Include stream processing inside cache function

Response will always be a stream now

index.js

@@ -61,15 +61,7 @@ function requestAsEventEmitter(opts) {
 				response.url = redirectUrl || requestUrl;
 				response.requestUrl = requestUrl;
 
-				const policy = new CachePolicy(opts, response);
-				if (opts.cache && policy.storable()) {
-					const encoding = opts.encoding === null ? 'buffer' : opts.encoding;
-					getStream(response, {encoding})
-						.then(body => {
-							response.body = body;
-							cacheResponse(response, policy, opts);
-						});
-				}
+				maybeCacheResponse(response, opts);
 
 				ee.emit('response', response);
 			});
@@ -335,20 +327,29 @@ function normalizeArguments(url, opts) {
 	return opts;
 }
 
-function cacheResponse(response, policy, opts) {
-	const key = cacheKey(opts);
-	const value = {
-		policy: policy.toObject(),
-		response: {
-			url: response.url,
-			statusCode: response.statusCode,
-			body: {
-				encoding: opts.encoding,
-				data: response.body
-			}
-		}
-	};
-	opts.cache.set(key, value);
+function maybeCacheResponse(response, opts) {
+	const policy = new CachePolicy(opts, response);
+	if (!(opts.cache && policy.storable())) {
+		return;
+	}
+	const encoding = opts.encoding === null ? 'buffer' : opts.encoding;
+	getStream(response, {encoding})
+		.then(body => {
+			response.body = body;
+			const key = cacheKey(opts);
+			const value = {
+				policy: policy.toObject(),
+				response: {
+					url: response.url,
+					statusCode: response.statusCode,
+					body: {
+						encoding: opts.encoding,
+						data: response.body
+					}
+				}
+			};
+			opts.cache.set(key, value);
+		});
 }
 
 function cacheKey(opts) {