#!/usr/bin/env python3
"""A script to set gitlab committers according to COMMITTERS.rst."""

import argparse
import json
import logging
import pathlib
import sys
import re
import urllib.request
import urllib.parse

from pprint import pformat
from typing import Any, Dict, List, Tuple


API_BASE = "https://gitlab.com/api/v4"


def main():
    """Parse CLI arguments and set up application state."""

    parser = argparse.ArgumentParser(
        description="Update gitlab committers according to COMMITTERS.rst"
    )
    parser.add_argument(
        "token", type=str,
        help="Your private access token. See https://gitlab.com/profile/personal_access_tokens."
    )
    parser.add_argument(
        "committers", type=pathlib.Path,
        help="The path to COMMITTERS.rst. Will try "
        "to find the one in the local git repository by default.",
        nargs="?",
        default=find_repository_root() / "COMMITTERS.rst"
    )
    parser.add_argument(
        "--repository", "-r", type=str,
        help="The repository whose committers to set.",
        default="BuildStream/buildstream"
    )
    parser.add_argument(
        "--dry-run", "-n",
        help="Do not update the actual member list.",
        action="store_false"
    )
    parser.add_argument(
        "--quiet", "-q",
        help="Run quietly",
        action="store_true"
    )
    parser.add_argument(
        "--debug", "-d",
        help="Show debug messages (WARNING: This *will* display the private token).",
        action="store_true"
    )
    args = parser.parse_args()

    if args.debug:
        logging.basicConfig(level=logging.DEBUG)
    elif not args.quiet:
        logging.basicConfig(level=logging.INFO)

    set_committers(args.repository, args.committers.read_text(), args.token, args.dry_run)


def set_committers(repository: str, committer_file: str, token: str, commit: bool):
    """Set GitLab members as defined in the committer_file."""
    new_committers = [get_user_by_username(committer[2], token)
                      for committer in parse_committer_list(committer_file)]
    old_committers = get_project_committers(repository, token)

    new_set = set(committer["id"] for committer in new_committers)
    old_set = set(committer["id"] for committer in old_committers)

    added = [committer for committer in new_committers if committer["id"] in new_set - old_set]
    removed = [committer for committer in new_committers if committer["id"] in old_set - new_set]

    logging.info("Adding:\n%s", pformat(added))
    logging.info("Removing:\n%s", pformat(removed))

    if commit:
        for committer in added:
            set_user_access_level(repository, committer, 40, token)
        for committer in removed:
            set_user_access_level(repository, committer, 30, token)


####################################################################################################
# Utility functions                                                                                #
####################################################################################################

class RepositoryException(Exception):
    """An exception raised when we can't deal with the repository."""


def find_repository_root() -> pathlib.Path:
    """Find the root directory of a git repository, starting at cwd()."""
    root = pathlib.Path.cwd()
    while not any(f.name == ".git" for f in root.iterdir()):
        if root == root.parent:
            raise RepositoryException("'{}' is not in a git repository.".format(pathlib.Path.cwd()))
        root = root.parent
    return root


def parse_committer_list(committer_text: str) -> List[Tuple[str, str, str]]:
    """Parse COMMITTERS.rst and retrieve a map of names, email addresses and usernames."""
    return [(committer[0].strip(), committer[1].strip(" <>"), committer[2].strip()) for committer in
            re.findall(r"\|([^|]+)\|([^|]+)\|([^|]+)\|\n\+-", committer_text)]


####################################################################################################
# GitLab API                                                                                       #
####################################################################################################

def make_request_url(*args: Tuple[str], **kwargs: Dict[str, str]) -> str:
    """Create a request url for the GitLab API."""
    return API_BASE + "/" + "/".join(args) + "?" + urllib.parse.urlencode(kwargs, safe='@')


def make_project_url(project: str, *args: Tuple[str], **kwargs: Dict[str, str]) -> str:
    """Create a request url for the given project."""
    return make_request_url("projects", urllib.parse.quote(project, safe=''), *args, **kwargs)


def urlopen(url: str, token: str, data=None, method='GET') -> Any:
    """Perform a paginated query to the GitLab API."""
    page = 1
    res = None
    result = []
    while not res or page:
        req = urllib.request.Request(url=url + "&" + urllib.parse.urlencode({"page": page}),
                                     data=data, method=method)
        req.add_header('PRIVATE-TOKEN', token)
        logging.debug("Making API request: %s", pformat(req.__dict__))
        try:
            res = urllib.request.urlopen(req)
        except urllib.error.HTTPError as err:
            logging.error("Could not access '%s': %s", url, err)
            sys.exit(1)
        result.extend(json.load(res))
        page = res.getheader('X-Next-Page')
    return result


def get_project_committers(project: str, token: str) -> List[Dict]:
    """Get a list of current committers."""
    return [committer for committer in
            urlopen(make_project_url(project, "members", "all"), token)
            if committer["access_level"] >= 40]


def get_user_by_username(username: str, token: str) -> Dict:
    """Get a user ID from their email address."""
    return urlopen(make_request_url("users",
                                    username=username),
                   token)[0]


def set_user_access_level(project: str, user: Dict, level: int, token: str) -> Dict:
    """Set a user's project access level."""
    return urlopen(make_project_url(project, "members", str(user["id"]),
                                    access_level=str(level)),
                   token,
                   method="PUT")


if __name__ == '__main__':
    main()