import type { IndexedDbStore } from "./indexedDbStore.svelte.js";
import { getOPFSRoot, type OPFSStorage } from "./opfsStorage.js";

const legacyArtPattern = /^art_(.+)_(128|512)$/;
const opfsStorageVersion = 1;

const migrateArtFiles = async (storage: OPFSStorage): Promise<void> => {
	if (!navigator.storage?.getDirectory) return;

	const legacyFiles = new Map<string, { low?: string; high?: string }>();
	const canonicalFiles = new Set<string>();

	for await (const [name, handle] of (await getOPFSRoot()).entries()) {
		if (handle.kind !== "file") continue;
		const match = name.match(legacyArtPattern);
		if (match) {
			const files = legacyFiles.get(match[1]) ?? {};
			files[match[2] === "512" ? "high" : "low"] = name;
			legacyFiles.set(match[1], files);
		} else if (name.startsWith("art_")) {
			canonicalFiles.add(name);
		}
	}

	for (const [id, files] of legacyFiles) {
		const canonical = `art_${id}`;
		if (!canonicalFiles.has(canonical)) {
			for (const source of [files.high, files.low]) {
				if (!source) continue;
				const blob = await storage.readBlob(source);
				if (!blob) continue;
				await storage.writeBlob(canonical, blob);
				break;
			}
		}

		for (const name of [files.low, files.high]) {
			if (name) await storage.deleteBlob(name);
		}
	}
};

export const migrateOfflineStorage = async (
	store: IndexedDbStore,
	storage: OPFSStorage,
): Promise<void> => {
	const currentOpfsVersion =
		(await store.getMetadata<number>("opfsVersion")) ?? 0;
	if (currentOpfsVersion >= opfsStorageVersion) return;

	try {
		await globalThis.caches?.delete("getCoverArt");
	} catch (err) {
		console.warn("failed to delete legacy cover art cache:", err);
	}
	try {
		globalThis.indexedDB?.deleteDatabase("tinysub_pwa");
	} catch (err) {
		console.warn("failed to delete legacy sync database:", err);
	}

	try {
		await migrateArtFiles(storage);
		await store.setMetadata("opfsVersion", opfsStorageVersion);
	} catch (err) {
		console.warn("failed to migrate cached art:", err);
	}
};