# phrevset.py - support for Phabricator revsets
#
# Copyright 2013 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""provides support for Phabricator revsets

Allows for queries such as `hg log -r D1234567` to find the commit which
corresponds to a specific Differential revision.
Automatically handles commits already in subversion, or whose hash has
changed since submitting to Differential (due to amends or rebasing).

Requires arcanist to be installed and properly configured.
Repositories should include a callsign in their hgrc.

Example for www:

[phrevset]
callsign = E

"""

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

try:
    from hgsubversion import util as svnutil
except ImportError:
    svnutil = None

import os
import signal
import json
import re
import subprocess

configtable = {}
configitem = registrar.configitem(configtable)

configitem('phrevset', 'callsign', default=None)

DIFFERENTIAL_REGEX = re.compile(
    'Differential Revision: http.+?/'  # Line start, URL
    'D(?P<id>[0-9]+)',  # Differential ID, just numeric part
    flags = re.LOCALE
)

DESCRIPTION_REGEX = re.compile(
    'Commit r'  # Prefix
    '(?P<callsign>[A-Z]{1,})'  # Callsign
    '(?P<id>[a-f0-9]+)',  # rev
    flags = re.LOCALE
)

def getdiff(repo, diffid):
    """Perform a Conduit API call by shelling out to `arc`

    Returns a subprocess.Popen instance"""

    try:
        proc = subprocess.Popen(['arc', 'call-conduit', 'differential.getdiff'],
                     stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                     preexec_fn=os.setsid)

        input = json.dumps({'revision_id': diffid})
        repo.ui.debug("[diffrev] echo '%s' | "
                      "arc call-conduit differential.getdiff\n" % input)
        proc.stdin.write(input)
        proc.stdin.close()

        return proc
    except Exception as e:
        raise error.Abort('Could not not call "arc call-conduit": %s' % e)

def finddiff(repo, diffid, proc=None):
    """Scans the changelog for commit lines mentioning the Differential ID

    If the optional proc parameter is provided, it must be a subprocess.Popen
    instance. It will be polled during the iteration and if it indicates that
    the process has returned, the function will raise StopIteration"""

    repo.ui.debug('[diffrev] Traversing log for %s\n' % diffid)

    # traverse the changelog backwards
    for rev in repo.changelog.revs(start=len(repo.changelog), stop=0):
        if rev % 100 == 0 and proc and proc.poll() is not None:
            raise StopIteration("Parallel proc call completed")

        changectx = repo[rev]
        desc = changectx.description()
        match = DIFFERENTIAL_REGEX.search(desc)

        if match and match.group('id') == diffid:
            return changectx.rev()

    return None

def forksearch(repo, diffid):
    """Perform a log traversal and Conduit call in parallel

    Returns a (revisions, arc_response) tuple, where one of the items will be
    None, depending on which process terminated first"""

    repo.ui.debug('[diffrev] Starting Conduit call\n')

    proc = getdiff(repo, diffid)

    try:
        repo.ui.debug('[diffrev] Starting log walk\n')
        rev = finddiff(repo, diffid, proc)

        repo.ui.debug('[diffrev] Parallel log walk completed with %s\n' % rev)
        os.killpg(proc.pid, signal.SIGTERM)

        if rev is None:
            # walked the entire repo and couldn't find the diff
            raise error.Abort('Could not find diff D%s in changelog' % diffid)

        return ([rev], None)

    except StopIteration:
        # search terminated because arc returned
        # if returncode == 0, return arc's output

        repo.ui.debug('[diffrev] Conduit call returned %i\n' % proc.returncode)

        if proc.returncode != 0:
            raise error.Abort('arc call returned status %i' % proc.returncode)

        resp = proc.stdout.read()
        return (None, resp)

def parsedesc(repo, resp, ignoreparsefailure):
    desc = resp['description']
    if desc is None:
        if ignoreparsefailure:
            return None
        else:
            raise error.Abort("No Conduit description")

    match = DESCRIPTION_REGEX.match(desc)

    if not match:
        if ignoreparsefailure:
            return None
        else:
            raise error.Abort("Cannot parse Conduit description '%s'"
                              % desc)

    callsign = match.group('callsign')
    repo_callsign = repo.ui.config('phrevset', 'callsign')

    if callsign != repo_callsign:
        raise error.Abort("Diff callsign '%s' is different from repo"
                           " callsign '%s'" % (callsign, repo_callsign))

    return match.group('id')

