#!/usr/bin/env python3
# -*- coding: utf-8 -*-
#
# Copyright 2017 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""This is a tool for picking patches from upstream and applying them."""

import argparse
import configparser
import functools
import mailbox
import os
import pprint
import re
import signal
import subprocess
import sys
import textwrap
import urllib.request
import xmlrpc.client

errprint = functools.partial(print, file=sys.stderr)

LINUX_URLS = (
    'git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git',
    'https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git',
    'https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux.git',
)

PATCHWORK_URLS = (
    'https://lore.kernel.org/patchwork',
    'https://patchwork.kernel.org',
    'https://patchwork.ozlabs.org',
    'https://patchwork.freedesktop.org',
    'https://patchwork.linux-mips.org',
)

COMMIT_MESSAGE_WIDTH = 75

_PWCLIENTRC = os.path.expanduser('~/.pwclientrc')

def _git(args, stdin=None, encoding='utf-8'):
    """Calls a git subcommand.

    Similar to subprocess.check_output.

    Args:
        args: subcommand + args passed to 'git'.
        stdin: a string or bytes (depending on encoding) that will be passed
            to the git subcommand.
        encoding: either 'utf-8' (default) or None. Override it to None if
            you want both stdin and stdout to be raw bytes.

    Returns:
        the stdout of the git subcommand, same type as stdin. The output is
        also run through strip to make sure there's no extra whitespace.

    Raises:
        subprocess.CalledProcessError: when return code is not zero.
            The exception has a .returncode attribute.
    """
    return subprocess.run(
        ['git'] + args,
        encoding=encoding,
        input=stdin,
        stdout=subprocess.PIPE,
        check=True,
    ).stdout.strip()

def _git_returncode(*args, **kwargs):
    """Same as _git, but return returncode instead of stdout.

    Similar to subprocess.call.

    Never raises subprocess.CalledProcessError.
    """
    try:
        _git(*args, **kwargs)
        return 0
    except subprocess.CalledProcessError as e:
        return e.returncode

def _get_conflicts():
    """Report conflicting files."""
    resolutions = ('DD', 'AU', 'UD', 'UA', 'DU', 'AA', 'UU')
    conflicts = []
    output = _git(['status', '--porcelain', '--untracked-files=no'])
    for line in output.splitlines():
        if not line:
            continue
        resolution, name = line.split(None, 1)
        if resolution in resolutions:
            conflicts.append('   ' + name)
    if not conflicts:
        return ''
    return '\nConflicts:\n%s\n' % '\n'.join(conflicts)

def _find_linux_remote():
    """Find a remote pointing to a Linux upstream repository."""
    for remote in _git(['remote']).splitlines():
        try:
            if _git(['remote', 'get-url', remote]) in LINUX_URLS:
                return remote
        except subprocess.CalledProcessError:
            # Kinda weird, get-url failing on an item that git just gave us.
            continue
    return None

def _pause_for_merge(conflicts):
    """Pause and go in the background till user resolves the conflicts."""

    git_root = _git(['rev-parse', '--show-toplevel'])
    previous_head_hash = _git(['rev-parse', 'HEAD'])

    paths = (
        os.path.join(git_root, '.git', 'rebase-apply'),
        os.path.join(git_root, '.git', 'CHERRY_PICK_HEAD'),
    )
    for path in paths:
        if os.path.exists(path):
            errprint('Found "%s".' % path)
            errprint(conflicts)
            errprint('Please resolve the conflicts and restart the '
                     'shell job when done. Kill this job if you '
                     'aborted the conflict.')
            os.kill(os.getpid(), signal.SIGTSTP)

    # Check the conflicts actually got resolved. Otherwise we'll end up
    # modifying the wrong commit message and probably confusing people.
    while previous_head_hash == _git(['rev-parse', 'HEAD']):
        errprint('Error: no new commit has been made. Did you forget to run '
                 '`git am --continue` or `git cherry-pick --continue`?')
        errprint('Please create a new commit and restart the shell job (or kill'
                 ' it if you aborted the conflict).')
        os.kill(os.getpid(), signal.SIGTSTP)

def _get_pw_url(project):
    """Retrieve the patchwork server URL from .pwclientrc.

