Track which account is interested in which events

Store a list of ids of events and slots that accounts have marked as
being interested in, and show aggeregate counts in the schedule.

server/api/account.patch.ts

@@ -0,0 +1,46 @@
+import { Account } from "~/shared/types/account";
+import { readAccounts, readSchedule, writeAccounts, writeSchedule } from "~/server/database";
+import { broadcastUpdate } from "~/server/streams";
+
+export default defineEventHandler(async (event) => {
+	const session = await requireAccountSession(event);
+	const body: Pick<Account, "interestedIds"> = await readBody(event);
+	if (
+		!(body.interestedIds instanceof Array)
+		|| !body.interestedIds.every(id => typeof id === "string")
+	) {
+		throw createError({
+			status: 400,
+			message: "Invalid interestedIds",
+		});
+	}
+
+	const accounts = await readAccounts();
+	const sessionAccount = accounts.find(account => account.id === session.accountId);
+	if (!sessionAccount) {
+		throw Error("Account does not exist");
+	}
+
+	if (body.interestedIds.length) {
+		sessionAccount.interestedIds = body.interestedIds;
+	} else {
+		delete sessionAccount.interestedIds;
+	}
+	await writeAccounts(accounts);
+
+	const counts = new Map();
+	for (const account of accounts)
+		if (account.interestedIds)
+			for (const id of account.interestedIds)
+				counts.set(id, (counts.get(id) ?? 0) + 1);
+
+	const schedule = await readSchedule();
+	for (const event of schedule.events) {
+		event.interested = counts.get(event.id);
+		for (const slot of event.slots) {
+			slot.interested = counts.get(slot.id);
+		}
+	}
+	await writeSchedule(schedule);
+	broadcastUpdate(schedule);
+})