MCP Time Server Node

import { toZonedTime, fromZonedTime } from 'date-fns-tz'; import type { RecurrencePattern, MonthlyParams } from '../../types/recurrence'; export class MonthlyRecurrence implements RecurrencePattern { calculate(from: Date, params: MonthlyParams): Date { const timezone = params.timezone ?? 'UTC'; if (timezone === 'UTC') { return this.calculateUTC(from, params); } return this.calculateWithTimezone(from, params, timezone); } private calculateUTC(from: Date, params: MonthlyParams): Date { const targetDay = params.dayOfMonth; const targetTime = params.time; // Start with current month const fromYear = from.getUTCFullYear(); const fromMonth = from.getUTCMonth(); // Calculate initial target date let targetDate = this.createUTCDate(fromYear, fromMonth, targetDay); // Set time if specified if (targetTime) { const [hours, minutes] = targetTime.split(':').map(Number); targetDate.setUTCHours(hours, minutes, 0, 0); } // Check if we need to advance to next month if (targetDate <= from) { // Calculate next month const nextMonth = fromMonth === 11 ? 0 : fromMonth + 1; const nextYear = fromMonth === 11 ? fromYear + 1 : fromYear; targetDate = this.createUTCDate(nextYear, nextMonth, targetDay); // Reapply time if specified if (targetTime) { const [hours, minutes] = targetTime.split(':').map(Number); targetDate.setUTCHours(hours, minutes, 0, 0); } } return targetDate; } private calculateWithTimezone(from: Date, params: MonthlyParams, timezone: string): Date { const targetDay = params.dayOfMonth; const targetTime = params.time; // Convert to timezone for calculations const fromInTz = toZonedTime(from, timezone); const year = fromInTz.getFullYear(); const month = fromInTz.getMonth(); // Calculate initial target date let targetDate = this.createTimezoneDate(year, month, targetDay, timezone); // Set time if specified if (targetTime) { targetDate = this.setTimeInTimezone(targetDate, targetTime, timezone); } // Check if we need to advance to next month if (targetDate <= from) { // Calculate next month const nextMonth = month === 11 ? 0 : month + 1; const nextYear = month === 11 ? year + 1 : year; targetDate = this.createTimezoneDate(nextYear, nextMonth, targetDay, timezone); // Reapply time if specified if (targetTime) { targetDate = this.setTimeInTimezone(targetDate, targetTime, timezone); } } return targetDate; } private createUTCDate(year: number, month: number, requestedDay: number): Date { if (requestedDay === -1) { // Last day of month return new Date(Date.UTC(year, month + 1, 0)); } // Get last day of month const lastDay = new Date(Date.UTC(year, month + 1, 0)).getUTCDate(); const actualDay = Math.min(requestedDay, lastDay); return new Date(Date.UTC(year, month, actualDay)); } private createTimezoneDate( year: number, month: number, requestedDay: number, timezone: string, ): Date { let actualDay: number; if (requestedDay === -1) { // Last day of month actualDay = new Date(year, month + 1, 0).getDate(); } else { // Get last day of month const lastDay = new Date(year, month + 1, 0).getDate(); actualDay = Math.min(requestedDay, lastDay); } // Create date in timezone context return fromZonedTime(new Date(year, month, actualDay), timezone); } private setTimeInTimezone(date: Date, timeStr: string, timezone: string): Date { const [hours, minutes] = timeStr.split(':').map(Number); const dateInTz = toZonedTime(date, timezone); dateInTz.setHours(hours, minutes, 0, 0); return fromZonedTime(dateInTz, timezone); } }