#! /usr/bin/env python3
#
# https://pypi.org/project/argcomplete/#global-completion
# PYTHON_ARGCOMPLETE_OK

"""This script provides tooling to administrate the github.com/zeek organization."""

import argparse
import json
import os
import sys
from enum import IntEnum
from pathlib import Path

# This is the high-level error for API problems, per
# https://github.com/fastai/ghapi/issues/138 and confirmed
# in manual testing
from urllib.error import HTTPError


def print_err(*args, **kwargs):
    print(*args, file=sys.stderr, **kwargs)


try:
    import yaml
except ImportError:
    # PyYAML is optional; we will see below whether we need it as we retrieve
    # the auth token.
    pass

try:
    from ghapi.all import GhApi, paged
except ImportError:
    print_err("This requires the Python Github API package: https://ghapi.fast.ai")
    sys.exit(1)

try:
    # Argcomplete provides command-line completion for users of argparse.
    # We support it if available, but don't complain when it isn't.
    import argcomplete
except ImportError:
    pass

GITHUB_SERVER = "github.com"
GITHUB_ORG = "zeek"

# There's a mismatch between how Github shows access levels in the UI vs how
# they work in the API. We use the UI-level ones here and provide helper
# functions to translate. The discrepancies are "read" being "pull" in the API,
# and "write" being "push". The others match.
AccessLevel = IntEnum("AccessLevel", ["READ", "TRIAGE", "WRITE", "MAINTAIN", "ADMIN"])


def get_api_token(args):
    if args.auth_token:
        return args.auth_token

    # This is the ghapi-recommended way to configure your token and works
    # transparently:
    token = os.getenv("GITHUB_TOKEN")
    if token:
        return token

    # Try somewhat hard to locate gh's config file:
    gh_host_config = (
        Path(os.getenv("XDG_CONFIG_HOME", default=Path.home() / ".config"))
        / "gh"
        / "hosts.yml"
    )
    if gh_host_config.is_file():
        if "yaml" not in sys.modules:
            print_err(
                "This requires PyYAML to use your existing gh config. See: https://pyyaml.org"
            )
            print_err(
                "Please set the GITHUB_TOKEN environment variable to your Github API token."
            )
            sys.exit(1)

        try:
            with open(gh_host_config) as stream:
                ymldata = yaml.safe_load(stream)
                return ymldata[GITHUB_SERVER]["oauth_token"]
        except (OSError, yaml.YAMLError, KeyError) as error:
            print_err(f"Unexpected gh configuration ({error}).")
            print_err(
                "Please set the GITHUB_TOKEN environment variable to your Github API token."
            )
            sys.exit(1)

    print_err(
        "Please provide a Github API token via --auth-token or set the GITHUB_TOKEN environment variable"
    )
    sys.exit(1)


def get_access_level_string(perms):
    res = get_access_level(perms)
    if not res:
        return None
    return res.name.lower()


def access_level_to_github(level):
    if level == AccessLevel.ADMIN:
        return "admin"
    if level == AccessLevel.MAINTAIN:
        return "maintain"
    if level == AccessLevel.WRITE:
        return "push"
    if level == AccessLevel.TRIAGE:
        return "triage"
    if level == AccessLevel.READ:
        return "pull"
    return None


def access_level_from_github(level):
    if level == "admin":
        return AccessLevel.ADMIN
    if level == "maintain":
        return AccessLevel.MAINTAIN
    if level == "push":
        return AccessLevel.WRITE
    if level == "triage":
        return AccessLevel.TRIAGE
    if level == "pull":
        return AccessLevel.READ
    return None


def get_access_level(perm):
    """Returns the access level for a given user/team as shown on the access
    settings page of a repo, based on the given set of permissions. This returns
    an AccessLevel, or None when no access level was identifiable.
    """
    # This is a bit messy because permissions are presented differently in
    # different corners of the API. Sometimes it's a string, sometimes an
    # object with individual permission bits. For now just check if it's a
    # string and handle that separately.
    if isinstance(perm, str):
        return access_level_from_github(perm)

    try:
        if perm.admin:
            return AccessLevel.ADMIN
        if perm.maintain:
            return AccessLevel.MAINTAIN
        if perm.push:
            return AccessLevel.WRITE
        if perm.triage:
            return AccessLevel.TRIAGE
        if perm.pull:
            return AccessLevel.READ
    except AttributeError:
        pass

