import type { CID } from 'multiformats/cid'

/** Minimal async block store interface — get/put/has. */
export interface BlockStore {
	get(cid: CID): Promise<Uint8Array>
	put(cid: CID, bytes: Uint8Array): Promise<void>
	has(cid: CID): Promise<boolean>
}

/**
 * A block store that reads locally first, with optional remote fallback.
 * On get: local hit → return; local miss + remote → fetch, write-back, return.
 * put/has always operate on local only.
 */
export class LocalFirstBlockStore implements BlockStore {
	constructor(
		private local: BlockStore,
		private remote?: Pick<BlockStore, 'get'>,
	) {}

	async get(cid: CID): Promise<Uint8Array> {
		if (await this.local.has(cid)) return this.local.get(cid)
		if (!this.remote) throw new Error(`Block not found: ${cid}`)
		const bytes = await this.remote.get(cid)
		await this.local.put(cid, bytes)
		return bytes
	}

	put(cid: CID, bytes: Uint8Array): Promise<void> {
		return this.local.put(cid, bytes)
	}

	has(cid: CID): Promise<boolean> {
		return this.local.has(cid)
	}
}