import { openDB, type IDBPDatabase } from 'idb';
import type { Diary, Product } from '$lib/types/api';

const DB_NAME = 'fooder';
const DB_VERSION = 2;

export interface QueuedMutation {
	id?: number;
	method: 'POST' | 'PATCH' | 'DELETE';
	url: string;
	body: unknown;
	createdAt: number;
}

let dbInstance: IDBPDatabase | null = null;

export async function getDb() {
	if (dbInstance) return dbInstance;
	dbInstance = await openDB(DB_NAME, DB_VERSION, {
		upgrade(db, oldVersion) {
			if (oldVersion < 1) {
				db.createObjectStore('diaries', { keyPath: 'date' });
				db.createObjectStore('mutation_queue', { keyPath: 'id', autoIncrement: true });
			}
			if (oldVersion < 2) {
				if (!db.objectStoreNames.contains('products')) {
					db.createObjectStore('products', { keyPath: 'id' });
				}
			}
		}
	});
	return dbInstance;
}

// ── Diary cache ──────────────────────────────────────────────────────────────

export async function cacheDiary(diary: Diary): Promise<void> {
	const db = await getDb();
	await db.put('diaries', diary);
}

export async function getCachedDiary(date: string): Promise<Diary | undefined> {
	const db = await getDb();
	return db.get('diaries', date);
}

// ── Product cache ─────────────────────────────────────────────────────────────

export async function cacheProducts(products: Product[]): Promise<void> {
	if (products.length === 0) return;
	const db = await getDb();
	const tx = db.transaction('products', 'readwrite');
	await Promise.all(products.map(p => tx.store.put(p)));
	await tx.done;
}

export async function searchCachedProducts(q: string): Promise<Product[]> {
	const db = await getDb();
	const all = await db.getAll('products');
	if (!q.trim()) return all.slice(0, 30);
	const lower = q.toLowerCase();
	return all
		.filter(p => p.name.toLowerCase().includes(lower))
		.sort((a, b) => (b.usage_count_cached ?? 0) - (a.usage_count_cached ?? 0))
		.slice(0, 30);
}

// ── Mutation queue ────────────────────────────────────────────────────────────

export async function enqueueMutation(mutation: Omit<QueuedMutation, 'id' | 'createdAt'>): Promise<void> {
	const db = await getDb();
	await db.add('mutation_queue', { ...mutation, createdAt: Date.now() });
}

export async function getMutationQueue(): Promise<QueuedMutation[]> {
	const db = await getDb();
	return db.getAll('mutation_queue');
}

export async function dequeueMutation(id: number): Promise<void> {
	const db = await getDb();
	await db.delete('mutation_queue', id);
}

export async function getMutationQueueLength(): Promise<number> {
	const db = await getDb();
	return db.count('mutation_queue');
}