# gitrevset.py
#
# Copyright 2014 Facebook, Inc.
"""map a git hash to a Mercurial hash:

    $ hg log -r "gitnode($HASH)"
    $ hg id -r "gitnode($HASH)"

short version:

    $ hg log -r "g$HASH"
    $ hg id -r "g$HASH"

"""

from __future__ import absolute_import

from mercurial import (
    error,
    extensions,
    hg,
    registrar,
    revset,
)
from mercurial.i18n import _
import re

revsetpredicate = registrar.revsetpredicate()

githashre = re.compile('g([0-9a-fA-F]{40,40})')

templatekeyword = registrar.templatekeyword()

@templatekeyword("gitnode")
def showgitnode(repo, ctx, templ, **args):
    """Return the git revision corresponding to a given hg rev"""
    hexgitnode = _lookup_node(repo, ctx.hex(), from_scm_type='hg')
    # templates are expected to return an empty string when no
    # data exists
    return hexgitnode.encode('hex') if hexgitnode else ''

@revsetpredicate('gitnode(id)')
def gitnode(repo, subset, x):
    """``gitnode(id)``
    Return the hg revision corresponding to a given git rev."""
    l = revset.getargs(x, 1, 1, _("id requires one argument"))
    n = revset.getstring(l[0], _("id requires a string"))

    hexhgnode = _lookup_node(repo, n, from_scm_type='git')
    if not hexhgnode:
        raise error.RepoLookupError(_("unknown revision '%s'") % n)

    rev = repo[hexhgnode].rev()
    return subset.filter(lambda r: r == rev)

def _lookup_node(repo, hexnode, from_scm_type):
    gitlookupnode = '_gitlookup_%s_%s' % (from_scm_type, hexnode)

    # ui.expandpath('default') returns 'default' if there is no default
    # path. This can be the case when command is ran on the server.
    # In that case let's run lookup() command locally.
    try:
        return repo.lookup(gitlookupnode)
    except error.RepoLookupError:
        # Note: RepoLookupError is caught here because repo.lookup()
        # can throw only this exception.
        peerpath = repo.ui.expandpath('default')

        # sshing can cause junk 'remote: ...' output to stdout, so we need to
        # redirect it temporarily so automation can parse the result easily.
        oldfout = repo.ui.fout
        try:
            repo.baseui.fout = repo.ui.ferr
            remoterepo = hg.peer(repo, {}, peerpath)
            return remoterepo.lookup(gitlookupnode)
        except error.RepoError:
            # Note: RepoError can be thrown by hg.peer(), RepoLookupError
            # can be thrown by remoterepo.lookup(). RepoLookupError is a
            # subclass of RepoError so catching just error.RepoError is enough.
            return None
        finally:
            repo.baseui.fout = oldfout

def overridestringset(orig, repo, subset, x, *args, **kwargs):
    m = githashre.match(x)
    if m is not None:
        return gitnode(repo, subset, ('string', m.group(1)))
    return orig(repo, subset, x, *args, **kwargs)

def extsetup(ui):
    extensions.wrapfunction(revset, 'stringset', overridestringset)
    revset.methods['string'] = revset.stringset
    revset.methods['symbol'] = revset.stringset