#!/usr/bin/env python3

# SPDX-FileCopyrightText: © 2020 Open Networking Foundation <support@opennetworking.org>
# SPDX-License-Identifier: Apache-2.0

from __future__ import absolute_import

import argparse
import json
import logging
import urllib.request
import urllib.parse
import base64

# create shared logger
logging.basicConfig()
logger = logging.getLogger("cg")

# global dict of jsonpath expressions -> compiled jsonpath parsers, as
# reparsing expressions in each loop results in 100x longer execution time
gjpaths = {}

# gerrit headers is cached
gerrit_headers = []

# gerrit_groups is a cache of groups, to prevent multiple lookups
gerrit_groups = {}


def parse_crowdgroups_args():
    """
    parse CLI arguments
    """

    parser = argparse.ArgumentParser(description="Crowd-Gerrit group sync")

    # Positional args
    parser.add_argument(
        "settings", type=argparse.FileType("r"), help="JSON settings file",
    )

    parser.add_argument(
        "--debug", action="store_true", help="Print additional debugging information"
    )

    return parser.parse_args()


def basic_auth_header(username, password):
    """
    returns a tuple containing a http basic auth header
    """
    creds_str = "%s:%s" % (username, password)
    creds_b64 = base64.standard_b64encode(creds_str.encode("utf-8"))

    return ("Authorization", "Basic %s" % creds_b64.decode("utf-8"))


def json_api_get(url, headers, data=None, trim_prefix=False, allow_failure=False):
    """
    Call JSON API endpoint, return data as a dict
    """

    # if data included, encode it as JSON
    if data:
        data_enc = str(json.dumps(data)).encode("utf-8")

        request = urllib.request.Request(url, data=data_enc, method="POST")
        request.add_header("Content-Type", "application/json; charset=UTF-8")
    else:
        request = urllib.request.Request(url)

    # add headers tuples
    for header in headers:
        request.add_header(*header)

    try:
        response = urllib.request.urlopen(request)
    except urllib.error.HTTPError:
        # asking for data that doesn't exist results in a 404, just return nothing
        if allow_failure:
            return None
        logger.exception("Server encountered an HTTPError at URL: '%s'", url)
    except urllib.error.URLError:
        logger.exception("An URLError occurred at URL: '%s'", url)
    else:
        # docs: https://docs.python.org/3/library/json.html
        jsondata = response.read()
        logger.debug("API response: %s", jsondata)

    # optionally remove the gerrit "magic prefix" - docs:
    # https://gerrit-review.googlesource.com/Documentation/rest-api.html#output
    if trim_prefix:
        jsondata = jsondata.lstrip(b")]}'\n")

    try:
        data = json.loads(jsondata)
    except json.decoder.JSONDecodeError:
        # allow return of no data
        if allow_failure:
            return None
        logger.exception("Unable to decode JSON")
    else:
        logger.debug("JSON decoded: %s", data)

    return data


def crowd_users_list(crowd_settings, groupname):
    """
    Returns dict of email addresses mapped to usernames from Crowd, given a
    group name
    """

    url = "%s/rest/usermanagement/1/group/user/direct?groupname=%s&expand=user" % (
        crowd_settings["url"],
        groupname,
    )

    crowd_headers = [
        basic_auth_header(crowd_settings["username"], crowd_settings["password"]),
        ("Accept", "application/json"),
    ]

    cout = json_api_get(url, crowd_headers)

    userlist = {}

    for user in cout["users"]:
        userlist[user["email"]] = user["name"]

    return userlist


def gerrit_group_id_by_name(gerrit_settings, groupname):
    """
    Returns a gerrit group ID given the name of a group
    Note - this is the "id" not the "group_id" in the dict.
    """

    # read from cache if found
    if groupname not in gerrit_groups:

        gurl = "%s/groups/?m=%s" % (gerrit_settings["url"], groupname)
        gout = json_api_get(gurl, gerrit_headers, None, True)

        gerrit_groups[groupname] = gout[groupname]["id"]

        logger.debug(
            "Group: '%s' has group-id: '%s'", groupname, gerrit_groups[groupname]
        )

    return gerrit_groups[groupname]


def gerrit_users_list(gerrit_settings, groupname):
    """
    Returns dict of lists of usernames and emails from Gerrit, given a group name
    """

    gid = gerrit_group_id_by_name(gerrit_settings, groupname)

    gurl = "%s/groups/%s/members" % (gerrit_settings["url"], gid)
    gout = json_api_get(gurl, gerrit_headers, None, True)

    userlist = {}

    for user in gout:
        userlist[user["email"]] = {
            "_account_id": user.get("_account_id"),
            "username": user.get("username", None),
        }

    return userlist


def gerrit_check_crowd_id(gerrit_settings, aid, crowdusername):
    """
    checks if a gerrit account has an external CrowdID identity string
    """

    gurl = "%s/accounts/%s/external_ids" % (gerrit_settings["url"], aid)
    gout = json_api_get(gurl, gerrit_headers, None, True)

    crowd_id_string = (
        "https://crowd.opennetworking.org/openidserver/users/%s" % crowdusername
    )

    for identity in gout:
        if identity["identity"] == crowd_id_string:
            return aid

    return None


def gerrit_find_account_id(gerrit_settings, email, crowdusername):
    """
    Returns a gerrit account ID given the email address of a user and the
    corresponding crowd username, or None if no account exists.
    """

    gurl = "%s/accounts/?q=email:%s" % (gerrit_settings["url"], email)
    gout = json_api_get(gurl, gerrit_headers, None, True, True)

