#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-3.0-or-later
# "git review download", like git review -d, but without need for ssh key. Run
# this script inside a git repository with the gerrit review ID as argument to
# fetch and checkout the patch.
import argparse
import configparser
import json
import os
import subprocess
import sys
import urllib.parse
import urllib.request


def get_topdir():
    try:
        return subprocess.run(
            ["git", "rev-parse", "--show-toplevel"],
            check=True,
            capture_output=True,
            encoding="UTF-8",
        ).stdout.rstrip()
    except subprocess.CalledProcessError:
        print("ERROR: not running inside a git repository")
        sys.exit(1)


def get_config_path():
    ret = f"{get_topdir()}/.gitreview"
    return ret if os.path.exists(ret) else None


def exit_gerrit_host_project_unknown():
    print("ERROR: failed to get gerrit host and project")
    print("Consider adding a .gitreview file:")
    print("  [gerrit]")
    print("  host=gerrit.osmocom.org")
    print("  project=…")
    sys.exit(1)


def get_config_from_origin_url():
    url = subprocess.run(
        ["git", "config", "--get", "remote.origin.url"],
        check=True,
        capture_output=True,
        encoding="UTF-8",
    ).stdout.rstrip()

    if not url.startswith("https://gerrit.osmocom.org/"):
        exit_gerrit_host_project_unknown()

    host = url.split("/")[2]
    project = "/".join(url.split("/")[3:])
    return host, project


def get_config():
    config_path = get_config_path()
    if not config_path:
        return get_config_from_origin_url()
    config = configparser.ConfigParser()
    config.read(config_path)
    return config["gerrit"]["host"], config["gerrit"]["project"]


def get_gerrit_details(host, project, patch_id, verbose):
    project_q = urllib.parse.quote(project, "")
    url = f"https://{host}/changes/{project_q}~{args.patch_id}/detail"
    print(f"Download {url}")
    with urllib.request.urlopen(url) as response:
        content = response.read().decode()
        content = "{" + content.split("{", 1)[1]
        ret = json.loads(content)
        if args.verbose:
            print(json.dumps(ret, indent=4))
    return ret


def get_highest_revision(details):
    ret = 1
    for message in details["messages"]:
        rev = message["_revision_number"]
        if rev > ret:
            ret = rev
    return ret


def git_fetch(host, project, patch_id, rev):
    last_digits = str(patch_id)[-2:]
    url = f"https://{host}/{project}"
    ref = f"refs/changes/{last_digits}/{patch_id}/{rev}"
    cmd = ["git", "fetch", url, ref]
    print(f"+ {' '.join(cmd)}")

    try:
        return subprocess.run(cmd, check=True)
    except subprocess.CalledProcessError:
        sys.exit(1)


def git_cherry_pick_fetch_head():
    cmd = ["git", "cherry-pick", "FETCH_HEAD"]
    print(f"+ {' '.join(cmd)}")

    try:
        return subprocess.run(cmd, check=True)
    except subprocess.CalledProcessError:
        sys.exit(1)


def git_checkout_fetch_head(patch_id, rev):
    cmd = ["git", "checkout", "-B", f"gerrit/{patch_id}_{rev}", "FETCH_HEAD"]
    print(f"+ {' '.join(cmd)}")

    try:
        return subprocess.run(cmd, check=True)
    except subprocess.CalledProcessError:
        sys.exit(1)


desc = "git review download: fetch and checkout a patch from gerrit"
parser = argparse.ArgumentParser(description=desc)
parser.add_argument(
    "patch_id",
    type=int,
    help="gerrit review ID",
)
parser.add_argument(
    "-c",
    "--cherry-pick",
    action="store_true",
    help="cherry-pick into current branch instead of fetching into a branch",
)
parser.add_argument(
    "-r",
    "--revision",
    type=int,
    help="patchset revision, default is latest",
)
parser.add_argument(
    "-v",
    "--verbose",
    action="store_true",
)
args = parser.parse_args()

host, project = get_config()
rev = args.revision

if not rev:
    details = get_gerrit_details(host, project, args.patch_id, args.verbose)
    rev = get_highest_revision(details)

git_fetch(host, project, args.patch_id, rev)
if args.cherry_pick:
    git_cherry_pick_fetch_head()
else:
    git_checkout_fetch_head(args.patch_id, rev)