# Copyright 2018 The ChromiumOS Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Create a manifest snapshot of a repo checkout.

This starts with the output of `repo manifest -r` and updates the manifest to
account for local changes that may not already be available remotely; for any
commits that aren't already reachable from the upstream tracking branch, push
refs to the remotes so that this snapshot can be reproduced remotely.
"""

import logging
import os
import sys

from chromite.lib import commandline
from chromite.lib import cros_build_lib
from chromite.lib import git
from chromite.lib import parallel
from chromite.lib import repo_util


BRANCH_REF_PREFIX = "refs/heads/"


def GetParser():
    """Creates the argparse parser."""
    parser = commandline.ArgumentParser(description=__doc__, dryrun=True)
    parser.add_argument(
        "--repo-path",
        type="path",
        default=".",
        help="Path to the repo to snapshot.",
    )
    parser.add_argument(
        "--snapshot-ref",
        help="Remote ref to create for projects whose HEAD is "
        "not reachable from its current upstream branch. "
        "Projects with multiple checkouts may have a "
        "unique suffix appended to this ref.",
    )
    parser.add_argument(
        "--output-file",
        type="path",
        help="Path to write the manifest snapshot XML to.",
    )
    # This is for limiting network traffic to the git remote(s).
    parser.add_argument(
        "--jobs",
        type=int,
        default=16,
        help="The number of parallel processes to run for "
        "git push operations.",
    )
    return parser


def _GetUpstreamBranch(project):
    """Return the best guess at the project's upstream branch name."""
    branch = project.upstream
    if branch and branch.startswith(BRANCH_REF_PREFIX):
        branch = branch[len(BRANCH_REF_PREFIX) :]
    return branch


def _NeedsSnapshot(repo_root, project):
    """Test if project's revision is reachable from its upstream ref."""
    # Some projects don't have an upstream set. Try 'main' anyway.
    branch = _GetUpstreamBranch(project) or "main"
    upstream_ref = "refs/remotes/%s/%s" % (project.Remote().GitName(), branch)
    project_path = os.path.join(repo_root, project.Path())
    try:
        if git.IsReachable(project_path, project.revision, upstream_ref):
            return False
    except cros_build_lib.RunCommandError as e:
        logging.debug("Reachability check failed: %s", e)
    logging.info(
        "Project %s revision %s not reachable from upstream %r.",
        project.name,
        project.revision,
        upstream_ref,
    )
    return True


def _MakeUniqueRef(project, base_ref, used_refs):
    """Return a git ref for project that isn't in used_refs.

    Args:
        project: The Project object to create a ref for.
        base_ref: A base ref name; this may be appended to, to generate a unique
            ref.
        used_refs: A set of ref names to uniquify against. It is updated with
            the newly generated ref.
    """
    ref = base_ref

    # If the project upstream is a non-main branch, append it to the ref.
    branch = _GetUpstreamBranch(project)
    if branch and branch != "main":
        ref = "%s/%s" % (ref, branch)

    if ref in used_refs:
        # Append incrementing numbers until we find an unused ref.
        for i in range(1, len(used_refs) + 2):
            numbered = "%s/%d" % (ref, i)
            if numbered not in used_refs:
                ref = numbered
                break
        else:
            raise AssertionError(
                "failed to make unique ref (ref=%s used_refs=%r)"
                % (ref, used_refs)
            )

    used_refs.add(ref)
    return ref


def _GitPushProjectUpstream(repo_root, project, dryrun):
    """Push the project revision to its remote upstream."""
    git.GitPush(
        os.path.join(repo_root, project.Path()),
        project.revision,
        git.RemoteRef(project.Remote().GitName(), project.upstream),
        dry_run=dryrun,
    )


def main(argv):
    parser = GetParser()
    options = parser.parse_args(argv)
    options.Freeze()

    snapshot_ref = options.snapshot_ref
    if snapshot_ref and not snapshot_ref.startswith("refs/"):
        snapshot_ref = BRANCH_REF_PREFIX + snapshot_ref

    repo = repo_util.Repository.Find(options.repo_path)
    if repo is None:
        cros_build_lib.Die(
            "No repo found in --repo_path %r.", options.repo_path
        )

    manifest = repo.Manifest(revision_locked=True)
    projects = list(manifest.Projects())

    # Check if projects need snapshots (in parallel).
    needs_snapshot_results = parallel.RunTasksInProcessPool(
        _NeedsSnapshot, [(repo.root, x) for x in projects]
    )

    # Group snapshot-needing projects by project name.
    snapshot_projects = {}
    for project, needs_snapshot in zip(projects, needs_snapshot_results):
        if needs_snapshot:
            snapshot_projects.setdefault(project.name, []).append(project)

    if snapshot_projects and not snapshot_ref:
        cros_build_lib.Die(
            "Some project(s) need snapshot refs but no "
            "--snapshot-ref specified."
        )

    # Push snapshot refs (in parallel).
    with parallel.BackgroundTaskRunner(
        _GitPushProjectUpstream,
        repo.root,
        dryrun=options.dryrun,
        processes=options.jobs,
    ) as queue:
        for projects in snapshot_projects.values():
            # Since some projects (e.g. chromiumos/third_party/kernel) are
            # checked out multiple places, we may need to push each checkout to
            # a unique ref.
            need_unique_refs = len(projects) > 1
            used_refs = set()
            for project in projects:
                if need_unique_refs:
                    ref = _MakeUniqueRef(project, snapshot_ref, used_refs)
                else:
                    ref = snapshot_ref
                # Update the upstream ref both for the push and the output XML.
                project.upstream = ref
                queue.put([project])

    dest = options.output_file
    if dest is None or dest == "-":
        dest = sys.stdout

    manifest.Write(dest)