/**
 * Local cache of today's calendar schedule.
 * Synced periodically from HF backend, checked locally for due slots.
 */

import type { CalendarSlotResponse } from "./types.js";

export class ScheduleCache {
  private slots: Map<string, CalendarSlotResponse> = new Map();
  private lastSyncAt: Date | null = null;
  private cachedDate: string | null = null; // YYYY-MM-DD

  /**
   * Replace the cache with a fresh schedule from backend.
   */
  sync(date: string, slots: CalendarSlotResponse[]): void {
    // If date changed, clear old data
    if (this.cachedDate !== date) {
      this.slots.clear();
    }
    this.cachedDate = date;

    // Merge: update existing slots, add new ones
    const incomingIds = new Set<string>();
    for (const slot of slots) {
      const id = this.getSlotId(slot);
      incomingIds.add(id);
      this.slots.set(id, slot);
    }

    // Remove slots that no longer exist on backend (cancelled etc.)
    for (const id of this.slots.keys()) {
      if (!incomingIds.has(id)) {
        this.slots.delete(id);
      }
    }

    this.lastSyncAt = new Date();
  }

  /**
   * Get slots that are due (scheduled_at <= now) and still pending.
   */
  getDueSlots(now: Date): CalendarSlotResponse[] {
    const results: CalendarSlotResponse[] = [];
    for (const slot of this.slots.values()) {
      if (slot.status !== "not_started" && slot.status !== "deferred") continue;
      if (!slot.scheduled_at) continue;

      const scheduledAt = this.parseScheduledTime(slot.scheduled_at);
      if (scheduledAt && scheduledAt <= now) {
        results.push(slot);
      }
    }
    // Sort by priority descending
    results.sort((a, b) => (b.priority ?? 0) - (a.priority ?? 0));
    return results;
  }

  /**
   * Update a slot locally (e.g., after status change).
   */
  updateSlot(slotId: string, update: Partial<CalendarSlotResponse>): void {
    const existing = this.slots.get(slotId);
    if (existing) {
      this.slots.set(slotId, { ...existing, ...update });
    }
  }

  /**
   * Remove a slot from cache.
   */
  removeSlot(slotId: string): void {
    this.slots.delete(slotId);
  }

  /**
   * Get all cached slots.
   */
  getAll(): CalendarSlotResponse[] {
    return Array.from(this.slots.values());
  }

  /**
   * Get cache metadata.
   */
  getStatus(): { slotCount: number; lastSyncAt: string | null; cachedDate: string | null } {
    return {
      slotCount: this.slots.size,
      lastSyncAt: this.lastSyncAt?.toISOString() ?? null,
      cachedDate: this.cachedDate,
    };
  }

  private getSlotId(slot: CalendarSlotResponse): string {
    return slot.virtual_id ?? String(slot.id);
  }

  private parseScheduledTime(scheduledAt: string): Date | null {
    // scheduled_at can be "HH:MM:SS" (time only) or full ISO
    if (/^\d{2}:\d{2}(:\d{2})?$/.test(scheduledAt)) {
      // Time-only: combine with cached date
      if (!this.cachedDate) return null;
      return new Date(`${this.cachedDate}T${scheduledAt}Z`);
    }
    const d = new Date(scheduledAt);
    return isNaN(d.getTime()) ? null : d;
  }
}