import { Injectable } from '@angular/core';
import {
  collection,
  getDocs,
  doc,
  getDoc,
  setDoc,
  deleteDoc,
  updateDoc
} from 'firebase/firestore';

import { db } from '../firebase';
import { Danka } from '../models/danka';

@Injectable({
  providedIn: 'root',
})
export class DankaService {
  private path = 'danka';
  private readonly recentDankaStorageKey = 'kaimyo-management.recent-danka';

  // 一覧
  async getDankaList(): Promise<Danka[]> {
    const snap = await getDocs(collection(db, this.path));

    return snap.docs.map(d => ({
      id: d.id,
      ...(d.data() as Omit<Danka, 'id'>)
    }));
  }

  // 1件
  async getDankaById(id: string): Promise<Danka | undefined> {
    const ref = doc(db, this.path, id);
    const snap = await getDoc(ref);

    if (!snap.exists()) return undefined;

    return {
      id: snap.id,
      ...(snap.data() as Omit<Danka, 'id'>)
    };
  }

  // 作成・更新
  async saveDanka(danka: Danka): Promise<void> {
    const ref = doc(db, this.path, danka.id);
    await setDoc(ref, danka);
  }

  // 部分更新
  async updateDanka(id: string, data: Partial<Danka>): Promise<void> {
    const ref = doc(db, this.path, id);
    await updateDoc(ref, data as any);
  }

  // 削除
  async deleteDanka(id: string): Promise<void> {
    const ref = doc(db, this.path, id);
    await deleteDoc(ref);
  }

  // -----------------------------
  // 最近開いた檀家
  // -----------------------------

  private getRecentDankaIds(): string[] {
    if (!this.canUseLocalStorage()) return [];

    const value = localStorage.getItem(this.recentDankaStorageKey);
    if (!value) return [];

    try {
      const parsed = JSON.parse(value);
      return Array.isArray(parsed)
        ? parsed.filter((id): id is string => typeof id === 'string')
        : [];
    } catch {
      return [];
    }
  }

  private saveRecentDankaIds(ids: string[]): void {
    if (!this.canUseLocalStorage()) return;
    localStorage.setItem(this.recentDankaStorageKey, JSON.stringify(ids));
  }

  private canUseLocalStorage(): boolean {
    return typeof localStorage !== 'undefined';
  }

  // ★ここが重要：async化
  async recordDankaOpened(id: string): Promise<void> {
    const danka = await this.getDankaById(id);
    if (!danka) return;

    const recentIds = [
      id,
      ...this.getRecentDankaIds().filter(rid => rid !== id),
    ].slice(0, 5);

    this.saveRecentDankaIds(recentIds);
  }

  // ★ここも async 必須
  async getRecentDankaList(limit = 5): Promise<Danka[]> {
    const ids = this.getRecentDankaIds().slice(0, limit);

    const list = await Promise.all(
      ids.map(id => this.getDankaById(id))
    );

    const filtered = list.filter((d): d is Danka => d !== undefined);

    if (filtered.length > 0) {
      return filtered;
    }

    // fallback（updatedAtがある前提なら）
    const all = await this.getDankaList();

    return [...all]
      .sort((a: any, b: any) =>
        (b.updatedAt ?? '').localeCompare(a.updatedAt ?? '')
      )
      .slice(0, limit);
  }
}