⚙️ Core Logic Engine: @glatam/calendar-core

This is the pure logical calculation engine for the @glatam/calendar suite. It is responsible for availability evaluations, timezone translations, and slot collision algorithms. It contains no DOM/UI dependencies and is completely platform-agnostic.

🛠️ Architecture: Strategy Pattern

The core scheduler utilizes a Strategy Pattern to evaluate availability rules:

1. Weekly Strategy (WeeklyStrategy): Handles recurring availability or blockages on specific days of the week (e.g., "Every Monday from 2:00 PM to 4:00 PM").
2. Date Range Strategy (DateRangeStrategy): Handles specific date-bound blockages or tasks (e.g., "Out of office from 2026-07-25 to 2026-07-28").
3. Strategy Factory (StrategyFactory): Automatically instantiates the correct parser based on the rule payload type.

🌎 Timezone Math & DST Safety

The engine handles cross-timezone bookings using the browser's native Intl API:

• Converts operating slots to UTC timestamps using the host's base timezone.
• Evaluates collisions and blocks on absolute timestamps.
• Translates UTC timestamps back into the buyer's local time dynamically at runtime, accounting for Daylight Saving Time (DST) changes.

📦 Usage Example (Pure Logic)

import { evaluateAvailability } from '@glatam/calendar-core';

const slots = [
  { start: '09:00', end: '10:00' },
  { start: '10:00', end: '11:00' }
];

const rules = [
  { id: '1', type: 'weekly', daysOfWeek: [0, 6], description: 'Closed Weekends' }
];

// Evaluate availability for a specific date
const availability = evaluateAvailability(new Date('2026-07-20'), slots, rules);
console.log(availability);
// Returns slots mapped with their availability status (blocked: false/true)