utils.ts

import { Buffer } from 'buffer'
import { EOF } from '@berty-tech/grpc-bridge'
import { WelshProtocolServiceClient } from '@berty-tech/grpc-bridge/welsh-clients.gen'

let cache: { cid: string; prom: Promise<string> }[] = []

export const base64ToURLBase64 = (str: string) =>
	str.replace(/\+/g, '-').replace(/\//g, '_').replace(/\=/g, '')

const fetchSource = async (
	protocolClient: WelshProtocolServiceClient,
	cid: string,
): Promise<string> => {
	const stream = await protocolClient.attachmentRetrieve({
		attachmentCid: Buffer.from(cid, 'base64'),
	})
	const data = await new Promise<Buffer>((resolve, reject) => {
		let buf = Buffer.from('')
		stream.onMessage((msg, err) => {
			if (err === EOF) {
				resolve(buf)
				return
			}
			if (err) {
				reject(err)
				return
			}
			if (msg?.block) {
				buf = Buffer.concat([buf, msg.block])
			}
		})
		stream.start()
	})
	return data.toString('base64')
}

export const getSource = async (
	protocolClient: WelshProtocolServiceClient,
	cid: string,
): Promise<string> => {
	if (!cache.find((item) => item.cid === cid)) {
		if (cache.length >= 20) {
			// evict
			cache = cache.slice(1)
		}
		cache.push({ cid, prom: fetchSource(protocolClient, cid) })
	}
	const cached = cache.find((item) => item.cid === cid)
	if (!cached) {
		throw new Error('unexpected cache miss')
	}
	return cached.prom
}