def revsetdiff(repo, subset, diffid):
    """Return a set of revisions corresponding to a given Differential ID """

    repo_callsign = repo.ui.config('phrevset', 'callsign')
    if repo_callsign is None:
        msg = _('phrevset.callsign is not set - doing a linear search\n')
        hint = _('This will be slow if the diff was not committed recently\n')
        repo.ui.warn(msg)
        repo.ui.warn(hint)
        rev = finddiff(repo, diffid)
        if rev is None:
            raise error.Abort('Could not find diff D%s in changelog' % diffid)
        else:
            return [rev]

    revs, resp = forksearch(repo, diffid)

    if revs is not None:
        # The log walk found the diff, nothing more to do
        return revs

    jsresp = json.loads(resp)
    if not jsresp:
        raise error.Abort('Could not decode Conduit response')

    resp = jsresp.get('response')
    if not resp:
        e = jsresp.get('errorMessage', 'unknown error')
        raise error.Abort('Conduit error: %s' % e)

    vcs = resp.get('sourceControlSystem')

    repo.ui.debug('[diffrev] VCS is %s\n' % vcs)

    if vcs == 'svn' and svnutil:
        # commit has landed in svn, parse the description to get the SVN
        # revision and delegate to hgsubversion for the rest

        svnrev = parsedesc(repo, resp, ignoreparsefailure=False)
        repo.ui.debug("[diffrev] SVN rev is r%s\n" % svnrev)

        args = ('string', svnrev)
        return svnutil.revset_svnrev(repo, subset, args)

    elif vcs == 'git':
        gitrev = parsedesc(repo, resp, ignoreparsefailure=False)
        repo.ui.debug("[diffrev] GIT rev is %s\n" % gitrev)

        peerpath = repo.ui.expandpath('default')
        remoterepo = hg.peer(repo, {}, peerpath)
        remoterev = remoterepo.lookup('_gitlookup_git_%s' % gitrev)

        repo.ui.debug("[diffrev] HG rev is %s\n" % remoterev.encode('hex'))
        if not remoterev:
            repo.ui.debug('[diffrev] Falling back to linear search\n')
            linear_search_result = finddiff(repo, diffid)
            if linear_search_result is None:
                # walked the entire repo and couldn't find the diff
                raise error.Abort(
                    'Could not find diff D%s in changelog' % diffid)

            return [linear_search_result]

        return [repo[remoterev].rev()]

    elif vcs == 'hg':
        rev = parsedesc(repo, resp, ignoreparsefailure=True)
        if rev:
            # The response from phabricator contains a changeset ID.
            # Convert it back to a rev number.
            try:
                node = repo[rev.encode('utf-8')]
            except error.RepoLookupError:
                raise error.Abort('Landed commit for diff D%s not available '
                                  'in current repository: run "hg pull" '
                                  'to retrieve it' % diffid)
            return [node.rev()]

        # commit is still local, get its hash

        props = resp['properties']
        commits = props['local:commits']

        # the JSON parser returns Unicode strings, convert to `str` in UTF-8
        revs = [c['commit'].encode('utf-8') for c in commits.values()]

        # verify all revisions exist in the current repo; if not, try to
        # find their counterpart by parsing the log
        results = set()
        for rev in revs:
            # TODO: This really should be searching in repo.unfiltered(),
            # and then resolving successors if the commit was hidden.
            try:
                node = repo[rev.encode('utf-8')]
                results.add(node.rev())
            except error.RepoLookupError:
                repo.ui.warn(_('Commit not found - doing a linear search\n'))
                parsed_rev = finddiff(repo, diffid)

                if not parsed_rev:
                    raise error.Abort('Could not find diff '
                                       'D%s in changelog' % diffid)

                results.add(parsed_rev)

        if not results:
            raise error.Abort('Could not find local commit for D%s' % diffid)

        return set(results)

    else:
        if not vcs:
            msg = "D%s does not have an associated version control system\n" \
                  "You can view the diff at http://phabricator.fb.com/D%s\n\n"
            repo.ui.warn(msg % (diffid, diffid))

            return []
        else:
            raise error.Abort('Conduit returned unknown '
                               'sourceControlSystem "%s"' % vcs)

def revsetstringset(orig, repo, subset, revstr, *args, **kwargs):
    """Wrapper that recognizes revisions starting with 'D'"""

    if revstr.startswith('D') and revstr[1:].isdigit():
        return smartset.baseset(revsetdiff(repo, subset, revstr[1:]))

    return orig(repo, subset, revstr, *args, **kwargs)

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