import weakref

from .i18n import _

    short,

    mdiff,

    pycompat,

    tr = pullop.trmanager.transaction()

    pullheads = pullop.heads or remoteheads

    _fetchchangesets(repo, tr, remote, common, fetch, pullheads)

def _fetchchangesets(repo, tr, remote, common, fetch, remoteheads):

    if not fetch:

        return

    # TODO consider adding a step here where we obtain the DAG shape first

    # (or ask the server to slice changesets into chunks for us) so that

    # we can perform multiple fetches in batches. This will facilitate

    # resuming interrupted clones, higher server-side cache hit rates due

    # to smaller segments, etc.

    with remote.commandexecutor() as e:

        objs = e.callcommand(b'changesetdata', {

            b'noderange': [sorted(common), sorted(remoteheads)],

            b'fields': {b'parents', b'revision'},

        }).result()

        # The context manager waits on all response data when exiting. So

        # we need to remain in the context manager in order to stream data.

        return _processchangesetdata(repo, tr, objs)

def _processchangesetdata(repo, tr, objs):

    repo.hook('prechangegroup', throw=True,

              **pycompat.strkwargs(tr.hookargs))

    urepo = repo.unfiltered()

    cl = urepo.changelog

    cl.delayupdate(tr)

    # The first emitted object is a header describing the data that

    # follows.

    meta = next(objs)

    progress = repo.ui.makeprogress(_('changesets'),

                                    unit=_('chunks'),

                                    total=meta.get(b'totalitems'))

    def linkrev(node):

        repo.ui.debug('add changeset %s\n' % short(node))

        # Linkrev for changelog is always self.

        return len(cl)

    def onchangeset(cl, node):

        progress.increment()

    # addgroup() expects a 7-tuple describing revisions. This normalizes

    # the wire data to that format.

    def iterrevisions():

        for cset in objs:

            assert b'revisionsize' in cset

            data = next(objs)

            yield (

                cset[b'node'],

                cset[b'parents'][0],

                cset[b'parents'][1],

                # Linknode is always itself for changesets.

                cset[b'node'],

                # We always send full revisions. So delta base is not set.

                nullid,

                mdiff.trivialdiffheader(len(data)) + data,

                # Flags not yet supported.

                0,

            )

    added = cl.addgroup(iterrevisions(), linkrev, weakref.proxy(tr),

                        addrevisioncb=onchangeset)

    progress.complete()

    return {

        'added': added,

    }