Add handlers for scene up- and downloads

package.json

@@ -7,6 +7,7 @@
     "@types/node": "14.14.31",
     "@typescript-eslint/eslint-plugin": "4.16.1",
     "@typescript-eslint/parser": "4.16.1",
+    "body-parser": "^1.20.3",
     "cross-env": "^7.0.3",
     "debug": "4.3.1",
     "dotenv": "^10.0.0",

src/index.ts

@@ -2,6 +2,8 @@ import debug from "debug";
 import express from "express";
 import http from "http";
 import { Server as SocketIO } from "socket.io";
+import { restHandler } from "./restHandler";
+import bodyParser from "body-parser";
 
 type UserToFollow = {
   socketId: string;
@@ -28,6 +30,10 @@ const port =
 
 app.use(express.static("public"));
 
+app.use(bodyParser.raw());
+
+app.use("/scene/:id", restHandler("scene"));
+
 app.get("/", (req, res) => {
   res.send("Excalidraw collaboration server is up :)");
 });

src/restHandler.ts

@@ -0,0 +1,95 @@
+import type { RequestHandler } from "express";
+
+interface Scene {
+    hash: string;
+    data: ArrayBuffer;
+}
+
+export function restHandler(_resourceName: string): RequestHandler {
+    const scenes: Record<string, Scene> = {};
+
+    const _put: RequestHandler = (req, res, next) => {
+        const sceneId = req.params.id;
+        const newSceneData = req.body as ArrayBuffer;
+        const newSceneHash = req.header("ETag");
+        const oldSceneHash = req.header("If-Match");
+        console.log(oldSceneHash, newSceneHash, newSceneData);
+
+        if (!newSceneHash || !newSceneData) {
+            res.status(400).send("Data or hash not provided.");
+            return;
+        }
+
+        if (scenes[sceneId] && scenes[sceneId].hash != oldSceneHash) {
+            res.status(409).send("Hash mismatch. Update denied.");
+            return;
+        }
+
+        scenes[sceneId] = {
+            hash: newSceneHash,
+            data: newSceneData,
+        };
+
+        res.status(200).send(`Scene with ID ${sceneId} has been upserted.`);
+        next();
+    };
+
+    const _get: RequestHandler = (req, res, next) => {
+        const sceneId = req.params.id;
+        const oldSceneHash = req.header("If-None-Match");
+
+        if (!scenes[sceneId]) {
+            res.status(404).send("Not found.");
+            return;
+        }
+
+        if (scenes[sceneId] && scenes[sceneId].hash == oldSceneHash) {
+            res.status(304).send("Not modified.");
+            return;
+        }
+
+        // TODO: Respect If-None-Match header
+
+        const scene = scenes[sceneId];
+        res.header("ETag", scene.hash).header("Content-Type", "application/octet-stream");
+        res.status(200).send(scene.data);
+        next();
+    };
+
+    const _options: RequestHandler = (req, res, next) => {
+        const sceneId = req.params.id;
+        delete scenes[sceneId];
+        res.status(200).end();
+        next();
+    };
+
+    const _delete: RequestHandler = (req, res, next) => {
+        const sceneId = req.params.id;
+        delete scenes[sceneId];
+        res.status(200).end();
+        next();
+    };
+
+    return (req, res, next) => {
+        const id = req.params.id;
+        res.header("Access-Control-Allow-Origin", process.env.CORS_ORIGIN || "*");
+        res.header("Access-Control-Allow-Methods", "GET, PUT, DELETE, OPTIONS");
+        res.header("Access-Control-Allow-Headers", "Content-Type, ETag, If-Match, If-None-Match");
+        switch (req.method) {
+            case "GET":
+                _get(req, res, next);
+                break;
+            case "PUT":
+                _put(req, res, next);
+                break;
+            case "OPTIONS":
+                _options(req, res, next);
+                break;
+            case "DELETE":
+                _delete(req, res, next);
+                break;
+            default:
+                next();
+        }
+    };
+}