    Args:
        project: patchwork project name; if None, we retrieve the default
            from pwclientrc
    """
    config = configparser.ConfigParser()
    config.read([_PWCLIENTRC])

    if project is None:
        try:
            project = config.get('options', 'default')
        except (configparser.NoSectionError, configparser.NoOptionError) as e:
            errprint('Error: no default patchwork project found in %s. (%r)'
                     % (_PWCLIENTRC, e))
            sys.exit(1)

    if not config.has_option(project, 'url'):
        errprint("Error: patchwork URL not found for project '%s'" % project)
        sys.exit(1)

    url = config.get(project, 'url')
    # Strip trailing 'xmlrpc' and/or trailing slash.
    return re.sub('/(xmlrpc/)?$', '', url)

def _wrap_commit_line(prefix, content):
    line = prefix + '=' + content
    indent = ' ' * (len(prefix) + 1)
    return textwrap.fill(line, COMMIT_MESSAGE_WIDTH, subsequent_indent=indent)

def _pick_patchwork(url, patch_id, args):
    if args['tag'] is None:
        args['tag'] = 'FROMLIST: '

    try:
        opener = urllib.request.urlopen('%s/patch/%d/mbox' % (url, patch_id))
    except urllib.error.HTTPError as e:
        errprint('Error: could not download patch: %s' % e)
        sys.exit(1)
    patch_contents = opener.read()

    if not patch_contents:
        errprint('Error: No patch content found')
        sys.exit(1)

    message_id = mailbox.Message(patch_contents)['Message-Id']
    message_id = re.sub('^<|>$', '', message_id.strip())
    if args['source_line'] is None:
        args['source_line'] = '(am from %s/patch/%d/)' % (url, patch_id)
        for url_template in [
            'https://lkml.kernel.org/r/%s',
            # hostap project (and others) are here, but not kernel.org.
            'https://marc.info/?i=%s',
            # public-inbox comes last as a "default"; it has a nice error page
            # pointing to other redirectors, even if it doesn't have what
            # you're looking for directly.
            'https://public-inbox.org/git/%s',
        ]:
            alt_url = url_template % message_id
            if args['debug']:
                print('Probing archive for message at: %s' % alt_url)
            try:
                urllib.request.urlopen(alt_url)
            except urllib.error.HTTPError as e:
                # Skip all HTTP errors. We can expect 404 for archives that
                # don't have this MessageId, or 300 for public-inbox ("not
                # found, but try these other redirects"). It's less clear what
                # to do with transitory (or is it permanent?) server failures.
                if args['debug']:
                    print('Skipping URL %s, error: %s' % (alt_url, e))
                continue
            # Success!
            if args['debug']:
                print('Found at %s' % alt_url)
            break
        else:
            errprint(
                "WARNING: couldn't find working MessageId URL; "
                'defaulting to "%s"' % alt_url)
        args['source_line'] += '\n(also found at %s)' % alt_url

    # Auto-snarf the Change-Id if it was encoded into the Message-Id.
    mo = re.match(r'.*(I[a-f0-9]{40})@changeid$', message_id)
    if mo and args['changeid'] is None:
        args['changeid'] = mo.group(1)

    if args['replace']:
        _git(['reset', '--hard', 'HEAD~1'])

    return _git_returncode(['am', '-3'], stdin=patch_contents, encoding=None)

def _match_patchwork(match, args):
    """Match location: pw://### or pw://PROJECT/###."""
    pw_project = match.group(2)
    patch_id = int(match.group(3))

    if args['debug']:
        print('_match_patchwork: pw_project=%s, patch_id=%d' %
              (pw_project, patch_id))

    url = _get_pw_url(pw_project)
    return _pick_patchwork(url, patch_id, args)

def _match_msgid(match, args):
    """Match location: msgid://MSGID."""
    msgid = match.group(1)

    if args['debug']:
        print('_match_msgid: message_id=%s' % (msgid))

    # Patchwork requires the brackets so force it
    msgid = '<' + msgid + '>'
    url = None
    for url in PATCHWORK_URLS:
        rpc = xmlrpc.client.ServerProxy(url + '/xmlrpc/')
        res = rpc.patch_list({'msgid': msgid})
        if res:
            patch_id = res[0]['id']
            break
    else:
        errprint('Error: could not find patch based on message id')
        sys.exit(1)

    return _pick_patchwork(url, patch_id, args)

def _match_linux(match, args):
    """Match location: linux://HASH."""
    commit = match.group(1)

    if args['debug']:
        print('_match_linux: commit=%s' % commit)

