Add schedule validation and service layer

src/lib/schedule-utils.ts

@@ -0,0 +1,109 @@
+// Isomorphic, dependency-free schedule helpers. Used by the server service
+// layer, the v2 serializers and the client-side Block modal (for live
+// pre-validation), so it must not import Prisma or any server-only code.
+
+export const MAX_BLOCKS = 4;
+export const MINUTES_PER_DAY = 24 * 60;
+export const SNAP_MINUTES = 15;
+export const MINUTE_STEP = 5;
+
+export type BlockSibling = {
+	id?: string;
+	startMinutes: number;
+	endMinutes: number;
+};
+
+export type BlockInput = {
+	startMinutes: number;
+	endMinutes: number;
+	proclamationIds: string[];
+};
+
+export type ValidationResult = { ok: true } | { ok: false; error: string };
+
+function normalizeMinutes(minutes: number): number {
+	return (((Math.trunc(minutes) % MINUTES_PER_DAY) + MINUTES_PER_DAY) % MINUTES_PER_DAY) | 0;
+}
+
+/** Format minutes-from-midnight as a 12-hour clock label, e.g. `6:00 AM`. */
+export function formatTime(minutes: number): string {
+	const normalized = normalizeMinutes(minutes);
+	const hours24 = Math.floor(normalized / 60);
+	const mins = normalized % 60;
+	const period = hours24 < 12 ? 'AM' : 'PM';
+	const hours12 = hours24 % 12 === 0 ? 12 : hours24 % 12;
+	return `${hours12}:${String(mins).padStart(2, '0')} ${period}`;
+}
+
+/** Format minutes-from-midnight as a 24-hour `HH:MM` string. */
+export function toHm(minutes: number): string {
+	const normalized = normalizeMinutes(minutes);
+	const hours = Math.floor(normalized / 60);
+	const mins = normalized % 60;
+	return `${String(hours).padStart(2, '0')}:${String(mins).padStart(2, '0')}`;
+}
+
+/** Snap a minute value to the nearest `SNAP_MINUTES` interval, clamped to 24h. */
+export function snapMinutes(minutes: number): number {
+	const snapped = Math.round(minutes / SNAP_MINUTES) * SNAP_MINUTES;
+	return Math.max(0, Math.min(MINUTES_PER_DAY, snapped));
+}
+
+/** First sibling whose half-open range [start, end) intersects the input. */
+export function findOverlap(
+	input: { startMinutes: number; endMinutes: number },
+	siblings: BlockSibling[]
+): BlockSibling | null {
+	for (const sibling of siblings) {
+		if (input.startMinutes < sibling.endMinutes && sibling.startMinutes < input.endMinutes) {
+			return sibling;
+		}
+	}
+	return null;
+}
+
+/**
+ * Validate a Block against the schedule's other Blocks. `siblings` must exclude
+ * the Block being edited. `isCreate` enables the 4-block maximum (an update
+ * never increases the count).
+ */
+export function validateBlock(
+	input: BlockInput,
+	siblings: BlockSibling[],
+	opts: { isCreate?: boolean } = {}
+): ValidationResult {
+	const { startMinutes, endMinutes, proclamationIds } = input;
+
+	if (
+		!Number.isInteger(startMinutes) ||
+		!Number.isInteger(endMinutes) ||
+		startMinutes < 0 ||
+		endMinutes > MINUTES_PER_DAY ||
+		startMinutes >= endMinutes
+	) {
+		return {
+			ok: false,
+			error: "Start time must be before end time. Overnight blocks aren't supported."
+		};
+	}
+
+	if (!Array.isArray(proclamationIds) || proclamationIds.length === 0) {
+		return { ok: false, error: 'Select at least one proclamation.' };
+	}
+
+	if (opts.isCreate && siblings.length >= MAX_BLOCKS) {
+		return { ok: false, error: `You can have at most ${MAX_BLOCKS} blocks.` };
+	}
+
+	const overlap = findOverlap(input, siblings);
+	if (overlap) {
+		return {
+			ok: false,
+			error: `This overlaps with your ${formatTime(overlap.startMinutes)}–${formatTime(
+				overlap.endMinutes
+			)} block.`
+		};
+	}
+
+	return { ok: true };
+}