fix: prevent using @everyone from an IRC channel

[me4502]

This prevents IRC users spamming @everyone in massive Discord chats :)

Fixed #494

[coveralls]

Coverage remained the same at 81.034% when pulling 8afec23 on me4502:patch-1 into ef553d3 on reactiflux:master.

[Throne3d]

It looks like this and #457 are designed to solve the same issue – the bot lets users from IRC use @everyone, without that necessarily being intended.

However, since sometimes it might be desirable to let users on IRC side use @everyone (say, on small servers where the security doesn't matter, or where the bridge is an announcements channel), it would be nice to let users turn this on sometimes. Additionally, since we already have a permission through Discord for whether the bot should be able to use @everyone or not, could we just disable it based on that?

We can check if the bot's got permission to use @everyone with:

const permissions = discordChannel.permissionsFor(this.discord.user);
let canPingEveryone = false;
if (permissions) {
  canPingEveryone = permissions.has(discord.Permissions.FLAGS.MENTION_EVERYONE);
}

Then later we can just use this in the sendMessage hash:

webhook.client.sendMessage(withMentions, {
  username,
  text,
  avatarURL,
  disableEveryone: !canPingEveryone,
}).catch(logger.error);

That way, we don't need a global configuration setting (like #457 did), nor are we blocking out flows where a bot operator might want this functionality.

At this point I suppose I could just write the PR myself, but it'd be nice to get some feedback on this idea before I just go about doing that (or you could implement it and maybe add tests for it?). :P

[me4502]

Yeah if we could make it just obey the permissions provided by Discord that would make the most sense. Especially from a usability perspective, where people will just assume removing @everyone permissions prevents it from happening.

[Throne3d]

I've set this up in #497!