    # Confirm a 'linux' remote is setup.
    linux_remote = _find_linux_remote()
    if not linux_remote:
        errprint('Error: need a valid upstream remote')
        sys.exit(1)

    linux_master = '%s/master' % linux_remote
    try:
        _git(['merge-base', '--is-ancestor', commit, linux_master])
    except subprocess.CalledProcessError:
        errprint('Error: Commit not in %s' % linux_master)
        sys.exit(1)

    if args['source_line'] is None:
        commit = _git(['rev-parse', commit])
        args['source_line'] = ('(cherry picked from commit %s)' %
                               (commit))
    if args['tag'] is None:
        args['tag'] = 'UPSTREAM: '

    if args['replace']:
        _git(['reset', '--hard', 'HEAD~1'])

    return _git_returncode(['cherry-pick', commit])

def _match_fromgit(match, args):
    """Match location: git://remote/branch/HASH."""
    remote = match.group(2)
    branch = match.group(3)
    commit = match.group(4)

    if args['debug']:
        print('_match_fromgit: remote=%s branch=%s commit=%s' %
              (remote, branch, commit))

    try:
        _git(['merge-base', '--is-ancestor', commit,
              '%s/%s' % (remote, branch)])
    except subprocess.CalledProcessError:
        errprint('Error: Commit not in %s/%s' % (remote, branch))
        sys.exit(1)

    url = _git(['remote', 'get-url', remote])

    if args['source_line'] is None:
        commit = _git(['rev-parse', commit])
        args['source_line'] = (
            '(cherry picked from commit %s\n %s %s)' % (commit, url, branch))
    if args['tag'] is None:
        args['tag'] = 'FROMGIT: '

    if args['replace']:
        _git(['reset', '--hard', 'HEAD~1'])

    return _git_returncode(['cherry-pick', commit])

def _match_gitfetch(match, args):
    """Match location: (git|https)://repoURL#branch/HASH."""
    remote = match.group(1)
    branch = match.group(3)
    commit = match.group(4)

    if args['debug']:
        print('_match_gitfetch: remote=%s branch=%s commit=%s' %
              (remote, branch, commit))

    try:
        _git(['fetch', remote, branch])
    except subprocess.CalledProcessError:
        errprint('Error: Branch not in %s' % remote)
        sys.exit(1)

    url = remote

    if args['source_line'] is None:
        commit = _git(['rev-parse', commit])
        args['source_line'] = (
            '(cherry picked from commit %s\n %s %s)' % (commit, url, branch))
    if args['tag'] is None:
        args['tag'] = 'FROMGIT: '

    if args['replace']:
        _git(['reset', '--hard', 'HEAD~1'])

    return _git_returncode(['cherry-pick', commit])

def _match_gitweb(match, args):
    """Match location: https://repoURL/commit/?h=branch&id=HASH."""
    remote = match.group(1)
    branch = match.group(2)
    commit = match.group(3)

    if args['debug']:
        print('_match_gitweb: remote=%s branch=%s commit=%s' %
              (remote, branch, commit))

    try:
        _git(['fetch', remote, branch])
    except subprocess.CalledProcessError:
        errprint('Error: Branch not in %s' % remote)
        sys.exit(1)

    url = remote

    if args['source_line'] is None:
        commit = _git(['rev-parse', commit])
        args['source_line'] = (
            '(cherry picked from commit %s\n %s %s)' % (commit, url, branch))
    if args['tag'] is None:
        args['tag'] = 'FROMGIT: '

    if args['replace']:
        _git(['reset', '--hard', 'HEAD~1'])

    return _git_returncode(['cherry-pick', commit])

def main(args):
    """This is the main entrypoint for fromupstream.

    Args:
        args: sys.argv[1:]

    Returns:
        An int return code.
    """
    parser = argparse.ArgumentParser()

    parser.add_argument('--bug', '-b',
                        type=str, help='BUG= line')
    parser.add_argument('--test', '-t',
                        type=str, help='TEST= line')
    parser.add_argument('--crbug', action='append',
                        type=int, help='BUG=chromium: line')
    parser.add_argument('--buganizer', action='append',
                        type=int, help='BUG=b: line')
    parser.add_argument('--changeid', '-c',
                        help='Overrides the gerrit generated Change-Id line')

    parser.add_argument('--replace', '-r',
                        action='store_true',
                        help='Replaces the HEAD commit with this one, taking '
                        'its properties(BUG, TEST, Change-Id). Useful for '
                        'updating commits.')
    parser.add_argument('--nosignoff',
                        dest='signoff', action='store_false')
    parser.add_argument('--debug', '-d', action='store_true',
                        help='Prints more verbose logs.')

