+ /**
+ * @module
+ */
+
+import { InvalidResponse } from './errors.js'
+import { fetch } from './got.js'
+import checkErrorResponse from './check-error-response.js'
+
+const oneDay = 24 * 3600 * 1000 // 1 day in milliseconds
+
+// Map from URL to { timestamp: last fetch time, data: data }.
+let resourceCache = Object.create(null)
+
+/**
+ * Make a HTTP request using an in-memory cache
+ *
+ * @param {object} attrs Refer to individual attrs
+ * @param {string} attrs.url URL to request
+ * @param {number} attrs.ttl Number of milliseconds to keep cached value for
+ * @param {boolean} [attrs.json=true] True if we expect to parse the response as JSON
+ * @param {Function} [attrs.scraper=buffer => buffer] Function to extract value from the response
+ * @param {object} [attrs.options={}] Options to pass to got
+ * @param {Function} [attrs.requestFetcher=fetch] Custom fetch function
+ * @returns {*} Parsed response
+ */
+async function getCachedResource({
+ url,
+ ttl = oneDay,
+ json = true,
+ scraper = buffer => buffer,
+ options = {},
+ requestFetcher = fetch,
+}) {
+ const timestamp = Date.now()
+ const cached = resourceCache[url]
+ if (cached != null && timestamp - cached.timestamp < ttl) {
+ return cached.data
+ }
+
+ const { buffer } = await checkErrorResponse({})(
+ await requestFetcher(url, options)
+ )
+
+ let reqData
+ if (json) {
+ try {
+ reqData = JSON.parse(buffer)
+ } catch (e) {
+ throw new InvalidResponse({
+ prettyMessage: 'unparseable intermediate json response',
+ underlyingError: e,
+ })
+ }
+ } else {
+ reqData = buffer
+ }
+
+ const data = scraper(reqData)
+ resourceCache[url] = { timestamp, data }
+ return data
+}
+
+function clearResourceCache() {
+ resourceCache = Object.create(null)
+}
+
+export { getCachedResource, clearResourceCache }
+
+
+