#!/usr/bin/env python
#
# Copyright (C) 2017 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

import argparse
import os
import re
import subprocess
import sys

from utils import *

PROJECT_PATH = (
    ('llvm', llvm_path()),
    ('cfe', llvm_path('tools/clang')),
    ('clang-tools-extra', llvm_path('tools/clang/tools/extra')),
    ('compiler-rt', llvm_path('projects/compiler-rt')),
    ('libcxx', llvm_path('projects/libcxx')),
    ('libcxxabi', llvm_path('projects/libcxxabi')),
    ('lld', llvm_path('tools/lld')),
    ('openmp', llvm_path('projects/openmp')),)


def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument(
        'revision', help='Revision number of llvm source.', type=int)
    parser.add_argument(
        '--create-new-branch',
        action='store_true',
        default=False,
        help='Create new branch using `repo start` before '
        'merging from upstream.')
    parser.add_argument(
        '--dry-run',
        action='store_true',
        default=False,
        help='Dry run, does not actually commit changes to local workspace.')
    return parser.parse_args()


def sync_upstream_branch(path):
    subprocess.check_call(['repo', 'sync', '.'], cwd=path)


def merge_projects(revision, create_new_branch, dry_run):
    project_sha_dict = {}
    for (project, path) in PROJECT_PATH:
        if not dry_run:
            sync_upstream_branch(path)
        sha = get_commit_hash(revision, path)
        if sha is None:
            return
        project_sha_dict[project] = sha
        print('Project %s git hash: %s' % (project, sha))

    for (project, path) in PROJECT_PATH:
        sha = project_sha_dict[project]
        if create_new_branch:
            branch_name = 'merge-upstream-r%s' % revision
            check_call_d(['repo', 'start', branch_name, '.'], cwd=path, dry_run=dry_run)

        # Get the info since the last tag, the format is
        #   llvm-svn.[svn]-[number of changes since tag]-[sha of the current commit]
        desc = subprocess.check_output(
            ['git', 'describe', '--tags', '--long', '--match', 'llvm-svn.[0-9]*'],
            cwd=path, universal_newlines=True).strip()
        _, svnNum, numChanges, _ = desc.split('-')

        # Check changes since the previous merge point
        reapplyList = []
        for i in range(int(numChanges) - 1, -1, -1):
            changeLog = subprocess.check_output(
                ['git', 'show', 'HEAD~' + str(i), '--quiet', '--format=%h%x1f%B%x1e'],
                cwd=path, universal_newlines=True
            )
            changeLog = changeLog.strip('\n\x1e')
            patchSha, patchRev = parse_log(changeLog)
            if patchRev is None or patchRev > revision:
                reapplyList.append(patchSha)

        # Reset to previous branch point, if necessary
        if int(numChanges) > 0:
            check_output_d(
                [
                    'git', 'revert', '--no-commit', '--no-merges',
                    'llvm-' + svnNum + '...HEAD'
                ],
                cwd=path,
                dry_run=dry_run
            )
            check_output_d(
                ['git', 'commit', '-m revert to previous base llvm-' + svnNum],
                cwd=path,
                dry_run=dry_run
            )

        # Merge upstream revision
        check_call_d(
            [
                'git', 'merge', '--quiet', sha, '-m',
                'Merge %s for LLVM update to %d' % (sha, revision)
            ],
            cwd=path,
            dry_run=dry_run
        )

        # Tag the merge point
        check_call_d(
            ['git', 'tag', '-f', 'llvm-svn.' + str(revision)],
            cwd=path,
            dry_run=dry_run
        )

        # Reapply
        FNULL = open(os.devnull, 'w')
        for sha in reapplyList:
            subprocess.check_call(
                ['git', '--no-pager', 'show', sha, '--quiet'],
                cwd=path
            )

            # Check whether applying this change will cause conflict
            ret_code = subprocess.call(
                ['git', 'cherry-pick', '--no-commit', '--no-ff', sha],
                cwd=path,
                stdout=FNULL,
                stderr=FNULL
            )
            subprocess.check_call(
                ['git', 'reset', '--hard'],
                cwd=path,
                stdout=FNULL,
                stderr=FNULL
            )

            if ret_code != 0:
                print 'Change cannot merge cleanly, please manual merge if needed'
                print
                keep_going = yes_or_no("Continue?", default=False)
                if not keep_going:
                    sys.exit(1)
                continue

            # Change can apply cleanly...
            reapply = yes_or_no("Reapply change?", default=True)
            if reapply:
                check_call_d(
                    ['git', 'cherry-pick', sha],
                    cwd=path,
                    stdout=FNULL,
                    stderr=FNULL,
                    dry_run=dry_run
                )
                # Now change the commit Change-Id.
                check_call_d(
                    ['git', 'commit', '--amend'],
                    cwd=path,
                    dry_run=dry_run
                )
            else:
                print 'Skipping ' + sha

            print

        print


def get_commit_hash(revision, path):
    # Get sha and commit message body for each log.
    p = subprocess.Popen(
        ['git', 'log', 'aosp/upstream-master', '--format=%h%x1f%B%x1e'],
        stdout=subprocess.PIPE,
        cwd=path)
    (log, _) = p.communicate()
    if p.returncode != 0:
        print('git log for path: %s failed!' % path)
        return

    # Log will be in reversed order.
    log = log.strip('\n\x1e').split('\x1e')

    # Binary search log data.
    low, high = 0, len(log) - 1
    while low < high:
        pos = (low + high) // 2
        (sha, cur_revision) = parse_log(log[pos])
        if cur_revision == revision:
            return sha
        elif cur_revision < revision:
            high = pos
        else:
            low = pos + 1
    (sha, _) = parse_log(log[high])
    return sha


def parse_log(raw_log):
    log = raw_log.strip().split('\x1f')
    # Extract revision number from log data.
    revision_string = log[1].strip().split('\n')[-1]
    revision = re.search(r'trunk@(\d+)', revision_string)
    if revision is None:
        return (log[0], None)
    return (log[0], int(revision.group(1)))


def main():
    args = parse_args()
    merge_projects(args.revision, args.create_new_branch, args.dry_run)


if __name__ == '__main__':
    main()