Initial commit: Kalendartool (Next.js, Prisma, Docker)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
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238
lib/reservations/service.ts
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238
lib/reservations/service.ts
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/**
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* Service-Schicht fuer Reservierungen (plan.md Abschnitt 5, 6 und 15).
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*
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* Die Doppelbuchungspruefung laeuft ATOMAR innerhalb einer serialisierbaren
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* Transaktion: Der Server validiert Berechtigung, Zeitraum, maximale
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* Dauer und Kollision in einem einzigen kritischen Abschnitt. Zwei
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* gleichzeitige Buchungen koennen so niemals denselben Slot belegen.
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*
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* Dauer: Reservierungen geben Start- und Endzeit an; die maximale
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* Dauer wird gegen die Kalender-Einstellung (max_reservation_minutes)
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* geprueft. 0 bedeutet unbegrenzt.
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*/
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import { prisma } from '@/lib/db/client';
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import { ReservationConflictError, validateReservationPeriod } from '@/lib/reservations/conflicts';
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import type { Reservation } from '@prisma/client';
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/** Zeitfenster-Puffer rund um den gebuchten Zeitraum (24 Stunden). */
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const WINDOW_BUFFER_MS = 24 * 60 * 60 * 1000;
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/**
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* Absolute Obergrenze fuer eine einzelne Reservierung (24 Stunden).
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* Gilt AUCH wenn der Kalender "unbegrenzt" (0) eingestellt ist, damit
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* kein Benutzer den Kalender mit jahrelangen Blockaden lahmlegen kann.
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*/
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export const ABSOLUTE_MAX_DURATION_MINUTES = 24 * 60;
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/** Fehler, wenn die maximale Reservierungsdauer ueberschritten wird. */
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export class MaxDurationExceededError extends Error {
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readonly maxMinutes: number;
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constructor(maxMinutes: number) {
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super(
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maxMinutes === 0
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? 'Die Reservierungsdauer ist ungueltig.'
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: `Maximale Reservierungsdauer ist ${formatDuration(maxMinutes)}.`,
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);
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this.name = 'MaxDurationExceededError';
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this.maxMinutes = maxMinutes;
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}
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}
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/** Fehler, wenn der Kalender nicht existiert oder deaktiviert ist. */
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export class CalendarInactiveError extends Error {
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constructor() {
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super('Kalender nicht gefunden oder deaktiviert.');
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this.name = 'CalendarInactiveError';
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}
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}
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/** Fehler, wenn die zu aendernde Reservierung nicht existiert. */
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export class ReservationNotFoundError extends Error {
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constructor() {
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super('Reservierung nicht gefunden.');
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this.name = 'ReservationNotFoundError';
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}
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}
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/** Formatiert Minuten als lesbare Angabe (z. B. "4 Stunden" / "90 Minuten"). */
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export function formatDuration(minutes: number): string {
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if (minutes < 60) {
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return `${minutes} Minuten`;
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}
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const hours = minutes / 60;
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return Number.isInteger(hours)
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? `${hours} ${hours === 1 ? 'Stunde' : 'Stunden'}`
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: `${hours.toFixed(1).replace('.', ',')} Stunden`;
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}
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/** Prueft, ob der Zeitraum die maximale Dauer des Kalenders einhaelt. */
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function assertMaxDuration(
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startAt: Date,
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endAt: Date,
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maxReservationMinutes: number,
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): void {
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const durationMinutes = (endAt.getTime() - startAt.getTime()) / 60_000;
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// Absolute Obergrenze gilt immer (DoS-Schutz gegen Blockaden).
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if (durationMinutes > ABSOLUTE_MAX_DURATION_MINUTES) {
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throw new MaxDurationExceededError(ABSOLUTE_MAX_DURATION_MINUTES);
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}
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if (maxReservationMinutes === 0) {
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return; // 0 = unbegrenzt (innerhalb der absoluten Obergrenze).
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}
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if (durationMinutes > maxReservationMinutes) {
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throw new MaxDurationExceededError(maxReservationMinutes);
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}
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}
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export interface CreateReservationInput {
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calendarId: string;
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userId: string;
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title: string;
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startAt: Date;
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endAt: Date;
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notes?: string | null;
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}
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export interface UpdateReservationInput {
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startAt?: Date;
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endAt?: Date;
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title?: string;
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notes?: string | null;
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status?: 'CONFIRMED' | 'CANCELLED';
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}
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/**
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* Erstellt eine Reservierung atomar.
