utils.py

"""
Bagelbot utility functions used by the different scripts.
"""
import contextlib
import os
import sys
import shelve

import boto3
from slackclient import SlackClient

from config import EMAIL_DOMAIN, S3_BUCKET, S3_PREFIX, SLACK_TOKEN, SHELVE_FILE

YES = frozenset(["yes", "y", "ye", ""])
NO = frozenset(["no", "n"])


def get_slack_client():
    """Initializes SlackClient for bagelbot's use.

    Note:
        It pulls the required Slack API token from config.py

    Returns:
        sc: A SlackClient instance
    """
    if not SLACK_TOKEN or SLACK_TOKEN == "yourtoken":
        sys.exit("Exiting... SLACK_TOKEN was empty or not updated from the default in config.py.")

    return SlackClient(SLACK_TOKEN)


def initialize(update_everyone=False):
    """Used to initalize resources - both the 'shelf' store and slack client - and return them.

    Args:
        update_everyone (Optional[bool]): If True, updates all users in the EMAIL_DOMAIN
            from slack. Defaults to False.

    Returns:
        store: A shelve instance
        sc: A SlackClient instance
    """
    store = open_store()
    sc = get_slack_client()
    if update_everyone:
        update_everyone_from_slack(store, sc)
    return store, sc


def open_store():
    """Open the SHELVE_FILE and return an open shelf instance.

    Returns:
        store: A shelve instance
    """
    return shelve.open(SHELVE_FILE, writeback=True)


def download_shelve_from_s3():
    """Download the SHELVE_FILE from S3_BUCKET & S3_PREFIX.
    """
    s3 = boto3.resource("s3")
    key = os.path.join(S3_PREFIX, SHELVE_FILE) if S3_PREFIX else SHELVE_FILE
    s3.meta.client.download_file(S3_BUCKET, key, SHELVE_FILE)


def upload_shelve_to_s3():
    """Upload the SHELVE_FILE to S3_BUCKET & S3_PREFIX.
    """
    s3 = boto3.resource("s3")
    key = os.path.join(S3_PREFIX, SHELVE_FILE) if S3_PREFIX else SHELVE_FILE
    s3.meta.client.upload_file(SHELVE_FILE, S3_BUCKET, key)


class DummyFile:
    """Used to silence stdout when scripts are ran from a cron.

    Note:
        http://stackoverflow.com/q/2828953/76267
    """

    def read(self):
        """
        DummyFile has no read method.
        """
        raise NotImplementedError("No read method for DummyFile")

    def write(self, x):
        """
        Provide a defunct write method to silence stdout.

        Args:
            self (object): DummyFile Instance
            x (str): Text passed to write to DummyFile
        """
        pass


@contextlib.contextmanager
def nostdout():
    """A context used to silence stdout from any bot functions.

    Used when a script is ran as `--from-cron`, that way no stdout is produced.

    Note:
        http://stackoverflow.com/q/2828953/76267
    """
    save_stdout = sys.stdout
    sys.stdout = DummyFile()
    yield
    sys.stdout = save_stdout


def update_everyone_from_slack(store, sc):
    """Updates our store's list of `everyone`.

    This list is comprised of all slack users with
    the specified EMAIL_DOMAIN in config.py that are not deleted or single-channel guests.

    Args:
        store (instance): A persistent, dictionary-like object used to keep
        information about past/future meetings.
        sc (SlackClient): An instance of SlackClient
    """
    if not sc:
        sc = get_slack_client()

    users = sc.api_call("users.list")
    store["everyone"] = [
        m["name"]
        for m in users["members"]
        if not m["deleted"]
        and not m["is_restricted"]
        and m["profile"].get("email")
        and m["profile"]["email"].endswith("@" + EMAIL_DOMAIN)
    ]