import { Injectable } from '@angular/core';
import { Preferences } from '@capacitor/preferences';
import { LocalNotifications, LocalNotificationSchema } from '@capacitor/local-notifications';
import { Haptics, ImpactStyle } from '@capacitor/haptics';
import { EventoAcademico } from './data';

@Injectable({
  providedIn: 'root'
})
export class EventosService {
  private readonly PREF_EVENTOS = 'eventos_academicos';
  private eventos: EventoAcademico[] = [];

  constructor() {
    this.loadEventos();
  }

  async loadEventos(): Promise<EventoAcademico[]> {
    const { value } = await Preferences.get({ key: this.PREF_EVENTOS });
    if (value) {
      this.eventos = JSON.parse(value);
    }
    return this.eventos;
  }

  getEventosByMateria(codigo: string): EventoAcademico[] {
    return this.eventos.filter(e => e.materiaCodigo === codigo);
  }

  getAllEventos(): EventoAcademico[] {
    return this.eventos;
  }

  async saveEvento(evento: EventoAcademico) {
    const index = this.eventos.findIndex(e => e.id === evento.id);
    if (index > -1) {
      this.eventos[index] = evento;
    } else {
      this.eventos.push(evento);
    }
    await this.syncStorage();
    await this.scheduleNotifications(evento);
    await Haptics.impact({ style: ImpactStyle.Medium }).catch(() => {});
  }

  async deleteEvento(id: string) {
    this.eventos = this.eventos.filter(e => e.id !== id);
    await this.syncStorage();
    await this.cancelNotifications(id);
    await Haptics.impact({ style: ImpactStyle.Light }).catch(() => {});
  }

  private async syncStorage() {
    await Preferences.set({
      key: this.PREF_EVENTOS,
      value: JSON.stringify(this.eventos)
    });
  }

  /**
   * Programa notificaciones escalonadas para un hito académico: 7 días, 1 día y 2 horas antes.
   */
  async scheduleNotifications(evento: EventoAcademico) {
    const now = new Date();
    const eventDate = new Date(evento.fecha);
    
    if (eventDate <= now) return;

    // Cancelamos notificaciones previas de este ID
    await this.cancelNotifications(evento.id);

    const notifs: LocalNotificationSchema[] = [];
    const baseId = this.stringToNumericId(evento.id);

    const milestones = [
      { label: 'en 7 días', offset: 7 * 24 * 60 * 60 * 1000, suffix: '7d' },
      { label: 'mañana', offset: 24 * 60 * 60 * 1000, suffix: '1d' },
      { label: 'en 2 horas', offset: 2 * 60 * 60 * 1000, suffix: '2h' }
    ];

    milestones.forEach((m, i) => {
      const scheduleAt = new Date(eventDate.getTime() - m.offset);
      if (scheduleAt > now) {
        notifs.push({
          id: baseId + i,
          title: `📌 Recordatorio: ${evento.tipo}`,
          body: `${evento.materiaCodigo}: ${m.label} es el examen/entrega.`,
          schedule: { at: scheduleAt },
          extra: { eventoId: evento.id, codigo: evento.materiaCodigo }
        });
      }
    });

    if (notifs.length > 0) {
      await LocalNotifications.schedule({ notifications: notifs });
    }
  }

  async cancelNotifications(eventoId: string) {
    const baseId = this.stringToNumericId(eventoId);
    const ids = [baseId, baseId + 1, baseId + 2];
    await LocalNotifications.cancel({ notifications: ids.map(id => ({ id })) }).catch(() => {});
  }

  private stringToNumericId(str: string): number {
    let hash = 0;
    for (let i = 0; i < str.length; i++) {
        hash = ((hash << 5) - hash) + str.charCodeAt(i);
        hash |= 0; 
    }
    return Math.abs(hash % 100000) + 200000;
  }
}