    # check for users with multiple email addresses
    if len(gout) > 1:
        logger.warning("Email: '%s' register for more than one Gerrit account", email)
        return None

    # may not have an account, return None if no account
    if len(gout) == 0:
        logger.warning("Email: '%s' doesn't have a Gerrit account", email)
        return None

    aid_dict = gout[0]
    logger.debug("Email: '%s' has account-id: '%s'", email, aid_dict["_account_id"])

    return aid_dict["_account_id"]


def gerrit_lookup_account_ids(gerrit_settings, users):
    """
    Returns a list of account-ids given a list of user tuples
    """

    account_ids = []

    for user in users:
        aid = gerrit_find_account_id(gerrit_settings, *user)

        if aid:
            account_ids.append(aid)

    return account_ids


def gerrit_add_accounts_to_group(gerrit_settings, groupname, account_ids):
    """
    Given a group name and a list of account-ids, add accounts from group
    """

    gid = gerrit_group_id_by_name(gerrit_settings, groupname)

    # https://gerrit-review.googlesource.com/Documentation/rest-api-groups.html#_add_group_members
    members = {"members": account_ids}

    gurl = "%s/groups/%s/members.add" % (gerrit_settings["url"], gid)
    gout = json_api_get(gurl, gerrit_headers, members, True)

    logger.debug("output of adding accounts to group: %s", gout)


def gerrit_remove_accounts_from_group(gerrit_settings, groupname, account_ids):
    """
    Given a group name and a list of account-ids, remove accounts from group
    """

    gid = gerrit_group_id_by_name(gerrit_settings, groupname)

    # https://gerrit-review.googlesource.com/Documentation/rest-api-groups.html#_add_group_members
    members = {"members": account_ids}

    gurl = "%s/groups/%s/members.delete" % (gerrit_settings["url"], gid)
    gout = json_api_get(gurl, gerrit_headers, members, True, True)

    logger.debug("output of removing accounts to group: %s", gout)


def sync_group(settings, groupname):
    """
    sync a group from Crowd to Gerrit
    """

    cusers = crowd_users_list(settings["crowd"], groupname)

    gusers = gerrit_users_list(settings["gerrit"], groupname)

    logger.info("Crowd users: %s" % cusers)
    logger.info("Gerrit users: %s" % gusers)

    # lists of users to add or remove from gerrit
    add_g = []
    rem_g = list(gusers.keys())  # default to removing all users

    # go through list of crowd users by email
    for cemail, cuserid in cusers.items():
        # if a user is found, remove from rem_g list
        if cemail in gusers:
            rem_g.remove(cemail)
        else:
            add_g.append((cemail, cuserid))

    logger.info("Users to add: %s" % add_g)
    logger.info("Users to remove: %s" % rem_g)

    add_aids = gerrit_lookup_account_ids(settings["gerrit"], add_g)

    logger.info("Account-ids to add: %s" % add_aids)

    gerrit_aids = [gusers[e]["_account_id"] for e in gusers.keys()]

    logger.info("All Gerrit account-ids: %s" % gerrit_aids)

    aa_nodupes = [a for a in add_aids if a not in gerrit_aids]

    logger.info("Duplicates removed: %s" % aa_nodupes)

    if aa_nodupes:
        gerrit_add_accounts_to_group(settings["gerrit"], groupname, aa_nodupes)

    remove_aids = [gusers[e]["_account_id"] for e in rem_g]

    # user with a different primary email could be in both add and remove lists
    rem_filtered = [a for a in remove_aids if a not in add_aids]

    logger.info("Account-ids to remove: %s" % rem_filtered)

    if rem_filtered:
        gerrit_remove_accounts_from_group(settings["gerrit"], groupname, rem_filtered)


# main function that calls other functions
if __name__ == "__main__":

    args = parse_crowdgroups_args()

    # only print log messages if debugging
    if args.debug:
        logger.setLevel(logging.DEBUG)
    else:
        logger.setLevel(logging.CRITICAL)

    # load settings from JSON file
    settings = json.loads(args.settings.read())

    # global, so this isn't run multiple times
    gerrit_headers = [
        basic_auth_header(
            settings["gerrit"]["username"], settings["gerrit"]["password"]
        ),
    ]

    # sync each group
    for groupname in settings["groups"]:
        sync_group(settings, groupname)