Clear obsolete mentions upon channel part

Currently, the mentions only track the chanID and MsgID.
However, when we part a channel the chanID becomes orphaned.

Considering that mentions from a parted channel probably aren't
that relevant, let's automatically clear them when we part.
Should the user really want to look at them again, they can re-join
the channel and get the scroll back that way.

src/client.js

@@ -649,6 +649,17 @@ Client.prototype.names = function (data) {
 	});
 };
 
+Client.prototype.part = function (network, chan) {
+	const client = this;
+	network.channels = _.without(network.channels, chan);
+	client.mentions = client.mentions.filter((msg) => !(msg.chanId === chan.id));
+	chan.destroy();
+	client.save();
+	client.emit("part", {
+		chan: chan.id,
+	});
+};
+
 Client.prototype.quit = function (signOut) {
 	const sockets = this.manager.sockets.sockets;
 	const room = sockets.adapter.rooms.get(this.id);

src/plugins/inputs/part.js

@@ -1,6 +1,5 @@
 "use strict";
 
-const _ = require("lodash");
 const Msg = require("../../models/msg");
 const Chan = require("../../models/chan");
 const Helper = require("../../helper");
@@ -41,12 +40,7 @@ exports.input = function (network, chan, cmd, args) {
 		!network.irc.connection ||
 		!network.irc.connection.connected
 	) {
-		network.channels = _.without(network.channels, target);
+		this.part(network, target);
-		target.destroy();
-		this.emit("part", {
-			chan: target.id,
-		});
-		this.save();
 	} else {
 		const partMessage = args.join(" ") || network.leaveMessage || Helper.config.leaveMessage;
 		network.irc.part(target.name, partMessage);

src/plugins/irc-events/part.js

@@ -1,6 +1,5 @@
 "use strict";
 
-const _ = require("lodash");
 const Msg = require("../../models/msg");
 
 module.exports = function (irc, network) {
@@ -25,12 +24,7 @@ module.exports = function (irc, network) {
 		chan.pushMessage(client, msg);
 
 		if (data.nick === irc.user.nick) {
-			network.channels = _.without(network.channels, chan);
+			client.part(network, chan);
-			chan.destroy();
-			client.save();
-			client.emit("part", {
-				chan: chan.id,
-			});
 		} else {
 			chan.removeUser(user);
 		}