    return None


def get_all_repos(api):
    """Returns a list of all repos in the GITHUB_ORG, sorted by name."""
    repos = []

    for page in paged(api.repos.list_for_org, org=GITHUB_ORG, per_page=100):
        repos.extend(page)

    repos.sort(key=lambda repo: repo.name)
    return repos


def cmd_repos_list_access(api, args):
    result = []

    for repo in get_all_repos(api):
        teams = api.repos.list_teams(repo.name)
        teams_results = []
        for team in sorted(teams, key=lambda t: t.name):
            teams_results.append(
                {
                    "name": team.name,
                    "access": get_access_level_string(team.permissions),
                }
            )

        # "direct" here means we don't list each individual member of teams that
        # also have access to the repo:
        users = api.repos.list_collaborators(repo.name, affiliation="direct")
        users_results = []
        for user in sorted(users, key=lambda u: u.login):
            users_results.append(
                {
                    "name": user.login,
                    "access": get_access_level_string(user.permissions),
                }
            )

        result.append(
            {
                "repo": repo.name,
                "teams": teams_results,
                "users": users_results,
            }
        )

    print(json.dumps(result, sort_keys=True))
    return True


def cmd_repos_list_redundant_users(api, args):
    result = []

    for repo in get_all_repos(api):
        teams = api.repos.list_teams(repo.name)
        teams_data = {}

        for team in teams:
            teams_data[team.name] = {
                "permission": team.permission,
                "users": [
                    member.login
                    for member in api.teams.list_members_in_org(GITHUB_ORG, team.slug)
                ],
            }

        # "direct" here means we don't list each individual member of teams that
        # also have access to the repo:
        users = api.repos.list_collaborators(repo.name, affiliation="direct")

        for user in sorted(users, key=lambda u: u.login):
            for team, data in teams_data.items():
                if user.login not in data["users"]:
                    continue
                # This repo gives access to a team that already includes the
                # explicitly listed user. See if the user is added with
                # greater permissions, otherwise this user is redundant.
                team_access = get_access_level(data["permission"])
                user_access = get_access_level(user.permissions)

                if user_access <= team_access:
                    result.append(
                        {
                            "repo": repo.name,
                            "user": user.login,
                            "redundancy": team,
                        }
                    )

    print(json.dumps(result, sort_keys=True))
    return True


def cmd_repos_remove_redundant_users(api, args):
    result = []
    outcome = True

    for repo in get_all_repos(api):
        teams = api.repos.list_teams(repo.name)
        teams_data = {}

        for team in teams:
            teams_data[team.name] = {
                "permission": team.permission,
                "users": [
                    member.login
                    for member in api.teams.list_members_in_org(GITHUB_ORG, team.slug)
                ],
            }

        # "direct" here means we don't list each individual member of teams that
        # also have access to the repo:
        users = api.repos.list_collaborators(repo.name, affiliation="direct")

        for user in sorted(users, key=lambda u: u.login):
            for team, data in teams_data.items():
                if user.login not in data["users"]:
                    continue
                # This repo gives access to a team that already includes the
                # explicitly listed user. See if the user is added with
                # greater permissions, otherwise this user is redundant.
                team_access = get_access_level(data["permission"])
                user_access = get_access_level(user.permissions)

                if user_access <= team_access:
                    try:
                        if not args.dry_run:
                            api.repos.remove_collaborator(repo.name, user.login)
                        result.append(
                            {
                                "repo": repo.name,
                                "user": user.login,
                                "success": True,
                            }
                        )
                    except HTTPError as err:
                        result.append(
                            {
                                "repo": repo.name,
                                "user": user.login,
                                "success": False,
                                "code": err.code,
                                "reason": err.reason,
                            }
                        )
                        outcome = False

    print(json.dumps(result, sort_keys=True))
    return outcome


def cmd_repos_add_team(api, args):
    if args.access_level not in [level.name.lower() for level in AccessLevel]:
        print_err(
            f"The given access level '{args.access_level}' is not valid. See --help.\n"
        )
        return False

    access_level = access_level_to_github(AccessLevel[args.access_level.upper()])

