    ui.write("%s: wall %f comb %f user %f sys %f\n"

             % (caption, wall, comb, user, sys))

def obsmarkerchainfrom(obsstore, nodes):

    """return all marker chain starting from node

    Starting from mean "use as successors"."""

    # XXX need something smarter for descendant of bumped changeset

    seennodes = set(nodes)

    seenmarkers = set()

    pendingnodes = set(nodes)

    precursorsmarkers = obsstore.precursors

    while pendingnodes:

        current = pendingnodes.pop()

        new = set()

        for precmark in precursorsmarkers.get(current, ()):

            if precmark in seenmarkers:

                continue

            seenmarkers.add(precmark)

            new.add(precmark[0])

            yield precmark

        new -= seennodes

        pendingnodes |= new

def stripmarker(ui, repo, markers):

    """remove <markers> from the repo obsstore

    The old obsstore content is saved in a `obsstore.prestrip` file

    """

    repo = repo.unfiltered()

    repo.destroying()

    oldmarkers = list(repo.obsstore._all)

    util.rename(repo.sjoin('obsstore'),

                repo.join('obsstore.prestrip'))

    del repo.obsstore # drop the cache

    newstore = repo.obsstore

    assert not newstore # should be empty after rename

    newmarkers = [m for m in oldmarkers if m not in markers]

    tr = repo.transaction('drophack')

    try:

        newstore.add(tr, newmarkers)

        tr.close()

    finally:

        tr.release()

    repo.destroyed()

@command('drop', [('r', 'rev', [], 'revision to update')], _('[-r] revs'))

def cmddrop(ui, repo, *revs, **opts):

    """I'm hacky do not use me!

    This command strip a changeset, its precursors and all obsolescence marker

    associated to its chain.

    There is no way to limit the extend of the purge yet. You may have to

    repull from other source to get some changeset and obsolescence marker

    back.

    This intended for Matt Mackall usage only. do not use me.

    """

    revs = list(revs)

    revs.extend(opts['rev'])

    if not revs:

        revs = ['.']

    # get the changeset

    revs = scmutil.revrange(repo, revs)

    if not revs:

        ui.write_err('no revision to drop\n')

        return 1

    # lock from the beginning to prevent race

    wlock = lock = None

    try:

        wlock = repo.wlock()

        lock = repo.lock()

        # check they have no children

        if repo.revs('%ld and public()', revs):

            ui.write_err('cannot drop public revision')

            return 1

        if repo.revs('children(%ld) - %ld', revs, revs):

            ui.write_err('cannot drop revision with children')

            return 1

        if repo.revs('. and %ld', revs):

            newrevs = repo.revs('max(::. - %ld)', revs)

            if newrevs:

                assert len(newrevs) == 1

                newrev = newrevs.first()

            else:

                newrev = -1

            commands.update(ui, repo, newrev)

            ui.status(_('working directory now at %s\n') % repo[newrev])

        # get all markers and successors up to root

        nodes = [repo[r].node() for r in revs]

        with timed(ui, 'search obsmarker'):

            markers = set(obsmarkerchainfrom(repo.obsstore, nodes))

        ui.write('%i obsmarkers found\n' % len(markers))

        cl = repo.unfiltered().changelog

        with timed(ui, 'search nodes'):

            allnodes = set(nodes)

            allnodes.update(m[0] for m in markers if cl.hasnode(m[0]))

        ui.write('%i nodes found\n' % len(allnodes))

        cl = repo.changelog

        visiblenodes = set(n for n in allnodes if cl.hasnode(n))

        # check constraint again

        if repo.revs('%ln and public()', visiblenodes):

            ui.write_err('cannot drop public revision')

            return 1

        if repo.revs('children(%ln) - %ln', visiblenodes, visiblenodes):

            ui.write_err('cannot drop revision with children')

            return 1

        if markers:

            # strip them

            with timed(ui, 'strip obsmarker'):

                stripmarker(ui, repo, markers)

        # strip the changeset

        with timed(ui, 'strip nodes'):

            repair.strip(ui, repo, list(allnodes), backup="all", topic='drophack')

    finally:

        lockmod.release(lock, wlock)

    # rewrite the whole file.

    # print data.

    # - time to compute the chain

    # - time to strip the changeset

    # - time to strip the obs marker.