update money tracker

src/lib/money-tracker/charts.ts

@@ -1,25 +1,44 @@
 export type ChartPoint = { date: string; value: number };
-export type ChartSeries = { label: string; color: string; points: ChartPoint[] };
+export type ChartSeries = {
+	label: string;
+	color: string;
+	points: ChartPoint[];
+	emphasis?: boolean;
+};
 
 export function balanceSeries(
 	accounts: { id: number; name: string; openingBalanceCents: number }[],
 	transactions: { accountId: number; date: string; amountCents: number }[]
 ): ChartSeries[] {
 	const palette = ['#0070f3', '#e5484d', '#46a758', '#ad7f00', '#8e4ec6', '#0091ad', '#e56910'];
-	const lastDate = transactions.at(-1)?.date;
-	return accounts.map((account, index) => {
-		let balance = account.openingBalanceCents;
-		const entries = transactions.filter((transaction) => transaction.accountId === account.id);
-		const points: ChartPoint[] = [];
-		if (entries.length) points.push({ date: entries[0].date, value: balance });
-		for (const entry of entries) {
-			balance += entry.amountCents;
-			points.push({ date: entry.date, value: balance });
+	const ordered = [...transactions].sort((a, b) => a.date.localeCompare(b.date));
+	const balances = new Map(accounts.map((account) => [account.id, account.openingBalanceCents]));
+	const accountPoints = new Map(accounts.map((account) => [account.id, [] as ChartPoint[]]));
+	const combinedPoints: ChartPoint[] = [];
+	for (let index = 0; index < ordered.length;) {
+		const date = ordered[index].date;
+		while (index < ordered.length && ordered[index].date === date) {
+			const transaction = ordered[index++];
+			balances.set(
+				transaction.accountId,
+				(balances.get(transaction.accountId) ?? 0) + transaction.amountCents
+			);
 		}
-		if (lastDate && entries.length && lastDate > entries.at(-1)!.date)
-			points.push({ date: lastDate, value: balance });
-		return { label: account.name, color: palette[index % palette.length], points };
-	});
+		for (const account of accounts)
+			accountPoints.get(account.id)!.push({ date, value: balances.get(account.id)! });
+		combinedPoints.push({
+			date,
+			value: [...balances.values()].reduce((sum, balance) => sum + balance, 0)
+		});
+	}
+	return [
+		...accounts.map((account, index) => ({
+			label: account.name,
+			color: palette[index % palette.length],
+			points: accountPoints.get(account.id)!
+		})),
+		{ label: 'All accounts', color: 'var(--site-muted)', points: combinedPoints }
+	];
 }
 
 export function accountBalances(
@@ -59,6 +78,122 @@ export function forecastSeries(
 	return [{ label: 'Projected total', color: '#0070f3', points }];
 }
 