    parser.add_argument('--tag',
                        help='Overrides the tag from the title')
    parser.add_argument('--source', '-s',
                        dest='source_line', type=str,
                        help='Overrides the source line, last line, ex: '
                        '(am from http://....)')
    parser.add_argument('locations',
                        nargs='+',
                        help='Patchwork ID (pw://### or pw://PROJECT/###, '
                        'where PROJECT is defined in ~/.pwclientrc; if no '
                        'PROJECT is specified, the default is retrieved from '
                        '~/.pwclientrc), '
                        'Message-ID (msgid://MSGID), '
                        'linux commit like linux://HASH, or '
                        'git reference like git://remote/branch/HASH or '
                        'git://repoURL#branch/HASH or '
                        'https://repoURL#branch/HASH or '
                        'https://repoURL/commit/?h=branch&id=HASH')

    args = vars(parser.parse_args(args))

    buglist = [args['bug']] if args['bug'] else []
    if args['buganizer']:
        buglist += ['b:{0}'.format(x) for x in args['buganizer']]
    if args['crbug']:
        buglist += ['chromium:{0}'.format(x) for x in args['crbug']]
    if buglist:
        args['bug'] = ', '.join(buglist)

    if args['replace']:
        old_commit_message = _git(['show', '-s', '--format=%B', 'HEAD'])

        # It is possible that multiple Change-Ids are in the commit message
        # (due to cherry picking).  We only want to pull out the first one.
        changeid_match = re.search('^Change-Id: (.*)$',
                                   old_commit_message, re.MULTILINE)
        if changeid_match:
            args['changeid'] = changeid_match.group(1)

        bugs = re.findall('^BUG=(.*)$', old_commit_message, re.MULTILINE)
        if args['bug'] is None and bugs:
            args['bug'] = '\nBUG='.join(bugs)

        tests = re.findall('^TEST=(.*)$', old_commit_message, re.MULTILINE)
        if args['test'] is None and tests:
            args['test'] = '\nTEST='.join(tests)
        # TODO: deal with multiline BUG/TEST better

    if args['bug'] is None or args['test'] is None:
        parser.error('BUG=/TEST= lines are required; --replace can help '
                     'automate, or set via --bug/--test')

    if args['debug']:
        pprint.pprint(args)

    re_matches = (
        (re.compile(r'^pw://(([^/]+)/)?(\d+)'), _match_patchwork),
        (re.compile(r'^msgid://<?([^>]*)>?'), _match_msgid),
        (re.compile(r'^linux://([0-9a-f]+)'), _match_linux),
        (re.compile(r'^(from)?git://([^/\#]+)/([^#]+)/([0-9a-f]+)$'),
         _match_fromgit),
        (re.compile(r'^((git|https)://.+)#(.+)/([0-9a-f]+)$'), _match_gitfetch),
        (re.compile(r'^(https://.+)/commit/\?h=(.+)\&id=([0-9a-f]+)$'), _match_gitweb),
    )

    for location in args['locations']:
        if args['debug']:
            print('location=%s' % location)

        for reg, handler in re_matches:
            match = reg.match(location)
            if match:
                ret = handler(match, args)
                break
        else:
            errprint('Don\'t know what "%s" means.' % location)
            sys.exit(1)

        if ret != 0:
            conflicts = _get_conflicts()
            if args['tag'] == 'UPSTREAM: ':
                args['tag'] = 'BACKPORT: '
            else:
                args['tag'] = 'BACKPORT: ' + args['tag']
            _pause_for_merge(conflicts)
        else:
            conflicts = ''

        # extract commit message
        commit_message = _git(['show', '-s', '--format=%B', 'HEAD'])

        # Remove stray Change-Id, most likely from merge resolution
        commit_message = re.sub(r'Change-Id:.*\n?', '', commit_message)

        # Note the source location before tagging anything else
        commit_message += '\n' + args['source_line']

        # add automatic Change ID, BUG, and TEST (and maybe signoff too) so
        # next commands know where to work on
        commit_message += '\n'
        commit_message += conflicts
        commit_message += '\n' + 'BUG=' + args['bug']
        commit_message += '\n' + _wrap_commit_line('TEST', args['test'])
        if args['signoff']:
            extra = ['-s']
        else:
            extra = []
        _git(['commit'] + extra + ['--amend', '-F', '-'], stdin=commit_message)

        # re-extract commit message
        commit_message = _git(['show', '-s', '--format=%B', 'HEAD'])

        # If we see a "Link: " that seems to point to a Message-Id with an
        # automatic Change-Id we'll snarf it out.
        mo = re.search(r'^Link:.*(I[a-f0-9]{40})@changeid', commit_message,
                       re.MULTILINE)
        if mo and args['changeid'] is None:
            args['changeid'] = mo.group(1)

        # replace changeid if needed
        if args['changeid'] is not None:
            commit_message = re.sub(r'(Change-Id: )(\w+)', r'\1%s' %
                                    args['changeid'], commit_message)
            args['changeid'] = None

        # decorate it that it's from outside
        commit_message = args['tag'] + commit_message

        # commit everything
        _git(['commit', '--amend', '-F', '-'], stdin=commit_message)

    return 0

if __name__ == '__main__':
    sys.exit(main(sys.argv[1:]))