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*
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* Ablauf innerhalb der Transaktion:
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* 1. Kalender laden und pruefen (aktiv? maximale Dauer?).
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* 2. Bestehende Reservierungen im Zeitfenster sperren/lesen.
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* 3. Kollision pruefen -> bei Konflikt ReservationConflictError.
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* 4. Reservierung anlegen.
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*
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* Das Isolation-Level SERIALIZABLE verhindert, dass zwei parallele
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* Transaktionen dieselbe Luecke gleichzeitig als frei einstufen.
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*/
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export async function createReservationAtomically(
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input: CreateReservationInput,
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): Promise<Reservation> {
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validateReservationPeriod(input.startAt, input.endAt);
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return prisma.$transaction(
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async (tx) => {
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const calendar = await tx.calendar.findUnique({
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where: { id: input.calendarId },
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select: { id: true, isActive: true, maxReservationMinutes: true },
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});
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if (!calendar || !calendar.isActive) {
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throw new CalendarInactiveError();
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}
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assertMaxDuration(input.startAt, input.endAt, calendar.maxReservationMinutes);
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// Zeitfenster mit Puffer lesen: alle Reservierungen, die den Tag
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// des neuen Zeitraums ueberdecken, genau genug fuer den Overlap-Check.
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const windowStart = new Date(input.startAt.getTime() - WINDOW_BUFFER_MS);
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const windowEnd = new Date(input.endAt.getTime() + WINDOW_BUFFER_MS);
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const overlapping = await tx.reservation.findMany({
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where: {
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calendarId: input.calendarId,
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status: 'CONFIRMED',
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startAt: { lt: windowEnd },
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endAt: { gt: windowStart },
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},
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select: { id: true, startAt: true, endAt: true },
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});
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const conflict = overlapping.some(
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(existing) => existing.startAt < input.endAt && input.startAt < existing.endAt,
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);
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if (conflict) {
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throw new ReservationConflictError();
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}
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return tx.reservation.create({
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data: {
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calendarId: input.calendarId,
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userId: input.userId,
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title: input.title,
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startAt: input.startAt,
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endAt: input.endAt,
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notes: input.notes ?? null,
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},
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});
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},
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{ isolationLevel: 'Serializable' },
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);
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}
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/**
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* Aktualisiert eine Reservierung atomar (gleiche Konflikt- und
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* Dauerlogik; die eigene Reservierung wird aus der Kollisionspruefung
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* ausgenommen).
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*/
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export async function updateReservationAtomically(
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reservationId: string,
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input: UpdateReservationInput,
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): Promise<Reservation> {
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return prisma.$transaction(
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async (tx) => {
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const existing = await tx.reservation.findUnique({
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where: { id: reservationId },
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});
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if (!existing) {
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throw new ReservationNotFoundError();
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}
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const startAt = input.startAt ?? existing.startAt;
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const endAt = input.endAt ?? existing.endAt;
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validateReservationPeriod(startAt, endAt);
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const calendar = await tx.calendar.findUnique({
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where: { id: existing.calendarId },
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select: { isActive: true, maxReservationMinutes: true },
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});
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// Konsistenz zum Anlegen: In deaktivierten Kalendern sind auch
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// Aenderungen bestehender Reservierungen nicht mehr moeglich.
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if (!calendar || !calendar.isActive) {
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throw new CalendarInactiveError();
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}
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assertMaxDuration(startAt, endAt, calendar.maxReservationMinutes);
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const windowStart = new Date(startAt.getTime() - WINDOW_BUFFER_MS);
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const windowEnd = new Date(endAt.getTime() + WINDOW_BUFFER_MS);
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const overlapping = await tx.reservation.findMany({
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where: {
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calendarId: existing.calendarId,
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status: 'CONFIRMED',
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id: { not: reservationId },
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startAt: { lt: windowEnd },
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endAt: { gt: windowStart },
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},
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select: { id: true, startAt: true, endAt: true },
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});
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const conflict = overlapping.some(
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(other) => other.startAt < endAt && startAt < other.endAt,
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);
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if (conflict) {
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throw new ReservationConflictError();
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}
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return tx.reservation.update({
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where: { id: reservationId },
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data: {
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startAt,
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endAt,
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title: input.title ?? existing.title,
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notes: input.notes === undefined ? existing.notes : input.notes,
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status: input.status ?? existing.status,
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},
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});
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},
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{ isolationLevel: 'Serializable' },
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);
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}
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