feat: redesign match play and add broadcast tooling

src/lib/broadcast/director.ts

@@ -0,0 +1,68 @@
+/**
+ * The director: which match a channel shows. Pure, so it is easy to test.
+ *
+ * It never cuts away from a map in progress, lingers on a result long enough
+ * for it to be seen, and otherwise goes where it is most exciting: tournament
+ * matches first, then close series near match point, tiebreakers, and crowds.
+ */
+import { DECIDED, type LiveMatch } from '$lib/live';
+import type { ChannelMode } from './channel';
+
+export const RESULT_LINGER_MS = 30_000;
+
+export interface DirectorInput {
+	mode: ChannelMode;
+	matchId: string | null;
+	tournamentId: string | null;
+	current: string | null;
+	/** When the current match was first seen decided. */
+	decidedSince: number | null;
+	live: LiveMatch[];
+	now: number;
+}
+
+export function pickMatch(input: DirectorInput): string | null {
+	if (input.mode === 'match') return input.matchId;
+	const candidates = input.live.filter(
+		(match) =>
+			input.mode === 'auto' ||
+			(input.tournamentId != null && match.tournament?.id === input.tournamentId)
+	);
+	const current = candidates.find((match) => match.id === input.current);
+	if (current) {
+		const decided = DECIDED.includes(current.phase);
+		if (!decided) {
+			// Stay through a map; between maps, only leave for a much better match.
+			const best = best_(candidates);
+			if (current.phase === 'playing' || !best || best.id === current.id) return current.id;
+			return interest(best) > interest(current) + 60 ? best.id : current.id;
+		}
+		if (input.decidedSince != null && input.now - input.decidedSince < RESULT_LINGER_MS)
+			return current.id;
+	}
+	return best_(candidates)?.id ?? null;
+}
+
+function best_(candidates: LiveMatch[]): LiveMatch | null {
+	return (
+		candidates
+			.filter((match) => !DECIDED.includes(match.phase))
+			.sort((a, b) => interest(b) - interest(a) || a.id.localeCompare(b.id))[0] ?? null
+	);
+}
+
+/** How much a match is worth watching right now. */
+export function interest(match: LiveMatch): number {
+	const [a, b] = match.sides;
+	const needed = Math.max(1, match.winsNeeded);
+	const closeness = 1 - Math.abs(a.points - b.points) / needed;
+	const progress = (a.points + b.points) / (2 * needed - 1);
+	return (
+		(match.tournament ? 100 : 0) +
+		(match.simulated ? 0 : 40) +
+		Math.min(80, match.viewers * 4) +
+		closeness * progress * 60 +
+		(match.phase === 'tb' || match.map?.category === 'TB' ? 50 : 0) +
+		(match.phase === 'playing' ? 15 : 0)
+	);
+}