    # Resolve the given team name to a slug:
    team_slug = None
    teams = sorted(api.teams.list(GITHUB_ORG), key=lambda t: t.name)
    for team in teams:
        if (
            team.name.lower() == args.team.lower()
            or team.slug.lower() == args.team.lower()
        ):
            team_slug = team.slug
            break

    if not team_slug:
        print_err(
            f"Team '{args.team}' is not valid for the '{GITHUB_ORG}' organization."
        )
        print_err(f"Must be one of {', '.join(["'" + t.name + "'" for t in teams])}.")
        return False

    result = []
    outcome = True

    for repo in get_all_repos(api):
        try:
            if not args.dry_run:
                api.teams.add_or_update_repo_permissions_in_org(
                    GITHUB_ORG, team_slug, repo.name, access_level
                )
            result.append(
                {
                    "repo": repo.name,
                    "success": True,
                }
            )
        except HTTPError as err:
            result.append(
                {
                    "repo": repo.name,
                    "success": False,
                    "code": err.code,
                    "reason": err.reason,
                }
            )
            outcome = False

    print(json.dumps(result, sort_keys=True))
    return outcome


def main():
    top_parser = argparse.ArgumentParser(
        description="Helpers for automated Zeek repo administration on Github."
    )

    top_parser.add_argument(
        "--auth-token",
        default=None,
        help="Your Github API token. You can also use the GITHUB_TOKEN environment "
        "variable to provide this. As a fallback, this script tries to use your "
        "gh configuration, if available.",
    )

    cmd_parser = top_parser.add_subparsers(
        title="commands",
        dest="command",
        help="See `%(prog)s <command> -h` for per-command usage info.",
    )

    repos_parser = cmd_parser.add_parser(
        "repos", help="Do something for every repo in the Zeek organization."
    )

    repos_cmd_parser = repos_parser.add_subparsers(
        title="commands",
        dest="command",
        help="See `%(prog)s <command> -h` for per-command usage info.",
    )

    repos_list_access_cmd_parser = repos_cmd_parser.add_parser(
        "list-access",
        help="List all users and teams that have access to a repo, along with the access level.",
    )
    repos_list_access_cmd_parser.set_defaults(run_cmd=cmd_repos_list_access)

    repos_list_redundant_users_cmd_parser = repos_cmd_parser.add_parser(
        "list-redundant-users",
        help="List users already covered via teams providing at least the same access level.",
    )
    repos_list_redundant_users_cmd_parser.set_defaults(
        run_cmd=cmd_repos_list_redundant_users
    )

    repos_remove_redundant_user_cmd_parser = repos_cmd_parser.add_parser(
        "remove-redundant-users",
        help="Remove users already included via a team that provides at least the same access level.",
    )
    repos_remove_redundant_user_cmd_parser.set_defaults(
        run_cmd=cmd_repos_remove_redundant_users
    )
    repos_remove_redundant_user_cmd_parser.add_argument(
        "--dry-run",
        action="store_true",
        help="Don't make any changes, just pretend API calls succeed",
    )

    repos_add_team_cmd_parser = repos_cmd_parser.add_parser(
        "add-team",
        help="Add the given team to each repository at the given access level. Teams that already have access are updated to the provided level.",
    )
    repos_add_team_cmd_parser.set_defaults(run_cmd=cmd_repos_add_team)

    repos_add_team_cmd_parser.add_argument(
        "--dry-run",
        action="store_true",
        help="Don't make any changes, just pretend API calls succeed",
    )
    repos_add_team_cmd_parser.add_argument(
        "--team", required=True, help="The name or slug of the team. Case-insensitive."
    )
    repos_add_team_cmd_parser.add_argument(
        "--access-level",
        required=True,
        help=f"The access level. One of {', '.join(["'" + level.name.lower() + "'" for level in AccessLevel])}.",
    )

    if "argcomplete" in sys.modules:
        argcomplete.autocomplete(top_parser)

    args = top_parser.parse_args()
    api = GhApi(owner=GITHUB_ORG, token=get_api_token(args))

    try:
        return args.run_cmd(api, args)
    except HTTPError as err:
        sys.stderr.write(f"API error at {err.url}: {err.code}, {err.reason}\n")
        return False
    except KeyboardInterrupt:
        return False


if __name__ == "__main__":
    sys.exit(0 if main() else 1)