+type ProjectionAccount = { id: number; kind: string; openingBalanceCents: number };
+type ProjectionMovement = { date: string; amountCents: number; accountId: number | null };
+type ProjectionRecurring = {
+	amountCents: number;
+	cadence: string;
+	accountId: number | null;
+	startsOn?: string | null;
+	endsOn?: string | null;
+};
+type ProjectionSettings = {
+	investmentAccountId?: number | null;
+	reserveCents: number;
+	annualReturnPercent: string | number;
+	contributionMode: string;
+	fixedMonthlyCents: number;
+	includeRecurring: number;
+	endDate?: string | null;
+};
+
+export function wealthProjection(
+	accounts: ProjectionAccount[],
+	balances: Map<number, number>,
+	futureTransactions: ProjectionMovement[],
+	forecasts: ProjectionMovement[],
+	recurring: ProjectionRecurring[],
+	settings: ProjectionSettings | null,
+	today: string
+): ChartSeries[] {
+	const accountKind = new Map(accounts.map((account) => [account.id, account.kind]));
+	const investmentId = settings?.investmentAccountId ?? null;
+	const validInvestmentId =
+		investmentId !== null && accountKind.get(investmentId) === 'investment' ? investmentId : null;
+	let spendable = 0;
+	let invested = 0;
+	for (const account of accounts) {
+		const value = balances.get(account.id) ?? 0;
+		if (account.kind === 'investment') invested += value;
+		else spendable += value;
+	}
+	let indexBalance = validInvestmentId === null ? 0 : (balances.get(validInvestmentId) ?? 0);
+	const totalPoints: ChartPoint[] = [{ date: today, value: spendable + invested }];
+	const spendablePoints: ChartPoint[] = [{ date: today, value: spendable }];
+	const investedPoints: ChartPoint[] = [{ date: today, value: invested }];
+	const movements = [...futureTransactions, ...forecasts].filter((entry) => entry.date > today);
+	const latestMovement = movements.reduce(
+		(latest, entry) => (entry.date > latest ? entry.date : latest),
+		''
+	);
+	const fallback = new Date(`${today}T12:00:00Z`);
+	fallback.setUTCFullYear(fallback.getUTCFullYear() + 1);
+	const horizon =
+		settings?.endDate && settings.endDate > today
+			? settings.endDate
+			: latestMovement || fallback.toISOString().slice(0, 10);
+	const monthEnd = (year: number, month: number) =>
+		new Date(Date.UTC(year, month + 1, 0)).toISOString().slice(0, 10);
+	const start = new Date(`${today}T12:00:00Z`);
+	let year = start.getUTCFullYear();
+	let month = start.getUTCMonth();
+	const yearly = Number(settings?.annualReturnPercent ?? 5) / 100;
+	const monthlyGrowth = Math.pow(1 + yearly, 1 / 12) - 1;
+	for (let index = 0; index < 240; index++) {
+		const first = `${year}-${String(month + 1).padStart(2, '0')}-01`;
+		const end = monthEnd(year, month);
+		const date = end < horizon ? end : horizon;
+		if (date > today) {
+			for (const entry of movements.filter(
+				(item) => (index === 0 ? item.date > today : item.date >= first) && item.date <= date
+			)) {
+				if (entry.accountId !== null && accountKind.get(entry.accountId) === 'investment') {
+					invested += entry.amountCents;
+					if (entry.accountId === validInvestmentId) indexBalance += entry.amountCents;
+				} else spendable += entry.amountCents;
+			}
+			if (settings?.includeRecurring !== 0 && index > 0) {
+				for (const item of recurring) {
+					if ((item.startsOn && item.startsOn > date) || (item.endsOn && item.endsOn < first))
+						continue;
+					const value = Math.round(monthlyCents(item.amountCents, item.cadence));
+					if (item.accountId !== null && accountKind.get(item.accountId) === 'investment') {
+						invested += value;
+						if (item.accountId === validInvestmentId) indexBalance += value;
+					} else spendable += value;
+				}
+			}
+			if (validInvestmentId !== null && index > 0) {
+				const growth = Math.round(indexBalance * monthlyGrowth);
+				invested += growth;
+				indexBalance += growth;
+				const excess = Math.max(0, spendable - (settings?.reserveCents ?? 100000));
+				const contribution =
+					settings?.contributionMode === 'fixed'
+						? Math.min(excess, settings.fixedMonthlyCents)
+						: excess;
+				spendable -= contribution;
+				invested += contribution;
+				indexBalance += contribution;
+			}
+			totalPoints.push({ date, value: spendable + invested });
+			spendablePoints.push({ date, value: spendable });
+			investedPoints.push({ date, value: invested });
+		}
+		if (end >= horizon) break;
+		month++;
+		if (month === 12) {
+			month = 0;
+			year++;
+		}
+	}
+	return [
+		{ label: 'Total wealth', color: '#0070f3', points: totalPoints, emphasis: true },
+		{ label: 'Spendable', color: '#46a758', points: spendablePoints },
+		{ label: 'Invested', color: '#8e4ec6', points: investedPoints }
+	];
+}
+
 export function utilityEstimate(
 	readings: { date: string; reading: string; kind: string }[],
 	kind: string,