add ETag to skipSegments byHash

src/middleware/cors.ts

@@ -3,6 +3,6 @@ import { NextFunction, Request, Response } from "express";
 export function corsMiddleware(req: Request, res: Response, next: NextFunction): void {
     res.header("Access-Control-Allow-Origin", "*");
     res.header("Access-Control-Allow-Methods", "GET, POST, OPTIONS, DELETE");
-    res.header("Access-Control-Allow-Headers", "Content-Type");
+    res.header("Access-Control-Allow-Headers", "Content-Type, If-None-Match");
     next();
 }

src/middleware/etag.ts

@@ -0,0 +1,48 @@
+import { NextFunction, Request, Response } from "express";
+import { VideoID, VideoIDHash, Service } from "../types/segments.model";
+import { QueryCacher } from "../utils/queryCacher";
+import { skipSegmentsHashKey, skipSegmentsKey, videoLabelsHashKey, videoLabelsKey } from "../utils/redisKeys";
+
+type hashType = "skipSegments" | "skipSegmentsHash" | "videoLabel" | "videoLabelHash";
+type ETag = `${hashType};${VideoIDHash};${Service};${number}`;
+
+export function cacheMiddlware(req: Request, res: Response, next: NextFunction): void {
+    const reqEtag = req.get("If-None-Match") as string;
+    // if weak etag, do not handle
+    if (!reqEtag || reqEtag.startsWith("W/")) return next();
+    // split into components
+    const [hashType, hashKey, service, lastModified] = reqEtag.split(";");
+    // fetch last-modified
+    getLastModified(hashType as hashType, hashKey as VideoIDHash, service as Service)
+        .then(redisLastModified => {
+            if (redisLastModified <= new Date(Number(lastModified) + 1000)) {
+                // match cache, generate etag
+                const etag = `${hashType};${hashKey};${service};${redisLastModified.getTime()}` as ETag;
+                res.status(304).set("etag", etag).send();
+            }
+            else next();
+        })
+        .catch(next);
+}
+
+function getLastModified(hashType: hashType, hashKey: (VideoID | VideoIDHash), service: Service): Promise<Date | null> {
+    let redisKey: string | null;
+    if (hashType === "skipSegments") redisKey = skipSegmentsKey(hashKey as VideoID, service);
+    else if (hashType === "skipSegmentsHash") redisKey = skipSegmentsHashKey(hashKey as VideoIDHash, service);
+    else if (hashType === "videoLabel") redisKey = videoLabelsKey(hashKey as VideoID, service);
+    else if (hashType === "videoLabelHash") redisKey = videoLabelsHashKey(hashKey as VideoIDHash, service);
+    else return Promise.reject();
+    return QueryCacher.getKeyLastModified(redisKey);
+}
+
+export async function getEtag(hashType: hashType, hashKey: VideoIDHash, service: Service): Promise<ETag> {
+    const lastModified = await getLastModified(hashType, hashKey, service);
+    return `${hashType};${hashKey};${service};${lastModified.getTime()}` as ETag;
+}
+
+/* example usage
+import { getEtag } from "../middleware/etag";
+await getEtag(hashType, hashPrefix, service)
+    .then(etag => res.set("ETag", etag))
+    .catch(() => null);
+*/