Refactor ISUPPORT handling

Add a helper class to parse ISUPPORT tokens. Instead of having
manual ISUPPORT handling all over the place, use pre-processed
values.

lib/irc.js

@@ -382,28 +382,88 @@ function unescapeISUPPORTValue(s) {
 	});
 }
 
-export function parseISUPPORT(tokens, params) {
-	let changed = [];
-	tokens.forEach((tok) => {
-		if (tok.startsWith("-")) {
-			let k = tok.slice(1);
-			params.delete(k.toUpperCase());
-			return;
+export class Isupport {
+	raw = new Map();
+
+	parse(tokens) {
+		tokens.forEach((tok) => {
+			if (tok.startsWith("-")) {
+				let k = tok.slice(1);
+				this.raw.delete(k.toUpperCase());
+				return;
+			}
+
+			let i = tok.indexOf("=");
+			let k = tok, v = "";
+			if (i >= 0) {
+				k = tok.slice(0, i);
+				v = unescapeISUPPORTValue(tok.slice(i + 1));
+			}
+
+			k = k.toUpperCase();
+
+			this.raw.set(k, v);
+		});
+	}
+
+	caseMapping() {
+		let name = this.raw.get("CASEMAPPING");
+		if (!name) {
+			return CaseMapping.RFC1459;
 		}
-
-		let i = tok.indexOf("=");
-		let k = tok, v = "";
-		if (i >= 0) {
-			k = tok.slice(0, i);
-			v = unescapeISUPPORTValue(tok.slice(i + 1));
+		let cm = CaseMapping.byName(name);
+		if (!cm) {
+			console.error("Unsupported case-mapping '" + name + "', falling back to RFC 1459");
+			return CaseMapping.RFC1459;
 		}
+		return cm;
+	}
 
-		k = k.toUpperCase();
+	monitor() {
+		if (!this.raw.has("MONITOR")) {
+			return 0;
+		}
+		let v = this.raw.get("MONITOR");
+		if (v === "") {
+			return Infinity;
+		}
+		return parseInt(v, 10);
+	}
 
-		params.set(k, v);
-		changed.push(k);
-	});
-	return changed;
+	whox() {
+		return this.raw.has("WHOX");
+	}
+
+	prefix() {
+		return this.raw.get("PREFIX") || "";
+	}
+
+	chanTypes() {
+		return this.raw.get("CHANTYPES") || STD_CHANTYPES;
+	}
+
+	statusMsg() {
+		return this.raw.get("STATUSMSG");
+	}
+
+	network() {
+		return this.raw.get("NETWORK");
+	}
+
+	chatHistory() {
+		if (!this.raw.has("CHATHISTORY")) {
+			return 0;
+		}
+		let n = parseInt(this.raw.get("CHATHISTORY"), 10);
+		if (n <= 0) {
+			return Infinity;
+		}
+		return n;
+	}
+
+	bouncerNetID() {
+		return this.raw.get("BOUNCER_NETID");
+	}
 }
 
 export const CaseMapping = {
@@ -612,8 +672,8 @@ export function getMessageLabel(msg) {
 }
 
 export function forEachChannelModeUpdate(msg, isupport, callback) {
-	let chanmodes = isupport.get("CHANMODES") || STD_CHANMODES;
-	let prefix = isupport.get("PREFIX") || "";
+	let chanmodes = isupport.chanModes();
+	let prefix = isupport.prefix();
 
 	let typeByMode = new Map();
 	let [a, b, c, d] = chanmodes.split(",");